A low serum concentration of vitamin E, an indicator of poor nutrition, was linked to a decline in physical function among those 65 and older, researchers found.
by Judith Groch, Senior Writer, MedPage Today
Press Release: January 22 — A low serum concentration of vitamin E, an indicator of poor nutrition, was linked to a decline in physical function among those 65 and older, researchers found.
In a study of serum micronutrient concentrations, the mean decline in physical function was just over 1 point on a four-point scale during a three-year follow-up in which only vitamin E was found significant, Benedetta Bartali, RD., Ph.D., of Yale University, and colleagues reported in the Jan. 23 issue of the Journal of the American Medical Association.
Maintaining independence for older persons is a public health priority, but the potential deleterious effect of poor nutrition on increasing frailty in older persons is not well understood, the researchers wrote.
To determine the role of micronutrient concentrations — vitamins E (alpha-tocopherol), B12, B6, and D, plus folic acid and iron — in subsequent physical decline, the researchers undertook a longitudinal study of 698 community-dwelling men and women, 65 or older.
The individuals were randomly selected from a population registry in Tuscany, Italy.
Participants completed the baseline examination from November 1, 1998 through May 28, 2000, and the three-year follow-up assessments were done from November 2001 through March 2003.
Decline in physical function was defined as a loss of at least one point in the Short Physical Performance Battery during the follow-up.
The performance score was derived from three objective tests including four-meter walking speed, repeated chair rises, and standing balance in progressively more challenging positions.
At baseline participants were classified in a range from sedentary and light physical activity (brief walking) to moderate and intense activity, such as swimming.
A validated food frequency questionnaire was used to estimate intake of energy and nutrients.
Odds ratios were calculated for the lowest quartile of each nutrient using the three other quartiles combined as the reference group. Two additional and complementary analytical approaches were used to confirm the validity of the results.
The mean decline in the Short Physical Performance Battery score was 1.1 point with 50.4% of the participants declining by this amount.
In a logistic regression analysis adjusted for potential confounders, only a low concentration of vitamin E (<1.1 μg/mL) was significantly associated with a subsequent decline in physical function, a decrease of 38% (OR: 1.62, 95% confidence interval: 1.11 to 2.36, P=0.01).
In a general linear model, the concentration of vitamin E at baseline, when analyzed as a continuous measure, was significantly associated with the physical performance score at follow-up after adjustment for potential confounders and the physical performance score at baseline (β=0.023, P=0.01).
In an additional analysis (classification and regression-tree analysis), age older than 81 and vitamin E (in participants ages 70 to 80) were identified as the strongest determinants of a decline in physical function, the investigators reported.
The hypothesis that antioxidants play a role in the etiology of the decline in physical function is supported by previous findings, the researchers wrote, suggesting that oxidative stress is involved in muscle fatigue and that antioxidants play a role in preventing muscle damage by reducing oxidative injury.
At least three different mechanisms may explain the effect of low vitamin E concentrations on subsequent physical decline, they said. These include increased oxidative stress leading to muscle or DNA damage, exacerbation of atherosclerosis or other pathologic conditions, and development of neurodegenerative disorders.
Participants in the study did not take vitamin supplements, and the authors did not recommend vitamin E supplements to increase levels.
Because the dietary intake of vitamin E includes not only alpha-tocopherol but also tocotrienols and all other tocopherols, these findings do not suggest that vitamin E supplementation would prevent decline in physical function, they said.
Instead, they suggested, approximately 15 to 30 mg a day of dietary alpha-tocopherol is needed to achieve a plasma alpha-tocopherol concentration of 1.3 μg/mL, and this amount can be reached easily through diet, from sources such as almonds, tomato sauce, and sunflower seeds, among other foods.
The researchers noted that, although the findings of this epidemiological study cannot establish causality, they provide a solid base for suggesting that low concentrations of vitamin E contribute to a decline in physical function.
Clinical trials may be warranted, they added, to determine whether an optimal concentration of vitamin E reduces functional decline and the onset of disability in older persons with a low concentration of vitamin E.
The study was supported by the Italian Ministry of Health and in part by contracts from the Intramural Research Program of the National Institute on Aging, National Institutes of Health.
Funding for the assessment of vitamin E was provided by Bracco Imaging SpA, Italy.
No financial conflicts were reported. Dr. Bartali reported that she is the recipient of a James Hudson Brown-Alexander B. Coxe Fellowship from Yale University School of Medicine.
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Primary source: Journal of the American Medical Association
Source reference: Bartali B, et al “Serum micronutrient concentrations and decline in physical function among older persons” JAMA 2008; 299: 308-315.