Vitamin D supplementation

 BASICS

• Vitamin D3 is also called cholecalciferol.
• Vitamin D2 is also called ergocalciferol.
• 25 hydroxycholecalciferol is abbreviated as 25(OH)D.
• 1,25 dihydroxycholecalciferol is abbreviated as 1,25(OH)2D.
• 25(OH)D is also called calcidiol.
• 1,25(OH)2D is also called calcitriol.
• Vitamin D3 is synthesized in the epidermis and vitamin D2 comes from plants and yeasts.
• Vitamin D2 is used to fortify various foods and is a constituent of calcium & vitamin D tablets.

  MORE BASICS

•  Cholecalciferol (D3) is formed in the epidermis of animals.
• It is hydroxylated to 25(OH)D in the liver.
• 25(OH)D is further hydroxylated to 1,25 (OH)2D in the kidney.
• 25(OH)D is the major circulating vitamin D.
• It is the storage form and not the active form.
• Blood testing is done principally of this form.
• Normal levels are 30 to 75 ng/ml.

Factors that reduce the production of vitamin D in the epidermis of skin are:

1. Increasing age
2. Greater melanin (darker skin)
3. Reduced sun exposure
4. Winter season
5. Prolonged use of sunscreen

• Most calcium preparations (e.g. Macalvit, Shelcal) contain 250 IU or less of vitamin D. This is not sufficient as the current recommendation in adults is 800 IU/day.

Examples of calcium preparations with 500 IU vitamin D are “Shelcal-HD”, “Gemcal-D3”.
Example of calcium preparation with 1000 IU vitamin D is “Tayo”.
Now, capsules of vitamin D3 are available in strengths of 1000, 2000 &  60,000 IU, e.g.: Uprise D3

•  Vitamin D needs are greater in pregnancy when even 1000IU/day may be   inadequate.  A suggestion is to give 1 sachet of 60,000 IU every month of pregnancy.

•  Units of vitamin D formulations are IU (international units) if content is cholecalciferol/ergocalciferol and mcg (microgram) if content is synthetic calcitriol or alfacalcidol.

•  Active forms of vitamin D (calcitriol/alfacalcidol) are costly and usually unnecessary. Their utility is in patients of CKD (where renal conversion from 25(OH) D to 1,25(OH)2D is poor) and in rare inborn errors of vitamin D metabolism.

•  Vitamin D deficiency is a cause of decreased bone density. Typically on bone densitometry (DXA) the Z score will be greater than or equal to the T score.

•  Laboratory abnormalities of vitamin D deficiency may include low 25(OH)D, raised alkaline phosphatase, hypocalcaemia, hypophosphatemia and raised PTH.

•  Vitamin D deficiency results in hypocalcaemia, secondary hyperparathyroidism, impaired mineralization of skeleton and proximal myopathy. Deficiency in childhood (esp. age <2) causes rickets. Deficiency in grown-ups causes osteomalacia.

•  Orlistat, a weight reduction drug, causes fat malabsorption and can cause vitamin D deficiency.

• Most commercial vitamin D tablets or granules contain plant-derived vitamin D2 which has a much lesser bioavailability then once believed. This is why we see a far superior response to injectable vitamin D than oral.

•  In the elderly, vitamin D supplementation improves muscle strength and reduces falls.

•  To obtain adequate vitamin D from sunshine the face, arms, hands and back must have sun exposure without sunscreen for 15 min at least twice a week if fair-skinned individual and at least 4 times/week in dark-skinned individual.

•  1,25 (OH) 2D is the active form. It stimulates intestinal absorption of calcium and phosphorus and promotes deposition of calcium hydroxyapatite in bones.

•  Overdose of vitamin D3 can cause hypercalcemia which can present with convulsions or simply with new kidney stones.

•  If suspecting hypervitaminosis D, test serum calcium for hypercalcemia and not vitamin D. If serum calcium is normal even a vitamin D>150 is clinically inconsequential.

•  A corollary to the previous THM- If a patient comes to you with a high vitamin D blood report (say >75), do remember to order a serum calcium immediately.

•  AKT and vitamin D:

1. Rifampicin causes accelerated inactivation of vitamin D by induction of hepatic cytochrome P450 enzyme.
2. INH impairs 25 hydroxylation of vitamin D.

Hence all patients on AKT should receive vitamin D supplementation.

Some brand names of formulations containing Vitamin D but not calcium

Brand Name	Formulation	Company
Vitanova	Cholecalciferol 6L I.U.	Zuventus
Arachitol	Cholecalciferol 6L I.U.	Abbot
T.Arachitol	60,000 I.U. chewable tablets	Abbot
C. D Rise 60K	60,000 I.U. cholecalciferol	USV
Calcirol granules	60,000 IU	Cadila
Uprise D3 60K	60,000 IU cholecalciferol	Bergen ( Division of Alkem)
Uprise D3 2K	2000 IU Cholecalciferol	Bergen
Uprise D3	1000 IU cholecalciferol	Bergen
Supradyn	Vitamin A 10,000 IU Cholecalciferol 1000 IU Thiamine 10 mg Cyancobalamine 15 mcg Nicotinamide 100 mg	Manufactured by Piramal, Marketed by Abbot
T. Consivas D3	Rosuvastatin 10 mg Cholecalciferol 1000 IU	Emcure

 

 

 

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