Fractures, calcium, and the modern diet.

Although high calcium intakes have long been recommended to prevent osteoporosis, there is little evidence that high calcium intakes effectively prevent fractures. Osteoporotic fractures are, like coronary artery disease, largely a disease of Western societies. Recent evidence that the statins that block the mevalonate pathway, lower serum cholesterol concentrations, and improve cardiovascular disease risk also prevent fractures, together with the increasing evidence that diets high in fruit and vegetables are beneficial in preventing fractures, suggest common dietary etiologic factors. Further research in this area should answer the long-standing question: Why do populations who consume low-calcium diets have fewer fractures than do Western societies who consume high-calcium diets?

Comparative cholesterol lowering properties of vegetable oils: beyond fatty acids.

OBJECTIVE: Our laboratory has previously reported that the hypolipidemic effect of rice bran oil (RBO) is not entirely explained by its fatty acid composition. Although RBO has up to three times more serum cholesterol-raising saturated fatty acids (SATS) than some unsaturated vegetable oils, we hypothesized that its greater content of the unsaponifiables would compensate for its high SATS and yield comparable cholesterol-lowering properties to other vegetable oils with less SATS. METHODS: To study the comparative effects of different unsaturated vegetable oils on serum lipoprotein levels, nine cynomologus monkeys (Macaca fascicularis) were fed diets, for four weeks, in a Latin square design, containing rice bran, canola or corn oils (as 20% of energy) in a basal mixture of other fats to yield a final dietary fat concentration of 30% of energy. All animals were fed a baseline diet containing 36% of energy as fat with 15% SATS, 15% monounsaturated fatty acids (MONOS) and 6% polyunsaturated fatty acids (POLYS). RESULTS: Despite the lower SATS and higher MONOS content of canola oil and the higher POLYS content of corn oil, RBO produced similar reductions in serum total cholesterol (TC) (-25%) and low density lipoprotein cholesterol (LDL-C) (-30%). In addition, as compared to the baseline diet, the reduction in serum TC and LDL-C cholesterol with RBO was not accompanied by reductions in high density lipoprotein cholesterol (HDL-C) which occurred with the other two dietary oils. Using predictive equations developed from data gathered from several studies with non-human primates, we noted that the observed serum TC and LDL-C lowering capabilities of the RBO diet were in excess of those predicted based on the fatty acid composition of RBO. CONCLUSIONS: These studies suggest that non-fatty acid components (unsaponifiables) of RBO can contribute significantly to its cholesterol-lowering capability.

From chick nutrition to nutrition policy.

It is difficult to abstract a summary of a lifetime of work. I have chosen to discuss research on protein, calcium, and the effects of dietary fat and cholesterol on serum cholesterol and on my activities that led to the publication of the Dietary Guidelines for Americans. Among the conclusions from studies on protein and calcium is that reasonably healthy people are adapted to their current diets. People all over the world, for example, are raised on relatively low calcium intakes yet have less osteoporosis than those who consume western-style diets. They also appear to do reasonably well on low-lysine intakes. Attempts to define requirements need to allow for adaptation, and we need to determine whether such adaptations are beneficial or detrimental to health. The studies on serum cholesterol defined the role of the various classes of fatty acids. The publication of the Dietary Guidelines for Americans introduced a new era of nutrition and has radically altered nutrition policy, nutrition standards, and education.

A look back at lessons learned and not learned.

Many of the issues and problems of concern to Atwater are still being studied and debated. However, the major nutrition issue today is balancing food preferences against the risk of disease. This affects the relationship between agriculture and nutrition interests. Successful modification of eating habits will rest primarily upon the food industries. Foods with desirable nutritional profiles will sell if they are tasty, competitively priced, and convenient. In developing dietary recommendations, the changes necessary in the food supply must be considered. Unreasonable recommendations should be avoided. In addition, serious consideration should be given to how food consumption data are obtained, what standards are used to evaluate the data, and what legitimate conclusions can be drawn from these data.

A comparison of serum retinol concentration between human and different species of normo and hypercholesterolemic nonhuman primates fed semi-purified diets with defined amounts of vitamin A.

1. Serum retinol and total cholesterol concentrations were determined in several species of nonhuman primates fed semipurified diets. Two species of Old World and three species of New World nonhuman primates were examined. 2. Retinol levels were significantly lower (up to four-fold) in the serum of the smaller New World than the larger Old World animals and the difference could not be explained by differences in dietary make-up. 3. Cholesterol levels were not different between the groups but differed within a species when type of dietary fat was altered. 4. Differences in circulating levels of retinol may reflect differences in levels of retinol binding protein between the groups.

Dietary fat and serum lipids: an evaluation of the experimental data.

Regression analysis of the combined published data on the effects of dietary fatty acids and cholesterol on serum cholesterol and lipoprotein cholesterol evaluated with groups of human subjects shows that 1) saturated fatty acids increase and are the primary determinants of serum cholesterol, 2) polyunsaturated fatty acids actively lower serum cholesterol, 3) monounsaturated fatty acids have no independent effect on serum cholesterol and, 4) dietary cholesterol increases serum cholesterol and must be considered when the effects of fatty acids are evaluated. More limited data on low-density-lipoprotein cholesterol (LDL-C) show that changes in LDL-C roughly parallel the changes in serum cholesterol but that changes in high-density-lipoprotein cholesterol cannot be satisfactorily predicted from available data.