By Alona Pulde, MD, LAc., Specializing In Lifestyle Medicine At Exsalus Health and Wellness Center
Vitamin D facts. Is Vitamin D really a vitamin? What are the benefits of vitamin D? What are vitamin D deficiency symptoms? What are the sources of vitamin D? Do we need to get vitamin D from sun exposure or take Vitamin D supplements? Will sun exposure increase the risk of cancer?Dr. Alona Pulde answers these questions and more!
Vitamin D is actually a fat soluble hormone, but for convenience we call it a vitamin. The two major forms are Vitamin D2 and Vitamin D3. Vit. D2 is found in fungi, plants, and fortified foods or supplements. Vit. D3 is synthesized in our skin when it's exposed to UVB light from the sun. It's also found in fish oil, and fortified foods or supplements.
Vitamin D synthesis starts in the skin. Then the liver and kidneys process Vit. D to it's final, active form - calcitriol. Some studies have found that Vit. D3 has longer lasting effects than Vit. D2, while other studies have found them equally effective.
Vitamin D is essential for the human body to function properly. It regulates over 200 genes, in cells all over the body - including the brain, heart, kidney, bone, intestine, skin, gonads, prostate, breast, parathyroid gland, and immune system.
Vitamin D is important for bone health because it regulates calcium and phosphorus levels in the blood. It can suppress the immune system, to fight against conditions like Rheumatoid Arthritis, Lupus, and Multiple Sclerosis.
Vit. D can activate the immune system, to fight cancer and infections like TB, Pneumonia, and Flu, and decrease the risk of heart attacks and strokes. Vit. D helps prevent diabetes by modifying the release and response to insulin.
We need up to 10,000 IU Vit. D daily to maintain adequate levels in our bodies. However, Vit. D levels fluctuate with geographical location, UV index, skin type, and exposure to the sun.
The best source of Vit. D is sunlight - when the UV (ultra-violet) index is 3 or higher. Most people can make up to 10,000 IU of Vit. D per day with maximum UVB exposure according to the chart below.
Other sources of Vit. D include supplementation and to a smaller extent foods such as cod liver oil.
Adequate sun exposure depends on the UV index (UVI) and skin type. It means 50-75% of your skin exposed (shorts, sleeveless T-shirt, or swimsuit) to the sun between 10:30am and 2 pm, about 3-4 times per week when your local UV index is 3 or higher.
Early in the day and late in the day, sunlight provides only UVA which doesn't help us make Vit. D but can still cause skin damage.
Note: You should double sun exposure time if you're over 50.
UV Index is an international standard measurement of UV (ultra-violet) radiation from the sun for a particular place and time. It takes into account UVA and UVB rays, with values ranging from 0 at night to 17 in areas where the ozone is depleted. It predicts how strong UV intensity will be at the sun's highest point - 2 to 4 hours either side of solar noon. The UV Index helps people protect themselves from UV light.
One hour of sun exposure at UV Index 10 is about the same as two hours of sun exposure at a UVI 5. The balance of UVA and UVB from sunlight depends on the time of day. Early in the day and late in the day sunlight provides only UVA. The closer you get to solar noon the more UVB is available from sun exposure.
The balance of UVA/UVB changes with latitude, time of day, and season. That's reflected in the UV index. E.G. in Chicago, during winter, the UV index will never get above 2. For roughly 6 months all you get are UVA rays, which damage the skin without any UVB benefit. Most people are covered up so they're protected, but you shouldn't intentionally expose your skin when the UV index is less than 3.
The Weather Channel lists the UV index on local weather reports. Visit the EPA Sunwise Index to find your local UV index for an hour each side of solar noon. This webpage warns you to cover up, use sunblock or stay out of the sun during that time, to avoid sun burns. Use the chart above for safe exposure times, and get your Vit. D before you cover up!
Web applications such as the iPhone will also give you local weather report updates including the UV index, for any time of day.
