You might have heard that dietary diversity isn't so good for you after all. But it depends on what you're eating.
You’re supposed to eat a variety of food, right? So what’s the deal with new research suggesting that dietary variety — aka dietary diversity — might actually be not so good for health? How do you interpret headlines like “A varied diet could lead to health problems” and “A diverse diet may not be the healthiest one”? If you didn’t read past the headlines, you might be thinking you better stick to a steady diet of salmon, sweet potatoes and broccoli — or maybe tofu, quinoa and kale.
Well, I’ve got good news for you.
When the American Heart Association published the research in question in their journal Circulation in August, I didn’t think much of it. I read the original article — not just the articles about the article — and didn’t read anything terribly surprising. Then I started hearing patients and non-dietitian friends say things like “So I guess I should limit how many foods I eat.” But what the article actually said was that dietary variety is a good thing — if the foods are nutritious, and if that variety is over time, rather than in a single meal.
It’s a well known phenomenon that the more foods — or more tastes — we have in a meal, the more we are likely to eat, even if we’re no longer hungry. “Sensory-specific satiety” is the reason it’s easier to overeat at a buffet, when ordering multiple restaurant dishes “for the table,” or when there are a zillion side dishes at Thanksgiving. It’s also why you can feel full but still manage to find “room” for dessert. You may feel like you’ve had enough roast chicken, potatoes and salad, but you haven’t had any apple pie, so you aren’t satiated for that particular taste yet.
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So what are we really talking about when we talk about dietary diversity?
When researchers measure dietary diversity, they generally look at how many foods are eaten in a specified time period. They might look at how evenly those foods are distributed (you might eat both cupcakes and broccoli, but not with the same frequency) and how similar those foods are (food choices might spread across several food groups or cluster within just a few groups).
I endorse variety because there are going to be nutritional differences within any particular food group. Almonds and pistachio nuts, for example, both provide protein, fiber and healthy fats, but almonds are also an excellent source of vitamin E, while pistachio nuts are an excellent source of vitamin B6. You might have almonds on your oatmeal today and pistachio nuts on your salad tomorrow. But as the Circulation article summarizes, studies of dietary diversity have found that eating a variety of nutritious foods is associated with desirable health traits; eating a variety of sweets and packaged snack foods is not.
If your pantry or break room is a veritable cornucopia of snack foods, research suggests you’ll eat more than if you had only a few options to choose from. So if you want to have cookies in the house but eat fewer cookies, stock one variety instead of three. If you want to eat more fruits and vegetables, keep more than just broccoli and apples in the fridge. And if you want to eat less at your favorite restaurant, limit the number of dishes you order — save some for your next visit.