Vitamin D is referred to medically as “calciferol” and colloquially as the “sunshine vitamin” because the body produces it in the presence of the sun’s ultraviolet-B (UVB) rays.

Vitamin D is a fat-soluble vitamin that is naturally present in a few foods. Some foods are fortified with it such as fortified milk and fortified cereal, and it is also available as a dietary supplement.

More importantly, it is also produced endogenously when the sun’s ultraviolet (UV) rays touch the skin and activate vitamin D synthesis.

Sunlight exposure to the skin is our most important source of this vitamin. Ninety percent of our requirement is made from sunlight exposure directly onto the skin. Exposure through glass or sunscreen deprives you of this benefit.

Only about 10 percent of vitamin D comes from the food that you eat. Main food sources include oily fish, fortified milk, and egg yolks.

Although it is called a vitamin, it is actually a hormone. In fact, it is both a nutrient and a hormone that our body makes.

It helps the body absorb and retain calcium and phosphorus both of which help to keep bones, teeth, and muscles healthy.

Major forms

Several forms of vitamin D exist. The two major forms in foods and dietary supplements are:

  1. Vitamin D2 or ergocalciferol (or pre-vitamin D). It is made from plant sources and is present in fortified foods and some supplements.
  2. Vitamin D3 or cholecalciferol. This is the form of this vitamin that is produced through the exposure of the skin to the sun’s ultraviolet A (UVA) and ultraviolet B (UVB) rays. It is, therefore, naturally produced in the human body and is found in animal foods.

D3 supplements act better in the sense they raise blood levels of the vitamin more and for a longer period than D2. Again, vitamin D3 is preferred as it is naturally produced in the body and found in most foods that naturally contain the vitamin.

Recommended daily intake

The recommended daily amount of vitamin D depends on your age:

  • For children up to age 12 months, it is 400 international units (IU) ( 10 mcg also written as μg)
  • For people between the age of one year to 70 years, the daily requirement is 600 IU (15 mcg).
  • For pregnant or lactating women, it is 600 IU (15 mcg)
  • For people over 70 years, the requirement is 800 IU (20 mcg)

Health benefits

Many of the body’s organs and tissues have vitamin D receptors (VDR), which suggest important functions of this vitamin besides giving you strong bones.

Organs and tissues that hold the strong expression of VDR are the intestines, bone, kidney, muscle, parathyroid glands, and skin.

The expression of VDR in these and other tissues suggests a multifocal role of this vitamin in our body, which is still not fully studied.

All said and done, it is an essential and crucial micronutrient for your health. You should know how to obtain it from sunlight and foods.  

Its benefits are tremendous and reading them described below will tell that.

Vitamin D gives you healthy bones

Vitamin D is essential for strong bones and muscles. Without it, our body cannot absorb calcium, which is the most important nutrient for good bone health.

It regulates calcium and phosphate plasma levels by promoting their absorption in the intestine. This promotes bone growth and keeps the bones strong and healthy, thereby preventing and lowering the risk of fractures.

Maintaining healthy vitamin D levels helps to prevent osteopenia and osteoporosis.

It slows down the process of bone loss and keeps your bones strong by helping your body absorb calcium and phosphorus. These are the key minerals that help to keep your bones strong.

If you suffer from osteomalacia, your doctor will treat you with vitamin D and calcium.

Good for muscles

Vitamin D is essential for muscle growth and development and in regulating the contraction of the muscles through its beneficial effect on muscle cell function.

Taking its supplements increases muscle strength, especially in people who have vitamin D deficiency.

In athletes, adequate serum levels of calciferol are associated with reduced injury rates and improved sports performance because of improved balance.

Vitamin D can help with faster muscle recovery from muscle fatigue after intense exercise, and may even prevent muscle damage caused by the exercise.

It also prevents muscle damage from intense physical activity and prevents cramps and spasms in the muscles.

Improves Immune function

Vitamin D balances our immune system so that it serves as a therapeutic resource to fight infections such as colds and influenza.

This balancing of the immune system is important because if there is excessive stimulation, autoimmune diseases can set in. Again, if there is not much immune activity, infections can frequently set in.

