Catch some rays

Catch some rays

Vitamin D is the only nutrient our body produces when exposed to sunlight, get some sunshine, writes Shalini Chakraborty

Vitamin D is unique because it can be made in the skin from exposure to sunlight. Vitamin D is a fat-soluble prohormone that was identified after the discovery of the anti-rachitic effect of cod liver oil in the early part of the 20th century. The two major biological precursors of vitamin D are vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol). Vitamin D3 is formed when the skin is exposed to solar ultraviolet rays. In a heat-dependent process, previtamin D3 is immediately converted to vitamin D. Vitamin D2 is plant-derived, produced exogenously by irradiation of ergosterol, and enters the circulation through diet.


Humans usually obtain vitamin D through dietary intake and exposure to sunlight. Very few foods naturally contain vitamin D. Oily fish such as salmon, mackerel, and sardines are rich in vitamin D3. Egg yolks reportedly contain vitamin D but the amounts are highly variable. Moreover, the cholesterol content of egg yolks makes it a poor source of vitamin D. Also, a small number of foods are fortified with vitamin D such as milk, orange juice, and some bread and cereals. Why is vitamin D so important? Vitamin D is one of many vitamins our body needs to stay healthy and it has many functions:

Keeping bones strong: Having healthy bones protects from various conditions — osteomalacia, osteoporosis including rickets. Rickets is a disorder that causes children to have weak and fragile bones. It is caused by low vitamin D, which is needed for the absorption of calcium and phosphorus in the body. In adults, having soft bones due to lack of absorption of calcium is a condition called Osteomalacia. Weak or soft bones can lead to osteoporosis, and a loss of bone density can lead to fractures. Vitamin D either taken orally or through a diet or supplement or from sunshine exposure, then converts to an active form of the vitamin. The active form promotes optimal absorption of calcium from the diet.

Working with parathyroid glands: The parathyroid glands work towards balancing the calcium in the blood by communicating with the kidneys, gut, and skeleton. When there is sufficient calcium in the diet and sufficient active Vitamin D, dietary calcium is absorbed and put to good use throughout the body. If calcium intake is insufficient or vitamin D is low, the parathyroid glands will ‘borrow’ calcium from the skeleton in order to keep the blood calcium in the normal range. 

Effects of vitamin D deficiency

Getting enough vitamin D protects against the following conditions:

Bone diseases such as osteoporosis or rickets

Heart disease and high blood pressure


Infections and immune system disorders

Falls in older people

Some types of cancer, such as colon, prostate, and breast cancers

Multiple sclerosis

Signs & symptoms of deficiency

Severe lack of vitamin D causes incorrect growth patterns, delayed mental development in children apart from weakness in muscles, pain in bones, and deformities in joints. Lack of vitamin D is not quite as obvious in adults. Signs and symptoms include:


Bone pain

Muscle weakness, muscle aches, or muscle cramps

Mood changes, like depression

Vitamin D in pregnancy & neonates: Vitamin D helps in promoting insulin action and secretion, immune modulation, and lung development. It, therefore, has the potential to influence many factors in the developing foetus.

The requirement for vitamin D in expecting and lactating women is up to 6000 iu/day.

Pre-eclampsia and neonatal hypocalcaemia are the most prevalent complications of maternal hypocalcaemia and are clearly associated with substantial morbidity. Maternal vitamin D level is also associated with fetal bone and lung development, and neonatal immune conditions such as asthma.

Maternal & fetal complications due to low vitamin D levels in the body lead to:


Low birth weight

Impaired glucose intolerance in pregnancy

Neonatal hypocalcaemic seizure

Impaired skeletal growth & development for neonates

Foetus lung development & childhood immune disorder

Treatment of vitamin D deficiency in women and vitamin D supplementation is safe and is recommended for all women who are pregnant or breastfeeding.
(The author is a nutritionist.)