Dietary variety is one of the core principles of nutrition. Most nutrition experts would agree that diversity is among the two or three most important qualities a diet can have; you would be hard pressed to find a nutrition expert who believes that dietary variety is not all that important.
I myself have often preached the importance of dietary variety in my writing. For example, in Maximum Strength, my coauthor Eric Cressey and I wrote:
Different foods offer different nutrition profiles. No food provides every nutrient your body needs, and many natural foods provide nutrients that few or no other foods provide. This is especially true of plant foods, which contain dozens of useful “phytonutrients” that help the body in many ways. So, the best way to ensure that your body gets enough of each nutrient is to consistently eat a wide variety of foods.
I’m not talking about merely hitting all of the basic food groups each day. I’m talking about getting as much variety as possible within each food group. Your animal protein should not always come from beef. Romaine lettuce should not be your only green vegetable. You get the idea.
I stand behind these words. However, I can’t say that I practice this principle as zealously as I’ve preached it. My diet contains a decent amount of variety, but not as much as it might have. I eat more or less the same breakfast (whole-grain cereal and milk, orange juice, and coffee) and the same lunch (half a tuna sandwich with greens and tomatoes on whole wheat, a salad, veggie chips, and a can of V-8 juice) almost every day. My dinners are all over the place, but only because my wife prepares them. If I cooked my own dinners I would probably have a three-recipe rotation.
The thing is, while my diet is somewhat monotonous, it’s pretty healthy. And I know a lot of other athletes whose diets are monotonously healthy, too. I don’t seem to suffer any consequences of eating many of the same foods day after day. So is lack of variety really such a bad thing?
This much is certain: a repetitive diet of healthy foods is better than a highly varied diet containing many unhealthy foods. Proof of this point comes from a British study of dietary variety involving a large pool of subjects, which found that those who ate the widest variety of healthy foods were in fact the healthiest, while those who ate the widest variety of unhealthy foods had the worst health. These findings are not the least bit surprising, of course, but they make a fundamental point that you never hear: dietary variety is not inherently beneficial.
You may have heard that eating the same foods over and over can cause allergies to those foods. I’ve heard this from a few different fringe nutrition “experts,” but I’ve had no luck in finding the source of this notion. In any case, it’s purely mythical. There is no research evidence that eating the same foods frequently for long periods of time creates allergies or intolerance to those foods. If it did, all of China would be allergic to rice, wouldn’t it?
Meanwhile, there may be some benefit to limiting the variety in one’s diet. The obvious advantage—and the reason my own dietary variety is limited—is convenience. When you eat some of the same foods more or less every day you don’t have to put a lot of thought and time into shopping for and preparing food.
A second advantage of food monotony is that it encourages healthy weight management. Several studies have found that people eat more when they eat a wider variety of foods, apparently because satiety results in part from tiring of the taste of food, which obviously happens faster when you’re eating just one thing. Even more compelling is a National Weight Control Registry study which found that men and women who had successfully maintained a large amount of weight loss for a long period of time had a less varied diet than dieters who regained lost weight. The authors of this study speculated that limiting the variety of foods in the diet might help people to better manage their total caloric intake.
On the other hand, there is also solid scientific evidence that dietary variety specifically in fruits and vegetables is beneficial for health. For example, in one study researchers from the University of Colorado divided 106 women into two groups and placed them on different diets. Both groups consumed 8-10 servings of fruits and vegetables per day, but one group ate 18 different varieties of fruits and vegetables while the other ate only five varieties. Blood tests taken after two weeks revealed that while both groups showed a reduction in lipid peroxidation (due to increased antioxidant intake), only the wide-variety group exhibited a reduction of DNA damage caused by free radicals.
Another study, published in the prestigious Journal of the American Medical Association, showed a 30 percent lower death rate over five and a half years within a population of 42,000 women among those whose healthy food variety in the diet was higher. Such findings are not surprising. The human genome is designed to benefit from dietary variety. Perhaps the most characteristic feature of the human diet as compared to the diets of other species is the sheer variety of foods we eat. When our ancestors diverged from chimpanzees more than four million years ago, the key trend in the evolution of our diet, which paralleled our genetic evolution, was a trend toward incorporating more and more foods. Paleolithic humans (living between 10,000 and 8,000 B.C.) are believed to have consumed anywhere from 100 to 200 different plant foods annually.
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The agricultural revolution and other historical events sharply reduced the variety in the human diet. Today the average American gets two-thirds of his daily calories from just four species: corn, soybeans, wheat and rice. That can’t be optimal.
So, just how much variety should we try to get in our diet? Based on the information given above, I think it’s best to focus first on the quality of the food you eat. There’s no point in trying to increase the variety of food in your diet if you’re eating a lot of crap. Getting rid of the crap is your top priority. Once your diet is basically healthy, then you can turn toward diversification. I don’t see anything wrong with a lot of repetition in your proteins, grains and dairy foods. Where variety matters is in your fruits and vegetables. Try to mix these up as much as conveniently possible. Eating mostly fruits and vegetables that are in season is a great way to get started.
Lucky for me, my wife likes to cook with a lot of different vegetables. You’ll have to find your own solution!
Matt Fitzgerald is the author of numerous books, including Racing Weight: How To Get Lean For Peak Performance (VeloPress, 2012). He is also a Training Intelligence Specialist for PEAR Sports. To learn more about Matt and his recent work visit www.mattfitzgerald.org.
Originally published June 2014