How Much Do Those Nutrients Really Help You?

Abstract & Commentary

By Eileen C. West, MD, Director of Primary Care Women's Health, Clinical Assistant Professor of Internal Medicine; University of Oklahoma School of Medicine, Oklahoma City. Dr. West reports no financial relationship to this field of study.

Synopsis: This study addresses the role of nutritional status in the disablement process. Low serum concentrations of vitamins B6, B12 and selenium seem to predict subsequent disability in activities of daily living (ADLs) in older women living in the community.

Source: Bartali B, et al. Low Micronutrient Levels as a Predictor of Incident Disability in Older Women. Arch Int Med. 2006;166:2335-2340.

Community-dwelling women aged 65 and older who were enrolled in the Women's Health and Aging Study were followed every six months for three years with bloodwork and standardized questionnaires designed to measure functional capacity. The objective was to determine whether low concentrations of nutrients predict eventual physical demise. The nutrients measured were: total carotenoids, retinol, 25-hydroxyvitamin D, Vitamin B6, Vitamin B12, folate, selenium, and zinc. At the beginning of the trial, women were screened to identify self-reported trouble in several domains: mobility, upper extremity function, higher functioning household management, and self-care. Those with difficulties in 2 or more domains but who could still perform all ADLs were enrolled in the study. The selected women were then given a standardized questionnaire at home by trained interviewers. Two weeks later a trained RN came to the home to examine each participant with physical performance measures and a physical exam. Follow-up was every six months, and progress or decline was self-reported after the initial physical exam.

After three years of follow-up, 208 of 643 (32.3%) of participants had progressed to ADL disability. Of those who progressed, the incidence rates were worst among women who fell in the lowest quartile vs those in the upper 3 quartiles of serum nutrient concentrations. Selenium, Vitamin B6, and Vitamin B12 were found to be significant and independent predictors of ADL disability. Furthermore, high levels of homocysteine at baseline predicted the development of ADL disability (P < 0.001).

Commentary

The beginning stages of research are seen in the above population-based study, and more research is needed. As with any study of this type, it is difficult to make assumptions about whether it is the low serum level of a nutrient or another factor which is responsible for a patient's deterioration in physical capacity. Also, serum levels do not necessarily predict response to supplementation, so making a leap to the concept that supplements (often at no small cost) provide benefit remains a risky affair. I have heard the old adage, "More than $20 per year spent on vitamins is a waste of money." Much more information is needed to determine the story for the nutrients studied here, and I am inclined to stick with the adage until we have more data.

Unfortunately, many studies using simple vitamins will not be completed as there is often no major financial incentive to doing them. Recent work regarding Vitamin E supplementation came out of the Women's Health Study subanalysis. The verdict? Some may be good, more may be harmful. Research analyzing Vitamin C supplementation did not prove clear superiority with supplementation (megadoses > 1 gram per day or otherwise). Such is the case with many of these trials. Omega-3 fatty acid supplementation appears currently on the "in demand" list, and there is some data to support the claims that it does have antioxidant and cholesterol-improving properties.

The finding for 25-hydroxyvitamin D (ie, no clear association) was surprising considering the discussion in the past 18 months implicating low levels of Vitamin D in gait disturbances, bone health, and falls.

This study offers a necessary first step to determine a simple association between low blood levels of specific nutrients and decline in physical function. If low serum levels of nutrients are normalized with a healthful diet, good nutrition alone, even in the absence of supplements, can prove to play a large role in slowing decline. Hopefully, the study will pave the way to more detailed study and valuable clinical results.

References:

1. Lee IM, et al. JAMA. 2005 Jul 6;294(1):56-65.

2. Gerdhem P, Ringsberg KA. Osteoporos Int. 2005;11:1425.