Nutrition Bytes

Alzheimer's disease (AD) is a form of dementia characterized by generalized and progressive cognitive dysfunction. Research has determined that an important pathological component of AD is neuronal damage and death in certain brain regions precipitated by oxidative damage. This paper reviews the pathology of AD, describes the biochemical processes pertaining to oxidative stress and antioxidant compounds, and reviews the evidence that one particular antioxidant, vitamin E, may be effective in ameliorating AD pathology. Preliminary evidence suggests that vitamin E may in fact be therapeutic in slowing the progression of AD.

Obesity, regarded as a chronic metabolic disease, is increasing in prevalence in the United States. Today, a combination of pharmacotherapy and life-style adjustments seem to provide an effective treatment. However, many controversies exist regarding the safety of weight reducing drugs. As older anorexigenic drugs, such as amphetamines and Phen/Fen have been recalled despite their effectiveness in reducing weight, due to their side effects, a new drug, Sibutramine (Meridia TM) is taking the center stage. Sibutramine exerts its effect by inhibiting the reuptake of serotonin and norepinephrine, a mechanism different from any other diet pill approved by FDA. By lowering blood triglycerides, colostral, and waist/hip ratio via its anorexic and thermogenic effects, sibutramine has great promises, despite the lack of established long-term side effects.

The nopal has been used as a medicinal plant and is a hallmark vegetable in the Latin American diet. Various studies have demonstrated Opuntia s ability to affect blood glucose and hypercholesterolemia. The intake of prickly pear pectin decreases plasma LDL levels, increases expression of apolipoprotein receptor expression, increases hepatic LDL turnover, and affects cholesterol homeostasis in guinea pigs. Prickly pear pectin, however does not affect absorption of cholesterol in guinea pigs. The prickly pear cactus demonstrates the ability to decrease blood glucose levels as well the hyperglycemic peak during glucose tolerance testing. In addition, Opuntia has demonstrated the ability to control experimentally induced diabetes. Similar studies, along with domestic surveys have prompted international evaluation of the prickly pear cactus to determine its ability to regulate glucose utilization. Currently, homeopathic industries have begun to incorporate opuntia into supplements intended to help regulate plasma glucose levels.

Hypertension affects millions of Americans. Twenty-five years ago, researchers observed that calcium might be inversely related to the development and severity of hypertension. Consequently, several epidemiological, animal, and clinical studies have addressed this potential correlation. Dietary deficiencies or altered calcium metabolism can result in low serum calcium levels. Disturbances in calcium metabolism include increased urinary calcium excretion and abundance of calcium-regulating hormones such as parathyroid hormone and calcitriol. These hormones cause decreases in bone mineral content and increase intracellular calcium in vascular smooth muscle. Increased [Ca2+]i produces contraction and therefore vasoconstriction. Low calcium levels and elevated PTH and calcitriol may also affect blood pressure control by the central and peripheral nervous systems by stimulating the release of norepinephrine (a potent vasoconstrictor) and increasing its post-synaptic effect. Calcium supplementation and/or increased dietary calcium have been used to increase calcium intake. Not all studies have shown a definite inverse correlation between calcium intake and hypertension, however certain patient groups (pregnant women, salt-sensitive hypertensives) clearly benefit from increased calcium intake. Calcium interacts with other nutrients (sodium, potassium, magnesium) in affecting blood pressure. Due to its probable beneficial effects on hypertension, osteoporosis, and other diseases, RDA intake for calcium should be strongly encouraged.

Vitamin A deficiency and anemia due to nutritional status are major problems worldwide, and are especially significant in developing countries, with children and pregnant women most often affected. Research during the 1920s suggested an interaction between vitamin A and iron, and interest in this interaction has continued in recent decades. A relationship between vitamin A and iron could have relevance to the treatment of nutritional anemia, and numerous studies have suggested that supplemental vitamin A in addition to iron is superior to iron alone in treating nutritional anemia. In this paper, human and animal studies of vitamin A in relation to iron and anemia are presented, and hypotheses regarding this relationship are given.

Originally isolated from muscle extracts at the beginning of the century, carnitine (L-trimethyl-3-hydroxy-ammoniobutanoate) is an endogenous compound with a significant role in cellular biochemistry. Carnitine is required for the transport of fatty acids (FA) from the cytosol into the mitochondrial matrix for b-oxidation, and also serves as a substrate for reversible acetylation by acetyl-coenzyme A (acetyl-CoA.) Because of its function in fatty acid oxidation and CoA metabolism, supplementary carnitine has been marketed as an ergogenic aid to boost physical performance. However, the results of research into the effects of carnitine supplementation on physical exercise is more ambiguous. Although some studies do indicate that carnitine supplementation has positive influence on maximal exercise capacity, a number of others fail to discern any such relationship. While further research is needed to make a firm conclusion, the current evidence suggests that carnitine supplementation may provide some slight ergogenic benefits.

For thousands of years, Chinese medicine has used the herb ginseng as a memory tonic with the belief that ginseng can improve learning and memory, especially in aging humans. Recent studies have sought to validate this claim. Experiments done on rats have shown that ginsenosides, the saponins of ginseng, can partially prevent scopolamine-induced memory deficits in rats. Ginsenosides are thought to increase choline uptake in the central cholinergic nervous system, which plays important roles in learning and memory. Further experiments have shown that ginseng extracts can improve the retention of learned behavior in young (aged 3 months) as well as old (aged 26 months) rats. The potential beneficial effects of the polysaccharide fractions of ginseng on learning and memory still warrant further experimentation. The favorable effects of ginseng on learning and memory make it a promising drug for the use in geriatric practice.