Food as Cancer Therapy:

Greger and Fuhrman on the Anti-Cancer Portfolio

Oct 27, 2026 · @Thomas Lee Abshier, ND

Introduction

The most powerful anti-cancer tool most people have is on their plate, and it is badly undervalued while screening and treatment are badly overvalued. That is the thesis of a recent conversation between Dr. Joel Fuhrman and Dr. Michael Greger, recorded for a plant-based cancer-protection conference and released on the Doctor Talks podcast. I stand with them on that thesis, and this essay lays out their case, adds context where the conversation was loose, and gathers the specific foods they named into a working portfolio.

The two men are well matched for the subject. Fuhrman is a physician who has built his career on what he calls nutritional excellence. Greger is a founding member of the American College of Lifestyle Medicine, the author of How Not to Die and How Not to Age, and the host of NutritionFacts.org, a nonprofit library of more than 2,000 videos and articles. He donates proceeds from his book and speaking fees to that work. Greger also announced that, beginning in 2027, he plans an 18-volume series on cancer: one book for each cancer that kills more than 5,000 Americans a year, each gathering every food ever associated with survival of that cancer.

The conversation moved through four arguments: that people overrate drugs and screening; that this overconfidence keeps them from doing what actually works; that specific foods have specific, documented anti-cancer effects; and that prevention and treatment of the common cancers are one continuous process rather than two separate ones.

The Overestimation of Pills, Procedures, and Screening

Fuhrman opened by claiming that the public holds an unrealistically optimistic view of what screening, chemotherapy, and radiation accomplish, and an unrealistically low view of what diet accomplishes. Greger agreed and supplied the evidence. Surveys show that patients and doctors alike greatly overestimate the benefit of pills and procedures. In one example he cited, people believed cholesterol-lowering statins to be about 20 times more effective at preventing heart attacks than they are. When patients are shown the real benefit of many routine drugs, such as blood-pressure, osteoporosis, and cholesterol medications, most say they would decline them. Greger’s summary was that our leading killers are not caused by a drug deficiency, and treating the actual cause through diet is safer, cheaper, and may be more effective.

The same overestimate applies to cancer screening. Greger was careful to note that screening, by definition, prevents nothing; it only finds cancer earlier. The hope is that earlier detection saves lives, and for most screening tests the trial evidence does not show it. He stated that neither PSA testing in men nor mammography in women, at any frequency, has been shown to reduce all-cause mortality. Certain forms of colorectal and cervical screening may save lives, but those are the exceptions.

Some screening, he said, does more harm than good. Teaching women breast self-examination produced more harm than benefit. A large skin-cancer screening effort in Germany likewise suggested that the risks exceeded the benefits. (See notes 1–3.)

Overdiagnosis and the Licensing Effect

Most people ask what risk a blood test or an X-ray could possibly carry. Greger listed three. Some procedures, such as colonoscopy, carry direct physical risk. False alarms bring biopsies and weeks of fear before a lesion proves benign. The largest harm, however, is overdiagnosis: finding and treating a cancer that would never have caused symptoms, a cancer the patient would have died with rather than from. Some breast cancers regress and disappear on their own. Such patients receive the full armamentarium of surgery, chemotherapy, and radiation for a disease that was never going to harm them, and chest radiation itself raises a woman’s later risk of heart disease. Fuhrman added that unnecessary chemotherapy can cause other illnesses and later cancers.

Greger pointed out a painful irony. The people who were overdiagnosed and then “cured” are screening’s most passionate advocates, because they believe it saved their lives. Those harmed most are the ones who claim the greatest benefit. This is why screening can prevent some breast-cancer deaths without reducing deaths overall.

The overestimate also does a second kind of damage, which Greger called a licensing effect. A clean screening result, or a “normal” cholesterol or blood pressure, is taken as a stamp of approval that excuses a person from changing his diet. Yet in our society it is normal to die of heart attack and stroke, so a normal number is not a reassuring one.

Both men stressed that they were not attacking doctors or alleging a conspiracy. Greger noted that statins save thousands of lives on a population scale even though the benefit to any one person is small. The U.S. Preventive Services Task Force now asks men to weigh the risks and benefits of PSA screening for themselves; Greger said he would not have one, but that the choice belongs to each person. Their point is that a realistic view of screening and drugs frees a person to take up the things that actually work.

