I expect I will receive more e-mails from this blog than from all the others together. Nutrition is fundamental, not only to life, but, as per Freud, the first stage of mental development. Our first sensation of love, warmth, and security was at our mother's breast. Because it has such a fundamental connection with our psyche, this is probably why we have more and different personal habits and religious taboos over food than any other aspect of our lives. We also have magical thinking about "good" foods and "bad" foods.
Mother's milk is heavy in sugar and fat, which is probably why we all love ice cream. (Separate thought:I prefer chocolate to vanilla, and I often wonder if people who prefer vanilla taste the chocolate in the same way that I do.) Fat is appreciated because it adds flavor and substance to food It also markedly slows stomach emptying, so we feel fuller for a longer period of time if the meal contains fat. Some of my patients equate "low fat" to "low taste" especially low-fat mayonnaise.
There are eight essential amino acids, which are called "essential" because every animal cell needs all eight to make proteins,and cannot synthesize them. Vegetables have at most seven of these amino acids, which is why a complete vegetable dish contains rice + beans, or corn + peas (aka the American Indians' succotash); that is, at least two vegetables.
There are also two or three essential fatty acids (depending on your definition), and again any animal cell contains all of them, which again is why you need at least two vegetables if no meat is eaten. This is probably why no one looks truly happy in a vegetarian restaurant, because they sense they are missing something (or subconsciously are aware of the fact that tofu lowers men's sperm count because soy is a phytoestrogen). On the other hand, everyone is all smiles in a steak restaurant.
Everyone should be aware that Vitamin B-12 is necessary for an animal cell to synthesize animal DNA, but not vegetable DNA. Vegetables contain no vitamin B-12 whatsoever. Therefore, if you eat neither meat nor fish nor eggs, you will eventually die from pernicious anemia. It as also a curious fact that no one is literally addicted to eating meat, or can achieve an altered mental state by eating meat (licking Colorado toads being a notable exception). All the addicting or mind-bending foods are vegetables, with their totally different chemistry: nicotine, alcohol, caffeine, opium, marijuana ,peyote, "magic" mushrooms, etc. In fact, if you kill an animal or fish at random and eat it, the odds are that it will agree with you. But if you eat a random vegetable or berry, there are good odds that it will make you ill or kill you (mushrooms, choke cherries, oleander, foxglove, mistletoe, rhubarb, yew, manicheel), not to mention the severe contact allergies from poison ivy, oak and sumac.
As for cholesterol, it is an essential component of the membrane of every animal cell, through which all nutrients pass. (Plant cells have a cell wall outside the cell membrane, which contains no cholesterol whatsoever.) So when we chemically lower cholesterol, we lower a constituent of the membrane of every cell of the body. This in turn alters trans-membrane potentials, ion fluxes, molecular transport, and sensitivity to neural stimulation. This may explain why some patients develop leg cramps (muscle cell irritability and sensitivity), or altered liver tests (? inflammation of the cell membrane and enzyme leakage), and sometimes just don't "feel right"(altered electric potentials in brain cells). If cholesterol is lowered by weight loss, the body responds as a whole, and therefore there are no such side effects. When Wise's Potato Chips tried to advertise their chips as "having absolutely no cholesterol", which is a literal scientific fact, the FTC pulled their add, claiming that patients would confuse "no cholesterol" with "no fat".
We don't even know how many meals we should eat daily: one, two, three,or six. We don't know the proper time of day to eat the largest meal, even though we know that all our minerals and hormones have a diurnal cycle (cortisol is highest in the AM, serum iron in the PM, etc.). We don't know if the fact semi-starved rats exceed their natural life span applies also to humans. We don't understand why, if a normal BMI is optimal for health, how is it that people with an elevated BMI survive heart attacks better.
As for vitamins, a vitamin is a chemical which, if you do not ingest, you get ill and may die (scurvy, beri-beri, pernicious anemia, etc.), because your body needs it as a co-factor for essential enzymes, and cannot synthesize it.A,D,E, and K are fat-soluble vitamins, but C and all the B's will be excreted in your urine, if ingested in excess. Oddly enough, an excess of daily vitamin B-6 causes neurological symptoms, just as a deficiency of the same vitamin does. (cf article in NEJM, more than 10 years ago; research done at Albert Einstein Hospital)Since it is a pure chemical, your body cannot tell the difference between "natural" and synthesized vitamins. Since the FDA does not regulate or supervise vitamin manufacture, there is also absolutely no guarantee as to if a capsule labeled "400 U of Vitamin E" contains 0, 400, or 1200. And the idea that too much of a vitamin cannot hurt you never applies to fat-soluble vitamins, which are stored in your body. We have already seen studies of the coronary artery dangers of too much daily Vitamin E.
Finally, all the suggestions about "healthy" diets are based on retrospective and/or epidemiological studies, which all fail to remember that correlation does not mean causation. The only food intervention shown to lengthen life, mostly by preventing heart attacks, is alcohol. I have read studies with beer, scotch slivovitz, red wine, etc. It is the C2H5OH molecule that saves you. There was an article as far back in 1974 in JAMA, in which comparative autopsies showed that moderate male drinkers had larger diameter (i.e. wider and less clogged) coronary arteries than age and weight matched controls (non-smokers only). Every time a forward study (low fat, beta-carotene, selenium) has been done, the results have been nil, or even negative (especially with vitamin E).
The overall problem is that no prospective food study has ever been done with adult humans, so all are beliefs are just that; beliefs without a sound foundation in experimental fact.