Vitamin A daily dose may help prevent skin cancer: Study

Published on March 4, 2012 at 8:49 PM · No Comments

By Dr Ananya Mandal, MD

A study has shown that a daily vitamin pill could help prevent skin cancer - particularly among women. Scientists say taking food supplements containing vitamin A can make people less likely to develop melanoma, the deadliest form of the disease.

A study found that retinol - a key component of Vitamin A - could protect against the illness. Retinol belongs to a class of compounds called retinoids that have been shown to stop cells dividing and spreading. The strongest protective effects were found in women and in sun exposed sites, suggesting retinol actually combats skin cancer. However, there was no association between dietary intake of vitamin A, found in liver, eggs and milk, and a reduction in risk.

In addition there was also no reduced risk seen by the intake of carotenoids, which are abundant in vegetables including carrots and tomatoes and absorb compounds that can damage the skin. Previous research with mice has shown retinol and carotenoids can shrink melanoma tumours and improve survival. Retinol is also good for the immune system and eyesight

Dermatologist Dr Maryam Asgari and colleagues analysed the disease risk in 69,635 men and women aged between 50 and 76 who consumed vitamin A through either dietary or supplementary methods. Their study is published in the Journal of Investigative Dermatology.

It showed that those who used retinol regularly were 60 per cent less likely to develop skin cancer, rising to 74 per cent among participants on the highest doses of more than 1,200 mg a day.

Dr Asgari, of the Kaiser Permanente Northern California Division of Research in Oakland, said, “Our data suggest a possible interaction between supplemental retinol use and the anatomic site of melanoma, with sun-exposed sites showing a stronger protective effect than sun-protected sites. It may be that retinol's effects may be mediated by sunlight exposure. This intriguing possibility warrants further exploration in future studies.”

“It was definitely linked with supplements, not diet,” says Asgari. She points out that the effects were only seen in people who were taking more vitamin A than what is found in multivitamins.

Dr Asgari said, “In summary, our data, which are based on a large prospective cohort, suggest retinol intake from individual supplements is associated with a reduction in risk for melanoma, especially among women. Our findings suggest vitamin A supplementation may hold promise as a chemopreventive agent for melanoma.” “People who are concerned about melanoma should avoid sun exposure, practice sun protection, and get annual skin checks,” she added.

Skin cancer is the most common type of cancer among white populations, in the UK and worldwide. Most are easy to treat and pose only a small threat to life, but melanoma is difficult to treat unless detected early. Over the past 25 years, rates of melanoma in the UK have risen faster than any other common cancer. About 1,800 people die from melanoma annually in the UK. Even so, nearly 80 per cent of men and over 90 per cent of women are alive at five years following treatment. Melanoma is the sixth leading cause of cancer in the U.S., according to the American Cancer Society. In 2012, about 76,250 new melanomas will be diagnosed, and about 9,180 people will die from this type of skin cancer, according to the American Cancer Society.

Dr Claire Knight, senior health information officer at Cancer Research UK, said, “We don't recommend people start taking retinol supplements based on this study, particularly as high doses can be toxic. The result was based on a very small number of people with melanoma, and the authors didn't account for other important factors that influence the risk of skin cancer, such as the number of moles a person has. And crucially, when the authors looked at whether a particular dose was linked to risk, the link between retinol and melanoma disappeared.”

The recommended daily amount of vitamin A is 700 micrograms for adult women and 900 micrograms for adult men, according to the National Institutes of Health. Taking more than 2,800 micrograms of vitamin A could lead to toxic symptoms in adults.

Still, too much vitamin A can be dangerous. Serious risks can include liver toxicity and bone pain. Darrell S. Rigel clinical professor of dermatology at New York University said, “There is no downside to this, but there are risks to overdoing vitamin A, including liver damage, dry skin, and hair loss.” Heidi Waldorf, dermatologist at Mount Sinai Medical Center in New York City added, “It is not surprising to me that vitamin A may be protective against melanoma… However, high doses of vitamin A can have serious side effects, including liver toxicity.” That said, “This may be an option for patients at high risk for melanoma because of prior diagnosis or family history, but not for the general population,” she said. People at high risk for melanoma also include those with fair skin, history of sunburn, and a lot of moles.

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