It's an example of an unforeseen consequence of wise behavior, but you can enjoy sun protection and strong bones, too, by taking vitamin supplements. Like politicians, doctors often have to compromise; when it comes to sunshine, most pols promise blue skies, while most docs turn out to be the shady guys — or, at least, sunscreen advocates. UVB provides the energy your skin needs to make vitamin D, but that energy can burn the skin and increase the cell damage that leads to cancer.
UVA also contributes to skin damage and premature aging. To protect yourself, avoid the summer sunshine, especially between 10 a. Whenever possible, wear a large-brimmed hat and a tightly woven, dark-colored long-sleeve shirt and long pants when you go out in the sun.
But summer garb is usually lightweight and exposes a lot of skin. That's where a sunscreen comes in. Look for a product with an SPF of 30 or higher. Apply your sunscreen early, often, and liberally. These many factors explain why vitamin D deficiencies are shockingly common in the United States. And low levels of vitamin D are common even in apparently healthy young adults; in one study, more than a third of people between the ages of 18 and 29 were deficient.
Numbers can never tell the whole story, but in this case, "D-ficiencies" add up to a wide range of health concerns. It's a paradox: Skeletal health is the best-known contribution of vitamin D, but it has also become the most controversial. Although doctors agree that vitamin D deficiency increases the risk of osteoporosis and fractures, they disagree about the benefits and optimal dosage of supplements.
Without enough vitamin D, the intestines cannot efficiently absorb calcium. But because blood calcium is critical for neuromuscular and cardiac function, the body does not allow levels to fall. Instead, it pours out parathyroid hormone, which mobilizes calcium from bone. Blood calcium levels remain normal, so your heart and nerves keep working nicely. But your bones bear the brunt: As bone calcium density falls, bones become weak and fracture-prone.
Most studies show that a lack of vitamin D increases the risk of osteoporosis and the likelihood of hip and other non-spinal fractures. But there is considerable disagreement about how much supplements reduce the risk of fractures. Some studies include only women, others both men and women; some include only frail, elderly, or institutionalized subjects, others physically active people; some use vitamin D alone, others a combination of D and varying doses of calcium; and some administer international units IU of vitamin D a day, others up to IU a day.
Some men mistakenly dismiss osteoporosis as a women's worry, but none fail to recognize the importance of prostate cancer. Vitamin D has an important role in regulating cell growth. During winter months, they cannot make vitamin D from sunlight, so they need to get it from foods or supplements.
Vitamin D is made from cholesterol in the skin. That means you need to expose lots of skin to the sunlight to make enough. Some scientists recommend exposing around a third of the area of your skin to the sun 5. According to this recommendation, wearing a tank top and shorts for 10—30 minutes three times per week during the summer should be sufficient for most people with lighter skin.
People with darker skin may need a bit longer than this. Instead, try going without sunscreen for just the first 10—30 minutes, depending on how sensitive your skin is to sunlight, and apply sunscreen before you start burning. Since the head is a small part of the body, it will only produce a small amount of vitamin D. You need to expose a sufficient amount of skin to sunlight to maintain healthy vitamin D blood levels. Wearing a tank top and shorts for 10—30 minutes three times per week is sufficient for lighter-skinned people, while those with darker skin may need longer.
When this happens, the skin is exposed to lower levels of harmful UV rays However, because UVB rays are essential for making vitamin D, sunscreen could prevent the skin from producing it. However, several studies have shown that wearing sunscreen only has a small impact on your blood levels during the summer 17 , 18 , One possible explanation is that even though you are wearing sunscreen, staying in the sun for a longer period of time may cause enough vitamin D to be made in the skin.
That said, most of these studies were conducted over a short period of time. In theory, wearing sunscreen may reduce the ability to produce vitamin D, but short-term studies have shown it has little or no impact on blood levels. Your exposure time should depend on how sensitive your skin is to sunlight. Although sunlight is great for making vitamin D, too much sunlight can be dangerous. Some consequences of too much sunlight include sunburn, eye damage, skin aging and other skin changes, heat stroke and skin cancer.
To maintain healthy blood levels, aim to get 10—30 minutes of midday sunlight, several times per week. People with darker skin may need a little more than this. It's not known exactly how much time is needed in the sun to make enough vitamin D to meet the body's requirements. This is because there are a number of factors that can affect how vitamin D is made, such as your skin colour or how much skin you have exposed.
But you should be careful not to burn in the sun, so take care to cover up or protect your skin with sunscreen before your skin starts to turn red or burn. People with dark skin, such as those of African, African-Caribbean or south Asian origin, will need to spend longer in the sun to produce the same amount of vitamin D as someone with lighter skin.
How long it takes for your skin to go red or burn varies from person to person. Cancer Research UK has tips to help you protect your skin in the sun. Your body can't make vitamin D if you're sitting indoors by a sunny window because ultraviolet B UVB rays the ones your body needs to make vitamin D can't get through the glass.
The longer you stay in the sun, especially for prolonged periods without sun protection, the greater your risk of skin cancer. If you plan to be out in the sun for long, cover up with suitable clothing, wrap-around sunglasses, seeking shade and applying at least SPF15 sunscreen.
During these months, we rely on getting our vitamin D from food sources including fortified foods and supplements. To ensure they get enough vitamin D, babies and children aged under 5 years should be given vitamin D supplements even if they do get out in the sun. Find out about vitamin D supplements for children. The Department of Health recommends that these people should take daily vitamin D supplements to make sure they get enough.
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