Higher Vitamin D (25-OH) was linked to more lean tissue in arms and legs: a 0.03 increase on the study’s scale, not proof of muscle gains. The 2026 study in Medicine explored Vitamin D (25-OH), muscle health, and lifestyle. It used pooled genetic data from people of European ancestry. Researchers looked at gene differences linked to higher blood levels. This approach helps explore cause and effect, but it does not test taking supplements. The clearest muscle finding involved lean tissue in the arms and legs. The estimate was 0.03, with an uncertainty range of 0.01 to 0.06. The supplied summary does not explain the units. That means we cannot translate this result into pounds of muscle. There was no evidence of a cause-and-effect link with low grip strength or Walking Speed. One analysis also linked higher levels to 8% higher odds of never smoking. That does not mean raising blood levels helps someone quit smoking. The authors drew a broad conclusion about muscle loss and smoking. Still, the muscle findings were narrower: more lean tissue, not clearly better function. For BioSocial members, blood levels and physical function are separate things to track. Comparing dated bloodwork with strength records could make community discussions more useful. Members tracking Muscle Mass (Lean Mass) can also note how those readings change over time. This study does not establish a target blood level or show that Vitamin D Supplementation builds muscle. What changes, if any, have you noticed in your strength alongside changes in your blood levels?