Dr. Ron’s Research Review – May 30, 2012

This week’s research review focuses on two recent reviews: Testosterone for heart failure, and dietary supplements and cancer prevention.

Dietary supplements and cancer prevention: balancing potential benefits against proven harms (Martinez, Jacobs et al. 2012)

Why do so many people in the United States continue to use dietary supplements? A large part of the answer lies in messages from supplement manufacturers, who suggest that there are health benefits, including cancer prevention, from supplements. Undoubtedly, use is driven by a common belief that supplements can improve health and protect against disease, and that at worst, they are harmless.

Low testosterone is an independent predictor of reduced exercise capacity and poor clinical outcomes in patients with heart failure. Testosterone therapy was associated with a significant improvement in exercise capacity. Given the unmet clinical needs, testosterone appears to be a promising therapy to improve functional capacity in patients with heart failure. (Toma, McAlister et al. 2012)

Dr. Ron


Articles

Dietary supplements and cancer prevention: balancing potential benefits against proven harms

            (Martinez, Jacobs et al. 2012) Download

Nutritional supplementation is now a multibillion-dollar industry, and about half of all US adults take supplements. Supplement use is fueled in part by the belief that nutritional supplements can ward off chronic disease, including cancer, although several expert committees and organizations have concluded that there is little to no scientific evidence that supplements reduce cancer risk. To the contrary, there is now evidence that high doses of some supplements increase cancer risk. Despite this evidence, marketing claims by the supplement industry continue to imply anticancer benefits. Insufficient government regulation of the marketing of dietary supplement products may continue to result in unsound advice to consumers. Both the scientific community and government regulators need to provide clear guidance to the public about the use of dietary supplements to lower cancer risk.

Testosterone supplementation in heart failure: a meta-analysis

            (Toma, McAlister et al. 2012) Download

Background- Low testosterone is an independent predictor of reduced exercise capacity and poor clinical outcomes in patients with heart failure (HF). We sought to determine whether testosterone therapy improves exercise capacity in patients with stable chronic HF. Methods and Results- We searched Medline, Embase, Web of Science, and Cochrane Central Register of Controlled Trials (1980-2010). Eligible studies included randomized controlled trials (RCTs) reporting the effects of testosterone on exercise capacity in patients with HF. Reviewers determined the methodological quality of studies and collected descriptive, quality, and outcome data. Four trials (n=198; men, 84%; mean age, 67 years) were identified that reported the 6-minute walk test (2 RCTs), incremental shuttle walk test (2 RCTs), or peak oxygen consumption (2 RCTs) to assess exercise capacity after up to 52 weeks of treatment. Testosterone therapy was associated with a significant improvement in exercise capacity compared with placebo. The mean increase in the 6-minute walk test, incremental shuttle walk test, and peak oxygen consumption between the testosterone and placebo groups was 54.0 m (95% CI, 43.0-65.0 m), 46.7 m (95% CI, 12.6-80.9 m), and 2.70 mL/kg per min (95% CI, 2.68-2.72 mL/kg per min), respectively. Testosterone therapy was associated with a significant increase in exercise capacity as measured by units of pooled SDs (net effect, 0.52 SD; 95% CI, 0.10-0.94 SD). No significant adverse cardiovascular events were noted. Conclusions- Given the unmet clinical needs, testosterone appears to be a promising therapy to improve functional capacity in patients with HF. Adequately powered RCTs are required to assess the benefits of testosterone in this high-risk population with regard to quality of life, clinical events, and safety.

References

Martinez, M. E., E. T. Jacobs, et al. (2012). "Dietary supplements and cancer prevention: balancing potential benefits against proven harms." J Natl Cancer Inst 104(10): 732-9.

Toma, M., F. A. McAlister, et al. (2012). "Testosterone supplementation in heart failure: a meta-analysis." Circ Heart Fail 5(3): 315-21.