Older men and women who take nutritional supplements are more likely to get adequate amounts of several vitamins and minerals than their peers who don't use supplements, a new study shows.

The researchers also found that while a substantial proportion of people 51 and older don't get enough vitamins and minerals from diet alone, fewer than half took supplements every day.

"These widespread inadequacies should be considered when developing recommendations for supplement use for clients in this age group," Rhonda S. Sebastian of the US Department of Agriculture in Beltsville, Maryland and colleagues conclude.

They analyzed 1994-1996 data on 4,384 men and women aged 51 and older to investigate if supplement users were actually better nourished, and also to determine which people were most likely to use supplements. Overall, abut 40 percent reported taking supplements daily.

While supplement users obtained more nutrients from food than people who didn't use supplements, both groups got far less folate, vitamin E and magnesium than they needed from diet alone, Sebastian and her team found. Eighty percent of supplement users got enough vitamin A, B-6, B-12, C and E; folate; iron; and zinc from diet and supplements.

The researchers also found that some supplement users, especially men, were consuming too much iron or zinc, while some female supplement users were getting too much vitamin A.

Excess iron consumption may be harmful to the heart, while getting too much zinc may impair immune function and reduce levels of the "good" cholesterol, high-density lipoprotein, the researchers point out. And for women, excessive vitamin A consumption has been tied to increased hip fracture risk.

People who were most concerned with the healthfulness of their diets and with meeting dietary recommendations were also the most likely to take supplements, the researchers found.

Given that the study was conducted before 1998, when fortification of grain products with folate was introduced, it's not clear if dietary folate inadequacy remains a problem for older adults, Sebastian and her team say.

But based on the findings, the researchers add, older people should avoid the routine use of supplements containing retinol (a form of vitamin A) and iron.