The answer to the simple question “What should we eat?” is remarkably contentious and fraught with strongly held personal beliefs and preferences, as well as substantial financial and disease implications. It is a question that patients and families often ask their physicians and health care teams, yet those teams generally have little training in nutrition and the science of dietary recommendations. The U.S. Department of Agriculture's (USDA's) Dietary Guidelines for Americans is where many look for guidance.1 Updated every five years by the USDA in partnership with the U.S. Department of Health and Human Services, the guidelines inform the general population and public health policy, including federal and state food programs. Materials based on these guidelines are the foundation of nutrition education for children and adults nationwide and are helpful and easy to use.
With each iteration, the report is praised and criticized by various groups. Although many of the recommendations are widely accepted, such as a focus on fruits and vegetables, whole grains, and patterns of eating, others are more controversial. Criticisms revolve around the authors' reported financial ties to the food industry and the discrepancies between the published guidelines and the recommendations submitted to the authors by the scientific advisory committee. This potential conflict of interest can lead health care professionals to doubt how tightly the recommendations adhere to scientific literature and wonder how to provide evidence-based information to patients.2
The 2020 guidelines continue to focus on the concept of eating patterns. The primary pattern, the healthy U.S.-style eating pattern, focuses on eating nutrient-dense foods with an emphasis on vegetables, fruits, grains, dairy, protein, and oils, while limiting sugar, saturated fat, sodium, and alcohol. Variations of this eating pattern include the healthy vegetarian and healthy Mediterranean-style dietary patterns, as well as the Dietary Approaches to Stop Hypertension (DASH) diet, and are ideally tailored based on cultural and personal preferences. The most accessible way to use the information included in the report is through the USDA's MyPlate website3 and app (https://www.myplate.gov/resources/tools/startsimple-myplate-app). Of note, the various dietary patterns are not found on MyPlate. Advice is organized by food groups and subgroups (e.g., vegetables are separated into dark green; red and orange; beans, peas, lentils; and starchy subgroups) with daily or weekly intake recommendations. The legumes group is now clearly labeled as beans, peas, and lentils. As in previous years, the general focus is on nutrient-dense foods and beverages that remain within designated caloric limits with less than 10% of calories per day coming from added sugars and saturated fats. The current report's strengths include the addition of dietary patterns for infants and toddlers, pregnant and breastfeeding patients, and older adults, and user-friendly images and text.
Compared with the scientific literature, the updated guidelines overemphasize the importance of consuming dairy and animal-based proteins such as beef, pork, and chicken, while underemphasizing the importance of consuming whole grains and completely avoiding the discussion of minimally processed grains.2 The scientific literature would support a stronger statement encouraging a primary focus on plant-based proteins and more emphasis on avoiding processed grains.4,5 The guidelines do call out vegetarian sources of protein such as beans, peas, nuts, and seeds. The focus on the importance of dairy as a source of calcium and other micronutrients, despite so many Americans being intolerant of dairy products (up to 70% of the world's population),6 appears to be fueled by the USDA's ongoing desire to support the dairy industry. The recommendations about alcohol have changed slightly to comment that less is better for health; however, many experts believe they do not go far enough in recommending people cut back further or stop drinking. The scientific committee specifically recommends that men and women limit alcohol intake to a maximum of one drink per day.7 The guidelines recommend sugar intake of less than 10% of calories, although the World Health Organization recommends no more than 5% to 10%.3
Other highlights from the 2020 report include a focus on eating based on stage of life and a review of eating frequency. One new recommendation is that infants exclusively consume human milk for the first six months of life with continued consumption of human milk in addition to complementary foods at least through the first year. When human milk is not available, an iron-fortified formula should be used. Vitamin D supplementation should be started in all breastfed infants soon after birth. Added sugars should be avoided in children younger than two years. There is an official recommendation to introduce potentially allergenic foods (i.e., peanuts, eggs, cow's milk products, tree nuts, wheat, crustacean shellfish, fish, and soy) starting at six months to prevent development of food allergies.1 Eating frequency (e.g., intermittent fasting) was examined by the scientific advisory committee but not included in the final guidelines because of insufficient evidence.1
The U.S. Dietary Guidelines and the accompanying materials give excellent guidance on choosing a healthy diet, with a focus on increasing consumption of vegetables and fruits and reducing consumption of refined sugar. If the authors' conflicts of interest with the agriculture and food industries are reduced, the guidelines will more closely align with the scientific data supporting a primarily plant-based, minimally processed diet for Americans. The scientific advisory committee notes the significance of the omission of questions about the impact of eating patterns and the U.S. food system on the environment. They acknowledge the impact of these factors on the diets of Americans and recommend that these topics be addressed in future versions of the guidelines.