A Thumbs Down Book Review
Eat to Live
By Joel Fuhrman, MD
New York: Little, Brown and Company, 2003
Reviewed by Chris Masterjohn
Dr. Joel Fuhrman’s Eat to Live presents a diet centered on a concept with which followers of Weston Price’s research are well familiar: nutrient density. His emphasis on maximizing nutrition is a refreshing change from the many weight loss manuals calling for the restriction of this or that macronutrient and the cutting of carbs or calories without regard for the life-promoting vitamins and minerals that Price considered to be the fundamental determinants of health. Unfortunately, Fuhrman’s profound bias against animal products leads the reader to believe that good nutrition comes only from vegetables. While many people will undoubtedly improve their health as they adopt Fuhrman’s regimen of unrefined, whole foods, a large number will inevitably reach a point at which they must begin including more nutrient-dense animal products in their diet. Others will never tolerate this plant-based way of eating to begin with.
The Health Equation
According to Fuhrman, health and well being can be reduced to a simple mathematical formula: health equals nutrients divided by calories. Accordingly, he has created a nutrient-density-per-calorie chart of foods wherein the top spots are occupied by green leafy vegetables, with other non-starchy vegetables following closely behind. Legumes and whole grains, which Fuhrman recommends soaking overnight to increase nutrient value and digestibility, starchy vegetables, fresh fruits, raw nuts and raw seeds also figure prominently in the chart. Animal products come in second to last, followed only by the category of “refined grains, oils and sweets.”
Since the book is written primarily for those trying to lose weight, Fuhrman directs the reader to eat primarily from foods at the top of this chart. For those who need to maintain their weight, he recommends eating more starchy vegetables and oil-rich whole foods such as avocados, nuts and seeds. He advises everyone, however, to eat two pounds per day of leafy vegetables, half raw and half cooked, and to restrict animal products to only ten percent of calories.
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.
How Much Is Really There?
Nutrients are often much more bioavailable from animal foods than they are from plant foods, a fact that Fuhrman’s ranking system does not take into account. The absorption of zinc, for example, is inhibited by phytate and a number of other plant chemicals, while it is stimulated by animal proteins. Absorption of zinc can be five times higher from animal foods than from high-phytate plant foods.9 Calcium is very bioavailable from some plant foods such as kale, broccoli and bok choy,10 but very little is absorbed from foods high in oxalate such as spinach.11 The absorption of fat-soluble vitamins and their precursors such as vitamin K and carotenes can be less than five percent in the absence of fat and still less than twenty percent with added fat.12,13 Pigments such as lutein are twice as available from egg yolks as they are from green vegetables such as spinach.14 As much as 80 percent of vitamin B6 in plant foods may be bound up with other substances that make it unavailable for absorption and use;15 even the portion that is available must be converted into its active form in the liver in a reaction that taxes the supply of vitamin B2.2 Fuhrman’s nutrient density chart would look very different if he adjusted a food’s score according to the bioavailability of the nutrients within it.
Not All Nutrients Are the Same
Even if it were true, as Fuhrman’s chart suggests, that kale is 40 times more nutritious than whole milk and that bananas are more nutritious than beef, it would not change the fact that one would develop severe nutrient deficiencies by eating nothing but kale and bananas. These foods contribute no vitamin B12, vitamin D or preformed vitamin A, and little iodine, for example.
Fuhrman notes that his patients may sometimes consume too little iodine because they follow his recommendation to limit their intake of salt, to which iodine is usually added. Yet one half of a serving of kelp, two servings of dairy foods, or six eggs would all be capable of fulfilling the officially recommended daily requirement for iodine.16 One serving of clams per month would fulfill the requirement for vitamin B12,17 and a half-teaspoon of high-vitamin cod liver oil per day would fulfill the requirements for vitamins A and D.18
It is therefore unfortunate that Fuhrman devotes no space within his book to instruct the reader on how to judiciously use the ten percent of calories allotted to animal foods. Not all of Price’s primitives ate diets rich in animal products. Some groups ate diets largely centered on plant foods; these groups, however, selected extremely nutrient-dense animal foods to satisfy their nutritional requirements, such as whole insects and frogs, crustaceans, and the heads and organs of fish. They valued these foods not simply because they contain a high concentration of total nutrients, but because the specific nutrients they provide are difficult to obtain from other foods.
Animal products not only provide micronutrients, but also provide proteins and fats, which make them dense in calories. Since Fuhrman’s ranking system defines density as nutrients per calorie, this pushes animal products even further down on the list. This system of ranking certainly has some value. Some nutrients are used up when we digest food, for example, so we want to consume more nutrients than we require for this process. The digestive requirement is not related to calories, however; starches and proteins contain many more bonds that must be broken down by enzymes compared to fats and sugars, and fermentation can dramatically change the digestibility of a substance without altering its caloric value. Some people may need to restrict total calories or calories of a certain type—those from carbohydrates, for example—and for these people a per-calorie nutrient density ranking may be very valuable.
