Vitamin D: More than just better calcium absorption
We don't just need vitamin D for bone health, it is absolutely essential for optimal health of all our organs. In fact, vitamin D is involved in the regulation of over 2,700 genes. It has been estimated that almost 50% of people have insufficient levels of vitamin D (Holick, M.F., 2007). This is literally a pandemic that could easily be eradicated. And, with strong evidence that vitamin D is of major importance in the prevention of cancer, heart disease, autoimmune diseases, diabetes, depression, and various infections such as tuberculosis and influenza, it is easy to see why supplementing with vitamin D is a great idea.
Of course vitamin D is important for bone health also. Numerous studies have consistently demonstrated that vitamin D improves bone mineral density and reduces fractures of the spine and hips. And, what is extremely interesting is that this improvement is not just because vitamin D helps us absorb more calcium.
A recent study with elderly men, showed that vitamin D (with calcium) improved bone mineral density and bone structural geometry. This improvement in the structural aspects of bone crystal formation was thought to actually be more important for the reduction in fractures than the improvement in bone density (Bassatne, et al. 2020).
What is so important about this finding is that while you might not see changes in your bone density on repeat DXA exams, your fracture risk might still be lower. We need to remember that DXA exams only look at bone density changes and do not register changes in bone quality. It can be extremely demoralizing, if on repeat DXA exams, there is little or no improvement in T-scores. Therefore, we need to always keep in mind three things: 1) bone mineral density does not equate to bone strength, 2) improvements in bone quality do not change DXA T-scores, and 3) bone strength is a combination of both bone density and bone quality.
Winter is coming and blood vitamin D levels typically decline with the lower sun intensity and less vitamin D production in the skin. So make sure you are getting enough vitamin D. The best way to know if you are is to have your doctor check your blood D level. Try to maintain 40 to 60 ng/mL. There is no need to have your vitamin D level any higher than 60 ng/mL. After a certain intake level of vitamin D, there does not appear to be additional health benefit (Bassatne, et al., 2020).