DEAR DR. ROACH: My family doctor said to stay away from multivitamins because they contain metal contaminants. Is this true, and is it good advice?

• J.K.

ANSWER: Your doctor is correct that many multivitamins have been shown to be contaminated with heavy metals. For example, in a recent article on prenatal vitamin and folic acid supplements, 80% contained quantifiable lead, while 15% had a greater amount than 0.5 mcg per serving (the limit from California’s Proposition 65).

Unfortunately they did not specify which brands are the ones without detectable heavy metals, but the article noted that supplements also containing calcium or iron were more likely to be contaminated. The article noted that products using an independent lab (such as the United States Pharmacopeia or the National Sanitation Foundation) to test purity were the safest.

Even though lead can be detected at very low levels, the magnitude of the risk at these small levels is thought to be small. Still, it is worthwhile considering what the benefits of multivitamins are against the potential risk.

Since many large, well-done studies have been published that do not show any consistent benefit to healthy adults taking multivitamin supplements, even a small amount of potential harm may make taking them not worth it.

DEAR DR. ROACH: I have read that taking 50 grams of dried prunes daily can help pause or even reverse the effects of osteoporosis. What have you heard about this treatment?

• E.M.

ANSWER: A 2022 study looked at women who were randomly assigned to eat prunes daily for a year. There was also a group who were assigned not to eat any. Although they slowly increased the amount of prunes eaten, 40% of the women in the 100-gram group dropped out of the study.

After a year, the control group who didn’t eat any prunes had a small drop in their bone density and a small increase in their risk of fracture (from 9.8% to 10.3%). In the 50-gram group, there was a small increase in bone density and a small increase in the risk of fracture (from 9.9% to 10%). The women who tolerated 100 grams of prunes a day had a small improvement in their fracture risk.

Although these differences were small, it is difficult to show large differences in a year as bone changes very slowly. I also conclude that prunes may stabilize the bone and slow or prevent the loss of bone, but I don’t think that the evidence supports the reversal of bone loss.

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