@gretchen1018 Your gut bacteria are the 'bugs' (microflora and fauna) that aid in digestion. Just like all bacteria, there are beneficial and not so beneficial bacteria. Poor diets 'starve' the beneficial bugs, and the "not so good" can take over. Fiber, leafy greens, sheep and goat's milk cheeses, low sugar, non-refined foods favor the good bacteria. Mediterranean diets, fermented foods, and avoiding too many "nightshades" and high lectin foods can help 'heal' a gut. Look up leaky gut syndrome, and it will explain a lot of these concepts. When your gut bacteria are not "healthy", digestion and nutrient absorption are compromised. Bones suffer.
Hope this helps