Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

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and school years. (See Energy: Measurement of Food

Energy.)

Protein

0011 Human beings require nine essential amino acids that

they cannot synthesize, the nonessential amino acids,

and additional nitrogen to fulfill their protein needs.

The amino acid composition of protein, the amount

of protein, the bioavailability of protein and the avail-

ability of the protein for building tissue instead of

being burned for energy are therefore all important.

(See Amino Acids: Metabolism; Protein: Require-

ments; Quality.)

0012 A major concern is that the individual be in energy

balance rather than in a hypocaloric state, since,

under such circumstances, protein will be used for

energy. The macrobiotic regimen potentially poses

both protein quality and quantity problems. On all

but the most severe macrobiotic regimes, enough pro-

tein is present to be adequate if sufficient energy is

provided. With regard to protein quality, legumes are

moderately high in protein quality. When they are

consumed along with rice and other plant proteins,

the biological value of the protein is adequate.

Animal proteins lack fewer amino acids than do

plant proteins, but macrobiotic diets are virtually

devoid of animal flesh, eggs, milk, and poultry, all

of which provide relatively complete proteins and all

the amino acids needed for building bodily protein.

Fish and seafood are consumed by macrobiotics in

small amounts, and these proteins are relatively com-

plete. Plant tissues are somewhat more variable in the

extent to which the nitrogen present in them is found

in protein, ranging from a high of about 95% in seeds

down to 50% in roots such as potatoes, carrots, and

cassava. The nonprotein nitrogen is in the form of

peptides and free amino acids. The amino acid com-

position of different plant proteins can complement

each other, making up their various deficits. Thus, the

aggregate of individual plant proteins provides a

mixture that matches body needs. The lack of most

animal protein does not necessarily mean that protein

nutritional status must be compromised. Macrobiot-

ics consume legumes such as soya beans and aduke

beans, which are high in the essential amino acids

lysine and threonine, and soya beans are also high in

tryptophan. However legumes are limited in methio-

nine, cystine, and (except for soya beans) tryptophan.

Grain proteins are high in methionine, cystine and

tryptophan (with the exception of cornmeal and rye,

which are low in tryptophan). Moreover, grains are

low in the essential amino acids lysine and isoleucine,

although these are high in legumes. Thus, combin-

ations of grains and legumes complement each other

and together provide for the amino acid needs of the

body if eaten in sufficient amounts. Mixtures of

grains, milk or eggs, and legumes with seeds or nuts

also complement each other well. Most nuts and

seeds are high in cystine, methionine, and tryptophan,

and low in lysine and isoleucine. The only exception

is peanuts, which are low in both methionine and

threonine. Other plant proteins are low in these

amino acids, whereas they are relatively high in lysine

and tryptophan. Thus, nuts, seeds, and legumes com-

plement other plant proteins well, as do grains and

legumes. Small amounts of animal foods such as sea-

food, milk products, and eggs also complement the

amino acid profile of plant proteins well. Therefore,

when a variety of complementary plant proteins are

consumed in sufficient quantity, and energy is pro-

vided in sufficient amounts, there is little reason for

concern. However, on the most rigorous macrobiotic

diets, at least in the past, energy intakes were some-

times inadequate, and when only one or two plant

protein sources were relied upon exclusively, protein

calorie malnutrition sometimes ensued. These prob-

lems were reported more commonly in the 1960s and

1970s than later. Practices may have changed, but

recent rigorous surveys of the nutritional status of

macrobiotics are not available. Caution is warranted

for the ill, who often consume hypocaloric diets, for

young infants who are growing rapidly and have been

weaned from the breast who may not be able to

consume sufficient energy on exclusively plant diets,

and for pregnant women and others who have espe-

cially high protein needs for growth. (See Protein:

Digestion and Absorption of Protein and Nitrogen

Balance; Deficiency.)

Fat and Cholesterol

0013Macrobiotic diets are low in fat (e.g., < 25% of energy,

and often as little as 15%), and especially saturated

fat and cholesterol. Those who consume such diets

often have low total and low-density lipoprotein

cholesterol levels, with decreased dietary risks of

coronary artery disease. Macrobiotics’ high intakes

of soluble fiber and their relatively low weights also

cause low serum cholesterol levels and lower the risk

of coronary artery disease.

0014When diets are below approximately 15% of food

energy, special care must be taken to ensure that

intakes of essential fatty acids are met. At least 3%

of energy should be from o-6 fatty acids and 2% from

o-3 fatty acids. Both of the essential fatty acids, lino-

leic acid, an o-6 fatty acid, and a-linolenic acid, an o-3

fatty acid, are required by human beings. Linoleic acid

is found in seeds, nuts and grains. a-Linolenic

acid is found in the green leaves of plants, and in

phytoplankton and algae, in certain seeds, nuts and

legumes, such as flax, canola, walnuts, hazelnuts, and

3634 MACROBIOTIC DIETS

soy. These can be converted into more highly unsatur-

ated fatty acids, with linoleic acid producing arachi-

donic acid, and a-linolenic acid being converted to

eicosapentaenoic acid (EPA) and docosahexaenoic

acid (DHA). Arachidonic acid is found in animal

foods such as meat, poultry, and eggs. EPA and

DHA are largely found in fish and seafood. Arachi-

donic acid and EPA serve as precursors for the

eicosanoids. Recommended intakes for these poly-

unsaturated fatty acids range from 3 to 10% of total

energy intakes. Vegan vegetarians have no direct

sources of long-chain o-3 fatty acids EPA and DHA

in their diets, and thus must convert a-linolenic acid

to them. There is concern that pregnant women who

are vegan-vegetarians, or macrobiotics who consume

little or no fish or other animal foods, may not obtain

enough of these fatty acids, especially during preg-

nancy and in early infancy, especially if the infants

are premature, and their conversion capacity of a-

linolenic acid to DHA is very limited. Such individ-

uals may need DHA supplements, either from fish oils

or from cultured microalgae. However, they should

only be dispensed under a physician’s direction, since

they are also anticoagulants. o-3 fatty acids are rich in

flaxseeds and flaxseed oil, hemp seed oil, purslane, a

dark green leafy vegetable, canola, walnut, and soy

oil. Flaxseed oil is also rich in a-linolenic acid.

