Jennifer Lovejoy, Arivale Chief Science Officer, PhD
The recommendation to “eat a variety of foods” was first introduced in the early 20th Century in response to a high amount of nutrient inadequacies in Americans. The idea that eating a wide variety of foods will ensure adequate intake of essential nutrients, leading to better overall diet quality, went on to become a long-standing part of public health guidelines. For example, the 2015-2020 Dietary Guidelines for Americans recommends choosing a variety of nutrient-dense foods across and within all food groups, with particular emphasis on variety of vegetables and protein sources. The guidelines define dietary variety as “a diverse assortment of foods and beverages across recommended food groups.”
However, a number of studies have focused on the idea of dietary quality – rather than simply variety. Dietary quality scores, such as the Healthy Eating Index, typically assign more “points” to healthy foods (e.g. vegetables, fruits, whole grains, and low-fat dairy) and fewer points for those foods or nutrients that have been associated with poorer health outcomes (e.g. sugars, saturated and total fat, cholesterol, and red meat). Higher dietary quality scores have consistently been associated with better health outcomes.
In a science advisory report released last week by the American Heart Association and covered by the New York Times, an expert panel reviewed the scientific literature from 2000 to 2017 on both dietary diversity and dietary quality. The specific focus was the impact of diversity versus quality on outcomes related to obesity, weight gain, and appetite.
The panel concluded that current evidence does not support the benefits of greater dietary diversity for a healthy weight or optimal eating patterns. In fact, some evidence suggests greater variety is associated with higher calorie intake and weight gain.
In contrast, dietary quality appears to be more consistently associated with better health and, in some research, lower body weights.
One reason for this finding may lie in a factor known as “sensory-specific satiety.” Basically, this means food characteristics like flavor, texture, and appearance can override the body’s natural “fullness” signals. Most of us have had the experience of finishing a meal and feeling quite full before seeing a dessert tray and thinking, “Well, I can probably eat a little more.”
Short-term feeding studies show exposure to a variety of foods may reduce sensory-specific satiety, increasing energy intake and food consumption.
Another possible reason for the panel’s conclusion could be that the nutrient deficiencies prevalent in the early 20th Century – when guidelines about dietary diversity were originally created – are no longer an issue today. Now, in the early 21st Century, over-nutrition is a bigger problem than under-nutrition because of an abundance of relatively cheap food sources.
The AHA report highlights important conclusions, including that emphasizing variety across all possible food choices available today is not likely to be good for your waistline.
The expert panel’s recommendations are completely aligned with Arivale recommendations: “Given the current state of the science on dietary diversity, it is appropriate to promote a healthy eating pattern that emphasizes adequate intake of plant foods, protein sources, low-fat dairy products, vegetable oils, and nuts and limits consumption of sweets, sugar-sweetened beverages, and red meats.”
In other words, aim to eat a diet focused on plants and whole foods.
However, we don’t agree with one of the report’s authors, who told the Times people don’t need to worry about the diversity of their diet – as long as they eat quality foods – “even if it means filling half your plate with one or two vegetables you like and avoiding others.” While this may be true from a strictly caloric point of view, there’s plenty of evidence (this study, for example) that greater variety of choices among fruits and vegetables is important for optimal health. In particular, different colored fruits and vegetables contain different phytonutrients, many of which have been shown to impact health outcomes.
Our overall advice is to focus on dietary quality but still try to “eat the rainbow” when it comes to fruits and vegetables.
- How to Meet Your Nutrition Needs as a Vegetarian or Vegan
- Have Benefits of Mediterranean Diet Been Overstated?
- Eating an Egg a Day May Actually Be Good for Your Heart
[Arivale Hot Topics address health stories currently in the news. The Arivale Clinical Team’s commentary on these news articles is not a review of the scientific evidence, nor an endorsement of a specific study, and is not meant as official medical opinion.]