They’re at it again. The federal government is about to issue new dietary guidelines, the first since 2010. The actual report is not yet available, but some of its contents has been leaked to the press. The committee charged with writing the guidelines is an interesting one. There are three physicians on it – a pediatrician, an oncologist, and an MD/PhD/MPH who is an epidemiologist specializing in the areas of dietary and lifestyle determinants of obesity, type 2 diabetes, and cardiovascular disease. The other 11 have terminal degrees other than the MD. The membership of this committee virtually assures that it will take itself more seriously than doctors in practice will. Practicing physicians are apt to view such pronunciomentos with a jaundiced eye.

Why are dietary guidelines issued? Presumably, because its authors believe that adhering to them will promote good health. Why they believe such is unclear as the guidelines change so often – every 5 years, in fact. If the early reports are correct, cholesterol is about to get a pardon and the optimum salt intake is to change – up, I suspect as it’s currently so low that there’s only one way it can go. As soon as the report is released I will comment on it in some detail.

Virtually without exception, dietary recommendations are based on extrapolations from data which show associations – ie, subjects with high cholesterol levels have an increased incidence of heart disease. They are not based on controlled studies. Such studies would put matched groups on various diets and follow them for a long time. Obviously, such studies are almost impossible to do. But without them dietary guidelines are educated guesses. They do not pass the test of Evidence Based Medicine.

For now, a few comments on good health. Suppose you are a healthy young adult. You are neither obese nor painfully skinny – your Body Mass Index is between 25-30 (or even a little higher). You are not sedentary. Is there a diet that will convey an obvious health advantage assuming the aforementioned conditions persist? None that I know of. Is there a diet that will decrease your likelihood of developing a serious illness? Again no.

What factors determine your health status over the next half century? Most of them involve luck. To begin with, how did you do in the genetic lottery? So far, there’s nothing you can do about your genetic lot except hope for the best. Next is how lucky you are in escaping the consequences of all the stupid things you do. And we all do a lot of stupid things. Did you run a red light without incident? Did an errant golf ball miss your head by inches instead of hitting it? You get the idea about the salutary health effects of good luck.

There’s even a very large component of luck that determines if you get cancer. Random mutations accumulating in healthy stem cells likely explain a large number of cancers. How large this fraction is remains controversial, but it’s definitely not small.

Do you live in a safe or dangerous part of the world? Are sanitary conditions good in your corner of the globe? If you get a serious acute illness, can you get prompt and effective medical treatment? Note the irrelevance of diet to how you do under the above circumstances.

What should a serious person do with respect to diet. Again assuming you do not have a chronic disease, eat whatever you wish as long as your weight stays within the limits mentioned above, also don’t go on a obviously crazy diet. Don’t go to the doctor unless you have a reason – ie, you think something is wrong. Do go to the dentist regularly. Brush your death and floss at least once a day – twice is better. Poor oral hygiene is a state of chronic inflammation which promotes a large number of chronic illnesses.

Also, wear your seat belt. Don’t drive like a lunatic. Don’t smoke. Don’t drink a lot of alcohol. In general, use common sense, aka good judgement. Don’t depend on the government for the minutia of good health. Let them keep the sewerage separate from the drinking water and get them to stop worrying about the size of a soda. After these, you and luck are on your own. I’m not discussing children here; they fall into a separate category.

Americans spend too much time worrying about their health. They persistently overestimate the positive health effects of diet and exercise. This is not to say the that the two may not have a beneficial effect – just that if it exists, it’s small.