Others, however, may find that they can only eat so much bulk. Bok choy, for instance, has four times more calcium per calorie than whole milk. Yet three and one half cups of whole milk per day will fulfill the recommended daily calcium requirement compared to six cups of bok choy. Many people may not be able to (or even want to) eat such a large volume of fibrous vegetables day in and day out.
Vegetables Are Not For Everyone
Fuhrman’s dietary regime contains an enormous amount of fruits and vegetables far beyond the quantity most people consume. Although the inclusion of such a large quantity of unrefined and nutritious whole food is likely to dramatically improve many people’s health, it could actually hurt the health of others. Fruits and vegetables contain chemicals called salicylates which are similar to aspirin. In some people, salicylates exert a drug-like effect that mimics an allergic reaction by causing the omega-6 fatty acid, arachidonic acid, to be converted into inflammatory chemicals called leukotrienes. These chemicals in turn cause the dilation of blood vessels, the constriction of bronchial passages and the production of mucus. Salicylate intolerance can result in asthma, hives, nasal polyps, chronic swelling and gastrointestinal symptoms. Two to four percent of outpatients attending allergy clinics, two percent of those with Crohn’s disease, seven percent of those with ulcerative colitis, and fifteen to twenty percent of those who attend ear, nose and throat clinics are salicylate intolerant. These people could never survive on Fuhrman’s salicylate-laden diet.19
The most compelling argument Fuhrman makes for his dietary plan is his claim of clinical success. Thousands of patients have made themselves examples of this success, he writes, and out of hundreds who have come to him with preexisting heart disease, only one has had to undergo repeat surgery after adopting his regime, and none has died of a heart attack.
There must undoubtedly be a large degree of truth to this claim. Fuhrman’s diet completely excludes refined foods, including vegetable oils, and emphasizes foods rich in certain important nutrients, especially vitamin C and other water-soluble vitamins found in plant foods. Because Fuhrman prohibits added fats and oils, his patients will synthesize the fats they need from carbohydrates and other building blocks; the primary fatty acid the body synthesizes in this way is the saturated fatty acid called palmitate. The oil-rich whole foods he allows provide many antioxidants to protect against damage that free radicals can cause to the small amount of polyunsaturated fat within them. The saturated fats produced within the bodies of his patients are themselves very stable and are therefore also protective.
Lipoproteins, which circulate in the blood and carry cholesterol, fat-soluble vitamins and many other substances, are not living cells and therefore cannot synthesize glutathione and the enzymes that constitute the primary antioxidant defense system of the cell. To the extent that heart disease may be accelerated by oxidative damage to the lipoproteins that circulate in the blood, we should expect Fuhrman’s diet to exert a considerable amount of protection. Patients who are wise enough to make judicious use of their ten percent of calories allotted to animal foods by consuming very nutrient-dense options like shellfish and liver, or who simply respect the guidance of their bodies enough to cheat on the diet when they feel they need to, may be able to reap the benefits of this approach for a long period of time.
Nevertheless, Fuhrman’s clinical experience is likely to exhibit substantial selection bias. Those who become weak without animal products or who develop eczema and hives when they eat too many fruits and vegetables are unlikely to go knocking on his office door and agree to a plan that includes nothing but the foods that make them feel the worst. The people with the highest needs for animal-based nutrients or the lowest tolerance for the foreign chemicals unique to plants are the people who would have the least clinical success on Fuhrman’s plan; these same people are unlikely to try it to begin with.
It will be interesting to see whether Fuhrman can produce a clinical trial showing positive results with his diet in a randomized sample of the population. In 1995, his similarly minded colleague, Dr. Caldwell Esselstyn Jr., published the results of a five-year intervention with a low-fat vegetarian diet combined with the individualized use of cholesterol-lowering drugs to bring cholesterol down to 150 mg/dL.20 Twenty-two percent of those who began the intervention dropped out of the study within the first two years; thirty-five percent of those who completed it did not submit to the follow-up analysis of their cardiovascular health; of the twenty-two patients who began the trial, only eleven remained in the final analysis. Of these eleven, occlusion of the blood vessels became better in five, stayed the same in one, and became worse in four. Since Esselstyn considered it unethical to allow patients under his supervision to eat a standard diet, there was no control group.
While many people would undoubtedly benefit from the restriction of polyunsaturated oils from the diet and the increased consumption of antioxidants from whole plant foods, many need vitamins B6 and B12, zinc, taurine, fat-soluble vitamins and other nutrients that are found much more abundantly or in much more available forms in animal foods. Naturally, these competing needs will produce the conflicting results that Esselstyn observed in his uncontrolled trial, including the ill health that may have driven some people to drop out of the study.
