Vitamin D (calciferol) is a vitamin, produced in body on exposure to the sunlight. It is a fat soluble vitamin that is stored in the body. It is found in very few foods naturally such as fish-liver oils, cod liver oil, fatty fish, mushrooms, egg yolks, and liver. Fortified milk products and other fortified foods such as breakfast cereals and orange juice also contain D vitamin. This vitamin is essential for strong and healthy bones and good overall health.
When our skin comes in direct contact with sun, vitamin D is produced using ultraviolet B (UVB) rays. This is sent to the liver where it is changed into 25(OH) D or 25-hydroxy vitamin D. From here, this chemical is sent all over body where different tissues, including kidney, turn it into activated vitamin D. The 25-hydroxy vitamin D, which is circulating in blood is measured by blood test to know the level of vitamin D in body. Low level means vitamin deficiency and must be treated using injections or supplements for proper functioning of body and prevention of certain diseases.
Vitamin D is must for absorption of calcium obtained from the food and supplements. Its deficiency causes weak, brittle and soft bones. It is used for preventing and treating rickets, weak bones (osteoporosis) and bone pain (osteomalacia). Vitamin D is also required for proper functioning of muscles, heart, lungs, brain and immune system.
Functions of Vitamin D in body
The major function of Vitamin D in body is to maintain serum calcium and phosphorus concentrations within the normal range by enhancing the efficiency of the small intestine to absorb these minerals from the diet.
- It is required for bone health.
- It improves body immunity against infections.
- It is required by muscles, nerves for proper functioning.
- It helps to regulate level of calcium and phosphorous levels in the body.
- It is required for healthy heart and blood circulation.
- It affects brain functions.
Sources of Vitamin D
Sunlight: The best source of Vitamin D is sunshine. Our body makes vitamin D when skin is directly exposed to the sun. Skin produces more vitamin D if it exposed to sun, during the middle of the day.
The ultraviolet B rays are required for synthesis of vitamin D. During the early and later parts of the day and during most of the day in the winter season the UVB rays are blocked by the earth's atmosphere. So during this period lesser vitamin D is produced on exposure to sun. Similarly, more vitamin D will be produced at the places near to equator.
There should be direct exposure to sunlight. Sun light coming through glass, window, and through other medium will not produce vitamin D.
Food items: Few food items such as fish-liver oils, cod liver oil, fatty fish, mushrooms, egg yolks, liver and fortified food items contain Vitamin D.
Supplements: In market various Vitamin D supplements are also available in two different forms;D2 (ergocalciferol) and D3 (cholecalciferol). Both increase vitamin D in the blood.
D2 originates from the yeast and plant sterol, and D3 originates from 7-dehydrocholesterol, a precursor of cholesterol, when synthesized in the skin.
Vitamin D Deficiency
It is very common today to suffer from vitamin D deficiency. Most of the time people protect themselves from direct exposure to sun by covering, using umbrella or applying sunscreens. Due to work timings, many people find it difficult to go outside during day time. Increasing pollution, lack of proper house designs, development of high-rises has further contributed to this condition.
For measuring the level of vitamin D in body 25-hydroxy vitamin D blood test is performed. In kidney, 25-hydroxy vitamin D Serum 25(OH) D, changes into vitamin D. Vitamin D is measured as nanograms per milliliter (ng/mL) or nanomoles per liter (nmol/L), where 1 nmol/L= 0.4 ng/mL.
Levels below 30 nmol/L (12 ng/mL) are too low and levels above 125 nmol/L (50 ng/mL) are too high. Levels of 50 nmol/L or above (20 ng/mL or above) are sufficient for most people.
Vitamin D deficiency affects overall health. It causes weak bones. Lack of vitamin D makes body susceptible to certain disorders. It can become reason for development of diabetes, Bone disorders, osteoporosis, fractures, hypertension, Alzheimer’s and autoimmune conditions such as multiple sclerosis.
