Short Summary: Vitamins, by definition, are not produced by the body. Vitamin D is in fact a hormone produced by UVB rays from the cholesterol in skin.
Most of Vitamin D stores in the liver before reaching the blood through the kidneys. It plays key role in bone health through absorption of calcium and phosphorus. Recent research shows additional critical roles in cardiovascular disease and in fighting over 15 different kind of cancers.
Despite plentiful sunlight, a large population is deficient as people proactively avoid sun.
Large part of North America (regions north of Phoenix, AZ or Bakersfield, CA) doesn’t receive the UVB rays from Nov to Mar as they are blocked by the ozone layer.
Fortified foods or supplements are very popular to make up for any deficiency. Medical professionals recommend maintaining levels of at least 20-30 ng/ml and an easy and simple at-home Vitamin D test kit can help check the levels.
Vitamin D toxicity is extremely rare.
Range of Vitamin D levels
Source: Evaluation, Treatment, and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline by Holick et. al. in The Journal of Clinical Endocrinology & Metabolism, Vol 96 (7), 2011, Pages 1911–1930.
Vitamins, by definition, are compounds that our body does not produce. However, Vitamin D is unique.
UVB rays (290-310 nm wavelengths) in sunlight convert a form of cholesterol in the skin into a form that our body utilizes.
Once ready, it stores in the liver–almost like water in a camel’s hump–until the time it releases into the kidneys. This release gives the final active form that circulates in our blood.
It is crucial for absorption of calcium and phosphorus–minerals essential for maintaining healthy bones, especially in children and elderly.
In recent years, research has shown that Vitamin D is essential for fighting over 15 different kind of cancers.
Despite abundant sunlight, a large population is Vitamin D deficient. That is because people proactively try to avoid exposure to sun.
Another problem is that a large part of North America (regions north of Phoenix, AZ & Bakersfield, CA & Charlotte, NC) doesn’t receive the UVB rays for almost 6 months a year. In winter months from Nov to Mar as these rays are blocked by the ozone layer.
Fortified foods and supplements are therefore popular sources to make up for any deficiency.
Medical professionals recommend maintaining levels of at least 20-30 nL/ml, which can be tested with a simple blood test using an at home Vitamin D test kit.
Toxicity is extremely rare but those taking the supplements should monitor their levels regularly.
Vit D is necessary for absorption of calcium and phosphorus in the body. Deficiency can have serious health impact in:
Source: Vitamin D Supplementation, Glycemic Control, and Insulin Resistance in Prediabetics: A Meta-Analysis by Mirhosseini et. al. inJournal of the Endocrine Society, Vol 2 (7), 2018, Pages 687–709.
The four key steps that start with sunlight to the final production of Vit D in our body are:
Metabolism happens through regular method and in the cells:
Source: Vitamin D Supplementation, Glycemic Control, and Insulin Resistance in Prediabetics: A Meta-Analysis by Mirhosseini et. al. in Journal of the Endocrine Society, Vol 2 (7), 2018, Pages 687–709.
The sources of Vitamin D include
Recommended daily allowance (RDA) as per the CDC direction are:
- US: milk, cereals, orange juice, margarine.
- Canada: only milk and margarine.
- Even fewer options for those who are lactose intolerant or vegetarian or vegan.
Most common sources of Vitamin D with approximate amounts include:
The most popular test for Vitamin D is using a simple finger prick blood sample. You can order an at-home Vitamin D test kit that can accurately measure the active form of Vitamin D (1,25-D3) in blood stream. The kit can be ordered online & a blood sample can be provided from home without the need to visit a doctor or any labs. The comprehensive lab report will clearly explain your results.
More comprehensive but expensive test is LC-MS/MS (liquid chromatography tandem mass spectroscopy).
It is always a good idea to test your Vitamin D levels before starting any supplements.
* November: onset of Vitamin D winter (fall)
* March: end of winter (spring)
What physicians normally suggest (although one should confirm with a physician before starting any of these regimens):
Excess Sun or skin based overdose is naturally protected by the body.
Overdose toxicity of 150 ng/ml can only be achieved by several months of >10,000 IU/day. It is very hard to get this level of overdose.
In reported literature, very few cases of overdose are reported. One case with 150,000 IU/day taken over two years resulted in 500 ng/ml but didn’t have any immediate health conditions after stopping.
Overdose (>150 ng/ml) results in elevated calcium in blood that can cause:
High levels are not for:
Source: Vitamin D Revolution by Soram Khalsa, M. D.
For more information & references, visit the NIH page on Vitamin D