The vitamin D paradox relates to the lower risk of osteoporosis in people of sub-Saharan African ancestry (Blacks) compared with people of European ancestry (Whites). The paradox implies that for bone health, Blacks require less vitamin D and calcium than Whites do. Why should populations that migrated northward out of Africa have ended up needing more vitamin D than tropical Blacks? Human skin color became lighter away from the tropics to permit greater skin penetration of the UVB light that generates vitamin D. Lack of vitamin D impairs intestinal calcium absorption and limits the amount of calcium that can deposit into the protein matrix of bone, causing rickets or osteomalacia. These can cause cephalopelvic disproportion and death in childbirth. Whiter skin was more fit for reproduction in UV-light restricted environments, but natural selection was also driven by the phenotype of bone per se. Bone formation starts with the deposition of bone-matrix proteins. Mineralization of the matrix happens more slowly, and it stiffens bone. If vitamin D and/or calcium supplies are marginal, larger bones will not be as fully mineralized as smaller bones. For the same amount of mineral, unmineralized or partially mineralized bone is more easily deformed than fully mineralized bone. The evidence leads to the hypothesis that to minimize the soft bone that causes pelvic deformation, a decrease in amount of bone, along with more rapid mineralization of osteoid improved reproductive fitness in Whites. Adaptation of bone biology for reproductive fitness in response to the environmental stress of limited availability of vitamin D and calcium came at the cost of greater risk of osteoporosis later in life.

中文翻译：

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较弱的骨骼和白色的皮肤是为了改善人类对北方环境的“适应性”。


维生素 D 悖论与撒哈拉以南非洲血统的人（黑人）相比欧洲血统的人（白人）患骨质疏松症的风险较低有关。这一悖论表明，为了骨骼健康，黑人需要的维生素 D 和钙比白人少。为什么从非洲向北迁移的人群最终比热带黑人需要更多的维生素 D？远离热带地区，人类肤色变浅，以便产生维生素 D 的 UVB 光能够更好地穿透皮肤。缺乏维生素 D 会损害肠道钙吸收，并限制沉积到骨骼蛋白质基质中的钙量，从而导致佝偻病或骨软化症。这些可能会导致头盆不称和分娩时死亡。更白的皮肤更适合在紫外线受限的环境中繁殖，但自然选择也是由骨骼本身的表型驱动的。骨形成始于骨基质蛋白的沉积。基质的矿化发生得更慢，并且会使骨骼变硬。如果维生素 D 和/或钙供应不足，较大的骨骼将不会像较小的骨骼那样完全矿化。对于相同量的矿物质，未矿化或部分矿化的骨骼比完全矿化的骨骼更容易变形。这些证据得出这样的假设：为了最大限度地减少导致骨盆变形的软骨，骨量的减少以及类骨质更快的矿化可以改善白人的生殖健康。为了应对维生素 D 和钙供应有限的环境压力，骨骼生物学适应了生殖健康，但代价是晚年罹患骨质疏松症的风险更大。