Vitamin D deficiency can be due to
- Lack of exposure to sunlight
- Lack of enough vitamin D in the diet
- Liver and kidney diseases
- Poor food absorption
- Use of certain medicines, including phenytoin, phenobarbital, and rifampin
Risk groups(People who can develop vitamin D deficiency)
- The risk to suffer vitamin D deficiency is higher is certain peoples.
- People who work indoor most of times and lack direct exposure to sun
- People avoiding direct sun exposure using clothes, scarf, sunscreen etc.
- Old people (due to unabilty to produce vitamin D efficienty when exposed to sun)
- Breastfed infants (Mother's milk does not contain enough vitamin D)
- Dark skin people
- Certain medical condition (Crohn's disease or celiac disease)
- Obesity (fat obstructs absorption of vitamin D)
Symptoms of vitamin D deficiency
There is no specific symptom that indicate vitamin D deficiency. The symptoms are sometimes vague. Many people have no symptoms. But in severe and chronic cases deformation of bones and fracture can occur.
Few symptoms of vitamin D deficiency include the following
- Muscle cramps, Irritability
- Soft skull or leg bones curved legs/bow-legged
- Rickets, Poor growth
- Delayed walking, delayed teething
- Seizures and breathing difficulties
- Recurrent infections
- Pain in bones, typically in the ribs, hips, pelvis, thighs and feet
- Pain in muscles
- Muscles weakness
- Tiredness and general aches and pains
- Profuse sweating, restlessness
- Muscle twitching (small, local, involuntary muscle contraction and relaxation which may be visible under the skin)
- Difficulty in walking, climbing stairs
- Headaches, migraine, Brain disorders, mood disorders, depression
- Impaired cognitive function, Lack of concentration, dementia, memory disorders
- Anxiety, low morale
- Hair loss, bald patches
- Dental problems, weak teeth
- Sensation of dizziness
- Erectile dysfunction
- Enlargement of wrists, ankles, pigeon breast
- Psoriasis, diabetes
- High blood pressure, cardiovascular disease
- Recurrent infections of respiratory tract
- Constipation or diarrhea
Treatment for vitamin D deficiency
Vitamin D deficiency is treated by taking vitamin D supplements, in form of ergocalciferol or calciferol or injections. Supplements of different strengths are available are taken either daily, weekly or monthly depending onn condition.
Vitamin D deficiency in adults is treated with 10 000 IU calciferol daily or 60 000 IU weekly for 8-12 weeks. Alternatively, 300 000 IU to 600 000 IU can be given orally or by injection, once or twice.
Treatment of vitamin D deficiency in children depends on the child's age. Under six months, 3000 IU calciferol per day is used for 8-12 weeks. In children over six months, 6000 IU is used daily, for the same length oftime. In children over one year, 300 000 IU tends to be given as a single one-offdose.
For Maintenance therapy after deficiency has been treated, adults need 1000-2000 IU calciferol daily or 10 000 IU weekly, Children under six months need 200-400 IU per day and over six months need 400-800 IU per day.
Daily requirement of Vitamin D
Per day requirement of Viamin D in body depends on age.
- Birth to 12 months:400 IU (international units)
- Children 1–13 years:600 IU
- Teens 14–18 years:600 IU
- Adults 19–70 years:600 IU
- Adults 71 years and older:800 IU
- Pregnant and breastfeeding women:600 IU
Upper limit of Vitamin D
Overuse/overdose of supplements can cause too high level of vitamin d in blood. Excessive sun exposure doesn't cause vitamin D poisoning because the body limits the amount of this vitamin it produces. Too high level of vitamin D in blood causes nausea, vomiting, poor appetite, constipation, weakness, weight loss, Hardening of the arteries, and damage to kidney.
Upper limit of Vitamin D for infants:1, 000 to 1, 500 IU/day
Upper limit of Vitamin D for children 1-8 years:2, 500 to 3, 000 IU/day
Upper limit of Vitamin D for children 9 years and older, adults, and pregnant and lactating teens and women:4, 000 IU/day.