Written by Dr. Sanjana V.B Bhms,dbrm,cdn

Founder & medical director of siahmsr wellness.in

Reviewed by SIAHMSR

all rights reserved with siahmsr digital healthcare[siahmsr wellness]

  Vitamin D is a fat-soluble vitamin that helps the body in absorbing and retaining calcium and phosphorus and help in maintaining bone health.This vitamin is also known as" sunshine vitamin" as it is formed in the skin by the ultraviolet rays of sun. The precursor for it is the UV activated dehydrocholesterol of skin. Vitamin D3 can be formed when a chemical reaction occurs on human skin, when a steroid called 7-dehydrocholesterol is broken down by the sun’s UVB light. 

Vitamin D production in the skin is the primary natural source of vitamin D. However, it has been found that many people have insufficient levels of vitamin D as they live in places where sunlight is limited in winter or they spend much of their time indoors.

   People with darker skin tend to have lower blood levels of vitamin D, as the pigment melanin of skin acts like a shade, reducing production of vitamin D.

 Vitamin D also can be obtained from dietary sources also. Butter, egg yolk, oily fish, oysters etc. 

Sources of Vitamin D

Cod liver oil

Salmon

Swordfish

Tuna fish

Sardines

Mackerel

Blue fish

Cat fish

Oysters

Beef liver

Egg yolk

Orange juice fortified with vitamin D

Dairy and plant milks fortified with vitamin D

Fortified cereals.

RDA- The Recommended Dietary Allowance of vitamin D 

 For adults [19 years and older] is 600 IU (15 mcg) daily

 for men and women, and for adults >70 years it is 800 IU (20 mcg) daily.

Health benefits of vitamin D

Bone health

·        Vitamin D may prevent osteoporotic fractures of old age. Several studies have found that low vitamin D blood levels  are linked with an increased risk of fractures in elderly people. Some studies suggest that vitamin D supplementation in certain amounts may prevent such fractures, while others do not support it.

     Anti cancer effect

·        Vitamin D can also reduce cancer cell growth, as it helps to control infections and reduce inflammation.

·        Vitamin D improves survival rate in cancer patients. Although vitamin D does not seem to be a major factor in reducing the occurrence of cancers some studies suggest that having higher vitamin D status may improve survival if one develops cancer.

      Cardiovascular health

·        Vitamin D helps in improving cardiovascular health and control hypertension. Immune and inflammatory cells that play a role in cardiovascular disease conditions like atherosclerosis are regulated by vitamin D.  The vitamin also helps to keep arteries flexible and relaxed, which in turn helps to control high blood pressure.

      Reduce type 2diabetes

·        Vitamin D has some role in type 2 diabetes. Prospective observational studies have shown that higher vitamin D blood levels are associated with lower rates of Type2 Diabetes.

      In Multiple sclerosis   

      In multiple sclerosis [MS], a person’s genetic background plus environmental factors including inadequate vitamin D and UVB exposure have been identified to increase the risk . Several clinical trials are ongoing to examine the role of vitamin D supplementation as an adjuvant treatment option in persons with MS.

      The current evidence suggests that low vitamin D may have a causative role in MS and if so, approximately 40% of cases of multiple sclerosis may be prevented by correcting vitamin D insufficiency.  This conclusion has been strengthened by the recent evidence that genetically determined low levels of vitamin D can predict higher risk of multiple sclerosis.

      Reduces respiratory infections

·        Children who have vitamin D-deficiency rickets are more likely to get respiratory infections, while children exposed to sunlight are less prone to respiratory infections.

·        Many organs and tissues of the body have receptors for vitamin D, which suggest  some other vital roles for this vitamin beyond bone health, and extensive researches are going on in this regard.

         Several case-control studies, when analyzed together, suggest that people diagnosed with tuberculosis have lower vitamin D levels than healthy people of similar age and other characteristics. However extensive studies are needed in this re

Vitamin D supplements

    Some foods like oily fish, oysters, eggs, liver etc. naturally contain vitamin D, and some foods are fortified with the vitamin D.

Vitamin D levels are lowest in the winter months and in those who spend much of their time indoors  even in sunny days. Vitamin D is not present in all vegetable foods. So pure vegans with no varied dietary choices may be deficient in vitamin D. For these people the best way to get enough vitamin D is taking a supplement because it is hard to consume enough through food.

     If you purchase vitamin D supplements, vitamin D2 and vitamin D3 forms are available. Vitamin D2 is made from plants and is found in fortified foods and some supplements.

Vitamin D3 is also naturally produced in the human body and is found in animal foods. Vitamin D3 can be formed when a chemical reaction occurs in human skin, when a steroid called 7-dehydrocholesterol is broken down by the sun’s UVB light.

Risk factors for the occurrence of vitamin D deficiency

  Poor exposure to sun-

 The following are conditions that decrease exposure to UVB light and therefore lessen vitamin D absorption:

·        Use of sunscreen; correctly applied sunscreen can reduce vitamin D absorption by more than 90%.

·        Wearing fully covered garments which do not expose the skin to sunlight.

·        Spending the time only in indoors and hence limited exposure to sunlight.

·        Darker skin tones having higher amounts of the pigment melanin, which acts as a type of natural sunscreen.

      Old age-

·        Older age groups are at risk. During old age, there is a decrease in 7-dehydrocholesterol levels.

·        Certain seasons like winter and living in northern latitudes above the equator where UVB light is weaker.

      Gastrointestinal diseases-

·        Vitamin D deficiency may occur from poor dietary intake, poor absorption, or having a metabolic need for higher amounts. People with inflammatory bowel disease (ulcerative colitis, Crohn’s disease) or other conditions gastrointestinal tract surgeries that disrupt the normal digestion of fat.  Vitamin D is a fat-soluble vitamin that depends on the ability of intestines[gut] to absorb dietary fat.

      Obesity

·        People who are obese tend to have lower blood vitamin D levels. Vitamin D accumulates in excess fat tissues but is not readily available for the use of the body. Higher doses of vitamin D supplementation may be needed to achieve adequate levels in these people.  Blood levels of vitamin D may rise when obese people start losing weight.

 Vitamin D deficiency & diseases:

v Rickets:

Vitamin D deficiency may eventually lead to a condition of soft bones and skeletal deformities in infants and children. It is due to failure of bone tissues to harden.

v Osteomalacia:

It is a condition of weak and softened bones in adults as a result of vitamin D deficiency that can be reversed with supplementation.

Vitamin D toxicity from supplement over dosage

Vitamin D toxicity most often occurs from taking excess of supplements for a prolonged period of time.

The low amounts of the vitamin found in food may not reach a toxic level. Similarly, a high amount of sun exposure does not lead to toxicity because excess heat on the skin prevents D3 from forming. However excessive UV rays of sunlight is not good for skin owing to the risk of skin cancers.

It is advised not  to take daily vitamin D supplements containing more than 4,000 IU unless monitored under the supervision of your doctor.

Symptoms of toxicity are:

Loss of appetite, weight loss, irregular heartbeat

Hardening of blood vessels and tissues due to increased blood levels of calcium, potentially leading to damage of the heart and kidneys

REFERENCES

https://www.thieme-connect.com/products/ejournals/abstract/10.1055/s-0036-1579693

https://www.hsph.harvard.edu/nutritionsource/vitamin-d/

https://pubmed.ncbi.nlm.nih.gov/10985437/

https://academic.oup.com/ageing/article/29/4/301/10120?login=false