With so much chatter around vitamin D and its importance, it is a good idea to know a bit more about the 'sunshine vitamin'. Vitamin D is a group of fat-soluble prohormones which were identified after the discovery of the anti-rachitic effect of cod liver oil in the early part of the 20th century. The two major biologically 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.
Vitamin D Sources
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 are reported to contain vitamin D though 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 bodies need to stay healthy. This vitamin has many functions, including:
- 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 absorption of calcium and phosphorus in 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, the loss of bone density which can lead to fractures. Vitamin D either taken orally through diet or supplement or from sunshine exposure, then converted to an active form of the vitamin. The active form promotes optimal absorption of calcium from diet.
- Working with parathyroid glands: The parathyroid glands help balance 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.
The health effects of vitamin D deficiency
Vitamin D plays a vital role in managing overall health and protecting against the following conditions and possibly helping to treat them. These conditions may include:
- 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 and symptoms of vitamin D deficiency
Studies have shown that severe lack of vitamin D causes in children as incorrect growth patterns, delayed mental development, weakness in muscles, pain in bones and deformities in joints.
Signs and symptoms among adults might 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 fetus.
It is recommended that 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, neonatal immune conditions such as asthma.
Maternal & fetal complications due to low vitamin D levels in body include:
- Low Birth weight
- Impaired glucose intolerance in pregnancy
- Neonatal hypocalcaemic seizure
- Impaired skeletal growth & development for neonates
- Fetus lung development & childhood immune disorder
Treatment of vitamin D deficient women and vitamin D supplementation is safe and is recommended for all women who are pregnant or breastfeeding. Low vitamin D concentrations have been associated with a wide range of adverse maternal and offspring health outcomes.
About Author: Shalini Chakraborty is Sr. Executive Nutritionist, Cloudnine Group of Hospitals , Bengaluru (Old Air Port Road)
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