Carbohydrate and Fiber

0015 Raw fruits, especially berries, vegetables, legumes

such as beans and peas, nuts, seeds, whole-grain

products, and seaweed provide relatively high

amounts of dietary fiber in the macrobiotic diet,

helping to promote laxation and perhaps lessening

symptoms of asymptomatic diverticular disease. It is

possible, but not yet proven, that high intakes of

dietary fiber reduce the risks of colon cancer; there

is no evidence that macrobiotic diets are especially

efficacious in these respects. The macrobiotic diet is

high in soluble sources of dietary fiber, such as

legumes, whole grain rice, barley, oats, and raw fruits

and vegetables. Soluble fiber may enhance glycemic

control and also lower serum cholesterol, contribut-

ing the low total and low-density-lipoprotein choles-

terol levels often evident in macrobiotics. Fiber

increases the dietary bulk and lowers the energy

density per gram of food consumed. The ill effects

of dietary fiber arise if very large amounts are fed to

young infants and weanlings under 2 years of age.

Macrobiotics sieve cereals, pulses, and vegetables

that are fed to infants to increase their digestibility,

but fiber intakes and bulk may still be rather high,

and the nutrient density of such feeds may still be

quite low. The partial replacement of whole-grain

cereals with more highly refined cereals that are

lower in fiber increases energy intakes and decreases

bulk in feeding infants.

0016Macrobiotics’ intakes of refined sugar are very low,

but other fermentable carbohydrates, such as sugars

found in fruits and starches, are consumed, so the risk

of dental caries is still present, especially if these are

consumed in forms that are retained in the oral cavity,

and oral hygiene is poor. (See Carbohydrates: Re-

quirements and Dietary Importance; Glucose: Glu-

cose Tolerance and the Glycemic (Glycaemic) Index.)

Vitamins

0017Vitamins B

and D may be in particularly short

supply in macrobiotic diets fed to rapidly growing

infants and children.

0018Vitamin B

Reliable plant sources of vitamin B

are vitamin B

-fortified soyamilk and formulas,

yeast grown on, and mixed with, vitamin B

enriched media, highly fortified breakfast cereals,

and vitamin B

supplements. Vitamin B

-containing

foods that are sometimes acceptable to those who

practice macrobiotics include fish such as sardines,

pilchard, mackerel, herring, salmon, and tuna. In

amounts of about an ounce a day, they may be suffi-

cient to avoid deficiencies in young children.

0019Animal foods have a high content of vitamin B

because they ingest vitamin B

-containing micro-

organisms or because the microflora in their guts

synthesize the vitamin. The richest sources of vitamin

provide over 19 mg per 100 g. They are lamb or

beef organ meats such as kidney and liver, bivalves

such as clams and oysters, which extract many micro-

organisms containing vitamin B

from sea water,

soyamilk that is fortified with vitamin B

, and vita-

min supplements. Other types of red meats, eggs, and

milk products are also good sources. Macrobiotics

rarely eat large amounts of any of these products on

a regular basis. Therefore, inadequate intakes of vita-

min B

may be a problem. Moderately good sources,

providing 3–10 mg per 100 g of vitamin B

include

seafood, such as lobster, scallops, haddock, tuna,

swordfish, and flounder, and egg yolks, fermented

cheeses, such as Camembert or Limburger, and non-

fat milk solids. Most other red meats and fish provide

less than this amount. Grains, fruits, and vegetables

are virtually devoid of B

, except for tiny amounts

present in root nodules of some legumes. Seaweed is

sometimes contaminated by plankton rich in vitamin

, but these are unreliable sources of the vitamin.

‘Sea vegetables’ such as wakame, arame, and kombu

and a seaweed known as spirulina contain very few

corrinoids that are available to humans. Other plant

foods such as certain fermented soya products like

miso (which is often served as a soup) and tempeh

MACROBIOTIC DIETS 3635

have not been tested for the bioavailablity of their

corrinoids to humans, although they may test positive

in microbiological assays for the vitamin. They

cannot be relied upon to provide sufficient amounts

of vitamin B

. Small amounts of vitamin B

may

also be present in some plant foods, owing to contam-

ination of food with insects or feces.

0020 The major risks of vitamin B

deficiency are in

pregnant women, growing infants, and children of

mothers who have followed a macrobiotic diet for

many years. Infants may be born with low stores of

the vitamin, are reported to exhibit biochemical in-

dices of vitamin B

deficiency, even when they are

suckling, and are at risk of deficiency after they have

been weaned from the breast to vegan-like diets.

(See Cobalamins: Physiology; Food Fortification.)

0021 Vitamin D Humans can synthesize vitamin D endo-

genously when the skin is exposed to ultraviolet

irradiation, but those who live in northern latitudes,

use sunscreen, or are confined indoors by illness may

not receive enough stimulation to meet their needs.

Supplies of the vitamin may pose problems for macro-

biotics. The naturally occurring food sources rich in

vitamin D are human milk, which provides low but

adequate amounts of the vitamin for human infants in

the first few months of life, egg yolks, liver, and some

fatty fish such as eel, herring, sardines, and salmon.

In the USA, milk and milk products are fortified

with vitamin D at approximately 0.5 IU g

1

(0–0.01

mgg

1

) wet weight, and margarine at about 5 IU g

1

(or 0.10 mgg

1

), so that food products containing

them will also contain some vitamin D. Vitamin D-

fortified milk products are also available in many

other Western countries. In the USA, highly fortified

cereals are sometimes fortified with vitamin D, often

at levels of 1.2 IU g

1

(0.02–0.04 mg) dry weight, as

packaged. Cod liver oil and menhaden oil macrobiot-

ics refuse to eat liver, egg yolk, butter, fluid milk, and

dried skim milk powder. The natural sources of vita-

min D they may be willing to eat are margarine and

fatty fish, and vitamin D-fortified soyamilk and other

plant foods. Vitamin D supplements are also available

without prescription in the USA at levels not

exceeding 5 mg (the current adequate intake) per cap-

sule, or at higher levels by prescription.

