October 26, 2011
Men who spend little time in the sun, live in northern locales or have dark skin may need to increase their intake of vitamin D to prevent deficiency, a Northwestern University medical researcher has found.
Vitamin D is required for the proper absorption of calcium and immune system and neuromuscular function. A deficiency may play a role in certain cancers, such as prostate, breast and colon cancers, scientists say.
Vitamin D is not naturally present in most foods, but skin can synthesize it upon exposure to sunlight. The recommended daily intake of vitamin D — through sun exposure, vitamin D-fortified foods and supplements — is 600 International Units, as determined by the Institute of Medicine of The National Academies.
In a recent study led by Dr. Adam Murphy, a clinical instructor in urology at Northwestern's Feinberg School of Medicine, blood samples were collected from 492 men visiting any of three urology clinics in Chicago.
Each man's body mass index, skin melanin content, time spent in the sun and vitamin D levels were measured and recorded. Melanin is a pigment in the skin that gives it color, and the skin increases its melanin content in response to sunlight. The more melanin in a person, the darker the skin.
The study revealed that being of African-American heritage, having a high body-mass index and not taking vitamin D supplements were all associated with vitamin D deficiency in Chicago.
Though time spent outdoors is correlated to vitamin D levels and black and white men spent equal amounts of time in the sun, black men in Chicago were up to 3½ times more likely than white men to be deficient in vitamin D.
African-American men also have a greater risk of prostate cancer, which Murphy says could be linked to vitamin D deficiency.
"Melanin protects our skin from the sun's damaging radiation. In the sun, the skin produces more melanin to protect cells better. But if you have a lot of melanin, the skin cannot make vitamin D from sunlight," said Murphy, who also is a physician at the Jesse Brown VA Medical Center in Chicago. "If you're dark-skinned, go out in the sun, but not for too long."
Murphy, who is black, is an avid runner who recently completed the Chicago Marathon. Despite spending many hours outdoors and taking vitamin D supplements, he is often at the low end of healthy vitamin D levels, he said.
A black man in Chicago needs at least 90 minutes, three times a week in the sun to produce the same amount of vitamin D a white man in Chicago can in 15 minutes three times per week, Murphy said.
He recommends everyone — and black men in particular — get more vitamin D. In addition to sun exposure, he says black men in Chicago should take at least 2500 IU of vitamin D each day.
"The point is there is a big variation in the amount of sun exposure across the U.S., and therefore there is going to be different levels of supplementation needed in different parts of country," Murphy said. "I think it's important and will explain some of disease differences between different groups. The disparity, when (vitamin D recommendations are) reported as 600 (International Units) per day, it will fix most European-Americans but it won't fix most people with darker skin — Arabs, Hispanics, Indians, African-Americans. It's not one size fits all."
— Kelly April Tyrell, special to the Tribune
Exercise may not limit weight gain during pregnancy
Exercising during pregnancy was safe for both moms and babies in a new study of heavy women in Brazil, but fitness classes and home exercise didn't keep moms-to-be from gaining too much weight.
The U.S.-based Institute of Medicine recommends that overweight women should gain between 15 and 25 pounds during pregnancy, and obese women 11 to 20 — less than the amount recommended for women of normal weight.
Being overweight or obese while pregnant, or gaining too much weight during pregnancy, increases the chance of having a large baby and needing a cesarean section. It also adds to the risk that babies will have birth defects or grow up to be obese, researchers said.
In the study, researchers led by Simony Nascimento from UNICAMP Medical School in Campinas recruited 82 heavy women who were 3 to 5 1/2 months pregnant.
Half went to weekly exercise classes and were counseled on nutrition, weight gain and home exercises. The other women received standard prenatal care advice.
Regardless of whether they were assigned to do group and at-home exercise, about half of the women gained more weight than recommended.
Male breast cancer rare but aggressive when diagnosed
Men are diagnosed with breast cancer at less than 1 percent the rate of women, according to a new analysis of cancer rates from six cities and countries.
But when they did get breast cancer, men were caught with more advanced disease, on average, and were more likely to die from it.
Men are most commonly in their 60s or 70s when diagnosed with breast cancer, according to the National Cancer Institute. Radiation exposure and diseases that increase estrogen levels — such as liver cirrhosis or Klinefelter syndrome, a genetic disorder — are among factors that raise a man's risk.
Researchers combined cancer registries from Denmark, Finland, Norway, Sweden, Singapore and Switzerland, with cases dating back to 1970. That included about 460,000 women diagnosed with breast cancer and about 2,700 men.
Men were more likely to have disease that had spread beyond the breast by the time they were diagnosed. They also had less surgery and radiation compared with women, but similar rates of chemotherapy and hormone therapy.
— From Tribune Newspapers, news services
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