Keith McCormick has a 2008 basic book on osteoporosis that goes over the effects of gut health and stress on bone health. I found out about him from others posting about him on here. He has a new book out; that one is 700 pages long, compared to the original, which is about 150. He's a chiropractor with a BA in human biology from Stanford and has osteoporosis himself. You could probably get his 2008 book used for a low price, tho a new one cost me about $15. I thought it was worth the read.