Some musings on phytates

[Guest guest]

Hi, ine,

>>>>I've been reading a little here and there about phytates. I know that

the

presence of phytates inhibits the absorption of minerals - notably zinc and

iron. I've also seen studies that show phytates act in an anti-carcinogenic

way and that it may in fact be the phytate concentration in whole grains

rather than the fiber that is beneficial in preventing colon cancer. For us

meat eaters, it makes me wonder if ridding the food of phytates is really

essential to good nutrition. Would the decrease in mineral absorption by

phytates really make a big difference on the iron, zinc and other minerals

we receive by ingesting meats and raw dairy?

****I believe it might, depending on the ratio of phytate-rich grains to

minerals in your diet.

The following passages are from " Health and the Rise of Civilization " by

Mark Cohen (professor of Anthropology at State U. of N.Y.), Yale

University Press: 1989. Cohen describes human dietary patterns from the time

we were hunter/gatherers who subsisted primarily on large game and wild

plants (this diet also likely provided a higher kcal return for effort,

which Cohen outlines) to modern 'civilized' societies consuming large

quantities of various grains. Using anthropological, archeological and

epidemiological evidence, Cohen provides an historic perspective on why

grains have become a staple in the diets of modern humans and how the

transition from wild meat/plants to grains may have resulted in a concurrent

loss of nutritional quality in the human diet.

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" Dietary quality may well have been adversely affected by the major changes

in our subsistence strategies.

<snip - author discusses reasons (mainly burgeoning population) why humans

transitioned from hunting/gathering to agriculture>

A decline in per-capita consumption of animal food would have had a number

of negative effects on the diet. Animal foods are the best sources of

complete protein (protein with the best balance of amino acids for human

needs). Animal foods are also the main source of vitamin B12, and they are

among the best sources of vitamins A and D. Various minerals, including iron

and zinc, are most readily available in meals containing meat. In addition,

animal fat has probably been a scarce and valuable nutrient for most

populations throughout most of human history.

In addition, the quality of vegetable food resources may have declined in

the course of our history. Small groups of hunter-gatherers can be

relatively selective, picking foods that are nutritious as well as easy to

process; larger groups cannot be so choosy. The broad spectrum revolution

may initially have increased dietary variety, but the foods added are likely

to have been those previously avoided. Moreover, growing population and the

disappearance of preferred resources would ultimately have forced human

groups to focus on " third choice " foods -- those that are relatively

plentiful but neither flavorful nor nutritious. Some, such as acorns and

buckeyes, the third choice foods of several American Indian groups, are

toxic unless carefully processed.

The third choice foods that ultimately became our staples (cereals and

tubers chosen for their prolific growth, their shelf life, and their ability

to respond to human manipulation) are not particularly rich sources of

nutrients other than energy. Most are poor sources of protein, vitamins, and

minerals when compared to meat and to the variety of wild vegetable foods

eaten by modern hunter-gatherers.

The major cereal grains, for example, all contain a class of chemicals

called phytates that tend to form insoluble bonds with metals in the human

intestine causing them to pass out with the feces rather than being

absorbed. As a result, significant dietary elements, including iron, zinc,

and calcium, can be relatively hard to obtain from diets that depend heavily

on some cereals, including wheat and maize, even if other dietary sources of

the minerals are available. Similarly, the oxalates and phosphates common in

staple tubers and in cereals inhibit iron absorption. The result may be an

increase in anemia and other mineral deficiencies associated with diets

focused heavily on these foods.

In addition to their common drawbacks, the various cereals each have

specific nutritional shortcomings that become important when they become a

staple of the diet. Maize is poor in the amino acids lysine and tryptophan

an in the vitamin niacin, as well as in iron content. It contains an

anti-niacin substance that may actually increase the need for this vitamin;

and it contains a poor balance of two amino acids, leucine and isoleucine.

Eaten exclusively or as a very high proportion of the diet, maize may

promote such deficiency diseases as anemia and pellagra. [ Part of the

footnote to this para reads: Speth (1988) has recently characterized the

choice of foods in agriculture as a " bizarre human focus on starch.]

