I took calcium for many years among other supplements as I competed in wrestling. I didn’t consider or investigate the supplements deeply. I just took them.
Vitamin D deficiencies have been linked to multiple health problems. Low levels of testosterone is one of the unwanted consequences of insufficient vitamin D supply.
For a baby, gluten is recommended to be added to the diet in most western countries at the age of 4 to 6 months. This recommendation is based on the thought that the babies would get used to gluten and would not get a celiac disease or other gluten intolerance conditions. Now many new studies show that the aforementioned recommendation may result in a completely opposite outcome.