Volume 8, Issue 1, 2002
New Developments in Creatine Supplementation Research: Mechanisms of Athletic Performance Enhancement
In the last decade creatine supplementation has become the most popular ergogenic aid among athletes, with particular performance enhancements found in high-power output, anaerobic exercises. Physiologically, creatine and phosphocreatine provide an energy reservoir in skeletal muscle. Recent studies have also shown that the ergogenic effects of creatine are caused by muscle protein metabolism (or reduced catabolism), satellite cell proliferation, protective oxidant scavenging, and membrane stabilization. In addition, creatine supplementation is considered to be a potential therapy for a wide variety of disease states including muscular dystrophy, heart failure, Parkinson's disease, Huntington's disease, and Alzheimer's disease. To date, a large number of studies have shown no serious side effects after short- (<10 days) and medium-term (<12 weeks) supplementation, and the first long-term (<5 years) study of supplementation found no effects on renal function. Still recent findings of cytotoxic creatine metabolites, along with two isolated reports of renal dysfunction, are some cause for concern, and more long-term research is required.
The use of cranberry juice for the treatment and prevention of urinary tract infections (UTI) has long been promoted by physicians and lay people alike. Although the research has been conflicting and controversial, it was once widely believed that cranberry juice possessed bactericidal activity due to the presence of hippuric acid, which was believed to acidify the urine and prevent microbial growth(1,2). More recently, it has been discovered that cranberries possess in high concentration a class of compounds known as anthocyanidins, that have been shown to effectively inhibit the adhesion of E. coli, the most common causative agent in UTI, to urinary epithelium (3, 4). Recent research suggests that these anthocyanidins may cause a 50% reduction in recurrence of UTI when cranberry juice is consumed at doses of 100 - 300 mL per day (5, 6), however more research is needed to conclusively prove beneficence. No research exists to support the use of cranberry juice as a treatment for UTI, however.
The standard protocol for the nutritional care of burn patients is a diet providing large amounts of protein and overall calories. However, recent studies seem to show that supplemental intake of certain dietary components can provide additional wound-healing effects and lead to a more rapid recovery from burn injury. Studies have already been conducted which show such clinical effects when ornithine a-ketoglutarate and certain trace elements are administered (7,8,17). Preliminary data regarding the efficacy of immune-enhancing diets (IEDs) in burn nutrition have provided ambiguous results so far (12,14) Further research is needed in order to establish whether existing IEDs can be beneficial in this type of application. It does seem, however, that most future advances in burn nutrition will be related to supplements and diet regimens that can enhance post-burn immune function.
In 1993 the FDA approved the commercial sale of milk from rbGH treated cows. Despite this approval, there are a number of public health concerns that have arisen about the safety of this milk. Specifically, there is concern that this milk may increase the risk and rate of cancer. Milk from rbGH treated cows has elevated levels of IGF-1. Furthermore, some amount of IGF-1 from the milk is orally active in humans. IGF-1 has a strong association with a number of cancers including breast, prostate and colorectal cancer. For these reasons, the safety of milk from rbGH treated cows seems very questionable.
Monosodium L-glutamate (MSG), the sodium salt of glutamic acid, is a widely used flavor enhancer. Early reports have claimed that it is the causal agent for adverse reactions experienced after consumption of MSG-containing meals. In 1995, the Food and Drug Administration approved MSG as "generally recognized as safe." Still, there have been much skepticism and controversy over its potential effects. Recently, numerous well-designed studies have been conducted to investigate the existence of the MSG symptom complex. Clinical studies of MSG ingested with food have demonstrated no difference in symptoms between placebo and MSG-treated groups (6)(9). Clinical studies of MSG ingested in the absence of food have suggested that there may be a MSG-sensitive subpopulation (1). Contrary to early experimental results, the relationship between MSG and asthmatic reactions could not be demonstrated (12)(13). Finally, dietary MSG consumption would not elevate plasma glutamate concentration enough to induce neural cell death. While the new evidences appear to demonstrate that it is safe, further investigation needs to be pursued to elucidate the biochemistry of MSG.
Making up about 25% of the current infant-formula market in the U.S., soy-based infant formulas are lifesaving alternatives for infants who cannot rely on traditional sources of milk for complete nutrition. While many studies have supported the effectiveness of soy-formula consumption for normal growth and development, the controversy over the potentially harmful effects of early exposure to isoflavones (phytoestrogens found in soy formulas) remains to be resolved. The plasma concentration of isoflavones in soy-fed infants is so high that it is more than 13,000 times higher than that of estradiol found in early life (9). Since the exposure to high levels of estrogen during critical periods of development can exert detrimental consequences on reproduction, the high plasma level of isoflavones in soy-fed infants may cause similar physiological effects via their estrogen-like behaviors. One recent epidemiological study on humans has found little association between consumption of soy formulas during infancy and reproductive health (7). However, human data on this subject is scarce and animal studies (2,3,22,24) have yielded conflicting and complicated results. Thus, more research is needed before further claims can be made about soy formulas and their potential damaging effects on reproductive health.
Regular, non-diet, soft drinks are responsible for one third of the excessive amount of added sweeteners in the diets of children and adolescents (5). Children and adolescents who drink regular soft drinks have a higher caloric intake than those who not drink regular soft drinks (3). Furthermore, BMI and the frequency of obesity were found to increase for each additional serving of sugar sweetened drink consumed by children (10 to 12 years) (6). The increased level of sweetener in regular soft drinks increases children's caloric intake and is a contributory factor in the development of pediatric and adolescent obesity. Obesity is caused by a variety of factors, and the role of beverage consumption on caloric intake has not been emphasized. Research and policy need to put more energy into examining the relationship between sugar sweetened beverages, especially regular soft drinks, and the development of obesity.