Vitamin D deficiency is a worldwide epidemic and 40-75% of the world's population is vitamin D deficient. Vitamin D is a hormone not just a vitamin where its intracellular receptors found in almost all body cells, bone, muscle, stomach, intestine, central nerve system, endocrine system, kidney, liver, lungs, heat, blood vessels soft tissues, skin and the root of a hair.

In USA, many healthcare societies and committees call for an action to alert the public about the importance of keeping vitamin D serum levels between 40 to 60 ng/ml (100-150 nmol/l). They supported their action by accumulating evidence-based published articles assuring that, vitamin D level of 40-60 ng/ml has preventive role, not just from bone diseases, but also against cancer, cardiovascular diseases, diabetes, Alzheimer, multiple sclerosis, autism, psoriasis, preeclampsia, gestational depression, etc. In 2012, Luxolda showed that our ancestors had an average of 46 ng/ml of vitamin D in their blood.

WHAT IS BEHIND THE SCENE?

These days there is still a big debate about what is vitamin D sufficiency versus deficiency among healthcare entities, on the national and international levels. In USA, there are different policies by many heath organizations and bodies regarding vitamin D deficiency versus sufficiency and recommended daily intake. After the testing of vitamin D (25-hydroxy cholecalciferol), we must understand the value of its blood level to have an action. Vitamin D blood level tell us how much vitamin D supplements we need daily or how much time we should expose to sunlight daily to reach the desired blood level. Different American health organizations and bodies use different reference ranges to illustrate the meaning of vitamin D deficiency, insufficiency or sufficiency.

The following table represents deficient, insufficient, or sufficient vitamin D blood level in nanogram/milliliter (ng/ml) among different US healthcare entities such as IOM (Institute of Medicine), American Endocrine Society, Vitamin D Council. The Table 1 illustrates the contradictions between these societies in terms of sufficient versus deficient. Also, it explains why the recommended daily allowance is different among them.

IU (INTERNATIONAL UNIT)

Scientists and experts illustrated that, the IOM report concerning the Recommended Dietary Intakes of 600 IU/day of vitamin D is below their expectations. They commented that this dietary intake will just protect 99% of children of having rickets and will satisfy their sufficient vitamin D level of 20 ng/ml. Others said that the IOM got it wrong in term of vitamin D and they have to increase their dietary allowance by 2-5 times. Also, in his review to IOM statistics, Dr. Veuglers showed that the IOM estimate was wrong in terms of their recommended dietary intakes (RDI). He found that, 600 IU/day of Vitamin D did not give 97.5% of the population the 20 ng/ml level in their blood and just 50% of them satisfied this level.

The American Endocrine Society recommended for 30-100 ng/ml to be sufficient and less than 20 ng/ml to be insufficient. This society urges to have 2000 IU/day of vitamin D supplements aiming to keep the vitamin D blood level 30 ng/ml or above. However, Vitamin D Council suggests that 50 ng/ml is the ideal level for everyone. For this reason, they recommend that the adults should take 5000 IU/day of vitamin D supplements to reach and maintain their targeted level (40-80 ng/ml).

In the end, although there are still gaps between different healthcare bodies, taking an action against vitamin D deficiency by having higher doses than the recommended daily intake is better than not. The Institute of Medicine (IOM) reported in 2010 that taking 4000 IU/day of vitamin D can be considered a safe upper intake level for adults aged 19 and older. Moreover, American Endocrine Society and Vitamin D Council indicate 10,000 IU/day is considered safe and with no observed adverse effect.