Minerals

0022 Certain mineral elements in the macrobiotic diet are

also sometimes limited.

0023 Calcium Macrobiotics rarely include foods from

the dairy group in their usual diets. Some plants

including kale, collards, dried peas, and beans

provide considerable amounts of calcium. However,

absorption of calcium from spinach, kale, collards,

and Swiss chard is inhibited by the presence of oxal-

ates that bind with calcium during digestion to form

insoluble calcium oxalate, which cannot be absorbed.

Whole grains contain phytates, substances that inter-

fere with calcium and zinc. However, some of the

calcium is available. Foods that may be acceptable

to macrobiotics that contain calcium include bony

fish such as sardines and foods fortified with calcium

(fortified soy milk, fortified rice beverage, fortified

juices, highly fortified breakfast cereals, and tofu

precipitated with calcium sulfate), and these provide

considerable amounts of calcium.

0024Iron Macrobiotics exclude all heme iron sources,

because they do not eat meat. Even lacto-ovovegetar-

ians have a very much lower iron absorption than do

omnivores. The bioavailabiliy is probably about 10%

compared with about twice that in omnivores, so this

is a potential risk factor. However, many other factors

affect iron absorption, and in many studies, iron

status does not seem to be adversely affected. It is

possible to estimate bioavailabiliy in the diet of

dietary iron. The amount of ascorbic acid and

presence of other iron absorption enhancers as well

as the presence of inhibitors must be measured. Foods

high in iron include peas, beans, and highly iron-

fortified breakfast cereals. During pregnancy, iron

supplements are required, because the iron needs are

so high.

0025Zinc The macrobiotic diet is low in meat and low in

other foods that are high in zinc. Milk products are a

good source of zinc for those who consume them.

Zinc absorption from plant foods is poor when the

foods contain phytate and oxalate inhibitors. Macro-

biotic diets are high in foods high in the zinc inhibitor

phytic acid (e.g., soy products, beans, lentils, peas,

nuts, and whole grains). Good plant sources of zinc

are zinc-fortified cereals, and yeast-fermented foods

that reduce the phytic acid content of whole-grain

breads, rather than refined white bread. Zinc supple-

ments are also good sources of zinc that may be

acceptable to some macrobiotics. Fermented soy-

foods, like tempeh and miso, and sprouted legumes

may have more bioavailable zinc than unfermented

foods like tofu and soymilk.

Conclusion

0026Many of the aspects of the macrobiotic diet that

convey risks to health can be easily corrected without

losing the positive aspects of the regimen or violating

philosophical principles. Vegetarian or vegan diets

that are carefully planned to include modern scientific

3636 MACROBIOTIC DIETS

knowledge of nutrition are associated with good

health. This is also possible for macrobiotic diets,

although, in reality, it does not always occur.

See also: Amino Acids: Metabolism; Carbohydrates:

Requirements and Dietary Importance; Cobalamins:

Physiology; Energy: Measurement of Food Energy; Food

Fortification; Glucose: Glucose Tolerance and the

Glycemic (Glycaemic) Index; Malnutrition: Malnutrition

in Developed Countries; Protein: Requirements; Quality;

Digestion and Absorption of Protein and Nitrogen

Balance; Deficiency; Vegetarian Diets

Further Reading

Abrams HL (2000) Vegetarianism: Another view. In: Kiple

KF and Connee K (eds) The Cambridge World History

of Food, vol. 2, pp. 1564–1573. Cambridge: Cambridge

University Press.

Alexander DB and Mann J (1994) Nutrient intake and

haematological status of vegetarians and age sex

matched omnivores. European Journal of Clinical Nu-

trition 48: 538–546.

Anderson B, Gibson RS and Sabry JH (1981) The iron and

zinc status of long-term vegetarian women. American

Journal of Clinical Nutrition 34: 1042–1048.

Coulston A (1999) The role of dietary fats in plant based

diets. American Journal of Clinical Nutrition 70: 512S–

515S.

Crane M, Register D and Lukens R (1999) Cobalamin

studies on 2 total vegetarian (vegan) families. American

Journal of Clinical Nutrition 70: 626S–627S.

Dagnelie P (1991) Vitamin B-12 from algae appears not to

be bioavailable. American Journal of Clinical Nutrition

53: 695–697.

Dagnelie P (1994) Macrobiotic nutrition and child health:

results of a population based, mixed longitudinal cohort

study in The Netherlands. American Journal of Clinical

Nutrition 59: 1187S–1196S.

Dagnelie P, Vergote FJVRA, Van Staveren WA et al. (1990)

High prevalence of rickets in infants on macrobiotic

diets. American Journal of Clinical Nutrition 51:

202–208.

Donovan U and Givson RS (1995) Iron and zinc status of

young women aged 14 to 19 years consuming vegetarian

and omnivorous diets. Journal of the American College

of Nutrition 14: 463–472.

Dwyer J and Jacobs C (1988) Vegetarian children: appro-

priate and inappropriate diets. American Journal of

Clinical Nutrition 48: 811S–818S.

Dwyer J and Lowe F (1994) Nutritional risks of vegan diets

to women and children: are they preventable? Journal of

Agricultural and Environmental Ethics 7: 87–109.

Dwyer JT (1999) Convergence of plant-rich and plant-only

diets. American Journal of Clinical Nutrition 70:

620S–622S.

Estes JW (2000) Food as medicine. In: Kiple KF and Connee

K(eds)The Cambridge World History of Food, vol. 2, pp.

1534–1553. Cambridge: Cambridge University Press.

