Power of Vitamin D for Optimal Health

Vitamin D is not only a fat soluble vitamin, but is also a ‘Hormone’ which plays a vital role in metabolism.

Role of Vitamin D in human body

• It promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable Normal Bone Mineralization.
• It is important for bone growth and bone remodeling by osteoblasts and osteoclasts
• It assists in reducing inflammation
• It assists in modulation of the processes such as cell growth, neuromuscular & immune function, and glucose metabolism
• It helps with modulation of various gene-encoding proteins that regulate cell proliferation, differentiation and apoptosis.

Sources 

1. It is produced endogenously by UV-B (Ultraviolet-B) rays in sunlight. Criteria to make Vitamin D from sunlight: 
   Criterion 1 - Sunlight should have optimum amount of UVB Rays 
   (However, due to environmental pollution, the UV-B rays are being absorbed by the Ozone layer and they don’t reach us as effectively as they used to.)

    Criterion 2 - Sunlight should fall on skin at a particular angle, during a particular duration of the day, for a particular amount of time, and the skin should have optimum amount of melanin. (Indians have high melanin content in our skin which prevents Vitamin D synthesis even if other criteria are matched.)

2. Dietary Sources: Milk, milk products, flesh of fatty fish (such as trout, salmon, tuna, and mackerel). (However, it’s not possible to get enough Vitamin D from only food to match the body’s demands. Hence, Vitamin D fortified food and supplements are needed to maintain Vitamin D level in the body.)

Vitamin D process in the body

Vitamin D obtained from sun exposure, foods, and supplements is biologically inert and must undergo two hydroxylations in the body for activation.

• The first hydroxylation which occurs in the liver, converts Vitamin D to 25-hydroxyvitamin D [25(OH)D], also known as calcidiol.
• The second hydroxylation occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D [1,25(OH)2D], also known as calcitriol.

Hence, patients with chronic kidney disease need an active form of Vitamin D supplements.

Difference between D2, D3 and Vitamin D

• In foods and dietary supplements, Vitamin D has two main forms, D2 (ergocalciferol) and D3 (cholecalciferol), with some difference in their chemical structures.
• Both forms are well absorbed in the small intestine. Absorption occurs by simple passive diffusion and by a mechanism that involves intestinal membrane carrier proteins.
• But because Vitamin D is a fat soluble vitamin, the concurrent presence of fat in the gut enhances vitamin D absorption, but some Vitamin D is absorbed even without dietary fat.
• Neither aging nor obesity alters Vitamin D absorption from the gut.

Global Burden of Vitamin D Deficiency

Various research data suggests global prevalence of Vitamin D deficiency as high as 49%. Due to unavailability of meta-analysis, it is estimated that in India, prevalence is as high as 76%.

Groups at risk of Vitamin D Deficiency

• Breastfed infants
• Older adults
• People with limited sun exposure
• People with dark skin
• People with conditions that limit fat absorption
• People with obesity or who have undergone gastric bypass surgery (Bariatric Surgery)

In recent years, accumulating epidemiological and laboratory evidence has documented that 25 (OH)D deficiency is correlated to the onset and progression of many chronic diseases.

1) Vitamin D and Heart Health

Vitamin D helps regulate the renin-angiotensin-aldosterone system (and thereby blood pressure), vascular cell growth, and inflammatory and fibrotic pathways. Vitamin D deficiency is associated with vascular dysfunction, arterial stiffening, left ventricular hypertrophy, and hyperlipidemia. For these reasons, vitamin D has been linked to heart health and risk of CVD.

2) Vitamin D and Diabetes Mellitus

Vitamin D plays a role in glucose metabolism. It stimulates insulin secretion via the vitamin D receptor on pancreatic beta cells and reduces peripheral insulin resistance through vitamin D receptors in the muscles and liver.

3) Vitamin D and Cancer

Vitamin D binding protein (VDBP) as a carrier of Vitamin D can be combined with Vitamin D and its metabolites to play a crucial role in transport to the cell. Deficiency in VDBP also affects the function of Vitamin D. For example, studies have demonstrated that low level of VDBP is related to a variety of malignant tumors, including breast, prostate and colorectal.  Both prospective and retrospective epidemiologic studies indicate that levels of 25(OH)D below 20 ng/ml are associated with a 30 to 50% increased risk of incident colon, prostate, and breast cancer, along with higher mortality from these cancers.

4) Vitamin D and Multiple Sclerosis

Many epidemiological and genetic studies have shown an association between MS and low 25(OH)D levels before and after the disease begins. Observational studies suggest that adequate Vitamin D levels might reduce the risk of contracting MS and, once MS is present, decrease the risk of relapse and slow the disease’s progression.

Laboratory Tests

• Serum concentration of 25(OH)D is currently the main indicator of Vitamin D status. (It reflects vitamin D produced endogenously and that obtained from foods and supplements)
• Serum concentrations of 25(OH)D are reported in both nanomoles per liter (nmol/L) and nanograms per milliliter (ng/mL). One nmol/L is equal to 0.4 ng/mL, and 1 ng/mL is equal to 2.5 nmol/L.

Daily requirement of Vitamin D

One should always check Vitamin D level before starting with the medication. If no report is available, it is advisable to start with 4000 IU/day in adults. In India, 60,000 IU tablets/liquids are available so one can take those medicines twice a month after discussing with your healthcare provider.

If you're seeking expert advice regarding Vitamin D deficiency and related effects, Dr. Gaurangi Shah, Consultant - General Medicine,  P. D. Hinduja Hospital & Medical Research Centre in Mahim, Mumbai can guide you. To book an appointment, please contact the hospital at the following phone numbers: 022 6766 8181 /022 4510 8181.