Cholesterol is bad. Cholesterol is an essential building block for important hormones.

Eggs are bad. Eggs are a complete protein food.

Salt is bad. Salt is essential for life.

High blood pressure kills people. No blood pressure defines death.

High blood sugar causes eye and kidney damage. Low blood sugar causes falls, fractures and car wrecks.

Low potassium causes heart rhythm problems. High potassium causes heart rhythm problems.

Too little vitamin B12 causes nerve damage. Too much vitamin B12 causes nerve damage.

The ancient physicians, from Hippocrates in Greece to the Yellow Emperor in China, to Ekiken in Japan and Charaka in India, all spoke of the virtues of moderation.

Why do we in our culture go to excess in our pursuit of wellness? We always seem to want to classify foods and nutrients as either good or bad. Depending on how we classify them, we go to excess in consuming them or we deprive ourselves of even necessary amounts of them.

There is even a newish disease, defining the extremes of such behavior, orthorexia nervosa.

The latest scuttlebutt of this sort is the new findings that low sodium diets are associated with greater risk of ending up dead than moderate salt diets. The editorial about the studies published in the New England Journal of Medicine made me late for my nightly rounds to check on the barn animals Wednesday night. The piece was interesting, but ultimately no more enlightening than reciting the old adages “everything in moderation” and “nothing to excess.”

Somehow, we here in America have been conditioned to seek expert guidance over our own common sense or our grandmothers’ advice. We listen to government advice about drinking eight glasses of water per day whether we are joggers in Memphis during August or mailmen in Anchorage during January. We even listen to medical experts in unrelated fields who promote the latest nutrition and supplement fads on TV for their own profit.

The problem with turning the findings of scientific studies into practical advice or medical treatments is that science only produces data. “Data-driven” has become a buzzword today, just like “evidence-based,” or a new one I heard recently, “evidence-supported.”

What is wrong with both data and evidence is that neither entity equals truth, value, practicality or wisdom, not to mention the fact that the scientific evidence has changed many times over about a great many things just in the last few decades. If people wearing astronaut-like Ebola suits are less likely to also get the flu, does that mean we should all wear them during the winter months? Probably not. If tall bachelors have more dates than short ones, should we issue platform shoes to the vertically challenged (my very first blog post)? It was tried to a degree in the 1980s, but never quite worked out.

Data is meaningless without context or “big picture.” Medical research, by its nature, analyzes small and easily defined parameters within the vast systems we call health and disease. What makes perfect sense to do for the well-being of one corner of our anatomy or physiology may have disastrous consequences for another and possibly for the whole organism. Each scientific study only aims at illuminating one small aspect of life. Only with an understanding of the bigger picture can we decide how to use the nuggets of fact science produces.

Even more than a view of the big picture is required to truly make use of data: Common sense, trivial as that may sound, is required when making judgments and setting priorities. This is what has gone missing in our collective enthusiasm at the advances of science in the past century. My grandmother, who would have been 114 this year, but only lived to be 96, already knew that a little salt, fat or sugar never hurt anyone, but eating anything to excess was not healthy.

Both Hippocrates and grandma, without the advantages of scientific data, knew in their hearts by virtue of their common sense what science has finally seemed to confirm.

We, as a culture, need to take advantage of both our shared, ancient wisdom and the advances of science, but either one without the other is likely to sometimes lead us astray.

Semmelweis’ analysis of why midwives’ postpartum infection rates were only a fraction of doctors’ and medical students’ is an example of science serving to explain what common sense already knew: Touching the dead before delivering babies made bad things happen.

Population studies, on the other hand, where we seek to find out if vegetarians, salt fiends, runners, nurses or yoga practitioners are healthier than others after decades of doing what they do are so fraught with uncontrollable variables that we are likely to be confused; it took twenty years to find out that postmenopausal estrogen treatment didn’t decrease heart attack rates in older women as the experts had speculated. Too many years of a good thing turned out to be bad.

My grandmother could have told us that taking drugs to thwart aging didn’t make any sense. So could Hippocrates. They both had common sense. We need to cultivate ours in order to properly make use of today’s exponentially increasing amount of data.

Come to think of it, data seems to be a little bit like salt: Either too little or too much can be debilitating. We should let our common sense regulate our consumption.

“A Country Doctor” is a family physician who blogs at A Country Doctor Writes:.