Haddad E, Berk LS, Kettering JD, Hubbard RW and Peters

WR (1999) Dietary intake and biochemical, hemato-

logic, and immune status of vegans compared with non-

vegetarians. American Journal of Clinical Nutrition 70:

586S–593S.

Hallberg L and Huthen L (2000) Prediction of dietary iron

absorption: an algorithm for calculating absorption and

bioavailability of dietary iron. American Journal of

Clinical Nutrition 71: 1147–1160.

Harland B and Oberleas D (1987) Phytate in foods. World

Review Nutrition and Dietetics 52: 235–259.

Hunt J, Gallagher SK, Johnson LK and Lykken GI (1995)

High versus low meat diets: effects on zinc absorption,

iron status, and calcium, copper, iron, magnesium, man-

ganese, nitrogen, phosphorus, and zinc balance in post-

menopausal women. American Journal of Clinical

Nutrition 62: 621–632.

Hun J, Matthys LA and Johnson LK (1998) Zinc absorp-

tion, mineral balance, and blood lipids in women con-

suming controlled lacto-ovovegetarian and omnivorous

diets for 8 wk. American Journal of Clinical Nutrition

67: 421–430.

Hunt J and Roughhead ZK (1999) Nonheme iron absorp-

tion, fecal ferritin excretion, and blood indexes of iron

status in women consuming controlled lactoovovegetar-

ian diets for 8 wk. American Journal of Clinical Nutri-

tion 69: 944–952.

Jacques P, Bostom AG, Williams RR et al. (1996) Relation

between folate status, a common mutation in methylene-

tetrahydrofolate reductase, and plasma homocystine

concentrations. Circulation 93: 7–9.

Key T, Fraser GE, Thorogood M et al. (1999) Mortality

in vegetarians and nonvegetarians: detailed findings

from a collaborative analysis of 5 prospective studies.

American Journal of Clinical Nutrition 70:

516S–524S.

Kushi L, Meyer KA and Jacobs DR (1999) Cereals, legumes

and chronic disease risk reduction: evidence from epide-

miologic studies. American Journal of Clinical Nutrition

70: 451S–458S.

Ladizesky M, Lu Z, Oliveri B et al. (1995) Solar ultraviolet

B radiation and photoproduction of vitamin D

in cen-

tral and southern areas of Argentina. Journal of Bone

and Research 10: 545–549.

Latta D and Liebman M (1984) The iron and zinc status of

longterm vegetarian women. American Journal of Clin-

ical Nutrition 34: 1042–1048.

Mann J, Appleby PN, Key TJ and Thorogood M (1997)

Dietary determinants of ischaemic heart disease in

health conscious individuals. Heart 78: 450–455.

Matsuoka L, Ide L, Wortsman J, MacLaughlin JA and

Holick MF (1987) Sunscreens suppress cutaneous vita-

min D

synthesis. Journal of Clinical Endocrinology and

Metabolism 64: 1165–1168.

Messina M and Messina V (1996) The Dietitian’s Guide to

Vegetarian Diets: Issues and Applications. Gaithersburg,

MD: Aspen.

Messina V and Burke KL (1997) Position of the American

Dietetic Association: vegetarian diets. Journal of the

American Dietetic Association 97: 1317–1321.

MACROBIOTIC DIETS 3637

Miller D, Specker BL, Ho ML and Norman EJ (1990)

Vitamin B

status in a macrobiotic community. Ameri-

can Journal of Clinical Nutrition 53: 524–529.

Resnicow K, Barone J, Engle A et al. (1991) Diet and serum

lipids in vegan vegetarians: a model for risk reduction.

Journal of the American Dietetic Association 91:

447–453.

Sanders T (1999) Essential fatty acid requirements of vege-

tarians in pregnancy, lactation, and infancy. American

Journal of Clinical Nutrition 70: 555S–559S.

Sanders T (1992) The influence of a vegetarian diet on the

fatty acid composition of human milk and the essential

fatty acid status of the infant. Journal of Pediatrics 120:

S71–S77.

Sandstrom B, Arvidsson B, Cederblad A and Bjorn-Rasmus-

sen E (1980) Zinc absorption from composite meals I.

The significance of wheat extraction rate, zinc, calcium,

and protein content in meals based on bread. American

Journal of Clinical Nutrition 33: 739–745.

Simopoulos A (1999) Essential fatty acids in health and

chronic disease. American Journal of Clinical Nutrition

70: 560S–569S.

Specker B, Miller D, Norman EJ, Greene H and Hayes KC

(1988) Increased urinary methylmalonic acid excre-

tion in breast fed infants of vegetarian mothers and

identification of an acceptable dietary source of vitamin

. American Journal of Clinical Nutrition 47: 89–92.

Van den Berg I (1991) Vitamin B-12 content and bioavail-

ability of spirulina and nor. Journal of Nutritional Bio-

chemistry 2: 314–318.

Weaver C, Proulx WR and Heaney R (1999) Choices for

achieving adequate dietary calcium with a vegetarian diet.

American Journal of Clinical Nutrition 70: 543S–548S.

Webb A, Kline L and Holick MF (1988) Influence of season

and latitude on the cutaneous synthesis of vitamin D

exposure to winter sunlight in Boston and Edmonton

will not promote vitamin D

synthesis in human skin.

Journal of Clinical Endocrinology and Metabolism 67:

373–378.

Whorton J (2000) Vegetarianism. In Kiple KF and Connee K

(eds) The Cambridge World History of Food,vol.2,pp.

1553–1565. Cambridge: Cambridge University Press.

Wood R and Fleet JC (1998) The genetics of osteoporosis:

Vitamin D receptor polymorphsims. Annual Review of

Nutrition 18: 233–258.

Worthingon-Roberts B, Breskin MW and Monsen ER

(1988) Iron status of premenopausal women in a univer-

sity community and its relationship to habitual dietary

sources of protein. American Journal of Clinical Nutri-

tion 47: 275–279.

