Dietitians are in consensus: diets are important. Individual nutrients, specific foods or single meals need to be considered as part of a person’s dietary pattern before they rise to the level of health significance.

For years, it’s been annoying to see the creeping acceptance of the contrary view, embracing a “good food/bad food” dichotomy based on the obvious fallacy that any food or any meal raises or lowers the likelihood of good or bad health outcomes. Groups like the Center for Science in the Public Interest (CSPI) take this wrong road right to the very end; their membership solicitations try to frighten the gullible into shunning “10 foods you should never eat.” Truth is: all of these foods can be part of a healthy diet. Not only is the variety of nutrients, foods and meals important, but examining dietary patterns allows consideration for the complex nutrient interactions that take place when we eat.

We’ve known the importance of healthy diets for centuries. Five years ago, Dr. Ashima Kant documented how dietary patterns (not foods, not meals) are related to chronic disease outcomes (JADA , 2004;104:615-35). Now, just in time for the 2010 revision of the Dietary Guidelines for Americans, two studies published in the past month offer further support to reversing the slide into the “good food/bad food” fallacy. Both employ rigorous scientific methodology to reach their conclusions. And those conclusions are:

• With regard to coronary heart disease there is “strong evidence of a causal link between CHD and dietary patterns ” with cohort studies demonstrating the protective effect of vegetables, nuts and monounsaturated fatty acids and three defined dietary patterns that incorporate these elements: the Mediterranean Diet and what Dr. Andrew Mente and colleagues at McMaster University call the “prudent” and “high quality” dietary patterns. On the other side, the current “western diet” and diets with high glycemic loads create health risks. Of these, only the Mediterranean Diet has been proven effective in randomized controlled trials. Think about all the dietary recommendations – and, even more, recommendations on various foods or types of meals – that are advocated constantly but which lack a foundation in medical science.
• Using dietary recall to evaluate dietary quality is difficult, so a simple surrogate indicator, a biomarker, would be a valuable aid to determine if our individual – or our population – diets are meeting our quality objectives. And now such a boimarker has been validated . That marker is urinary potassium. The higher the urinary potassium, the better the diet. Given that sodium is the electrolyte that’s been accorded the most emphasis (on food labels, in advertising, etc.) the researchers also examined urinary sodium as a marker of diet quality. They found sodium to be a poor surrogate for overall dietary quality (despite the fact that the model included a sodium component whereby higher sodium intakes would be “unhealthy” so that modeled disadvantage was overcome by other dietary factors). Dr. Mente, this time with a team at Toronto’s Mount Sinai Hospital, conducted the analysis. They concluded that “a single 24-h urinary K+ measure is a clinically valid, simple, and inexpensive ($10.00 in Canada) test of overall diet quality.”

So, when you hear CSPI or some other do-good advocate suggest that eating a particular food or avoiding another is good for you, take it with a grain of salt. If they tell you that meals with too much of any nutrient (sodium, certainly, but also fat or some other target of opportunity) is bad for you, tell them to read the science first.

The Mediterranean Diet, the only one proven in controlled trials to actually improve health, has about 30% more salt than the average American diet today. Perhaps coincidentally the only randomized controlled trial of the health outcomes of a low-salt diet was also done in Italy. It confirmed that low-salt diets not only failed to deliver expected health benefits, but actually placed those cutting back on salt at additional risk.

Perhaps the quality science pushing forward our understanding of the importance of dietary patterns and overall diet quality will displace the loud, but scientifically-unsupported calls to cut out this nutrient or that, forego eating traditional and tasty foods and avoiding meals that don’t pass muster with the food police.