The Scoring Algorithm

What the Health Score Measures

Rapid Prime Diet Quality Score Screener (rPDQS) was developed by Dr. Selma Kronsteiner-Gicevic, Dr. Walter Willett, and their colleagues at Harvard TH Chan School’s Department of Nutrition and other Boston medical institutions. It was developed as a brief diet-quality screener for primary health care settings and validated against the Healthy Eating Index (a collaboration of the U.S. Department of Agriculture and the National Cancer Institute).

A high health score indicates a lower risk of a serious chronic disease, including obesity, type 2 diabetes, numerous cancers, heart attacks, and strokes. Consuming plenty of beans, nuts, vegetables, fruits, whole grains, low-fat dairy foods, and non-fried poultry will give you a high score. On the other hand, diets rich in meat, full-fat dairy products, sugar drinks and desserts, and alcoholic beverages result in lower scores. In terms of nutrients, it’s best to choose foods low in saturated fat, added sugars, sodium, and alcohol, and high in dietary fiber (found naturally only in plants and mushrooms).

Our Calculator is based on only 16 dietary habits and cannot cover every detail of an individual’s diet. Restaurant meals are particularly challenging because they vary from small, healthy salads to voluminous, fatty, salty multi-course meals with few vegetables or fruit. Restaurant scores are based on estimated saturated-fat content. Also tough to evaluate are stews, casseroles, other mixed dishes, and packaged foods, in which the ingredients could vary tremendously; the algorithm assigns the typical ingredients and nutrients of such foods to the various food categories. You should feel free to adjust your number of servings or your scores if your servings are particularly small or large, or when you realize something that the algorithm does not. Low-fat or fat-free dairy foods are lower in saturated fat and healthier for consumers than their full-fat versions. However, yogurt and cheese are fermented, and even high-fat versions may be less unhealthy than once thought. Still, milkfat adds calories that most people don’t need.

What the Environment Score Measures

Environmental scores, not included in the rPDQS, are based on per-kilogram amounts of food and the associated amounts of greenhouse gas emissions (35%), stress-weighted water use (25%), eutrophying emissions (15%), land use (15%), and acidifying emissions (10%). The best way to get a high Environment score is to eat less (or no!) food, but doing that could mean eating fewer healthy foods, thereby holding down the Health score. And please don’t feel miffed that eating fruits or vegetables reduces your Environmental score; growing, shipping, and storing anything has an environmental cost.

What This Calculator Does Not Consider

Some of the factors not included in the scoring algorithm deserve a few words of explanation.

• Salt/sodium: Diets high in sodium cause as many as 100,000 premature deaths annually, but because salt is used so widely throughout the food supply, with amounts varying greatly from brand to brand and with some people adding salt to some meals, it is impossible to estimate accurately how much sodium people are consuming. Two major sources of sodium: (a) bread, pizza crust, tortillas (because most people eat many grain products in a day) and (b) table-service restaurant meals (because portions are often huge, highly salted, and contain cheese, processed meat, and dressings and sauces high in sodium.
• Organic foods: Organically produced vegetables, meat, eggs, and other foods are a great benefit to farmers and farm workers because they minimize exposure to harmful pesticides and antibiotics. Consumers may benefit from smaller amounts of pesticides in their food and fewer antibiotic-resistant bacteria. The environmental impacts are mixed. Insecticides may kill beneficial insects and reduce the food supply available for birds and other animals, and herbicides may reduce weed populations that otherwise provide food and shelter for insects, birds, and small mammals. However, crop yields are generally lower for organic crops, meaning that it takes more land to produce the same amount of food.
• Animal welfare: Pigs not raised in cages, broiler chickens not confined to huge windowless warehouses, layer hens not crammed into tiny cages, and cattle raised on pastureland for their entire lives instead of being “finished” at feedlots are hugely beneficial to the animals. Note, though, that grass-fed cattle take longer to mature and therefore emit larger quantities of greenhouse gases (methane and carbon dioxide) and a greater need for pastureland. Grass-fed cattle—with their higher cost and tougher meat—will inevitably comprise only a small fraction of the beef Americans consume.
• Food waste: Roughly one-third of all food produced is wasted. That includes crops left on farms; spoilage at packinghouses, factories, and supermarkets; and uneaten food in homes. And that includes perfectly healthful and edible produce that is discarded because of blemishes and packaged foods that passed their “best by” dates, even though they were still perfectly edible. Reducing food waste could reduce the amount of food that needs to be produced and the food and packaging dumped in landfills.
• Genetically modified (GE) ingredients: Countless packaged foods contain ingredients derived from wheat, corn, and soy crops grown from seeds that were modified to resist the effects of herbicides or to contain a harmless insecticide. A few minor crops have been safely engineered to provide a consumer benefit, such as Hawaiian papayas modified to resist a crop-killing virus, and potatoes and apples modified to resist browning when sliced. The oils, starches, and other common ingredients made from GE crops have been purified to such a great extent that they do not contain any modified genetic material whatsoever. There is no evidence that foods containing ingredients from GE crops have harmed anyone’s health. However, some evidence indicates that glyphosate, the key ingredient in the widely used Roundup herbicide used on GE corn, soybeans, canola, and other crops, may be carcinogenic. GE crops have both positive (e.g., reduced use of more toxic pesticides) and negative (e.g., herbicide-resistant weeds and insecticide-resistant insects) environmental consequences.