Q. Is it safe to give vitamins with fluoride to my 6-year-old twins?

A. There's a lot of hype about fluoride, but it's a naturally occurring mineral in water. Experts attest to fluoride's safety with regard to harms like cancer and other diseases. Hawai'i's water has little fluoride. The fluoride in supplements would give you the amount you'd get drinking from natural water sources in other states.

The standard advice here is to take fluoride from 6 months to 11 years of age. Well, the American Dental Association had researchers from the University of Michigan School of Dentistry do a systematic review in November 2008, which I think will change guidelines due this summer. They found only weak and inconsistent evidence that fluoride supplements prevent cavities in kids under 6 years, a finding also confirmed by the Centers for Disease Control. And fluorosis (teeth staining) can sometimes occur.

Supplements did reduce cavities in kids age 6 and above, primarily through a topical (surface) effect.

I'd follow CDC advice and give fluoride supplements only for infants and children at higher risk for cavities. They should also get fluoride varnish every 6 months by a dentist. For most kids, just start using fluoride toothpaste at age 1, and supervise tooth brushing.

I'm also worried about other vitamins often combined with fluoride. Last year, the highly regarded Cochrane group analyzed 47 studies involving 180,000 adults and found that taking extra beta-carotene, vitamin A, and vitamin E, either alone or combined, increased the statistical incidence of dying.

Taking antioxidants such as vitamin E, A and beta carotene reduces free radicals, but the body uses free radicals for detoxification and to destroy germs, aged cells and cancers. A Cochrane review also done last year unexpectedly found several studies showing that vitamin A increased lung infections in children younger than 7.

Most infant vitamin and fluoride drops contain 5 IU of vitamin E and 1500 IU of vitamin A. Cochrane found that an average dose of 20,000 IU vitamin A increased death rates 16 percent, but I'd avoid extra vitamin A or E at any age.

The only vitamin kids need is vitamin D, 400 IU a day, starting within a few days of birth and continuing into adulthood. From 27 to 32 ounces of baby formula has this amount, but breast milk has virtually none. Vitamin D-only drops include Bio-D-Mulsion, Carlson Laboratories, and Just D — if you can't find these, get Nature Made Liquid Softgel 1000 IU, puncture the end, and squeeze the liquid into your baby's cheek three days a week.