A few thoughts from an autistic bro scientist... Not being deficient in Vitamin D is not the same as having optimal levels of Vitamin D. Optimal levels of Vita

A few thoughts from an autistic bro scientist... Not being deficient in Vitamin D is not the same as having optimal levels of Vitamin D. Optimal levels of Vitamin D are probably around 60-70ng/ml, with a bias to upper end of that range (in my opinion anyway). I say this because individuals with a lot of sun exposure will typically have Vitamin D levels around 70ng/ml so this is in my opinion is likely closer to the levels of our ancestors. However, a lot of experts would argue 50ng/ml is optimal, but I disagree with this primarily because the number is based on population averages in populations that are largely Vitamin D deficient. In comparison, to be considered deficient you would generally need levels below 20ng/ml which less than a third of what I suspect is optimal (and natural). Again, I'm just an autistic bro scientist, but my understanding is that low levels of Vitamin D are strongly associated to higher levels of inflammation in the body. We also know that higher levels of inflammation in the body are linked to various negative health outcomes like depression, impaired immune function, and increased cancer risk. If I were to guess most individuals who develop cancer are older and generally less healthy. Given that most people in the West don't have optimal levels of Vitamin D in the first place we can only assume that those with cancer have even less optimal levels. Therefore the idea that supplementing Vitamin D in a population highly likely to have suboptimal levels of Vitamin D would reduce cancer mortality should not be surprising at all. If you live in the West you really should consider taking 1,000 - 2,000 IU of Vitamin D a day – and perhaps more if you're able to monitor your levels to ensure you're not taking too much. I'm really not a fan of taking supplements in general, but Vitamin D is one of the few most people in the West probably would benefit from taking at a low dose.