It's called the NuVal Nutritional Scoring System, and it summarizes the overall nutritional value of food, using the Institute of Medicine's Dietary Reference Intakes (quantitative reference values for recommended intakes of nutrients) and the Dietary Guidelines For Americans (advice from the Department of Health and Human Services, HHS, and the Department of Agriculture, USDA, about how good dietary habits can promote health and reduce risk for major chronic diseases) to quantify the presence of more than 30 nutrients.

These 30 nutrients include vitamins, minerals, fibre, and antioxidants; sugar, salt, trans fat, saturated fat, and cholesterol.

The system also incorporates measures for the quality of protein, fat, and carbohydrates, as well as calories and omega-3 fats. The system also takes into account how these nutrients influence health, based on broadly accepted, published scientific literature.

How is a NuVal score calculated?

The NuVal Nutritional Scoring System takes more than 30 different nutrients and nutrition factors into account when developing a score, making it a very robust food rating system.

The nutrient content for a food is processed through a complex algorithm developed through a rigorous process by a team of 12 experts. Boiled down to its simplest description, here is how the NuVal Nutritional Scoring System works:

Nutrients with generally favourable effects on health are placed in the numerator, where higher values increase the NuVal score.

Nutrients with generally unfavourable effects on health are placed in the denominator, where higher values decrease the NuVal score.

In addition to the numerator and denominator nutrients, the algorithm takes into account other key factors that measure the quality and density of nutrients, as well as the strength of their association with specific health conditions.

For example, trans fat has a very strong association with heart disease, a highly prevalent and serious condition. Therefore, the algorithm assigns a "weighting coefficient" to trans fat which substantially lowers the Score of foods containing it. Those weighting coefficients are determined by the prevalence, severity, and strength of association with health conditions.

The quality of macronutrients (fats, proteins, carbohydrates) is another key factor in the overall equation. Fat quality, protein quality, carbohydrate quality, and glycemic load (a measure of carbohydrate quality) are among the "universal adjustors" that can move a NuVal score higher or lower. The higher the quality, the higher the score.

Foods with higher nutrient density — a significant amount of vitamins and mineral, but relatively few calories — also receive extra credit and higher scores.

The greater a food's "trajectory" toward numerator nutrients (generally favourable) and away from denominator nutrients (generally unfavourable), the greater the score.

Fruits and vegetables

Many of the most nutritious items in the supermarket are found in the produce aisle, where NuVal scores range from 100 to 24. While vegetables and fruits tend to score very high on the range of NuVal Scores, they don't all score exactly the same.

Scores vary in the produce category based on the concentration of vitamins, minerals, antioxidants, and fibre in particular. Those at the very top of the range are very highly concentrated in many nutrients and low in calories. The lower scoring produce items are less packed with nutrients (as in the case of iceberg lettuce) or higher in calories (as in the case of passion fruit).

Apricots: 100
Asparagus: 100
Beans (yellow and green): 100
Blueberries: 100
Broccoli: 100
Cabbage: 100
Cauliflower: 100
Kiwi: 100
Lettuce (Green Leaf, Red Leaf & Romaine): 100
Mustard greens: 100
Okra: 100
Orange: 100
Spinach: 100
Strawberries: 100
Turnip: 100
Carrots: 99
Grapefruit: 99
Pineapple: 99
Plums: 99
Mango: 93
Potatoes: 93
Red onions: 93
Tangerines: 93
Bananas: 91
Corn: 91
Grapes: 91
Honeydew melon: 91
Rhubarb: 91
Iceberg lettuce: 82
Bok choy: 81
Passion fruit: 78
Coconut: 24

Meats and poultry

All meats provide nearly perfect protein — only egg white is a more perfect source of the essential amino acids.

Meat also is a good source of some B vitamins and minerals such as zinc. But meats can also provide saturated fat, cholesterol, and varying amounts of sodium.

Scores in this category range from 53 to 24. They tend to vary based on the content of saturated fat and sodium in particular; when these are more concentrated in a product, the NuVal Score will tend to be lower.

Processed meats with added sodium will also tend to score lower. The saturated fat content of poultry varies between white and dark meat (white meat tends to have less), and whether it is skinless or not (the skin is very fatty).

Remember that while lean meat may be a very important part of a balanced diet, it will never score as high as most vegetables. That is because the NuVal System measures the ratio of nutrients to calories, and meats are generally a much more concentrated source of calories than fresh produce.

So don't look for a NuVal Score of 100 in this category; instead, just compare meat scores to one another to find the items that are the most nutritious in this category.

Turkey Breast (skinless): 48
Chicken Breast (boneless): 39
Pork Tenderloin: 35
Bottom round roast (beef): 34
Flank steak (beef): 34
Turkey breast: 31
Veal chop: 31
Veal leg cutlet: 31
Beef tenderloin: 30
Chicken drumstick: 30
Ground sirloin (beef – 90/10): 30
Pork chop (boneless centre cut): 28
Chicken wings: 28
Ground round (beef - 85/15): 28
Lamb Chops (loin): 28
Leg of lamb: 28
Ham (whole): 27
Ground chuck (beef – 80/20): 26
Pork ribs, country style: 25
Beef spareribs: 24
Pork baby back ribs: 24

Seafood

Like meat and poultry, seafood is a source of neatly perfect protein. But unlike most other meats, fish tends to be low in saturated fat, and is often a concentrated source of fish oil, which is rich in health-promoting omega-3 fats.

Because omega-3 fats are so important for health, they get a lot of credit in the calculation of NuVal scores — which range from 87 to 36 in the seafood category.

For this reason, the fish that are richest in omega-3 fats, such as salmon, get very high scores. Fish and seafood with lesser amounts of omega-3 and higher concentrations of sodium get lower scores. Hence the score of 36 for lobster, which is fairly high in sodium and, by and large, lacking in omega-3 fats.

Atlantic salmon fillet: 87
Atlantic halibut fillet: 82
Catfish fillet: 82
Cod fillet: 82
Tilapia fillet: 82
Oysters: 81
Swordfish steak: 81
Prawns: 75
Shrimp: 75
Clams: 71
Monkfish fillet: 64
Bay scallops: 51
Turbot fillet: 51
Lobster: 36