Dietary Diversity

One of the biggest nutritional challenges of the Standard American Diet is that, while it may feel like you’re eating a wide variety of foods, with so many being made from only a handful of ingredients (wheat, corn, soy, and dairy), the diet isn’t actually diverse. We can increase variety and nutrient density by replacing these types of foods (breads, cereals, pasta, pizza, crackers, cookies, etc.) with a diversity of whole foods instead.

Health Benefits of a Diverse Diet

Dietary diversity is typically defined as the total number of different food items in a diet. One way to measure dietary diversity this is Dietary Species Richness, the number of different species represented in the diet during a 1-year period.

In a 2021 study that included nearly half a million people living in nine European countries and followed for 22 years, the people in the highest quintile of Dietary Species Richness (81 or more different species in the diet over the course of a year) had a 37% reduced risk of all-cause mortality (a general indicator of health and longevity) than those in the lowest quintile of Dietary Species Richness (48 or fewer different species in the diet over the course of a year). The authors calculated that, for every additional 10 species we consume annually, all-cause mortality decreases by 10%!

While a variety of studies show benefits to eating a diversity of vegetables and fruit (including some discussed below, and see Importance of Vegetables and Fruit), it appears as though total dietary diversity is more important than diversity of any one food group. In this study, the authors further analyzed 10 different food groups (vegetables, tubers, legumes, fruit+nuts+seeds, dairy, cereals, meat, fish+shellfish, eggs and condiments) and showed that, while variety in veggies was slightly more important, there was no one food group that was substantially more important to mix it up than any other. Quite simply: the more different foods we eat, the healthier (on average) we’ll be!

Other studies have found similar results in other populations. For example, a 2019 study from Japan evaluated the impact of dietary diversity by measuring the average number of different foods in the diet in a single day. Comparing the highest quintile (34.9 or more different food items for men, and 39.8 or more different food items for women) to the lowest (13.4 of fewer different food items for men, and 15.4 or fewer different food items for women), high dietary diversity reduced risk of all-cause mortality by 19% in women. The 4% reduction in all-cause mortality in men was not statistically significant, although fruit diversity reduced all-cause mortality by 13% in men.

Another way that dietary diversity is measured is the Dietary Diversity Score, which reflects the number of different food groups represented in the diet over a 24 hours period. Exactly how food groups are defined for the Dietary Diversity Score is not standardized across studies; but for example, a 2022 study of a Mediterranean population awarded up to two points for different subgroups within fruits, vegetables, dairy products, cereals, and proteins, for a total score out of 10. Comparing the highest dietary diversity quartile (a Dietary Diversity Score higher than 6.1) to the lowest quartile (a Dietary Diversity Score less than 4.5), high dietary diversity reduced risk of all-cause mortality by 32% and reduced risk of cardiovascular disease mortality by 45%. This study also found that diversity of vegetables was important, with the highest quartile of vegetable diversity having 30% reduced risk of all-cause mortality and a 48% reduced risk of cardiovascular disease mortality than the lowest quartile.

And, a 2022 meta-analysis that included data from 20 longitudinal studies found that high dietary diversity reduced all-cause mortality risk by 22% compared to low dietary diversity, as well as reducing cardiovascular disease mortality by 17% and cancer mortality by 10%. Interestingly, this meta-analysis also showed that total dietary diversity was more important than any particular subgroup of food; vegetable diversity only accounted for a 5% reduced risk of all-cause mortality.

Overall, studies show that more diverse diets are higher quality and more nutrient-dense diets. People are more likely to eat more vegetables and fruit, if they eat a wide variety of them. In fact, Dietary Diversity Scores can be used as a proxy for nutrition, with low scores equating to malnourishment and high scores equating to healthy diets. Essentially, a diversity of different foods equates to a diversity of nutrients, increasing the likelihood of nutrient sufficiency, i.e., Nutrivore!

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Dietary Diversity Goals

All in all, these studies make a compelling case to eat as many different foods as possible. While more studies are needed to determine the best target number of different foods per day or per week, a case can be made to aim for 12 different whole foods per day, and 35 different whole foods over the course of the week.

Remember though that every little bit counts, so a great goal is to simply mix it up in whatever way feels achievable to you right now. Maybe that’s just adding a single new vegetable or fruit to your rotation, or trying a new recipe once per week.

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Tips for Diversifying Your Diet

Here are some easy ways to increase dietary diversity:

• Embrace soups, stir-fries and salads. These are easy dishes to pack a bunch of different foods into, often containing 8 to 10 different foods, or more!
• Think of easy swaps. If you normally make a dish with salmon, try it with trout instead. Swap your go-to cut of steak for a different cut, or meat from a different animal (like lamb chops!). If you normally put blueberries on your yogurt, mix it up with some blackberries. If you normally put lettuce on your sandwich, try spinach or chard instead. Love mashed potatoes? Try mashing other root veggies instead.
• Try different varieties of your staple foods. Look for different varieties of apples, bananas, grapes, oranges, pears, kiwis, carrots, kale, lettuce, potatoes, sweet potatoes, snap beans, asparagus, cauliflower, broccoli, Brussels sprouts, cabbage, summer and winter squash, etc. You can usually find even more varieties at a local Farmers Market.
• Add variety with garnishes! Add fresh chopped herbs to your roasted veggies, toss a handful of nuts or sliced fruit into your salad, or serve a chutney or salsa with your steak or fish.
• Eat seasonally! In-season vegetables and fruit (like peaches and cherries in the summer, apples and squashes in early fall, pomegranates and persimmons in the late fall, citrus in winter, and berries in springs) are more likely to be fresher, cheaper and locally-grown, even from large grocery store chains.
• Be adventurous! If you see a fruit or vegetable you’ve never tried at the store, get some! Once you’re home, you can search online for how to prepare and eat it. Try different meals at your favorite restaurants, and cook different recipes out of your go-to cookbooks! Try some new cuisines, new flavors, new ingredients… you might just find some new favorites, too.

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