|Vitamin A Vagary|
|Written by Sally Fallon|
|Saturday, 01 January 2000 20:03|
"Eat carrots for vitamin A." Such statements, found in many popular diet and nutrition books, create the impression that the body's requirements for this essential nutrient can be exclusively met with plant foods like carrots, squash, green leafy vegetables and orange colored fruits. The low fat school of nutrition benefits greatly from the fact that the public has only vague notions about vitamin A; for the family of water-soluble nutrients called carotenes are not true vitamin A, but are more accurately termed provitamin A. True vitamin A, or retinol, is found only in animal products like cod liver oil, liver and other organ meats, fish, shell fish and butterfat from cows eating green grass.
Under optimal conditions, humans convert carotenes to vitamin A in the upper intestinal tract by the action of bile salts and fat-splitting enzymes. Of the entire family of carotenes, beta-carotene is most easily converted to vitamin A. Early studies indicated an equivalency of 4:1 of beta-carotene to retinol. In other words, four units of beta-carotene were needed to produce one unit of vitamin A. This ratio was later revised to 6:1 and recent research suggests an even higher ratio.1 This means that you have to eat an awful lot of vegetables and fruits to obtain even the daily minimal requirements of vitamin A, assuming optimal conversion.
But the transformation of carotene to retinol is rarely optimal. Diabetics and those with poor thyroid function, a group that includes at least half the adult US population, cannot make the conversion. Children make the conversion very poorly and infants not at all â€”they must obtain their precious stores of vitamin A from animal fats â€”yet the low-fat diet is often recommended for children.2 Strenuous physical exercise, excessive consumption of alcohol, excessive consumption of iron (especially from "fortified" white flour and breakfast cereal), use of a number of popular drugs, excessive consumption of polyunsaturated fatty acids, zinc deficiency and even cold weather can hinder the conversion of carotenes to vitamin A3, as does the low-fat diet.
Carotenes are converted by the action of bile salts, and very little bile reaches the intestine when a meal is low in fat. The epicure who puts butter on his vegetables and adds cream to his vegetable soup is wiser than he knows. Butterfat stimulates the secretion of bile needed to convert carotenes from vegetables into vitamin A and at the same time, supplies very easily absorbed true vitamin A. Polyunsaturated oils also stimulate the secretion of bile salts but can cause rapid destruction of carotene unless antioxidants are present.
It is very unwise, therefore, to depend on plant sources for vitamin A. This vital nutrient is needed for the growth and repair of body tissues; it helps protect mucous membranes of the mouth, nose, throat and lungs; it prompts the secretion of gastric juices necessary for proper digestion of protein; it helps to build strong bones and teeth and rich blood; it is essential for good eyesight; it aids in the production of RNA; and contributes to the health of the immune system. Vitamin A deficiency in pregnant mothers results in offspring with eye defects, displaced kidneys, harelip, cleft palate and abnormalities of the heart and larger blood vessels.
Nutrition pioneer Weston Price considered the fat soluble vitamins, especially vitamin A, to be the catalysts on which all other biological processes depend. Efficient mineral uptake and utilization of water-soluble vitamins require sufficient vitamin A in the diet. His research demonstrated that generous amounts of vitamin A insure healthy reproduction and offspring with attractive wide faces, straight teeth and strong sturdy bodies. He discovered that healthy primitives especially value vitamin-A-rich foods for growing children and pregnant mothers. Working in the 1930's, he found that their diets contained ten times more vitamin A than the typical American diet of the time. This disparity is almost certainly greater today as Americans have forsworn butter and cod liver oil for foods based on polyunsaturated oils.
In third world communities that have come into contact with the West, vitamin A deficiencies are widespread and contribute to high infant mortality, blindness, stunting, bone deformities and susceptibility to infection.4 These occur even in communities that have access to plentiful carotenes in vegetables and fruits. Scarcity of good quality dairy products, a rejection of organ meats as old fashioned or unhealthful, and a substitution of vegetable oil for animal fat in cooking all contribute to the physical degeneration and suffering of third world peoples.
Supplies of vitamin A are so vital to human health that we are able to store large quantities of it in the liver and other organs. Thus it is possible to subsist on a diet low in animal fatfor a considerable period of time before overt symptoms of deficiency appear. But during times of stress, vitamin A stores are rapidly depleted. Strenuous physical exercise, periods of physical growth, pregnancy, lactation and infection are stresses that quickly deplete vitamin A stores. Children with measles rapidly use up vitamin A, often resulting in irreversible blindness. An interval of three years between pregnancies allows mothers to rebuild vitamin A stores so that subsequent children will not suffer diminished vitality.
One aspect of vitamin A that deserves more emphasis is its role in protein utilization. Kwashiorkor is as much a disease of vitamin A deficiency, leading to impaired protein absorption, as it is a result of absence of protein in the diet. High protein, lowfat diets in children induce rapid growth along with depletion of vitamin A supplies. The results â€”tall, myopic, lanky individuals with crowded teeth, and poor bone structure â€”are a fixture in America. Growing children actually benefit from a diet that contains more calories as fat than as protein.5 Such a diet, rich in vitamin A, will result in steady, even growth, a sturdy physique and high immunity to disease.
So it's a bit embarrassing to the low-fat people, especially as the truth is beginning to come out, even in orthodox publications. A recent New York Times article noted that vitamin-A-rich foods like liver, egg yolk, cream and shellfish confer resistance to infectious diseases in children and prevent cancer in adults.6 A Washington Post article hailed vitamin A as "cheap and effective, with wonders still being (re)discovered," noting that recent studies have found that vitamin A supplements help prevent infant mortality in third world counties, protect measles victims from severe complications and prevent mother-to-child transmission of HIV virus.7 The article lists butter, egg yolk and liver as important sources of vitamin A but claims, unfortunately, that carotenes from vegetables are "equally important." So vagueness about vitamin A continues, even among science writers.
Those familiar with the work of nutrition pioneer Weston Price are not so easily fooled. They know that vitamin-A-rich foods like liver, eggs, and cod liver oil are vital to good health. If you--or your children--don't like liver, eggs and cod liver oil, don't despair. Studies show that the best and most easily absorbed source of vitamin A is butterfat,8 a food relished by young and old alike. So use plenty of butter and cream from pasture-fed cows for good taste and wise nutritional practice.
Copyright: "Vitamin A Vagary" was first published in the Price-Pottenger Health Journal. (619) 574-7763
About the Author
|Last Updated on Friday, 01 May 2009 18:02|