Preventive Medicine Column

Dr. David L. Katz

As you read this, I am likely on a flight back from Orlando, where I spoke at the Food Marketing Institute’s Health and Wellness Conference 2011.  My general theme was that food is just about the best medicine we’ve got, provided we find the needed ways to make that medicine go down (and no, more spoons full of sugar is not the answer!).

I also warned against the ONAAT fallacy.  ‘ONAAT,’ which I made up, stands for ‘one nutrient at a time.’  It’s the false, insidious notion that the nutritional quality of a food, or the relevant nutrition guidance for a given patient, can be gauged just that way, one nutrient at a time.  The food industry exploits this fallacy in a variety of ways, particularly by calling out the one most favorable nutrient characteristic of a food on the front-of-pack, and letting that substitute for the whole truth.

My physician colleagues are, with all due respect to our clan, contributors to the fallacy as well.  Because of relative neglect of nutrition in medical education, physicians tend to ignore the topic, or when addressing it at all, to offer limited advice directly related to their field.

So, rather than providing advice about food, let alone the whole diet, cardiologists may be prone to advise against an excess of saturated and trans fat, and dietary cholesterol.  Endocrinologists may emphasize avoidance of sugar and refined starches.  Gastroenterologists may focus on fiber.  Nephrologists and others treating high blood pressure may focus on sodium.  And so on.  There are exceptions, of course, but the rule prevails.

In my own primary care practice over the years, I have encountered many patients who were trying to follow exactly that kind of dietary advice, imparted by some medical specialist focusing on some particular condition or risk factor.  The trouble with “one nutrient at a time” guidance is of the classic “mistaking the part for the elephant” variety.  The nutritional properties of a food cannot reliably be captured in any given nutrient.

A food may be a source of whole grain, but also a concentrated source of sugar and salt.  A food may be low in sugar, but high in salt- or vice versa.  A food may be low in sugar, but a delivery vehicle for trans fat.  It may be trans fat free, because it is comprised entirely of sugar and food dyes.  Such a food- gummy bears, for instance- may be organic into the bargain, without that signifying anything commendable about its nutritional profile.

Food cannot be judged one component at a time any better than elephants can.  What about health?

A normal resting heart rate does not rule out multiple sclerosis.  A cholesterol value in the desired range does not preclude HIV.

Being free of cancer does not mean good health in someone dying of emphysema.  Being free of emphysema would provide scant comfort to someone with advanced pancreatic or ovarian cancer.  Being free of cancer would not count as vitality in someone with severe heart failure, or cerebral malaria.  Hardly anyone would take pleasure in the robust good health of the left side of their body, while the right side was bleeding profusely.

And then there is the relationship between diet and health, where the fallacy pertains as well.  True, someone with diabetes is well advised to be cautious about sugar, refined starch, and glycemic load.  But diabetes, and the insulin resistance that precedes it, is very often accompanied by hypertension- so this group can’t neglect sodium.

And, the leading cause of death in diabetes is cardiovascular disease.  So if trans fat and certain saturated fats are of concern in heart disease, they must be of concern in diabetes, and pre-diabetes, as well.

We know that inflammation is a major contributor to diabetes, heart disease, cancer, and the aging process- and that high levels of insulin can foster inflammation.  So sugar, starch, and glycemic load are of concern across the board.  Omega-3 fats can reduce inflammation, so they are beneficial to almost everyone.

Dietary fibers can lower blood pressure, and cholesterol, and insulin; can stabilize blood sugar; can improve gastrointestinal health, and potentially lower cancer risk; and can help produce satiety that facilitates weight control.  So they are only important for anyone at risk for conditions that cumulatively affect… at least 80% of the entire population!

In short, you cannot use one nutrient at a time to protect one component of health at a time.  You can, of course, use foods of high overall nutritional quality, making up a wholesome diet, as a potent defense against virtually all forms of ill health, and a pillar of vitality.

Good food is among the best medicines we have.   Good nutrition, like good health, is best viewed holistically.  So beware the ONAAT fallacy- because we are unlikely to get to either good food, or good health, one nutrient at a time.




Dr. David L. Katz;