| The problem before (and I think what is still the problem): 1) We talk about very broad macronutrient classes as though much could be said about them that is meaningful. Fats are not interchangeable; carbs are not interchangeable; proteins are not interchangeable. Talking about grams of fat doesn't actually tell you much (nutritionally). On a related note, calories are also not nutritionally generic, and our bodies are not simple input/output machines. Calories in / calories out is a gross oversimplification. 2) A substance that is eaten, and the same substance elsewhere in the body, do not have a direct 1-for-1 relationship. Dietary cholesterol, for example, is not directly deposited in artherosclerosis, and the pathology may have nothing to do with consumed cholesterol at all. (That is, the problem may not be how much you eat, but what causes it to build up as deposits that aren't cleared away.) 3) Measuring blood plasma is a poor metric for many, many things. Intercellular, extracellular, and stored elsewhere (liver, pancreas, bone, etc.) often have nothing to do with plasma values. And we know this. But we still use it because it's all we can easily do for now. So when we measure your nutrition by comparing blood plasma values of magnesium, for example, we are using a metric we already know correlates poorly with actual magnesium status. 4) Environment matters. Cellular environments are extremely complex. Speaking about nutrition without discussing the thousands of other molecules and tissue structure it interacts with, and where, isn't very helpful. These factors-- conflating macronutrients, conflating consumption with pathology, using bad metrics for nutrition, and ignoring cellular environment-- are much of what results in all of this nutritional confusion. We substitute fads or the latest half-understood data for real knowledge, because we don't have much real knowledge. (Despite being able to fill textbooks with what we do know.) |