MADEIRA AND RELATED PRODUCTS

R W Goswell, Stoke Bishop, Bristol, UK

This article is reproduced from Encyclopaedia of Food Science,

Definition

0001 Madeira is the name given to a number of related

types of dessert wine originally developed in the

islands of Madeira and Porto Santo. It owes much

of its characteristic flavor to a period of maturation at

a relatively elevated temperature. Similar products

are produced elsewhere under other names. Now-

adays, the designation ‘Madeira’ is rarely used for

wines not produced on the island.

Legal Definition

0002 The Madeira wine region is one of the oldest demar-

cated areas of Portugal. Since April 1979, the method

of production of Madeira has been controlled by the

newly created Madeira Wine Institute.

Vineyards

0003 The soil is volcanic, of acid pH, and with a high

organic content. Vineyards are typically small (2 ha

or less), at altitudes of between 100 and 700 m, and

southerly aspects are preferred.

0004The climate is temperate, humid, and often misty.

Planting, Training, and Pruning

0005Vines are trained on very low trellises or low wires.

Planting density is high (7000 vines per ha). A variety

of virus-free rootstocks, including R99, 1103P,

and R110, are available to suit the various soils and

climatic conditions.

0006The Guyot pruning system is most often used, leaving

many buds and cropping heavily to give 10–15 t ha

1

Grape Varieties

0007Historically, the important (noble) varieties in

Madeira were Sercial, Verdelho, Boal, and Malvasia;

their origin is not known for certain, but except

for Malvasia, they probably originated in Portugal.

There seem to have been several different types of

Malvasia; the desirable version is the Malvasia Can-

dida, which is thought to be of Greek origin. Less

important ‘noble’ varieties, also capable of producing

superior wine, are Terrantez, Bastardo, and Listrao.

Because of the humid climate, the viticulture was

3638 MADEIRA AND RELATED PRODUCTS

severely affected by Oidium and Plasmopora when

these fungus diseases arrived in the nineteenth cen-

tury, and also by Phylloxera, a bug which attacks

the vine roots. Most farmers, searching for a cure,

replaced the sensitive classic varieties by direct

producing hybrids, such as Jacquez, Cunningham,

or Isabella, or at best by more robust vinifera var-

ieties, such as Malvasia Complexa and Tinta Negra

Mole. The viniferas were of course grafted on to

American root stocks. Since Portugal joined the Euro-

pean Community, growers have come under pressure

to eliminate the direct producing hybrids, and vine-

yards are being converted by grafting to vinefera

varieties. Good clones of the classic varieties Malva-

sia Candida, Verdelho, Boal, Sercial, Terrantez,

Bastardo, and Listrao are available from the official

service, but the grapes are not yet widely available for

processing.

Vintage

0008 Near sea level, the vintage begins in August but con-

tinues into October on the highest ground. The steep

slopes and difficult terrain mean that the grapes must

be picked by hand and often carried considerable

distances on the pickers’ backs.

Wine-making

0009 Practices vary: roller crushers are used with or with-

out destalking; red grapes are normally fermented on

skins; white wines may or may not be pressed before

fermentation. Depending on the scale, fermentation

may be in stainless steel tanks, concrete tanks, Alger-

ian-type autofermenters, or wooden casks. The same

casks are used from year to year. There seems to be no

temperature control, so that in the larger vessels,



C may be reached. In contrast to other areas,

such temperatures are not considered deleterious.

Grape concentrate is sometimes added to the fermen-

tation to increase alcohol production. Cultured yeast

is rarely required. Traditionally, all wines were fer-

mented dry, and sweetening wine was added later as

in sherry production, but nowadays, some producers,

particularly of wines intended for the sweeter styles,

prefer to stop the fermentation at the required sweet-

ness by adding brandy, as port producers do. (See

Port: The Product and its Manufacture; Sherry: The

Product and its Manufacture.)

Fortification

0010 Some producers fortify immediately; this prevents

the malolactic fermentation and inhibits acetic acid

bacteria. Other producers delay fortification until

January, accepting the slight increase in volatile acid-

ity, which they regard as traditional and a contribu-

tion to the complexity of flavor. Fortification is to

between 17 and 18% alcohol by volume: grape alco-

hol obtained from the Instituto da Vinha e do Vinha

must be used. Cheaper wines are sometimes not forti-

fied until after the heating process, ‘estufagem,’

(see below) to avoid heavy losses of alcohol during

the heating process.

Maturation

0011As soon as a suitable vessel becomes available, estu-

fagem takes place, and it is largely this process which

gives Madeira wines their characteristic flavor. Estu-

fagem must take place during the first 3 years and

involves heating in a concrete tank at 40–50



C for

a minimum of 3 months. Lower temperatures and a

longer heating period are conducive to quality.

0012Some wines are not heated in concrete tanks but

matured in wooden casks stored in a warm part of the

warehouse. Sometimes, they are transferred between

hot and cool areas alternately each 15 days.

0013Before estufagem, the wine is sweetened to between

1 and 5



Baume

according to style. (For the purposes

of comparison, it can be assumed that 1



Baume



1.79



Brix 1.79 g of sucrose per 100 g of solution at



C.) Because of its relatively high total acidity, Ma-

deira is not normally consumed completely unsweet-

ened. Three sweetening materials are in use: surdo,

which is essentially a mistela, i.e., fortified grape

juice; caldo, which is essentially hydrolyzed cane

sugar syrup; and rectified concentrated grape must.

Caldo has probably the longest history and gives the

authentic Madeira style, but there is a prejudice

against nongrape sugar in wines in some markets.

0014After estufagem, the wine requires some clarifica-

tion, and albumen and bentonite are used. Some, but

not all, producers regard a treatment with charcoal

immediately after heating as highly beneficial. What-

ever treatment is given, a further extended matur-

ation in oak casks at normal temperatures is required.

Commercial Styles of Madeira

0015Vintage Madeira, while a year-old wine, is selected as

being of superior quality. Once selected, the casks are

sealed and monitored by the Madeira Wine Institute.

