Many products are useful, and there are also principles of a healthy diet: mixed, varied, complete, seasonal fruits, norms of daily nutrient intake. The fact is that it is not the products taken separately that make the "weather", but the radio-electronic food taking into account the principles. For example, sitting on oatmeal alone in the morning is harmful, although oats are an excellent food rich in trace elements and low GI (glycemic index), but if there is a lot of oatmeal, then there is a risk of calcium leaching. Because cereals contain poison (F Acid). Therefore, you need to know how to neutralize the poison (fermentation, germination, pour kefir overnight). If you like oatmeal, then eat no more than 2 weeks, then a break for 2 weeks. This is for example. Mixing principle. It is known that the combination of plant and animal proteins makes them more digestible (by 30%). It is known that fats are needed in moderation (because they are needed for the construction of hormones, for fat-soluble vitamins). For fruits, there is the rainbow principle - that is, a range of multi-colored fruits combine to provide excellent antioxidant effects. In general, it's easier not to get hung up on individual products. And to eat varied, not very refined (processed) food, observe the measure, follow the mode of work and rest, avoid excess weight, exclude bad habits, more positive emotions - and everything will be good)
There are so-called superfoods, the benefits of which have been scientifically proven (either in mice or in humans). For example, cocoa beans, chia seeds, spirulina, shiitaki mushrooms, and much more. But there are also familiar foods that are not exotic, but very healthy: fatty fish (due to omega-3), fiber (vegetables, fruits), dark colored berries, vegetables and fruits (carotenoids), artichoke, herbs, cruciferous vegetables (broccoli, and all types of cabbage), spinach (many B vitamins), and much more. But the main thing in the pursuit of health is not to go too far and do not eat only these products, since variety and the correct ratio of BJU are very important.
Yes, there are no "most" useful products in general. And the most harmful do not exist. It all depends on the tasks and metabolism of the body as a whole. And it is unlikely that mono-eating will come out,