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Some good news about vitamins

February 23, 2009 |  1:00 pm

It’s a good week for vitamins and minerals in the Archives of Internal Medicine.

Tuesday’s edition includes a study of nearly 500,000 men and women that linked calcium to a reduced risk of cancer. The report looked at calcium consumption from food and supplements among participants in the National Institutes of Health AARP Diet and Health Study. Subjects were at least 50 years old when the study began, and they were tracked for an average of seven years.

Jrvnvznc_3 Among women, the risk of being diagnosed with any kind of cancer fell in inverse proportion to the amount of calcium consumed from food, up to a limit of 1,300 milligrams per day. (The Institute of Medicine recommends adults age 50 and older get 1,200 mg of calcium per day.) Pills, however, didn’t contribute to the benefit.

Calcium didn’t help men reduce their overall cancer risk, but it did appear to ward off cancers of the digestive system. The 20% of men who consumed the most calcium through food and supplements were 16% less likely to get one of those cancers than the 20% of men who consumed the least calcium.
For women, those who got the most calcium had a 23% lower risk of digestive system cancers compared with those who got the least.

A second study found that vitamin D might reduce the risk of catching a cold. Researchers examined levels of vitamin D in the blood of 18,883 Americans who participated in the Third National Health and Nutrition Examination Survey and sorted them into three groups.

After controlling for factors like age, gender and smoking status, they found that people in the lowest group had a 36% increased risk of coming down with a cold compared with those in the highest group. People in the intermediate group saw their risk rise by 24%.

The effect of vitamin D was greatest for people with asthma — subjects in the group with the lowest vitamin D levels were nearly six times as vulnerable to colds as those in the highest-level group. For people with chronic obstructive pulmonary disease, low levels of vitamin D more than doubled the risk of a cold.

Neither of those studies was the kind of randomized controlled clinical trial that scientists find most persuasive. But a third study that pitted vitamin B compounds against a placebo found the vitamins reduced the risk of developing age-related macular degeneration (AMD), the most common form of severe, irreversible vision lost among older Americans.

The study piggybacked on the Women’s Antioxidant and Folic Acid Cardiovascular Study, a trial involving an amino acid found in blood called homocysteine that, at high levels, appears to increase the risk of heart disease. Since high levels of homocysteine have also been implicated in AMD, researchers decided to see whether they could prevent vision loss by attacking homocysteine with folic acid and antioxidant B vitamins.

A total of 2,607 women took a combination of 2.5 milligrams of folic acid (also known as vitamin B9), 50 milligrams of vitamin B6 and 1 milligram of vitamin B12 each day; another 2,598 women got dummy pills. During the course of the study 55 women in the treatment group developed AMD, compared with 82 among women taking the placebo. The researchers concluded that the vitamins reduced the risk of AMD by 34%.

All three studies were funded by the National Institutes of Health.

-- Karen Kaplan

Photo credit: Jim Craigmyle/Corbis