Storage must last a minimum of 20 years in wood,

and at least 2 years in glass. Rebottling, under super-

vision, every few years is not unusual.

0016Superior Madeira is a wine of outstanding quality

produced from the noble varieties. The denomination

is usually used for single variety wines, e.g., Superior

Bual.

MADEIRA AND RELATED PRODUCTS 3639

0017 Reserva Velha or Muito Velho requires a minimum

of 10 years’ maturation, Reserva or Velho requires a

minimum of 5 years’ maturation, and Selecionado

requires a minimum of 3 years’ maturation.

0018 Solera is matured in a fractional blending system,

and a number of restrictions apply, e.g., no wine can

be withdrawn in the first 5 years and only 10% per

annum thereafter. The year when the system was

established may be given.

0019 Wines may be labeled according to sweetness as

follows:

0020 Sercial: 1–1.2



Baume

0021 Verdelho: 2–2.2



Baume

0022 Boal: 3.5



Baume

0023 Malmsey: 4.5–5



Baume

This is a traditional way of indicating sweetness,

except that, in the case of vintage and superior

wines, it is not an indication that the corresponding

noble varieties have been used.

California Baked Sherry

0024 This wine, which originated in the Central Valley in

the nineteenth century, is produced by a technique

very similar to that used for Madeira. Although the

amount manufactured has declined significantly since

1960, it is still substantially greater than that

of Madeira wine, and, together with the Madeira

wines of Russia, probably represents the most signifi-

cant volume of heat-matured dessert wines.

Vineyards

0025 The wine is manufactured from grapes grown in the

high-yielding Central Valley of California. The Palo-

mino, the traditional grape of the sherry district of

Spain, has been preferred, but historically, there was

a surplus of Thompson Seedless, a high-yielding,

neutral grape that has proved adequate for stand-

ard-quality wine.

0026 Acid grapes (pH 3.2) are preferred, and fermenta-

tion at 25–30



C is carried out by cultured yeasts, the

Montrachet strain of Saccharomyces cerevisiae or

similar, until more or less dry. The wine is fortified

with neutral grape spirit to 17–18% alcohol by

volume.

0027 An acidity of 0.4–0.5 (g per 100 ml of tartaric acid)

is preferred. Most producers sweeten the wine to

about 2% before baking.

Baking

0028 Temperatures of 55–60



C are maintained for 9–20

weeks. The tendency is for lower temperatures and

shorter times to be used than in the past. Some pro-

ducers also expose the wine to contact with oak

chips to increase the complexity of flavor. Relatively

little further ageing after cooling is used. The wine

is stabilized usually with charcoal, bentonite, and

refrigeration.

Commercial Styles

0029Dry sherry is characterized by 1–2.2% reducing

sugar, medium sherry by 2.7–3.5% reducing sugar,

and sweet (cream) by 7.5–10% reducing sugar.

Baked Sherry of the Eastern USA

0030Most types of baked sherry are produced by a method

patented by Tressler in 1939. The base wine is a

fortified wine made from the non-Vinifera labrusca

varieties grown locally (Concord, Catawba, etc.). The

heating is for approximately 6 weeks at 60



Oxygen is injected through fine diffusers. The oxygen

leaving is passed through a trap of cold wine, which

retains some of the alcohols and esters that would

otherwise be lost.

Heated Dessert Wines made in the UK

0031There is a substantial production in the UK of alco-

holic beverages made by the fermentation of reconsti-

tuted concentrated grape musts imported from

Mediterranean countries. Selected yeasts are used to

produce highly alcoholic wines (15–17% alcohol)

without fortification with distilled spirit. The best of

the wines are subjected to an extended period of

maturation at elevated temperatures to improve the

flavor. Specific information on the times and tempera-

tures used is not available. In some cases, oak chips

may be exposed to increase the complexity of the

flavor.

See also: Port: The Product and its Manufacture; Sherry:

The Product and its Manufacture

Further Reading

Amerine MA, Berg HW, Kunkee RE et al. (1980) The

Technology of Wine Making, 4th edn, pp. 391–403.

Westport, CT: AVI.

Cossart N (1981) Madeira: The Island Vineyard. London:

Christies Wine Publications.

Goswell RW and Kunkee RE (1977) Fortified Wines,

Economic Microbiology, vol. 1, pp. 477–535. London:

Academic Press.

Nogueira JM and Nascimento AM (1999) Analytical char-

acterization of Madeira wine. Journal of Agriculture

Food Chemistry 47(2): 566–575.

3640 MADEIRA AND RELATED PRODUCTS

MAGNESIUM

I J Griffin, Baylor College of Medicine, Houston,

TX, USA

Introduction

0001 Magnesium, a soft, silvery-gray metal, is the eighth

most common element in the earth core, with an

abundance of 2.5%. Magnesium is found in many

geological minerals, including asbestos, brucite, mag-

nesite, dolomite, talc, and meerschaum. It has an

atomic number of 12, and a mass of 24.31. Mag-

nesium is a member of the alkaline earth metals

(Periodic Table IIa), which include calcium, barium,

beryllium, and strontium. It exists as three natural

isotopes, the most common being magnesium-24

(79%), with magnesium-25 and magnesium-26

each comprising 10–11% of naturally occurring

magnesium.

0002 Magnesium was known to the ancient Romans as

magnesia alba in acknowledgment of the white color

of its carbonate salts found in Magnesia, Greece. Sir

Humphry Davy in England first described the element

in 1808, when he mixed magnesia, water, and mer-

curic oxide, heated them, and found that a previously

unknown element, magnesium, was left after evapor-

ation. Antoine Bussy further purified and isolated the

metal in 1828. Magnesium was first detected in the

serum of healthy adults by Denis in 1915. In 1926,

LeRoy demonstrated that it was essential for the

health and well-being of animals.

