Vitamin D

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Overview

Vitamin D is a fat soluble vitamin, which is essential for life. Unlike other vitamins, it can be produced by our body. The skin synthesizes it with the help of ultra violet radiation from the sun. This is the main source of vitamin D for our body. Only few foods have vitamin D in considerable amounts. Our body has the ability to store this vitamin for longer periods of  time.

Functions of vitamin D.

Strong bones and teeth: The main benefit of vitamin D is maintaining calcium balance in the body. calcium is a mineral mainly found in bones and teeth. It gives strength. vitamin D is essential for the absorption of calcium from the digestive system. In addition, it helps deposit calcium and phosphate into the bones and teeth. Adequate levels of vitamin D help prevent rickets in children and osteomalacia  in adults. Furthermore, it  help reduce the incidence of osteoporosis. So one of the main benefits is strengthening our bones and teeth.


Helps boost immunity: Vitamin D help increase the efficiency of immune system, which protects our body from harmful pathogens such as bacteria and viruses. Low levels of vitamin D is associated with increased incidence of infections.

Prevents cancer: Vitamin D may help reduce the risk of developing cancer. Scientific studies of the association between vitamin D and the risk of cancer have provided some indications that high levels of intake are associated with reduced risk of colo-rectal cancer.

Regulates blood pressure: Vitamin D plays an important role in regulating our blood pressure. This is achieved through inhibition of renin angiotensin mechanism. Vitamin D deficiency has been shown to be a risk factor for developing hypertension in many studies.

Other benefits of vitamin D:

• It regulates the metabolism of insulin. By this mechanism, vitamin D lowers the risk of type 2 diabetes.
• It reduces the risk of multiple sclerosis, which is rare in tropical countries where there is much more sunlight.
• It protects from low levels of ionizing radiation.
• It stabilizes our mood, and boost our memory later in life.
• Helps prevent muscle pain and muscle weakness.
• Reduces chronic fatigue.
• Lowers inflammation in the body.
• It may help reduce overweight and obesity.
• It helps maintain healthy skin and healthy hair.
• It has been shown to reduce the risk of developing rheumatoid arthritis and other auto immune diseases.

Note: Some of the benefits from vitamin D are yet to be proven by scientific research. However, taking adequate amounts of vitamin D does not cause any harm.

Food sources of vitamin D.

Vitamin D is naturally found only in few foods, however, our body can produce adequate amounts with the help of ultra-violet rays from the sun. Many people are scared about the skin cancer risk of these rays. So, how can we get the vitamin D from foods?
Fortunately some food contain significant amounts of vitamin D. Here are some examples;

Oily fish.

Fish such as salmon, mackerel and tuna are good sources of vitamin D. 100 grams of salmon flesh have about 500 IU.

Eat these fishes at least three to four times a week to get adequate amounts. In addition these fish contain high amounts of omega 3 fatty acids.
Other fishes that contain high amount of vitamin D are; cat fish, sardines, eels and herrings.

Fortified foods.

Hence very few natural foods contain vitamin D; it is artificially added to several foods. Almost all milk products are fortified with vitamin D in many countries including the USA and Canada. Some other fortified foods available in the markets are; margarine, breakfast cereals and orange juice.

Cod liver oil.

Cod liver oil is taken as a supplement, which contain very high amount of vitamin D and vitamin A, both can cause toxic effects in high doses. So, taking too much fish oil is not recommended.

Many people think that eggs have high amounts of vit D, but that is not true. One whole egg has only 20-25 IU, which is about 4% of the daily requirement.

Vitamin D from the Sun.

You can get vitamin D from the sun free of charge. Most people are able to produce adequate amounts of vitamin D from exposure to sunlight. It is responsible for up to 90 percent of vitamin D requirements. However, some people may find it difficult to balance healthy vitamin D levels against the well known risk of skin cancer.

I will tell you the safe way of getting free vitamin D from the sun. The only needed thing is safe sun exposure.

Only a small amount of sunlight is needed to maintain healthy vitamin D levels. For most people, being outdoors for 5-10 minutes three times a week in sunny days is sufficient.

People with dark skin need more sun exposure to produce enough vitamin D. Similarly, elderly people also require more sun exposure to achieve adequate levels of vitamin D.

Vitamin D is produced in ideal quantities when the skin is exposed to low levels of sunlight. Over exposure does not increase the production, instead it will cause harmful effects on the skin.

