A recently released study called VITAL initially seemed to put the final “nail in the coffin” regarding the use of supplemental vitamin D. As the accompanying editorial stated, the study showed that vitamin D did not reduce risk of bone fractures, and therefore the authors recommended stopping routine measurement of vitamin D levels.
So, what’s the real story on vitamin D?
In general, there seems to be two schools of thought regarding vitamin and mineral supplementation. The first held by most traditional doctors is that most supplements are useless, poorly regulated and only result in very expensive urine where most are metabolized and excreted from the body. The second, held by most integrative medicine physicians, is that due to reasons such as reduced nutrient content in our food, poor quality diets of most Americans and specific genetic abnormalities there is a need for a specific and broad use of supplemental vitamins and minerals to replace those essential (meaning your body is unable to manufacture them) compounds.
So, which one is it? And specific to vitamin D what is the evidence of benefits?
Vitamin D is a complex vitamin with multiple effects on our bodies. According to a recently posted article by the National Institute of Health, here are the main effects of vitamin D:
Regulates absorption from gut and maintenance of an adequate serum calcium and phosphorus levels necessary for bone mineralization
Reduction of inflammation
Modulation of the immune system
Regulation of glucose metabolism
Modifying encoding of proteins which regulate cell proliferation, differentiation and apoptosis (cell death) with important implications for cancer
They seem to be pretty important, so how do we determine if we have enough? As is said, in life nothing is easy!
Vitamin D levels measure 25, hydroxyvitamin D. Vitamin D can be ingested from multiple sources of foods and dietary supplements. It can also be produced by exposure to ultraviolet radiation in your skin. It is known as calciferol which is then converted to 25 hydroxy vitamin D in the liver. It undergoes a special conversion in our kidneys to 1, 25 hydroxyvitamin D, also known as calcitriol. This is the biologically active form of the vitamin.
Measuring vitamin D levels involves a simple blood test. It actually measures the level of 25 hydroxyvitamin D since the active form of 1, 25 hydroxyvitamin D fluctuates rapidly due to day to day metabolic demands. The measurement is usually expressed as nanograms per milliliter (ng/ml) but can also be shown as nanomoles per liter (nmol/l) just to increase confusion. Here are the values considered to be normal from the NIH Fact Sheet:
There is an ongoing debate regarding what is considered normal and what are considered optimal levels for your metabolism. According to the American Endocrine Society, levels below 20 ng/ml are considered deficient. Some recommend levels of 50 to 70 ng/mL as the ‘optimal range’.
In a study conducted by the Mayo Clinic, there was one adverse effect seen due to supplementation. This was in a person that was taking 50,000 units per day for three months. That is an extraordinary dose since most supplements are in the 1,000-5,000 units per day range (or 25-125 mcg). A study of breast cancer patients showed an 87% reduction of risk in those with levels greater than 60 versus less than 20 ng/ml.
So back to the headline study, the one that showed no benefit of supplementation of vitamin D for fractures. An excellent analysis done by Dr. Peter Attia’s team, which points out several deficiencies in the study, is here.
Combine this with the large volume of published studies showing patients with adequate vitamin D levels versus suboptimal:
Reduction in cancer deaths here
Reductions in mortality from Covid here
Reduction in rates of depression here
Reductions in rates of dementia here
Improvement in symptoms from rheumatoid arthritis here
Impact on insulin sensitivity here
While the literature will continue to define specific patients who will benefit from Vitamin D supplementation, I tend to follow what is called the precautionary principle. The precautionary principle is a useful strategy for decision-making when physicians and patients lack evidence relating to the potential outcomes associated with various choices. According to a version of the principle, one should take reasonable measures to avoid threats that are serious and plausible.
In my opinion the use of Vitamin D supplementation is consistent with minimizing risk and maximizing benefit when the information is conflicting.
My recommendation: get your Vitamin D Level checked and supplement if under 30 ng/ml.