By ABIMBOLA ADELAKUN
Wednesday, 26 May 2010
Studies show how inadequate contact between the sun and the skin portends danger, writes ABIMBOLA ADELAKUN.
The sun isn‘t just a big hot ball in the sky that dries up wet clothes and makes us sweat. It is a highly valuable source of production of Vitamin D; the vitamin that has been identified with a whole lot of benefits: from reducing obesity to reducing chances of getting cancer. However, to get Vitamin D to work for one, the skin needs to be exposed to the sun.
Yet, many people would rather not have the sun on their bodies because of sunburn, skin darkening and other discomforts associated with exposure.
“Vitamin D is made principally in the skin,” says Dr. Biodun Osinubi, a dermatologist with many years experience. “The vitamin is good in the body for so many different things, especially for the control of calcium. Calcium is useful for so many defences.”
Vitamin D is a group of fat-soluble secosteroids produced in the skin of vertebrates after exposure to ultraviolet B light, and is found in a small range of foods such as oily fish and dairy products. It is also available as a supplement in pill form.
According to Ms. Joy Ayodele, an Ibadan-based writer, the effect of sunlight on her skin is the reason she chooses cream with sunscreen.
“I am told that it protects the skin from rays of the sun that can cause cancer. I am not aware I am depriving my body of Vitamin D.”
Other people who spoke to our correspondents say they are not even aware whether the cosmetics they buy contain sunscreen or not.
Mr. Osita Nwanna says he merely chooses what suits him and has never been bothered about sunscreen.
By avoiding the sun, the body, however, is deprived of Vitamin D because its production by the skin is in response to exposure to ultraviolet radiation from natural sunlight. Yet, sunscreen is needed to protect the skin from sunburn and ultraviolet rays that can lead to cancer.
Osinubi says using sunscreen means cutting off ultra violet rays of sunlight which might be damaging to the skin and at the same time, it hinders the body from getting enough vitamin D.
“In most cases, there is a relationship between skin cancer and sun exposure. You need sunscreen to cut off the dangerous part of the sun that can give you skin cancer,” Osinubi points out.
By trying to prevent cancer of the skin with sunscreen, susceptibility to different kinds of cancer occurs.
Studies indicate that vitamin D is capable of preventing osteoporosis, rickets, depression, prostate cancer, breast cancer, and even affects diabetes and obesity. Vitamin D in the body also reduces the risk of developing serious diseases like diabetes and cancer by 50 - 80 per cent, derived through simple, sensible exposure to natural sunlight 2-3 times each week.
Even weak sunscreens with Sun Protection Factor can block the body’s ability to generate vitamin D by 95 per cent. This explains how sunscreen products actually cause disease — by creating a critical vitamin deficiency in the body.
“If a cream does not have either sunscreen or SPF of at least 15, I don’t touch it,” says Miss Bukola Adeyemi, a writer. “I know that sunscreens are good and protect the body from ultraviolet rays of the sun. I am not aware of the Vitamin D and cancer thing.”
Research shows that vitamin D‘s main purpose is to help keep normal levels of calcium and phosphorus in the bloodstream. Calcium needs vitamin D to help transport it from digested food in the stomach and small intestines to the bloodstream. In the body, calcium keeps bones strong. There are two forms of vitamin D that are important in humans: Vitamin D2: Ergocalciferol, which comes from plants and Vitamin D3: Cholecalciferol, which comes from exposure to UV radiation and certain foods.
The American Cancer Society, for instance, recommends the use of sunscreen because it prevents the squamous cell carcinoma (a form of cancer) and the basal cell carcinoma (a malignant form of skin cancer). However, the use of sunscreens does not necessarily guarantee the blockage of UVA radiation (long wave rays), which does not cause sunburn but can increase the rate of melanoma, another kind of skin cancer. People using sunscreens may actually be getting too much UVA without realising it. At the same time, the sunscreen blocks UVB (short wave rays), and if used consistently this can cause a deficiency of vitamin D.
Both UVA and UVB have been identified in studies as responsible for conditions such as premature skin aging, eye damage (including cataracts), and skin cancers. They also suppress the immune system, reducing your ability to fight off these and other maladies.
Cosmetics company however are unlikely to talk about the damaging effects of sunscreen, a kind of cream that comes in form of lotion, spray, gel or other tropical product. Instead, skin lightening products usually has sunscreen to protect toned and bleached skin.
“Bleaching wears away melanin and exposes the skin to the sun but that is not the only reason for skin cancer anyway. The melanin is a form of sunscreen. It limits the amount of sun that can damage the skin. Vitamin D helps in the maturation of cells and reduces the body‘s chances of being prone to some cancer.”
The melanin is a skin pigmentation that is formed as part of the process of metabolising an amino acid called tyrosine. In the skin, melanin is formed by cells called melanocytes. Certain medical conditions, such as albinism, are associated with the lack of melanin. Blacks have more melanin in their system and that suggests reason for the colour of their skin.
One of the most recognised benefits of melanin in the body involves a natural protection from the ultraviolet rays of the sun. However, it does not provide complete protection from the sun, and individuals with darker skin tones are not exempt from the risk of the sun‘s damaging rays.
Black skinned individual are thus generally able to tolerate exposure to the sun for hours without getting sunburn.
“If you look at two groups of people living around the equator, the white of Australia and the black of Africa, the rate of skin cancer are more in the white people than in West Africa probably because of melanin. Nature provides a kind of balance for those of us here. We are exposed to the sun and melanin protects us from the sun rays.”
Osinubi states that in some instances, if the effect on the skin causes darkening, sunscreen might be recommended.
Scientific studies also advises that people who sit in air-conditioned offices, cars and homes all day are doing themselves a lot of disfavour because vitamin D cannot penetrate the glass screen erected around them. They cannot adequately make up for the sunshine by diet and drugs either. Staple diet, other studies suggest, still does not make up for the shortfall of vitamin D in the body because a person would have to drink ten tall glasses of vitamin D fortified milk each day just to get minimum levels of vitamin D into their system. Lack of vitamin D in the body also prevents absorption of calcium such that it renders calcium supplements useless.
The good thing about vitamin D through sunlight exposure is that there is no overdose of it: the body will self-regulate and only generate what it needs. Osinubi says that there is no measuring how much sunshine the skin needs but the exposure should be done in moderation.
Good news for those in the tropics: the sun is free and ever shining in our skies but even then, moderation is the word.
“Even if you are exposed to the sun, there is a level to which your body can take it. The rest is frittered away. If the sun gets too much, use an umbrella,” advises Osinubi.
（摘自Vitamin D Today）