The solution is to drop the ideological opposition to animal products and recognize that both animal and plant products—when in their unrefined state, produced under natural conditions, grown in well-tended soil, and prepared and consumed according to the traditions on which our ancestors thrived for millennia—can make important nutritional contributions to the diet. Some people may do well on a diet centered on plant products if they also carefully take advantage of certain nutrient-dense animal products; but for many others this approach will not work. Restricting polyunsaturated oils and supporting the body’s own antioxidant defense systems with the vitamins and minerals it needs would by itself likely provide many of the benefits that Fuhrman observes in his practice while simultaneously allowing us to take advantage of the rich nutrition contained in traditional animal products as well.
- Fuhrman J. Nutrient Density. http://www.drfuhrman.com/library/article17.aspx. Published 2004. Accessed February 13, 2007.
- Gropper SS, Smith JL, Groff JL. Advanced Nutrition and Human Metabolism. Fourth Edition. Wadsworth Publishing. 2004.
- Griffith, Owen W. Biologic and pharmacologic regulation of mammalian glutathione synthesis. Free Radic Biol Med. 1999; 27(9-10): 922-935.
- Wenzel U, Kuntz S, Brendel MD, Daniel H. Dietary Flavone Is a Potent Apoptosis Inducer in Human Colon Carcinoma Cells. Cancer Res. 2000; 60: 3823-3831.
- Wang L-Q, James MO. Inhibition of Sulfotransferases by Xenobiotics. Curr Drug Metab. 2006; 7: 83-104.
- Lin J, Zhang SM, Wu K, Willett WC, Fuchs CS, Giovanucci E. Flavonoid Intake and Colorectal Cancer Risk in Men and Women. Am J Epidemiol. 2006; 164(7): 644-651.
- Bender DA. Nutritional Biochemistry of the Vitamins. Second Edition. Cambridge: Cambridge University Press. 2003.
- Hipkiss AR. Would carnosine or a carnivorous diet help suppress aging and associated pathologies? Ann NY Acad Sci. 2006; 1067: 369-74.
- Sandstrom B. Bioavailability of zinc. Eur J Clin Nutr. 1997; 51(Suppl 1): S17-S19.
- Heaney RP, Weaver CM, Hinders SM, Martin B, Packard PT. Absorbability of Calcium from Brassica Vegetables: Broccoli, Bok Choy, and Kale. J Food Sci. 1993; 58(6): 1378-1380.
- Heaney RP, Weaver CM, Recker RR. Calcium absorbability from spinach. Am J Clin Nutr. 1988; 47(4): 707-9.
- West CE, Eilander A, van Lieschout M. Consequences of revised estimates of carotenoid bioefficacy for dietary control of vitamin A deficiency in developing countries. J Nutr. 2002; 132(9 Suppl): 2920S-2926S.
- Gijsbers BLMG, Jie K-SG, Vermeer C. Effect of food composition on vitamin K absorption in human volunteers. Br J Nutr. 1996; 76: 223-229.
- Chung HY, Rasmussen HM, Johson EJ. Lutein Bioavailability Is Higher from Lutein-Enriched Eggs than from Supplements and Spinach in Men. J Nutr 2004; 134: 1887-1893.
- Reynolds RD. Bioavailability of vitamin B-6 from plant foods. Am J Clin Nutr. 1988; 48: 863-7.
- George Matelijan Foundation. The World’s Healthiest Foods. http://www.whfoods.com/genpage.php?tname=nutrient&dbid=69. Accessed February 13, 2007.
- United States Department of Agriculture. USDA National Nutrient Database for Standard Reference, Release 17. http://www.nal.usda.gov/fnic/foodcomp/Data/SR17/wtrank/wt_rank.html. Accessed February 13, 2007.
- Green Pastures. High-Vitamin Cod Liver Oil – Nutrition Information. http://www.greenpasture.org/products/cod_liver_oil. Accessed February 14, 2007.
- Raithel M, Baenkler HW, Naegel A, Buchwald F, Schultis HW, Backhaus B, Kimpel S, Koch H, Mach K, Hahn EG, Konturek PC. Significance of salicylate intolerance in diseases of the lower gastrointestinal tract. J Physiol Pharmacol. 2005; 56(Supple5): 89-102.
- Esselstyn CB Jr., Ellis SG, Medendorp SV, Crowe TD. A strategy to arrest and reverse coronary artery disease: a 5-year longitudinal study of a single physician’s practice. J Fam Pract. 1995; 41(6): 560-8.
This article appeared in Wise Traditions in Food, Farming and the Healing Arts, the quarterly magazine of the Weston A. Price Foundation, Spring 2007.