In 2009, the National Institute of Health stated that low vitamin D levels are often associated with frequent colds and flu attacks.

Improves depression symptoms

Besides the benefits of vitamin D on physical health, it plays a crucial role in maintaining mental health.

Sufficient research exists that shows its deficiency in the body can lead to depression. It is also seen many times that people with depression exhibit low levels of this vitamin.

A good amount of it in your body improves your mental setup and improves depression symptoms.

Lowers risk of autoimmune diseases like Multiple Sclerosis (MS)

Studies show having adequate vitamin D may lower your chance of getting multiple sclerosis. MS is an autoimmune disease in which our own immune system attacks the nervous system.

In a person who already has this disease, its supplements can give relief from its symptoms and can even slow down its progression.

According to Mayo Clinic, people who are adequately exposed to sunlight and have a good amount of vitamin D foods have a lower risk of contracting this disease. It protects you and significantly lowers your risk of developing multiple sclerosis.

Lowers cancer risk

Sufficient vitamin D level in the body lowers your risk of getting cancer – studies have proven that.

It reduces cancer mortality rates by decreasing the invasiveness nature of the tumor and its property to metastasize. This benefit is enhanced when its intake is paired with calcium supplements.

Studies have shown that it can reduce cancer cell growth, help control infections and reduce inflammation.

Helps in weight loss

Vitamin D supplements when taken with calcium can keep you from feeling hungry, leading to lesser consumption of calories. In addition, it also helps to get rid of belly fat.

A 2017 study found that combining aerobic exercise and resistance training with vitamin D supplements can help you lose more calories than exercise alone.

Benefits on hair loss

Research has discovered a strong link between vitamin D deficiency and certain types of hair loss.

This deficiency may particularly play an important role in the development of alopecia areata and pattern baldness.

It binds to the vitamin D receptors (VDR) found in the hair follicles. It helps to regulate cell cycles, which is important for hair growth.

It is metabolized in the skin by the skin cells called keratinocytes. These skin cells process keratin, which is a protein present in hair, nails, and skin

In the presence of vitamin D deficiency, the keratinocytes in the hair follicles cannot process keratin and hence cannot facilitate hair growth. This results in the shedding of hair. Taking its supplements will stop hair loss and make your hair grow back.

Benefits on liver

Vitamin D is one of the essential vitamins for liver function. It can influence liver function through its receptor (VDR) that is naturally present in the liver cells.

It reduces inflammation in chronic liver diseases because of its anti−fibrotic, antiproliferative, and anti-inflammatory effects on the liver.

Benefits on skin

Vitamin D exhibits anti-microbial and anti-inflammatory properties that can help treat skin conditions like dryness, acne, psoriasis, eczema, and vitiligo.

This vitamin contributes to the growth and repair of skin tissue and cellular metabolism. Its positive effect on the skin’s immune system helps to destroy free radicals that can cause premature aging.

That is why many manufacturers of cosmetic products and even dermatologists use and prescribe this vitamin in night creams and moisturizers to improve your skin and give it a clearer and bright appearance.

Vitamin D toxicity

Vitamin D toxicity is rare but can cause serious side effects. It occurs when your body accumulates excessive amounts of it.

The U.S. Recommended Dietary Allowance (RDA) a day for adults is 600 IU  of vitamin D a day. Its toxicity usually occurs due to taking large doses of its supplements.

If you take 60,000 international units (IU) of this vitamin a day through supplements for several months, you can develop its toxicity.

Its toxicity does not occur due to excessive exposure to sunlight or eating too much of its food.

That’s because your body controls the amount of vitamin D it produces from sunlight. Foods and even fortified foods don’t contain that large amounts to cause toxicity.

Its toxicity leads to an excessive buildup of calcium in your blood. This is called hypercalcemia.

It can cause nausea and vomiting, weakness, and increased frequency of urination. Later you may experience bone pain and the formation of kidney stones (calcium stones).

Treatment of vitamin D toxicity includes completely stopping its intake and restricting foods that contain calcium.

You may be given intravenous fluids and meds such as corticosteroids or bisphosphonates.

To prevent vitamin D toxicity you should undergo the vitamin D test to monitor its blood levels when you are taking high doses of its supplements for its deficiency.