Barbara F. Harland

Phytate: A good or a bad food component?

Abstract Since phytate was first identified as a naturally-occurring organic compound found in all plant life, phytate has been badly maligned. Most studies concentrated on its mineral-binding capacity which may result in marginal or frank mineral deficiencies in animals and humans. Currently, there is evidence that dietary phytate may have beneficial effects. Positive effects against carcinogenesis have been shown with in vitro cell culture systems, in mice, rats and guinea pigs, but the mechanism of action is not understood. Additional foods have been analyzed for phytate content, albeit by methodology which does not differentiate between phytate and its hydrolysis products. Analytical methodology is now available which provides precise estimates of phytate and inositol phosphate hydrolysis products in foods thereby making possible a database from which more precise estimates of the extent to which mineral homeostasis may be compromised. Microbial phytase preparations are being studied as a means of improving the utilization of dietary phytate phosphorus, decreasing the need for inorganic phosphorus supplements in animal feeds and, in turn, lessen the environmental impact of phosphorus in excreta from animal feeding operations. Thus, there is a strong impetus to continue the study of this naturally-occurring molecule and what we learn through further study will hopefully improve the quality of life.

Is vanadium of human nutritional importance yet

The trace element vanadium has been studied by the nutrition community for four decades, yet has not achieved essential status for human beings. It is found in compounds at valences of 2, 3, 4, or 5, with the tetravalent and pentavalent forms being the most common. In human beings, pharmacologic amounts of vanadium (ie, 10 to 100 times normal intake) affect cholesterol and triglyceride metabolism, influence the shape of erythrocytes, and stimulate glucose oxidation and glycogen synthesis in the liver. Vanadiums primary mode of action is as a cofactor that enhances or inhibits enzymes. Recent evidence suggests that vanadium may be essential for higher animals. After their mothers had been fed carefully formulated vanadium-deficient diets, second-generation goat kids suffered skeletal damage and died within 3 days of parturition. Although ubiquitous in air, soil, water, and the food supply, vanadium is generally found in nanogram or microgram quantities, which makes it difficult to measure. Estimates for the American intake of vanadium (based on a food intake of 500 g dry weight) are 10 to 60 micrograms/day. Vanadium levels in diets from five regions of the United States range from 30.9 +/- 1.5 in the Southeast to 50.5 +/- 1.5 micrograms/kg dry weight in the West. Although vanadium is thought to be essential for goats, new data may soon support its essentiality in human beings.

Food phytate and its hydrolysis products

In mature seeds, phytate (IP6, myo-inositol) is present primarily as the hexaphosphate. Processing of food, however, leads to hydrolysis of this hexaphosphate to tri, tetra, and penta inositol phosphate. Evidence suggests that at least some of these hydrolysis products have much less affinity or less potential for reducing the bioavailability of minerals. Hence a better understanding of the role of phytate and its hydrolysis products in processed foods would be of value. In a previous review by Harland and Morris (1), the authors presented limited data on phytate-containing foods and their hydrolysis products. In this publication, additional foods with the phytate content and their hyudrolysis products will be presented. Although a number of investigators have addressed this issue, due to differences in their findings, there is a general lack of consistency in the results. This publication contains a summary of current research involving humans, animals, plants, soils, phytases and genetic engineering to reduce phytate levels in foods and feeds. A table of values for phytate in foods and the hydrolysis products is also presented.

Treatment of zinc deficiency without zinc fortification

Zinc (Zn) deficiency in animals became of interest until the 1950s. In this paper, progresses in researches on physiology of Zn deficiency in animals, phytate effect on bioavailability of Zn, and role of phytase in healing Zn deficiency of animals were reviewed. Several studies demonstrated that Zn is recycled via the pancreas; the problem of Zn deficiency was controlled by Zn homeostasis. The endogenous secretion of Zn is considered as an important factor influencing Zn deficiency, and the critical molar ratio is 10. Phytate (inositol hexaphosphate) constituted up to 90% of the organically bound phosphorus in seeds. Great improvement has been made in recent years on isolating and measuring phytate, and its structure is clear. Phytate is considered to reduce Zn bioavailability in animal. Phytase is the enzyme that hydrolyzes phytate and is present in yeast, rye bran, wheat bran, barley, triticale, and many bacteria and fungi. Zinc nutrition and bioavailability can be enhanced by addition of phytase to animal feeds. Therefore, using phytase as supplements, the most prevalent Zn deficiency in animals may be effectively corrected without the mining and smelting of several tons of zinc daily needed to correct this deficiency by fortification worldwide.

AN ASSESSMENT OF DIETARY INTAKES OF THE WOMEN’S BASKETBALL, SWIMMING, AND VOLLEYBALL TEAMS AT HOWARD UNIVERSITY

African Americans have become dominant in sports teams. It was questioned in the Nutritional Sciences Department as to whether there were any outstanding dietary and nutritional characteristics of Howard University’s women’s basketball, swimming, and volleyball teams to explain this. The teams were 76 per cent Black. The mean body mass index (BMI) among all team members was 22.5. Dietary intakes were essentially unremarkable, but surprisingly, iron intakes were adequate. All teams, however, averaged only 50 per cent of the Dietary Reference Intakes (DRIs) for calcium. Efforts need to focus on coaches who may encourage a higher intake of dairy products and dark green, leafy vegetables to increase bone health and prevent osteoporosis later in life.

Effects of gamma irradiated, cooked soy‐, beef‐, and soy/meat‐based diets in rats

There is increased demand for microbiologically safe foods. Ionizing energy (referred to as radiation pasteurization or irradiation) is effective in reducing the level of pathogenic organisms such as Salmonella, Trichinae, and Campylobacter which affect the health each year of many people. The irradiation of phytate (IP6), known to bind essential minerals in beef, soy, and soy‐extended beef, at an absorbed dosage of less than 4 kilogray (kGy) caused no difference (P > 0.05) in the level of IP3–6 compared with non‐irradiated samples. In a 3‐wk study, 84 weanling rats (12 groups, 7 per group) consumed diets containing irradiated and non‐irradiated soy, beef, and a soy‐beef combination fed at 20% of the diet. There were no differences in liver and tibia mineral concentrations. Moreover, there was no measurable effect on body weight, feed efficiency, survival of experimental animals, nor on any of the 4 blood or 7 biochemical parameters measured. In addition, the phytate:zinc and the [phytate × calcium]:zinc ...

Dietary Phytate:Zinc and Phytate X Calcium:Zinc Ratios of Lacto-Ovo Vegetarian Trappist Monks

One of the Dietary Guidelines proposed to reap health benefits for the United States population is to increase the intake of dietary fiber. Because dietary fiber is not a discrete nutritional component, the recommendation promotes alterations in other aspects of the diet as well: a decrease in animal fat and protein and an increase in vegetable fat and protein. Implicit, though not stated, is a decrease in mineral-rich foods devoid of phytate to be replaced by foods higher in phytate. The primary concern from a trace element standpoint is that the recommended increase in whole grains, fruits and vegetables as a way of increasing total dietary fiber also increases phytate intake.