Bioavailability of foods: is it the nature of the food or the health of [the] gut or both?

Both, definitely. I’ve written a lot about this. Bioavailability of different foods in terms of nutrient absorption, interaction with other types of food, for example, we know that phytic acid and grains and certain vegetables can inhibit the absorption of minerals like iron and calcium, and then there’s, of course, the health of the gut. If somebody has ​H. pylori​ [​Helicobacter pylori]​ or gastritis, or they’ve got SIBO or some other condition that impairs the absorption of food, that will make a difference, as well.