Just how much selenium is safe to take every day?

You wrote that three or four Brazil nuts daily supplied enough selenium to cause toxicity. I'm taking 100 micrograms of selenium daily to ward off prostate cancer. Is this safe?

Preliminary studies suggest that when people get adequate amounts of selenium in their diet, they have better immune function and reduced risk of osteoarthritis. A few studies hint that selenium may help ward off prostate cancer. Too much selenium, however, can be toxic, with symptoms including rash, hair and nail brittleness, garlic breath, upset stomach and nerve damage. The adult tolerable upper limit is set at 400 micrograms per day, so your dose is safe.

An ounce of Brazil nuts (about six) contains roughly 800 micrograms. So we suggest not eating more than a couple of the nuts three or four times a week.



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My 5-year-old granddaughter sucks her thumb. Is there something unpleasant-tasting I can put on her thumb to remind her to not suck it?

Most children stop thumb sucking before age 5. The American Dental Assn. says that thumb sucking does not cause problems until after this age.

You might be successful distracting her with activities that require two hands. If she wants to stop sucking her thumb, painting something yucky on it may help. Some parents use pickle juice or vinegar. Others use commercial products: Thum has cayenne pepper extract and citric acid. Control-It has denatonium. There is also a Lycra glovelike device called Thumbusters that covers the thumb.

Nagging is counterproductive. Most kids will stop when they encounter peer pressure.

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Joe Graedon, a pharmacologist, and Teresa Graedon, an expert in medical anthropology and nutrition, can be reached at http://www.peoplespharmacy.com or care of this newspaper.