Once adequate vitamin D has been produced, it is stored in the body tissue. Our kidneys activate the vitamin into usable form.

Safe ways to get vitamin D from the sun.

• Expose to sunlight for 5-10 minutes at least three times a week.
• Prolonged sunlight exposure does not increase vitamin D levels. Instead, it will increase the risk of long term skin damage.
• If you have dark skin, you need more time in the sun to produce adequate levels. One good news is; prolong exposure would not affect your skin much.
• Sunscreen creams block useful sunlight from penetrating the skin, thus prevent vitamin D synthesis.
• The UVB rays of natural sunlight cannot penetrate glass. So you cannot produce vitamin D when sitting in your car or inside your home.
• Only few foods have vitamin D in considerable amounts. You cannot get enough from foods alone. Exposure to sun is the only reliable way.
• If you cannot go out in the sun, you should take a vitamin D supplement, specially in the winter months.
• Exposure to sun between 11am and 3pm should be avoided.
• Vitamin D is the only nutrient that is available free of charge. So get it from the nature. At the same time remember to practice "safe sun exposure."

Vitamin D deficiency.

Vitamin D deficiency in children causes rickets, which is a common disease in many developing countries. Children who are affected by severe malnutrition are more prone to get this disease. Osteomalacia is a similar illness occurring in adults due to the lack of vit D.


The following people are at risk of developing vitamin D deficiency.

• Exclusively breast-fed infants.
• People with fat mal-absorption syndrome.
• Severely malnourished people.
• People who live in extreme latitudes, because less amount of vitamin D production from the sun.
• People suffering from celiac disease.
• Black skinned people.
• Bed ridden people.

Vit D is important for the growth and strength of bones. It helps deposit calcium and phosphate in the bone and teeth. So, lack of this vitamin mostly affects these structures.

Symptoms and signs.

• Bone pain and tenderness mainly in arms, legs, and spine.
• Back pain.
• Bone deformities such as bowlegs, skull deformities, bumps in the ribs, pigeon chest, and scoliosis (abnormal spinal curvature).
• Increased incidents of bone fractures.
• Impaired growth and short stature in children.
• Tooth deformities.
• Decreased muscle strength.

How vitamin D deficiency is treated?

Replacing vitamin D, calcium and phosphate is the main mode of treatment. Vit D is usually replaced with supplements such as fish oil. It should be noted that very high doses of commercial supplements may cause vitamin d toxicity.

Children with rickets should be encouraged to eat foods containing vitamin D such as oily fish.

Vitamin D toxicity.

Vitamin D toxicity is an uncommon condition where too much vitamin D is found in the blood. It occurs as a result of consumption of large doses of commercial supplements such as fish oil for long period of time.


As vit D is fat soluble, it can't be excreted through the kidneys. Because of that excess amounts consumed are stored in our body and causes vitamin d toxicity symptoms.

Over exposure to sun does not cause hypervitaminosis D, because our body has built in feedback mechanism that prevents excessive production of vitamin D. However high level of sun exposure should be avoided, because ultra violet (UV) rays will harm your skin and may lead to skin cancer.


Very few foods naturally contain vitamin D in considerable concentrations, so it is unlikely to develop toxicity by consuming these foods.

The recommended daily intake of vit D is 600-800 IU (international units). Consumption of just more than this amount does not cause poisoning. If you take very high doses such as 5000IU three times a day for few weeks or months, you will develop toxic symptoms.

Symptoms and signs.

Vit D plays an important role in calcium absorption, deposition, and excretion. So excess amounts of this vitamin brings our calcium level up. The clinical features are mainly due to increased calcium level in the blood (Hypercalcemia).

• Poor apatite, nausea and vomiting.
• Constipation.
• Weigh loss and weakness.
• Confusion.
• Peri-oral numbness.
• Cardiac arrhythmia.

How vitamin D toxicity is detected. 

Blood level of 25-hydroxy vitamin D is measured to detect overdose or deficiency. After four hours of fasting, the blood is drown from a vein in the arm. After that it is analyzed in the laboratory. The normal range is 30-70 nano grams per milliliter (ng/ml).

Many commercial supplements contain more than the required amount. For example;
Medicinal nutraceutics - high potency vitamin D - 5000IU.
Country life dry vitamin D - 1000IU.
Source naturals vitamin D3 - 1000IU.
Swanson premium high potency vitamin D3 - 1000IU

So, it is important to consult a health care professional before taking the high potency vitamin supplements because of the risk of toxicity.