What is vitamin D?
Vitamin D is actually considered a pro-hormone and not a vitamin, despite the name. Vitamins are nutrients that cannot be created by the body and therefore must be taken in through our diet.
However, vitamin D can be synthesized by our body when our skin is exposed to sunlight.
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Sun exposure on bare skin for 5-10 minutes 2-3 times weekly allows most people to produce sufficient vitamin D, but vitamin D breaks down quite quickly, meaning that stores can run low, especially in cold weather when the sun is low, like in winter.
Vitamin D, also known as the sunshine vitamin, is produced by the body as a response to sun exposure. It can also be consumed in food or supplements.
Vitamin D is essential in maintaining healthy bones and teeth. It may also protect against a range of conditions such as type 1 diabetes, cancer, and multiple sclerosis.
Functions of Vitamin D in the Body
- Support the health of the immune system, brain, and nervous system.
- Maintain the health of bones and teeth.
- Regulate insulinlevels and aid diabetes
- Support lung function and cardiovascular health.
- Influence the expression of genes involved in cancer development.
Health Benefits of Vitamin D
- Healthy bones
Vitamin D helps in maintaining healthy bones by regulating calcium and maintaining phosphorus levels in the blood. Vitamin D is needed to absorb calcium in the intestines and to reclaim calcium that would otherwise be excreted through the kidneys.
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Vitamin D deficiency in children can lead to rickets, a disease characterized by a severely bow-legged appearance due to softening of the bones.
In adults, vitamin D deficiency manifests as osteomalacia (softening of the bones) or osteoporosis. Osteomalacia results in poor bone density and muscular weakness. Osteoporosis is the most common bone disease among post-menopausal women and older men.
2) Reduced risk of flu
The risk of children getting influenza was reduced by over 40% when they were given 1,200 International Units of vitamin D per day for 4 months during the winter.
3) Reduced risk of diabetes
Several observational studies have shown an inverse relationship between blood concentrations of vitamin D in the body and risk of type 2 diabetes. In people with type 2 diabetes, insufficient vitamin D levels may negatively affect insulin secretion and glucose tolerance.
4) Healthy infants
Children with normal blood pressure who were given 2,000 International Units (IU) per day had lower arterial wall stiffness after 16 weeks compared with children who were given only 400 IU per day. Vitamin D deficiency has also been linked to a higher risk and severity of atopic childhood diseases and allergic diseases, including atopic dermatitis, eczema, and asthma. Vitamin D may boost the anti-inflammatory effects of glucocorticoids, making it possibly useful as a supportive treatment for people with steroid-resistant asthma.
5) Healthy pregnancy
Pregnant women who have low levels of vitamin D tends to be at greater risk of developing preeclampsia and needing a cesarean section. Vitamin D deficiency in pregnant women is connected to bacterial vaginosis and gestational diabetes mellitus.
6) Cancer prevention
Vitamin D is extremely important for regulating cell growth and for cell-to-cell communication. Studies have suggested that calcitriol (the hormonally active form of vitamin D) can decrease the advancement of cancer by slowing the growth and development of new blood vessels in cancerous tissue, increasing cancer cell death, and reducing cell proliferation and metastases. Vitamin D influences more than 200 human genes, which could be impaired when we do not have enough vitamin D.
Recommended intake of vitamin D
Vitamin D intake can be measured in two ways: in micrograms (mcg) and International Units (IU).
One microgram of vitamin D is equal to 40 IU of vitamin D.
The recommended intakes of vitamin D throughout life were updated by the U.S. Institutes of Medicine (IOM) in 2010 and are currently set at:
- Infants 0-12 months – 400 IU (10 mcg).
- Children 1-18 years – 600 IU (15 mcg).
- Adults to age 70 – 600 IU (15 mcg).
- Adults over 70 – 800 IU (20 mcg).
- Pregnant or lactating women – 600 IU (15 mcg).
Vitamin D deficiency
Granting the body can create vitamin D, there are many reasons deficiency can occur. For instance, darker skin color and the use of sunscreen may reduce the ability of the body to absorb the ultraviolet radiation B (UVB) rays from the sun required to produce vitamin D.
A sunscreen with sun protection factor (SPF) 30 can reduce the body’s ability to synthesize the vitamin by 95 percent. To start vitamin D production, the skin has to be exposed to sunlight directly, not covered by clothing.
People who live in northern latitudes or areas of high pollution, work at night and stay home during the day, or are homebound should target to consume extra vitamin D from food sources whenever possible. Infants who are exclusively breast-fed need a vitamin D supplement, especially if they are dark-skinned or have minimal sun exposure. Although vitamin D supplements can be taken, it is best to obtain any vitamin or mineral through natural sources.
Symptoms of vitamin D deficiency
Symptoms of vitamin D deficiency may include:
- Getting sick more often
- Painful bones and back.
- Depressed mood.
- Impaired wound healing.
- Hair loss
- Muscle pain.
If Vitamin D deficiency continues for long periods of time it can lead to:
- chronic fatigue syndrome
- neurodegenerative diseases, such as Alzheimer’s disease
Vitamin D deficiency may also contribute to the development of certain cancers, especially breast, prostate, and colon cancers. We explain this in a little more detail later.
Food Sources Rich in Vitamin D
Sunlight is the most common and efficient source of vitamin D. The richest food sources of vitamin D are fish oil and fatty fish. Here is a list of foods with good levels of vitamin D:
- salmon, sockeye, cooked, 4 ounces: 596 IU
- cod liver oil, 1 tablespoon: 1,360 IU
- egg, chicken, whole large: 44 IU
- swordfish, cooked, 4 ounces: 941 IU
- raw maitake mushrooms, 1 cup: 786 IU
- sardines, canned, 4 ounces: 336 IU
- herring, fresh, raw, 4 ounces: 1,056 IU
- fortified skim milk, 1 cup: 120 IU
- tuna, canned in water, drained, 3 ounces: 68 IU
Potential health risks of consuming vitamin D
The Upper Level limit recommended for vitamin D is 4,000 IU per day. However, the National Institutes of Health (NIH) has suggested that vitamin D toxicity is unlikely at daily intakes below 10,000 IU per day.
Excessive consumption of vitamin D (hypervitaminosis D) can lead to over calcification of bones and hardening of blood vessels, kidney, lungs, and heart. The most common symptoms of hypervitaminosis D are headache and nausea but can also include loss of appetite, dry mouth, a metallic taste, vomiting, constipation, and diarrhea.
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Vitamin D is best gotten from natural sources. When choosing supplements, choose your brand carefully as the FDA does not monitor safety or purity of supplements.