David L. Katz

Healthy living: Accept no substitute. There is none. There, I've said it.

I've said it before now, and at every opportunity. Lifestyle is medicine, and the best we've ever identified. Feet (physical activity), forks (dietary pattern) and fingers (not holding cigarettes!) are the master levers of medical destiny. We can round out that list to the "Super Six": feet, forks, fingers, sleep, stress and love. Deal effectively with all of these, and almost everything else is substantially less important.

But that does not rule out the use of strategies that fortify or supplement the benefits of healthy living. It does not rule out some degree of reliance on judicious insurance policies against our gaps and lapses.

And in that space of gaps and lapses, nutrient supplements figure prominently, as indeed they should. Our love affair with them began in the late 19th and early 20th centuries, the golden era of linking prevailing public health problems with specific nutrient deficiencies. It's rather hard not to fall in love with the simple, safe, inexpensive remedies for scurvy, beriberi and rickets.

And fall in love we did, with more fidelity than love often enjoys--for that love clearly persists a century later. Use of nutrient supplements is widespread, and the sale of them is big business.

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In some cases, the arguments in favor of this persistent passion are entirely persuasive. We are widely subject to vitamin D deficiency, given our penchant for clothes, air conditioning, cozy indoor comfort in winter and sunscreen. While vitamin D should really be a hormone our bodies make from sunlight; in the absence of that sunlight, it devolves to a nutrient most of us consume in less than optimal quantity. Supplementation fixes this problem, and is a sensible response.

Similarly, relative if not overt omega-3 fatty acid deficiency prevails, and for comparably culture-wide reasons. We have domesticated omega-3 fat out of many of its native repositories in the food supply--such as the flesh of animals. The flesh of antelope and deer contains omega-3; the flesh of grain-fed cattle does not. And since most Americans don't eat fatty fish several times a week, supplementation is again a judicious defense against potential deficiency.

Other such cases can be made as well, although most other nutrient supplements are better addressed on a case-by-case basis. My clinical team and I use nutriceuticals therapeutically as a matter of routine, but we customize such uses to individual circumstance.

The easiest, most tempting, and in many ways most logical form of self-defense against potential, nominal nutrient deficiencies is a daily multi-vitamin. (I use the term "nominal nutrient deficiencies" to mean suboptimal intake, but without any overt evidence of a bona fide deficiency syndrome) is a daily multivitamin. For many years, I both routinely recommended a multivitamin to almost all of my patients and took one myself. Recently, however, things have gotten a bit more complicated.

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To be sure, there have been studies showing benefit from a daily multi. This is impressive, and in some ways rather surprising. All good epidemiologic research is about two groups that are alike in all ways but the one being investigated. So, to show a benefit from a multivitamin, that means the benefit would still be visible after matching for diet, exercise, smoking, alcohol, medications and more. That multivitamins appear to reduce cancer risk once all such other factors are accounted for suggests an effect that is surprisingly robust.

However, we have also seen a sequence of studies suggesting that multis may confer no benefit, and even that they may do harm. That latter possibility is something of a game changer, for we have long recommended multis with confidence that they might help and, at the very least, "couldn't hurt." But if they can hurt, their use should be more circumscribed, and circumspect.

I think there is, in general, a case for multis. Many Americans, and certainly our kids, have important dietary deficiencies (along with the obvious excesses), and nutrient supplements can help plug these gaps. But I do look for gaps before advising use of such plugs. In other words, I want to know something about dietary pattern before deciding which nutrient supplements make sense.

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As for the possibility of harm from multis, it does make sense. Some popular multis seem to be based on the "if some is good, more is better" premise, providing nutrients at many multiples of the recommended daily allowance. But more is not necessarily better and might even be harmful. We may at times also be choosing the wrong formulations. Or, perhaps, we may provide nutrients in the wrong context.

Nutrients work in concert with other nutrients--and a concert analogy may be especially apt. While a jazz pianist, rock guitarist and opera singer may all be great--they might not sound great all together at the same time. Mixing nutrients together in arbitrary combinations could, conceivably, produce the metabolic equivalent of noise--rather than making the beautiful music for which we are hoping.

One potential remedy to this resides with so-called "whole food supplements." These are nutrient supplements that, as the name implies, encapsulate all of the nutrients found in foods. The brand I know best is Juice Plus. These capsules contain all of the nutrients found in many servings of vegetables and fruits, condensed into a powder and packed into a capsule. The nutrients in these supplements are both the ones we know and many we don't. And they are provided in dose combinations designed by nature, not by us.

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I find this approach logical and compelling. And there is some research to support it--including some from my own lab. But to date, there are more questions than answers. Would we all benefit from such supplements? Are they most useful for those who eat few vegetables and fruits? Can food-based supplements help us all "go native," meaning better approximate the nutrient intake levels of our Stone Age ancestors? And if they can, would our health improve as a result?

We don't know if our "native" nutrient intake represents the optimal level in every case, although some examples--including omega-3s, folate and vitamin E--suggest they might. Another possibility is that optimal nutrient intake levels are proportionate to calorie intake--meaning we need higher nutrient levels with more overall food intake. Or maybe optimal nutrient intake is better related to our activity levels and the calories we burn, rather than those we consume. Honestly, we just don't have these answers. I hope to see research address the questions and hope to be involved in it.

For now, I am a proponent of judicious nutrient supplementation. Whenever possible, supplementation practices should be customized to address medical history, lifestyle, activity level and dietary pattern. The selection of supplements should be guided by some genuine knowledge, so find a dietitian or health professional you trust to offer guidance in this area.

Above all, avoid the prevalent tendency to let supplementation grow beyond its mandate into substitution. There is no evidence to support supplemenstitution; or maybe it's substitumentation. Either way, just say no. We have evidence that well-chosen nutrient supplements can support health. We have no evidence whatsoever that they can substitute for a healthy lifestyle.

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So supplement healthy living? Sure. But substitute for healthy living? There is no substitute.

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David L. Katz, MD, MPH, FACPM, FACP, is a specialist in internal medicine and preventive medicine, with particular expertise in nutrition, weight management, and chronic-disease prevention. He is the founding director of Yale University's Prevention Research Center, and principal inventor of the NuVal nutrition guidance system. Katz was named editor-in-chief of Childhood Obesity in 2011, and is president-elect of the American College of Lifestyle Medicine.