Dear colleague

At first there is hardly any vitamin D in eggs and milk. If you are looking for high content food than you should consider fatty fish and sun-grown mushrooms.

I have never heard of chemicals in food that limit the absorption of vitamin D from food.

The main cause of this epidemic of vit D deficiency is that people do not expose themselves enough to the sun, either for cultural/religious reason, either because they are living insides their homes (elderly, office workers) and even in our free time, we are sitting more and more inside (posing questions and answering them, or just playing games). There is plenty of literature on this.

Finally dermatologists even warn for moderate sunexposure (1/2 to 1 hour per day, around midday), so people avoid the sun or use sunscreen preparations.

Its time to re-modify the normal values of Vitamin D. Even though we, Indians are exposed to more sunlight, vitamin D Deficiency is more common among women.

Agree with the point that the lack of sunlight is a main reason for vitamin D deficiency. Some previous studies suggested that vitamin D produced in the skin can last longer in the blood compared with ingested vitamin D, while being exposed to one minimal erythemal dose of UV radiation can produce vitamin D produced equivalent to ingesting between 10,000 and 25,000 IU.

Ref:

Article Vitamin D: The "sunshine" vitamin

Vitamin D deficiency is most often caused by insufficient exposure to sunlight and nutritional deficiency but can be secondary to a wide range of other underlying causes, such as disorders of the gut, pancreas, liver and kidney.

· Gastrointestinal malabsorption: eg, surgery (stomach and bowel resections), other causes of short bowel syndrome, chronic pancreatic disease, cystic fibrosis, biliary disease (eg, primary biliary cirrhosis, biliary fistulae, biliary atresia), Crohn's disease and coeliac disease.

· Liver disease - eg, cirrhosis.

· Renal disease causing defective 1,25-dihydroxyvitamin D synthesis.

· Drug causes include anticonvulsants (particularly phenytoin, carbamazepine, phenobarbital), rifampicin, highly active antiretroviral therapy (HAART), colestyramine and cadmium.

· Severe dietary calcium deficiency can cause rickets despite adequate vitamin D.

· Rare causes:

· Hypophosphataemia: tumour-induced, Fanconi's syndrome, phosphate depletion, metals such as cadmium and lead that may lead to renal phosphate wasting.

· Systemic acidosis, renal tubular acidosis.

· Intoxication with diphosphonate, fluoride, aluminum (caused by excessive antacid ingestion, or in fluids used in dialysis).

· Autonomous hyperparathyroidism presenting as vitamin D-deficient osteomalacia.

· Mesenchymal tumour - oncogenic osteomalacia.

· Genetic causes:

· Hypophosphataemic rickets: X-linked dominant disorder characterised by growth restriction, inadequate mineralisation of bone, hypophosphataemia and renal defects in phosphate reabsorption and vitamin D metabolism.

· Vitamin D-dependent rickets type I (failure of conversion of 25-hydroxyvitamin D (25-OHD) to 1,25-dihydroxyvitamin D) and II (end-organ insensitivity to 1,25-dihydroxyvitamin D).

· Adult-onset vitamin D-resistant hypophosphataemic osteomalacia (autosomal dominant).

· Proximal renal tubule dysfunction: hereditary Fanconi's syndrome.

References

1. Wharton B, Bishop N; Rickets. Lancet. 2003 Oct 25362(9393):1389-400.

2. Lee JY, So TY, Thackray J; A review on vitamin d deficiency treatment in pediatric patients. J Pediatr Pharmacol Ther. 2013 Oct18(4):277-91.

most often caused by insufficient exposure to sunlight and nutritional deficiency

Food can take care of 10 - 20 % of an estimated minimum daily need of about 1000 iU. Others say you need at least 2000 iE/day.

This daily amount is build up from vit D synthesis in the skin and from taking supplements or (fortified) food. As said before, unless you eat large amounts of fatty fish or sun-grown mushrooms, non-fortified food gives only a small fraction of the vit D needed. Therefor is the lack of sunexposure (for all kinds of reason) the main cause of the worldwide vit D deficiency epidemic.

Vitamin D is found naturally only in a limited number of foods, the usual dietary intake of vitamin D in many populations is not enough to maintain an adequate level . In addition to this, the limited exposure to sunlight is the result of the Vitamin D deficiency with all the necessary consequences.

I have been working on Vitamin D deficiency (VDD) for more than five years. It has been documented that VDD is also present in healthy people living in areas of adequate sunlight exposure.This paradox is still unresolved.Although, healthy person with adequate sunshine and physical activity generally have better Vitamin D(25-hydroxyvitamin D) status compared to those who have limited/no sunlight exposure.In order to increase vitamin D level, there should be adequate duration and skin area exposed to sunlight , sufficient dietray intake of Vitamin D containing food items and physically active life style along with supplemental Vitamin D intake in the persons who are at the risk of developing VDD.