The main cause is lack of sunlight. This may be due to geography (living above latitudes of 35 degrees - north of Los Angeles and Atlanta), skin color (darker skinned people need more time in the sun), application of sunscreen (SPF 15 sunscreen can block 99% of Vit. D synthesis), or avoiding the sun for fear of sun damage.
Inadequate Vit. D intake (from fortified foods or supplements) and diseases of the liver and kidneys (which may affect conversion of Vit. D to its active form) also promote deficiency.
Obesity promotes Vit. D deficiency because Vit. D is a fat soluble hormone that is sequestered into fat cells, and as a result is not available for circulation.
Old age contributes to Vit. D deficiency, because it's more difficult to synthesize vitamin D as you age. After equal doses of sunlight exposure, a 70 year old produces 25% less vitamin D3 than a 20 year old. That's why people 50 or older should double their sun exposure time on the chart above.
Up to 50% of young adults and children are Vit. D deficient. And 25-57% of adults in the United States are deficient. Likely even more people are deficient as Vit. D levels aren't checked nearly as often as they should be.
Low Vit. D levels are associated with higher death rates, myalgias (nonspecific muscle aches and pains), cancer, diabetes, high blood pressure, congestive heart failure, impaired bone mineralization (leading to rickets in children, osteomalacia and osteoporosis in adults), several autoimmune conditions (including rheumatoid arthritis, multiple sclerosis, and lupus), depression, and seasonal affective disorder among others.
During pregnancy and early childhood, normal Vit. D levels are essential, to prevent infections, osteoporosis, autoimmune diseases, and cancer. Nursing mothers must have optimal Vit. D levels to provide enough Vit. D for their babies.
A growing number of studies highlight the benefits of Vit. D and the hazards of Vit. D deficiency. In 2005, a meta-analysis of 63 studies showed that "an additional 1,000 international units (IU) (or 25 micrograms) of Vit. D daily reduced an individual's colon cancer risk by 50%, and breast and ovarian cancer risks by 30%."
The effects of Vit. D on cell growth, differentiation, and death are all important components in the development of cancer. Other studies demonstrate the positive role Vit. D plays in preventing heart disease. A study published in the Journal of Circulation found that heart attack risks were 53 - 80% higher in people with low levels of Vit. D.
Another study looked at 150 patients with nonspecific musculoskeletal pains and found that Vit. D levels were "insufficient in 93% of individuals and severely deficient in 28%." Low Vit. D levels have also been correlated with increased death rates.
One study of 57,000 people, found that 500 IU or more per day of Vit. D lowered death rates. Researchers found that low levels of Vit. D were associated with a sharp increase in death rates. Clearly Vit. D is an important factor in overall health and should be studied more.
The safe upper limit of Vit. D for a healthy adult is 250 micrograms, or 10,000 IU daily. Vitamin D toxicity results mostly from hypercalcemia - too much calcium in the blood. Symptoms of Vit. D toxicity include high blood pressure, nausea, vomiting, constipation, weakness, decreasing kidney function with increased urination, confusion, and lethargy.
Overexposure to sunlight doesn't cause Vit. D toxicity. Once Vit.D synthesis has reached a saturated state, the rest of the Vit. D is degraded. Too much Vit. D can be toxic, although this isn't very common. High doses of Vit. D supplements should only be taken under a doctor's supervision.
UV light can damage cellular DNA, which may lead to skin cancer. But that doesn't mean we should go to the other extreme. Studies have shown that people who work both indoors and outdoors have the lowest risk of melanoma, compared to indoor and outdoor workers. This supports the idea that some sun exposure protects against cancer. Sun burn is probably cancer promoting, but so is no sun exposure.
One study points out that melanomas or skin cancers often show up on areas that haven't been damaged by the sun. This suggests that sunlight exposure isn't the only important factor in skin cancer. People should get enough sun exposure for Vit. D synthesis, based on the UV index and their skin type (see chart above). After that, use a sun block or cover up with shirts, hats, etc. Sun blocks are great at protecting us from burns and skin damage, but they don't prevent cancer.
