Supplements may not fix middle-aged, elderly dietary deficiencies

Taking vitamins makes it more likely that people older than 45 will get all the nutrients they need, but it does not solve the problem of malnutrition in this age group, according to a study in the March Journal of the American Dietetic Assn. (link).

"If patients are unable to meet the [recommended dietary allowances] for their age and gender with food, they probably should be recommended a supplement. But they need to be monitored," said Pamela Schreiner, PhD, professor in the division of epidemiology and community health at the University of Minnesota. "So many people are not reaching RDA goals."

Researchers analyzed food frequency questionnaires with regard to the calcium, magnesium, potassium and vitamin C intake of 6,237 participants in the Multi-Ethnic Study of Atherosclerosis. Nearly 51% of those taking calcium got enough of this substance, but only 16% of those who did not take these supplements could say the same. Almost 50% of those ingesting magnesium were sufficient in it compared with only 16% of those not taking it as a supplement. Taking additional vitamin C increased the percentage of those who had enough in their diet from nearly 60% to more than 98%. But supplement use had almost no impact on potassium levels.

The authors suspect that multivitamins may not be putting all who take them on nutritionally sound footing because of the limitations of what a pill can achieve.

"Multivitamins are constricted by the size of the actual tablet. You can only swallow so much," said Andrea Burnett-Hartman, MPH, lead author and pre-doctoral research assistant at the University of Washington.

Also, these products will not solve all the problems inherent to a very poor diet.

On the flip side, those who took high-dose supplements increased their risk of overdoing it. For instance, 15% of this group exceeded the upper limits for calcium intake. Nearly 7% took excessive vitamin C, and slightly more than 35% took too much magnesium. The authors say, however, that excess intake is not as common as deficiencies. As people grow older, they tend to cut back on food, and nutritional deficiencies become far more common.

The authors are calling for the development of additional strategies to address nutritional needs as people age and studies that investigate how supplements affect morbidity and mortality.