Vitamin D is necessary for proper bone and teeth formation and for the healthy functioning of the thyroid gland. It assists in the assimilation of calcium, phosphorus and other minerals from the digestive tract. This vitamin is found in the rays of the sun, fish,milk, eggs, butter and sprouted seeds. A deficiency can cause gross deformation of bones and severe tooth decay.

The recommended daily allowance of this vitamin for both adults and children is 400 to 500 international units. Therepeutically, upto 4,000 to 5,000 units a day for adult or half of this for children, is a safe dose, if taken for not longer than one month. It is beneficial in the treatment of muscular fatigue, constipation and nervousness. It can be toxic if taken in excessive doses, especially for children. Signs of toxicity are unusual thirst, sore eyes, itching skin, vomiting, diarrhoea, urinary urgency, abnormal calcium deposits in blood vessel walls, liver, lungs, kidneys and stomach.
Vitamin D is also referred to as calciferol and can rightly be called the sunshine vitamin, since the body, in a sunny climate can manufacture this nutrient from sunshine on your skin using cholesterol from your body to do so.
Please remember that this can be achieved in about 30 minutes by fair skinned people, while dark skinned people, because of the pigmentation need about 3 hours to reach the same level of manufacture. The sunlight needed for this process is pure unfiltered sunlight.

Vitamin D is required for

Vitamin D helps with increasing the absorption of calcium, assists in bone growth and the integrity of bone and promotes strong teeth.

It also helps regulate the amount of phosphorus in the body as well as assisting in a healthy heart and nervous system. In some recent studies it has also shown great promise in assisting psoriasis, the immune system, thyroid function as well as normal blood clotting.

Deficiency of vitamin D

A shortage can lead to softening of the bone and muscle twitching and convulsions, and in children it causes rickets - resulting in bent legs. In adults, the shortage causes loss of minerals from the bones, (osteomalacia) where the bones are sore, tender, and weak muscles with the possibility of deafness developing. In older people, osteoporosis may appear when protein is also lost from the bone. Vitamin D in short supply is also linked to having a burning sensation in the mouth and throat, diarrhea, insomnia and visual problems.

Dosage

The dosage underneath is the Recommended Dietary Allowance (RDA), but be aware that this dosage is the minimum that you require per day, to ward off serious deficiency of this particular nutrient. In the therapeutic use of this nutrient, the dosage is usually increased considerably, but the toxicity level must be kept in mind.
Male 400 iu, female 400 iu.

Toxicity and symptoms of high intake

Some clinical guidelines for toxicity are sometimes set as 5,000 to 10,000 iu per day to cause toxicity, but other researchers place the value much higher to reach toxicity. You are however advised to keep your supplement intake to no more than 600 iu per day. Having too much vitamin D in your system could leave a too elevated calcium level, a lower appetite, increased thirst, nausea, vomiting, drowsiness, abdominal pain. A long-term effect of too much vitamin D is the deposit of calcium in soft tissues of the body including the blood vessel walls and kidneys where it can cause serious damage.

Best used with

Check to have vitamin A around this vitamin as well as calcium and phosphorus.

When more may be required

When you are very seldom exposed to sunlight, or if you always wear sunscreens with a SPF factor higher than 8, you might need extra vitamin D. This is also the case if you are on a strict vegan diet and older people are also advised to check their level of vitamin D. People with compromised kidneys or liver are at risk of too little of this vitamin, since the kidneys and liver are required to activate this vitamin in processes taking place in those organs.

Other interesting points

Vitamin D is also classified as a hormone by certain people.

Food sources of vitamin D

Vitamin D is present in fatty fish like kipper, sardines, salmon, tuna and mackerel, liver, egg yolk and butter. Smaller amounts are also present in dark leafy vegetables.