Fuhrman’s calculations of nutrient density suffer from three fatal flaws: first, he excludes from these calculations many nutrients known to be essential to the body while doubling the score of other putative nutrients whose physiological functions are uncertain; second, he fails to account for variations in the bioavailability of nutrients between foods; third, he groups all nutrients present in a food into a single score as if they were interchangeable, rather than acknowledging that different types of foods provide different types of nutrients.
His definition of nutrient density as nutrients per calorie can be valuable for someone whose first priority is to restrict calories, but it can be inappropriate for others. Rather than instructing the reader about how to judiciously use the ten percent of calories allotted to animal products to select the most nutrient-dense of these foods, Fuhrman dismisses their nutritional contribution as insignificant. Although the premise of Eat to Live—nutrient density—is solid, his assumptions in the application of this principle seriously diminish the value that this book will have to many readers and may even lead some down a path that will ultimately damage their health.
Not All Nutrients Count
Fuhrman lists five nutrient deficiencies his patients—especially the vegans—sometimes develop when following his regimen: vitamin D, vitamin B12, taurine, DHA and iodine. This should come as no surprise to his readers since vitamin B12 is the only one of these nutrients included in his nutrient-density ranking system. Vitamin D, DHA, taurine and iodine are not.
According to the explanation of this ranking system posted on Fuhrman’s web site,1 he also excludes a number of other important nutrients. The B vitamins biotin and pantothenic acid, preformed vitamin A, and vitamins K1 and K2 are among those absent. Major minerals such as sodium, chloride, potassium, sulfur, and phosphorus are excluded. Essential trace minerals such as copper, manganese, boron, molybdenum, and chromium are nowhere to be found in Fuhrman’s list. Essential fatty acids like EPA, DHA and arachidonic acid are likewise absent. Finally, none of the eight essential amino acids is included in his ranking system.
Fuhrman excludes a whole host of essential nutrients from his list while including a number of non-essential nutrients. Some non-essential nutrients are actually required by the body but are not considered essential because we can synthesize them ourselves. Other non-essential nutrients are not required by the body but may nevertheless be beneficial because they can absorb free radicals—dangerous compounds with unpaired electrons that can wreak havoc on the cell—and thereby act as antioxidants. The selectivity with which Fuhrman includes non-essential nutrients heavily favors plant foods over animal foods and likewise favors compounds that play no essential role in the body and may even be harmful under certain circumstances over compounds that do play essential roles.
Fuhrman includes in his system carotenes and other pigments, the thyroid-suppressing agents found in the cabbage family called glucosinolates, and fiber. He also includes the oxygen radical absorbance capacity (ORAC) score. This is a measure of how well chemicals act as antioxidants in an isolated setting in a laboratory, not a measure of their effect within the body. Although we know very little about the importance of the chemicals that contribute to the ORAC score, Fuhrman actually doubles their contribution to his nutrient-density ranking.
These plant chemicals, whether they act as antioxidants in test tubes or in cells, are not essential nutrients. Each cell within the body synthesizes the master antioxidant glutathione, which neutralizes free radicals and also regenerates vitamins E and C.2 The synthesis of glutathione requires either dietary cysteine, an amino acid that is only bioavailable from raw proteins, or vitamin B6.3 Glutathione, in conjunction with several vitamins and enzymes, protects the cell from free radicals. These enzymes require selenium, iron, manganese, copper and zinc to function. Plant chemicals that contribute to the ORAC score may augment this defense system, but they are not an essential part of it and do not fulfill any role within it that the basic components synthesized within the cell and the other essential vitamins cannot fulfill.
Many of the “antioxidants” in fruits and vegetables are actually potent inhibitors of enzyme activity. Some of them may reduce the levels of certain enzymes that some researchers believe promote cancer.4 Many of them, however, especially those found in onions, kale, broccoli, apples, cherries, berries, tea and red wine, are potent inhibitors of a process that takes place in the liver called sulfonation.5 Sulfonation is necessary for the detoxification of drugs and environmental pollutants and the normal activity of steroid hormones and thyroid hormone. Because sulfonation can also make some chemicals more toxic, researchers have proposed that the inhibition of this process could be beneficial. Perhaps because the absorption of these compounds from many foods is negligible, or perhaps because they have so many conflicting effects on our metabolic processes, they are not associated with either an increase or a decrease in the risk of cancer.6
Prudence dictates excluding these “nutrients” from any ranking system until further research can elucidate the true effects they actually have within our bodies; but rather than excluding them, however, Fuhrman counts each of them as two nutrients instead of one.
While Fuhrman doubles the score of plant chemicals that play no essential role in the body, he completely excludes many nutrients found in animal foods that do play essential roles. Creatine is vital for muscle function; taurine is essential to digestion and the functioning of the brain and retina; carnitine and coenzyme Q10 are required for energy metabolism;7 carnosine functions as an antioxidant, protects DNA and proteins from being destroyed by sugars that run amuck, and plays important roles in the nervous system.8 None of these nutrients—not even taurine, which Fuhrman himself says is sometimes deficient in his vegan patients—is included.It should come as no surprise, then, that his chart shows green leafy vegetables to be superior to meat, eggs and shellfish. Were organ meats such as liver even included on this chart, they would probably fare just as poorly—not because they aren’t nutrient-dense, but because Fuhrman’s chart of nutrient density completely ignores more than two dozen of the nutrients that they contain.