Tanning booths aren't all the same. Some use light bulbs that emit only UVA light, some emit UVA and UVB light, and some UVA, UVB, and UVC light. UVC light is normally blocked by the ozone and very damaging, so it should be avoided at all costs. UVA light causes skin to tan quickly and is preferred by tanning salons. However, UVA rays do not promote vitamin D production. UVB light is the only wavelength that promotes Vit. D production, so only bulbs that emit UVB light will have any potential benefit.
The ratio of UVA:UVB light from the sun is 10:1 to 20:1. But some tanning bulbs have a ratio as high as 100:1. What this means for cancer risk still isn't clear, but high levels of UVA exposure is probably a bad idea. There are some studies that show that people who use tanning booths have increased rates of skin cancer. But it isn't always clear what type of UV light they were using, what the UVA:UVB ratios were, or whether they were overexposed.
Other research shows that people who use tanning salons have healthy Vit. D levels. No matter what you choose, be careful when tanning as the light bulbs are very strong and have a UV index of approximately 7-8! We need a study to show how tanning and supplements compare to sunlight, but getting enough sun is still your best bet for safe accumulation of Vit. D.
The sun has gotten a bad rap, but studies show that areas with greater sun exposure have reduced risks of cancers and heart disease. In addition, sunlight has positive effects on rickets, osteomalacia, high blood pressure, depression, sleep disorders, ADHD, premenstrual syndrome, and acne.
Getting enough sun isn't always possible. For those living in areas with little to no sun exposure and/or for people such as the elderly, nursing home residents, or hospitalized patients, Vit. D supplements may be necessary and recommended.
People with optimum levels of Vit. D are much healthier than those with lower levels of Vit. D. We also know that a low level of Vit. D is really a sign of sunlight deficiency. At this point we can't say for sure that Vit. D supplements will make you as healthy as someone who gets their Vit. D from sunlight.
Doubling Vit. D levels doubles our ability to absorb calcium. We also know that parathyroid hormone (PTH) levels normalize at optimum Vit D levels. When Vit. D levels are too low for adequate calcium absorption, PTH stimulates bone breakdown, to maintain constant calcium levels in the blood. This is very damaging to our bones.
In one study of 1100 postmenopausal women, subjects took 1100 IU daily of Vit. D3, plus calcium. Unlike this study, most studies in the past were not randomized and placebo-controlled. Those studies that were randomized, used small amounts of Vit. D3 that barely raised Vit. D levels. The postmenopausal study increased Vit. D levels over 30% on average, and showed a 4-5% cancer risk reduction at the end of 4 years.
If we can't get enough sun, the best strategy is to use supplements to get our Vit. D up to optimum levels, boosting calcium absorption, protecting our bones and improving our overall health.
The average American needs about 20 to 25 IU of Vit. D per pound of body weight to get their levels up high enough. This is much more Vit. D than the current RDA. Keep in mind that getting enough sun for one day (see chart above) can give you up to 10,000 IU's of Vit. D.
We should get Vit. D levels up as high as we can through sun exposure. If Vit. D levels still test below normal, then use supplements. Even then, some people may have symptoms that could be due to Vit. D deficiency: certain autoimmune diseases, fibromyalgia, seasonal affective disorder, particular musculoskeletal problems, etc. Those people may benefit from a trial of increased Vit. D supplementation. If symptoms don't improve, they should decrease their supplements to the recommended level.
We should try to spend more time in the sun - between 10:30 AM and 2:00 PM with UV index of 3 or greater - to reduce our dependence on Vit. D supplements.
Vitamin D deficiency is a sign of sunlight deficiency.
Vitamin D is necessary for proper functioning of many organ systems, and optimim health.
Low Vitamin D levels are associated with cancer, heart disease, diabetes, rickets, osteomalacia, and osteoporosis, among other diseases.
Vitamin D supplements can't replace our human need for sunlight! For those who can, pack a picnic or grab your Frisbee, and head out for some fun in the sun!
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