After reviewing the publication on the Vitamin D/osteoporosis paradox in African Americans, my main take-aways are that although African Americans have significantly lower serum 25(OH)D levels than the white population partly due to their dark skin pigmentation interfering with ultraviolet light absorption, African Americans still have a lower risk of developing osteoporotic fractures due to having a more efficient calcium economy and subsequently higher average bone mass. In addition, this paradox at face-value may imply that African Americans don’t need as much Vitamin D as their white counterparts, but research shows that they do need just as much or more Vitamin D for their skeletal health. Also, a decrease in serum 25(OH)D stimulates parathyroid hormone (PTH) secretion that reduces the amount of calcium lost through kidney filtration, resulting in a higher resistance to skeletal fractures.
I would utilize this information in my future practice by not only pointing out the differences between African American Vitamin D/calcium levels and other populations, but also by emphasizing the importance of how the body uses these nutrients to maintain multiple systems simultaneously. For example, most people think of bone density when discussing Vitamin D/calcium, but they are also vital for proper muscular system function that often works hand-in-hand with our skeletal health. Calcium helps contract the muscles, and low levels can lead to chronic muscle weakness. What the average person fails to realize is that bone formation is often stimulated by mechanical stress via muscular contraction (Minimal Essential Strain), and without Vitamin D/calcium to assist the contractions it is difficult to stress the bones enough to adapt to the strain and rebuild.1 This is just one example of how fluctuations of essential micronutrients affect the body in more ways than most may anticipate, especially when a certain population is at risk of deficiency.
Why do African Americans have a higher calcium economy than other populations? The article discusses the benefits of PTH helping with superior renal conservation and the resulting higher levels of retained calcium, but I wonder if this is an evolutionary trait developed specifically because African Americans do not absorb Vitamin D through ultraviolet light as efficiently? Let me know what you think!
Reference:
1) Hart NH, Nimphius S, Rantalainen T, Ireland A, Siafarikas A, Newton RU. Mechanical basis of bone strength: influence of bone material, bone structure and muscle action. J Musculoskelet Neuronal Interact. 2017;17(3):114-139. PMID: 28860414