Wheat is poor in the amino acids lysine, theorine, and tryptophan. In

addition, in parts of the Middle East, wheat-rich diets are associated with

zinc deficiency. Rice is poor in protein, and populations that depend

heavily on its consumption are often deficient in protein. The low protein

content of rice also inhibits the activity of vitamin A in rice-eating

populations, even when the vitamin itself is available in the diet.

Excessive dependence on rice can produce beriberi or thiamine deficiency,

although in this case it is the processing of the rice rather than the

cereal itself that is the key.

Other cereals less well known to Western populations are also associated

with nutritional problems. Sorghum, an important staple grain in north

Africa, can produce pellagra. Although it is richer in niacin and tryptophan

than maize, its high leucine content may interfere with niacin utilization.

Pennisetum millet, another staple grain in northeast Africa and India, is

associated with thyroid gland dysfunction (and goiterous enlargement of the

thyroid gland similar to that caused by iodine deficiency) because it

contains a chemical that interferes with thyroid hormone production.

The various tubers and vegetable starches that are the staple crops of

populations of the moist tropics -- yams, sweet potatoes, manioc, sago palm,

bananas, and plantains -- are relatively poor sources of protein and some

vitamins and minerals for the number of calories they provide (even when

compared to cereals), and many contain mild toxins that can have serious

cumulative effects.

<snip>

Reliance on stored food is likely to mean a further reduction in nutrient

quality, partly because crops are chosen with storage rather than nutrition

in mind and partly because the storage process itself tends to reduce

vitamin content.

<snip>

Pickling can increase the amount of vitamin C in foods. Fermentation, which

helps make foods immune to spoilage, may also add to the nutrient value. "

(app.-60)

END QUOTE

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In a relatively short time period in our evolutionary history (approx.

10,000+ years), we went from subsisting on wild game and carefully selected

plant material to diets relying heavily on

modern over-processed grains as a staple food. IMO, we may be walking

around with bodies well adapted to a Paleolithic diet, well adapted to wild

lean meats and fresh

wild vegetation, but now consuming diets of too many grains, too many

processed

foods in general, to many 'freak' animals produced by factory farming, too

much sugar,

and not nearly enough fiber from non-grain plants - an alien diet to the

human body, IMHO.

In another section of the chapter quoted above, Cohen discusses the

*texture* and *composition* of food that hunter/gatherers historically

consumed and how the roughness of much of the diet kept their teeth clean

and developed their jaw bones and muscles in childhood. Quote:

" Although trends in dietary quality and reliability are uncertain, the

pattern of changes in the texture of food is relatively clear. Hunting and

gathering populations eat foods that are coarse and tough in two senses:

they are tough to chew, and they contain a high proportion of inert,

indigestible matter of fiber that must be processed by the intestine. In the

evolution of civilized diets, foods have gradually been altered -- first

eliminating much of the need for chewing and much more recently, eliminating

bulk. These changes produce mixed consequences, at best, for health.

The first major steps in the process are associated with sedentism and

farming. Compared to many wild vegetable foods, domestic grains and tubers

are relatively soft concentrated packages of calories. In addition,

sedentary populations with grindstones and with pottery can soften foods by

boiling, producing mush or gruel -- foods easier to chew, although they

retain their fiber. Much more recently -- particularly with the past

century -- incentives for efficient transport and storage have resulted in

further refinement of food, producing ever more concentrated packages of

calories with the indigestible fiber removed.

Coarse foods have important effects on jaws and teeth. The development of

the jaws during childhood depends on the chewing force exerted. Strenuous

chewing is necessary for the development of facial muscles and bones. It may

also determine alignment of the teeth. Apparently, human jaws initially

evolved to meet in such a manner that the cutting edges of incisors met

directly. It is only since the adoption of relatively soft diets following

the rise of farming -- and the adoption of modern eating utensils -- that

human beings developed the slight overbite that we now consider normal. "

(p.70)

>>>> I am really ignorant in this

whole area and I would really like to understand the role of phytates

better. I just believe that God made all food with a delicate balance of

vitamins, minerals, fiber, etc. and I guess I think of grains the same way.

***God may have made all food with a delicate balance of nutrients, but

*humans* are the ones who designed the modern grain-heavy diet. The reasons

may be varied, including a burgeoning population, but at the cost of

nutritional quality, it would seem.

Suze Fisher

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