Vitamin D is a fat-soluble and promotes the absorption of calcium, regulates bone growth and plays a role in immune function. Your skin produces vitamin D when it’s exposed to sunlight. If you spend most of your time indoors or live at a high latitude, you’ll need to get this vitamin from your diet.
Good dietary sources include fatty fish, fish oils, egg yolk, butter and liver. However, it may be difficult to get adequate amounts of this vitamin from your diet alone, as rich natural sources are rare. For these reasons, it’s common for people to not get enough. Consequently many food manufacturers add it to their products, especially milk, margarine and breakfast cereals. Supplements are also popular. Also, it seems that doctors prescribe it a lot for old people.
Vitamin D is unique because your skin actually produces it by using sunlight. Fair-skinned individuals and those who are younger convert sunshine into vitamin D far better than those who are darker-skinned and over age 50.
Vitamin D is needed to keep your body functioning well, but it’s bad to get too much. Vitamin D toxicity, also called hypervitaminosis D, is a rare but potentially serious condition that occurs when you have excessive amounts of vitamin D in your body.
The condition is usually caused by megadoses of vitamin D supplements and not by diet or sun exposure. That's because your body regulates the amount of vitamin D produced by sun exposure, and even fortified foods don't contain large amounts of vitamin D. 60,000 international units (IU) a day, many times higher than the Recommended Dietary Allowance (RDA) for most adults of 600 IU, for several months has been shown to cause toxicity. The main consequence of vitamin D toxicity is a buildup of calcium in your blood (hypercalcemia), which can cause nausea and vomiting, weakness, and frequent urination. Symptoms might progress to bone pain and kidney problems, such as the formation of calcium stones.
Vitamin D helps with strong bones and may help prevent some cancers. Symptoms of vitamin D deficiency can include muscle weakness, pain, fatigue and depression. Some of its functions are:
# Keeps bones strong. You need vitamin D so that calcium and phosphorus can be used to build bones.
# Absorbing calcium. Calcium helps build bones and keep them strong and healthy. Weak bones can lead to osteoporosis, the loss of bone density, which can lead to fractures.
# Works with parathyroid glands: The parathyroid glands work to balance the calcium in the blood by communicating with the kidneys, gut and skeleton. When there is sufficient calcium in the diet and sufficient active Vitamin D, dietary calcium is absorbed. If calcium intake is insufficient, or vitamin D is low, the parathyroid glands will ‘borrow’ calcium from the bones in order to keep the blood calcium in the normal range.
Several studies have suggested that the symptoms of Seasonal Affective Disorder (SAD), a type of depression that's related to changes in seasons, may be due to changing levels of vitamin D3, which may affect serotonin levels in the brain.
Although vitamin D supplementation may improve mood, vitamin D is only a small, but critical, part of treatment; depression has myriad causes. Low blood levels of vitamin D are linked to more signs of depression, but depression can have many causes and a Vitamin D problem may be only one. The research is still unclear on whether vitamin D will help prevent or ease the problem.
Getting enough vitamin D may also play a role in protecting against the following conditions and possibly helping to treat them:
# Heart disease and high blood pressure
# Diabetes # Infections and immune system disorders
# Falls in older people
# Some types of cancer, such as colon, prostate and breast cancers
# Multiple sclerosis.
The amount of vitamin D that your skin makes depends on such factors as:
# The season: This factor depends on where you live. In areas such as Cleveland, Ohio or Buffalo, New York, the UV-B light does not reach the earth for six months out of the year due to the ozone layer and the zenith of the sun.
# The time of day: The sun's rays are most powerful between 10 a.m. and 3 p.m.
# The amount of cloud cover and air pollution.
# Where you live: Cities near the equator have higher ultraviolet (UV) light levels. It is the UV-B light in sunlight that causes your skin to make vitamin D.
# The melanin content of your skin: Melanin is a brown-black pigment in the eyes, hair and skin. Melanin causes skin to tan. The darker your skin, the more sun exposure is needed in order to get sufficient vitamin D from the sun.
Medical News Today - What are the health benefits of Vitamin D?
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