I recently read a copy of Isaac Asimov's "The Chemicals of Life." Written in 1954, the book talks about how and why our bodies work. It hardly mentions DNA and focuses on the larger structures of enzymes, proteins, vitamins, and hormones. Some of the information is outdated in its presentation, but the book still holds up in almost all areas. (Also, I had never realized Asimov was a Professor of Biochemistry. He knew his stuff in this area.)
The first chapter of the book is titled, "The All-Important Protein." This struck my 2020, DNA-oriented mind as an odd starting point, yet Asimov was very clear: "all life is protein." The book is remarkably lucid, and here's one of the best portions of the book:
"Suppose the food you ate contained very little fat. That wouldn't bother your body a bit. It would take the carbohydrate you eat and turn it into fat. It happens all the time. Everyone knows what starchy foods will do for the waistline.
"If both fats and carbohydrates are low, the body is still not at a loss. It can manufacture both out of the proteins of the diet.
"Where the body does get stuck is in the case of a shortage of proteins. It cannot manufacture proteins out of fats and carbohydrates. Proteins require nitrogen, and neither fats nor carbohydrates have any. So proteins can only be obtained for the body by making certain that protein is in the food. It is impossible to live on a diet of starch, butter and sugar. You can get all the energy you need, but you can't build tissue."
Asimov places heavy emphasis on the two primary categories of what our body cannot naturally produce: essential amino acids and vitamins. Amino acids are the building blocks of proteins. The human body cannot produce nine of these amino acids, and we term these to be "essential" (Asimov said there were only eight; the necessity of histidine for adults was not yet established in 1954.) We must acquire the essential amino acids from a source outside our body. If we don't acquire these essential amino acids, our bodies will fall apart. Wikipedia says "protein deficiency has been shown to affect all of the body's organs and many of its systems" [1]. Asimov later discusses the importance of vitamins, or "atom groupings, which the body cannot make for itself and must get from the food it eats." Without vitamins, we cannot produce certain coenzymes and will fall ill and possibly die.
Essential amino acids and vitamins. I've been focusing my diet on the acquisition of those in correct quantities. My diet-optimizing function seeks to minimize sugar, maximize protein, and moderate the rest. So far, it seems to be working well; I still build muscle at the gym and fat stays off. Wonder if this is what keto basically optimizes for as well.
So many articles about bodily function I've seen online jump straight to considerations of DNA. Certainly, this approach is more accurate, though I do wonder if we the layperson are approaching health issues with too much detail. To analogize to software, it's like we're trying to debug our complex C++ program by pouring over the binary. The issues are far more likely to be with what we're putting in than what's already there.
Sources:
[1] https://en.wikipedia.org/wiki/Essential_amino_acid