Measuring Nutrient Density Made Easy

Our foods contain both nutrients and calories. Nutrient density is the amount of nutrients that a food provides per unit weight, per calorie, or per serving.  The concept of nutrient density allows us to identify those foods that have the most nutritional value, packing the most nutrients per bite. The latest Dietary Guidelines for Americans specifically say that households must prioritize diets built on whole, nutrient-dense foods—protein, dairy, vegetables, fruits, healthy fats, and whole grains.  Nutrient dense foods and beverages are described as those that provide protein, vitamins, minerals and other health-promoting components with little to no saturated fat, added sugars or salt.

The Nutrient Rich Food Index (NRF) is a simple metric used to assess nutrient density.  First, it balances nutrients to encourage – that is protein, fiber, vitamins and minerals – against nutrients to limit: saturated fat, added sugar, and salt.  The calculation is very simple, being based on percent daily values per calorie or per serving.  The NRF was developed about 20 years ago, published and placed in the public domain.  Since then, many studies, including some from France, Spain, Sweden, Japan, and the Netherlands have used the NRF to assess nutrient density of foods in relation to diet quality or health outcomes.  We ourselves have applied it to diverse databases including international nutrient composition databases from the Food and Agriculture Organization of the United Nations (FAO).  Companies have used the NRF approach to benchmark product innovation and reformulation.

The Nutrient Density Calculator takes the NRF approach several steps further.  First the Calculator uses both nutrients and ingredients to calculate nutrient density of dishes and meals.  The two positive components: nutrients to encourage and ingredients to encourage are balanced against nutrients to limit.  Nutrient density is calculated per serving to answer the simple question – which provides more nutrients, a hamburger or a slice of pizza.  The servings-based Calculator is ideally suited to help benchmark improvements in nutrient density of mixed dishes, where changing the recipe ingredient can alter nutrient profile of the dish.

Making sure that the Nutrient Density Calculator would be sensitive to recipe adjustments was an important consideration for us.  Reducing saturated fat, added sugar and salt is one way to improve nutrient density.  Adjusting the balance of ingredients or adding protein or fiber is another.  We wanted to make sure that different creative ways of improving recipes for better health would be captured by our instrument. There was one more important consideration. Innovation sometimes represents gradual progress towards a goal.  We felt that a continuous 10-point score would assist and guide innovation much better than a categorical pass/fail system. Pass/fail systems do not tell you what worked and what did not.

Nutrient density is becoming a bridge between nutrition and economics. My work has identified nutrient density scores as a way to compare the affordability of different foods.  The concept of affordable nutrient density, promoted by FAO, can now be expressed as maximum nutrients per penny.  We also have a Nutrient Rich Food Price Index to assess food inflation, especially for nutrient rich foods.  Mathematical calculations of nutrient density and monetary cost can be extended to the environmental cost of different foods.  Rather than calculate greenhouse gas emissions per kilogram of food, we ought to look at the environmental cost of providing 50 grams (100% Daily Value) of high-quality protein or a bundle of key nutrients.  Nutrient density is at the center of the food sustainability framework, helping to bring together health, economics and the environment.  I find those new directions to be very compelling.