What are RDAs and how do they apply to foods such as walnuts?

“Recommended Daily Allowance,” or RDA, is a term used by the National Academy of Sciences (NAS) to refer to the recommended daily intake of nutrients such as vitamin C, zinc, or protein but does not recommend the daily intake of specific foods such as walnuts. At the present time, RDAs are actually part of a much broader recommendation system put forth by the NAS called Dietary Reference Intakes (DRIs). The DRI recommendation system includes many different levels of nutrient recommendation, including RDAs, AIs (Adequate Intakes), Tolerable Upper Limits (ULs), and others. These recommendations are always for nutrients (like vitamins, minerals, proteins, or calories) and never for foods.

The reason there aren’t any RDAs for food is very simple: many different foods could provide us with the nutrients we need, and we have many excellent options for putting together a fully nourishing Healthiest Way of Eating. Therefore, while there is no requirement that any of us consume walnuts, we include them on our list of the WHF because they can make such an important nutritional contribution to your Healthiest Way of Eating and are a particularly good way to bump up a person’s omega-3 fatty acid intake.

Sometimes food companies want to make labeling claims on their packaging about the health benefits of a particular food. Rulemaking in this area involves the U.S. Food and Drug Administration (FDA). The FDA has recently allowed a qualified health claim to be placed on packages of nuts, including walnuts, which says “Scientific evidence suggests but does not prove that eating 1.5 ounces per day of most nuts, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease.”

This 1.5-ounce serving would equal about 20 walnut halves, which would have about 277 calories, about 14% of a 2,000-calorie diet. For some people, this amount of walnuts, and this amount of calories from one food, would be excessive and would not be a prudent step to take towards their health goals. Yet, for other people this amount would fit perfectly in a meal plan and would increase its health benefits.

The serving size we feature on our website, one-quarter (1/4) cup (approximately 10 walnut halves), still provides a good amount of nutrients, but only has about 160 calories—approximately 8% of a 2,000 calorie diet. Yet, whether a person should eat walnuts every day, and how much, really depends upon their individual health, nutrition, and caloric goals. If you are unsure as to how walnuts fit into your individual diet and how they may help you meet your personal goals, I would suggest meeting with a licensed healthcare practitioner skilled in nutrition who can help answer questions such as this one.

For more information on this topic, please see:

• Walnuts