0003 Magnesium is relatively reactive, and is rarely

found in its metallic form in nature. When exposed

to air, magnesium is rapidly oxidized, producing a

dull-gray layer of magnesium oxide that protects the

rest of the metal from oxidation. Magnesium is best

known as a component of Epsom salts (magnesium

sulfate) and magnesia or milk of magnesia (magne-

sium oxide). Sea water, which contains about 0.13%

magnesium, is the most important commercial source

of metallic magnesium. Eighty percent of commercial

magnesium is extracted from sea water by precipita-

tion with calcium hydroxide, chloride conversion with

hydrochloric acid, and electrolysis. The remaining

20% of commercial production is achieved by thermal

extraction from the magnesium-rich mineral, dolcite.

0004 Magnesium has proven useful in numerous indus-

trial applications. Its reactivity has been employed in

photographic flashes, fireworks, and incendiary

devices, which take advantage of the rapid, explosive

oxidation of finely divided magnesium powder in air.

Because of its light weight, magnesium has found uses

in the automobile, aviation, and space industries.

Magnesium has poor intrinsic structural strength,

but can be bolstered by alloying it with other metals

(particularly aluminum, zinc, and manganese).

0005In recent years, much has been learned about its

biological importance, but many areas of uncertainty

remain, especially the effects of marginal magnesium

status on human health.

Biological Role of Magnesium

0006Magnesium is the second most common cation within

living cells, exceeded only by potassium. The body of

a typical adult contains 20–28 g of magnesium, the

majority within skeletal and cardiac muscle (ﬃ60%)

and bone (ﬃ30%). Only 1–2% of magnesium is

found in extracellular tissues, and less than 0.5%

is found in plasma. The concentration of magnesium

in the plasma is about 0.75–1.25 mmol l

1

(1.5–

2.5 mEq l

1

), and is regulated within a relatively

narrow range by poorly understood mechanisms.

Hypomagnesemia is generally diagnosed when

serum magnesium levels fall below 0.75 mmol l

1

and hypermagnesemia when the levels exceed

1.25 mmol l

1

. Red blood cells contain about 2–

3 mmol l

1

magnesium, while skeletal and cardiac

muscle contains 5–10 mmol l

1

magnesium.

0007Magnesium plays a number of vital physiological

and biochemical roles in humans. Its highest concen-

tration within the cell is in the mitochondria, where it

is an essential cofactor for carboxylase and coenzyme

Q. It is vital for energy metabolism and the conver-

sion of adenosine diphosphate (ADP) to adenosine

triphosphate (ATP). It is important in maintaining

normal chromatin structure, hence, normal gene tran-

scription. It is present in a variety of metalloenzymes,

is a component of teeth and bones, and takes part in

complex interactions (both antagonistic and synergis-

tic) with calcium metabolism. Magnesium is required

for normal vitamin D metabolism; patients with

hypocalcemia may not respond to treatment with

calcium if coexisting magnesium depletion is not rec-

ognized and treated. Magnesium is required for cyclic

adenosine monophosphate (cAMP) production and

associated intracellular signaling. Intracellular ion-

ized magnesium is essential for muscle contraction

and nerve function. Many magnesium-containing

enzymes have been identified, including enolases,

phosphates, transphosphates, choline oxidase, and

pyruvate oxidase. Magnesium is required for purine

and pyrimidine biosynthesis, and therefore, synthesis

MAGNESIUM 3641

of RNA and DNA. Finally, magnesium in the form of

magnesium-porphyrin is present in plant chlorophyl,

and is therefore essential for fixing the solar energy

upon which all life on earth ultimately relies.

Magnesium Metabolism and Homeostasis

Absorption

0008 Magnesium is absorbed predominantly in the small

intestine, mainly in the ileum. A small amount of

magnesium may be absorbed in the colon and a

number of prebiotic sugars, such as inulin and oligo-

fructose, may enhance colonic magnesium absorp-

tion, either through a change in colonic flora, or,

less likely, via a trophic effect on the gut. Other

factors are known to inhibit or enhance magnesium

absorption (Table 1).

0009 Typically, 20–50% of dietary magnesium is

absorbed, but much more can be absorbed when

dietary magnesium intakes are low. Studies in humans

have shown that up to 75% of dietary magnesium can

be absorbed when intakes are low, a figure that falls

to 10–15% when intakes are high. The kinetics of

magnesium absorption are consistent with a relatively

low-capacity, saturable, active transport mechanism,

and a higher-capacity, nonsaturable, passive trans-

port mechanism. Although the molecular basis of

magnesium absorption is not clear, congenital cases

of isolated magnesium malabsorption have been

described.

Distribution

0010 Magnesium is transported in the plasma, where about

45% is bound to proteins and other ligands, and

about 55% is in the ionized form. Magnesium uptake

into the cell is an active process, and is probably

coupled to sodium efflux. It is modified by a number

of hormones and drugs, including insulin, growth

hormone, and b-agonists.

Excretion

0011 Some magnesium is secreted into the gut in digestive

secretions, but most of this is absorbed in the

enterohepatic circulation. Magnesium is also ex-

creted into the urine. Approximately 70% is filtered

into the glomerulus, and most is subsequently re-

absorbed. Between 30 and 40% is reabsorbed in the

proximal convoluted tubule, and most of what

remains is reabsorbed in the ascending loop of

Henle. This is a major source of magnesium homeo-

stasis. Reabsorption in the proximal convoluted

tubule appears to be passive, but reabsorption in the

loop of Henle is active, although the hormone or

hormones regulating this are not clear. Renal losses

increase with alcohol consumption and diuretic use,

both of which may predispose to magnesium defi-

ciency. Under normal circumstances, at least 90% of

filtered magnesium is reabsorbed in the kidney.

During periods of severe magnesium restriction, how-

ever, urinary magnesium excretion can fall to very

low levels within 7 days. High levels of magnesium

supplementation, in contrast, increase the filtered

magnesium load at the kidney, and urinary magne-

sium excretion increases significantly. Because of the

high percentage of magnesium that is reabsorbed in

the kidney, medications that interfere with this (such

as some diuretics) may lead to magnesium deficiency

and hypomagnesemia.

