Q. I've only seen negative articles from you regarding the dangers of vitamins. Are there any vitamins you believe in?

A. Vitamin D is important in the regulation of cell growth, so low levels could perhaps cause cancers.

A 2007 randomized study in 1,179 healthy women over age 55 in Nebraska by Joan Lappe and others found that 1,100 IU of vitamin D3 plus 1,400 mg of calcium a day decreased cancers by 60 percent. It is also important for immunity, cardiovascular health and muscle strength, as well as reducing falls in the elderly. And in an astounding 2007 meta-analysis of 18 randomized studies in the Archives of Internal Medicine, Drs. Autier and Gandini found that older folks taking an average of 400 to 800 IU of vitamin D lived longer. Although the mortality decrease was only 7 percent, this is in stark contrast to vitamins E, A and beta-carotene, which actually seem to shorten life. Google "Landis Lum beta" to see why.

Both the U.S. Preventive Services Task Force and the superlative Cochrane group found no evidence that antioxidants; vitamins A, C or E; folic acid; or multivitamins prevent cancers, and an observational study found that zinc in doses greater than 100 mg daily doubles the risk of prostate cancer.

Sun exposure provides up to 80 percent to 90 percent of our vitamin D, so does that mean no worries for us in Hawai'i? Well, in the June 2007 Journal of Clinical Endocrinology & Metabolism, folks from the University of Wisconsin and University of Hawai'i nutrition researchers Rachel Novotny and Y.G. Daida studied 30 women and 63 men — some from UH and others patrons of the 'A'ala Park Skateboard Shop who were in sunlight three or more hours at least five days a week. They found that 51 percent had low vitamin D levels. Many folks in southern Arizona also had low levels. Food may not make up the deficiency: 70 percent of folks age 50 to 70 and more than 90 percent over age 70 don't get enough vitamin D from foods. I'd check levels in the elderly and in folks with fibromyalgia.

Vitamin D increases calcium absorption. Prehistoric humans ate a higher calcium diet and were exposed to far more sunlight, so perhaps there was no need for higher vitamin D levels in an evolutionary sense.

Adults under age 50 need 400 to 800 IU of vitamin D a day, and for those over age 50, 800 to 1,000 IU a day. And all women should be taking at least 0.4 milligrams of folic acid daily even before pregnancy to prevent birth defects. But forget the vitamin E!

Dr. Landis Lum is a family-practice physician for Kaiser Permanente and an associate clinical professor at the University of Hawai'i-Manoa John A. Burns School of Medicine. Send your questions to: Prescriptions, Island Life, The Advertiser, P.O. Box 3110, Honolulu, HI 96802; islandlife@honoluluadvertiser.com; or fax 535-8170. This column is not intended to provide medical advice.