Homeostasis

0012The molecular control of magnesium homeostasis is

not known. Homeostasis seems to be achieved by a

combination of the regulation of absorption and urin-

ary excretion. Endogenous fecal excretion does not

appear to be important in magnesium homeostasis, as

most of this magnesium is reabsorbed by the entero-

hepatic circulation. The kidney is remarkably adept

at maintaining magnesium homeostasis; it is only in

the latter stages of chronic renal failure that magne-

sium concentrations begin to rise in the plasma.

Assessing Magnesium Status

0013It is difficult to assess magnesium status accurately.

Studies in humans have been limited, as the radio-

active isotope magnesium-28, and the two stable iso-

topes, magnesium-25 and magnesium-26, are poorly

suited to metabolic studies. The radioisotope is too

short-lived to be useful, and the stable isotopes are

insufficiently rare to be easily used as tracers. It is

possible to measure the magnesium concentration in

serum, either total or ionized. The former can vary

with albumin concentration and serum pH, but the

serum magnesium concentration does fall during

experimental magnesium depletion in humans. It

has been suggested that ionized magnesium may be

a more useful measurement of magnesium status. In

practice, however, the two correlate well, and there is

tbl0001 Table 1 Enhancers and inhibitors of magnesium absorption

Enhancers of magnesium absorption Inhibitors of magnesium

absorption

Lactose Calcium

Vitamin D Phosphate

Parathyroid hormone Phytate

High-fiber diets

Oxalic acid

Some fats

3642 MAGNESIUM

little evidence to suggest the superiority of ionized

magnesium concentrations.

0014 Magnesium can be measured in red blood cells,

white blood cells, and hair. It has been suggested

that the magnesium concentration in mononuclear

cells is a better index of magnesium status than the

serum magnesium concentration, although definite

evidence is lacking.

0015 The urinary excretion of magnesium after an intra-

venous load has been used as a measure of magnesium

status, but its usefulness as an assessment of magne-

sium status is limited.

0016 Magnesium kinetics can be measured using stable

isotopes and compartmental models, but this remains

an evasive research technique. This model can iden-

tify one pool corresponding to plasma magnesium,

another approximating to magnesium in muscle, and

a third approximating magnesium in bone. The use of

such models has demonstrated a reduction in these

pool sizes in rats placed on magnesium-deficient

diets. However, these measures are complex and ex-

pensive, and very few centers are able to carry them

out. They are unlikely to become a clinical measure of

magnesium status, although they may prove of use in

research settings. Similarly, intracellular magnesium

concentration can be measured by nuclear magnetic

resonance spectroscopy, but the clinical utility of this

method is unclear.

0017 Greater understanding of the importance of mar-

ginal magnesium status in human disease is severely

limited by the lack of a reproducible, sensitive, and

specific measure of magnesium status. Although

many measures have been proposed, there is little

conclusive evidence to support their use.

Dietary Sources of Magnesium

0018 The highest concentration of magnesium is found in

nuts, vegetables, and legumes. Cashew nuts are the

richest source, containing 270 mg magnesium g

1

mostly in the outer layers; a significant proportion is

lost during processing. Green vegetables contain sig-

nificant amounts of magnesium. Meat, fish, and diary

products contain relatively little magnesium. Drink-

ing water contains variable amounts of magnesium,

but particularly high levels are found in so-called hard

water.

0019 The average intake of magnesium has steadily de-

clined during most of the twentieth century as the

consumption of processed foods has increased and

the intake of unprocessed whole foods has decreased.

0020 In 1994, the US Department of Agriculture’s Con-

tinuing Survey of Food Intake in Individuals (CSFII)

estimated that magnesium intake in males aged 9

years or older averaged 323 mg, but only 228 mg in

females in the same age range. Ethnic differences have

also been found in magnesium intake. The third

National Health and Nutrition Examination Sur-

vey, known as NHANES III, showed that African-

Americans consumed significantly less magnesium

than Caucasians or Hispanics.

Magnesium Deficiency

0021Overt magnesium deficiency is rare in otherwise

healthy humans. However, it is seen in association

with a number of other diseases (Table 2). These are

usually associated with excessive losses (e.g., renal

disease, aldosteronism) or poor absorption (gastro-

intestinal causes).

0022After starting on a magnesium-free diet, symptoms

of deficiency can appear with a month, but in some

individuals, they may not be seen for more than 3

months. Symptoms include nausea, muscle weakness,

anorexia, ataxia, tetany, convulsions, mental confu-

sion, and irritability. Often, magnesium deficiency

will coexist with deficiencies of vitamins, calcium,

and potassium, especially if the underlying cause is

malnutrition. Magnesium deficiency is characterized

by a fall in urinary magnesium and a decrease in loss

of magnesium into the gastrointestinal tract. These

are presumably adaptive mechanisms designed to

conserve magnesium and ameliorate magnesium

deficiency. Magnesium absorption may be very low

during magnesium deficiency if poor absorption is the

underlying cause, or increased as an adaptation to

magnesium deficiency from other causes.

tbl0002Table 2 Conditions associated with magnesium deficiency

Causes Examples

Renal dysfunction Renal tubular acidosis

Diuretic use

Chronic glomerulonephritis

Bartter’s syndrome

Endocrine causes Hyperthyroidism

Primary aldosteronism

Secondary aldosteronism

Gastrointestinal causes Malabsorption

Steatorrrhea (e.g., cystic fibrosis)

Short-gut syndrome

Prolonged diarrhea

Celiac disease

Tropical sprue

Inflammatory bowel disease

Excessive losses

Prolonged vomiting

Prolonged diarrhea

Inadequate intake Malnutrition

Iatrogenic (e.g., TPN with Mg

2þ

)

Others Alcoholism

Primary idiopathic hypomagnesemia

TPN, total parenteral nutrition.

MAGNESIUM 3643