Responsibility as Good News

Fuhrman observed that people who lose faith in conventional treatment often turn to alternative treatments instead, still looking for a remedy to apply from outside. Greger’s quip was that people decide their doctors are bad and go find a witch doctor, when the real answer is to treat the underlying cause. Neither conventional nor alternative treatment is the thing that works best; the food is.

Our culture avoids talking about cause because it seems to blame the sick. Greger turned that around. If a person had a role in his breast cancer, heart disease, or obesity, then he has power over it. If disease were purely a spin of a genetic roulette wheel, that would be the truly bad news, because then nobody could do anything. In Greger’s view, most premature death and disability can be prevented with a sufficiently healthy plant-based diet and lifestyle, and it is never too late to begin eating better, moving more, or quitting smoking.

The Portfolio Approach: Specific Foods, Specific Effects

“Eat more plants” is not precise enough. Greger borrowed the model of the Portfolio Diet developed by David Jenkins at the University of Toronto. That diet first removes the saturated fat, trans fat, and cholesterol that raise blood cholesterol, then adds a set of foods that each lower cholesterol by a different mechanism. Together they lower LDL about as much as a first-line statin. Fuhrman’s stated mission is to build the same kind of portfolio against cancer.

The reason is that plant foods are not interchangeable. Iceberg lettuce is not collard greens; bananas are not blueberries. Some nutrients, like vitamin C, are spread widely through the plant kingdom, but others are concentrated in a few foods. The lignans of flaxseed and the glucosinolates of cruciferous vegetables are two examples. A person who eats no crucifers and no flax simply does not receive those compounds, whatever else he eats.

Research studies one variable at a time, for good reason: if a trial gives flax and broccoli together, no one can say which one worked. Greger’s response was that a practitioner does not need to know. When the interventions are safe, simple, and free of side effects, and the stakes are life and death, the sensible course is to use all of them at once. Some may share mechanisms and add little to one another, but there is no downside in trying. Fuhrman added that if single foods show measurable effects in isolation, the effect of changing thirty variables at once, while removing the harmful foods, should be far larger.

Flaxseed, Chia, and Wheat Germ

Flax was the conversation’s leading example. Greger said flaxseed contains roughly 100 times the lignan concentration of most other foods, with sesame a distant second. The evidence is not merely observational. He described a double-blind trial in women with newly diagnosed breast cancer, who were randomized to muffins with or without flaxseed and could not tell which they were eating. Tumor biopsies taken before and after showed favorable changes in cancer markers in the flax group. (Greger recalled the interval as six months; see note 4.)

Greger recommends one tablespoon of ground flaxseed daily, part of his “Daily Dozen” checklist. That provides about 2.2 grams of alpha-linolenic acid, the plant omega-3, plus the lignans. He is cautious about eating more than about a tablespoon and a half of raw flax daily over the long term, though cooked flax is less of a concern.

Fuhrman grinds flax and chia together and puts a couple of tablespoons on his morning oats. He favors variety among omega-3 seeds, including hemp. Greger noted that chia and hemp provide soluble fiber and omega-3s but not flax’s lignans. Fuhrman countered that chia does carry some lignan, by his figure about a third of flax’s; Greger accepted the point and said he could diversify. (See note 5.)

Greger mixes his flax one-to-one with raw wheat germ, the most concentrated dietary source of spermidine, a compound that stimulates autophagy, the cell’s self-cleaning process. He researched spermidine while writing How Not to Age. Wheat germ is inexpensive because it is a byproduct of flour milling. He has added other neutral-tasting items to this mixture, including phytosterols and psyllium, and is considering taurine. These additions are aimed chiefly at lowering LDL cholesterol, not at cancer.

Greens, Onions, Mushrooms, Berries, and Green Tea

Cruciferous vegetables. Greger eats about two pounds of crucifers a day, usually kale; he prefers Lacinato (“dinosaur”) kale. He uses what he calls the hack-and-hold method. Chopping a crucifer mixes the plant’s glucosinolates with its enzyme myrosinase, which produces sulforaphane. Cooking destroys the enzyme, but sulforaphane already formed survives heat. So he chops the greens, waits about 45 minutes, and then steams them for about a minute in a pressure cooker, which he considers the most nutrient-preserving method.

Fuhrman pressed him on raw foods: broccoli sprouts, raw lettuces, and raw onion and scallion in salads. He argued that chewing raw salad thoroughly, mixing it with saliva and the mouth’s bacteria, has its own advantages. Greger agreed that he should resume broccoli sprouts, which he had dropped while traveling because they molded before he could use them.

Mushrooms. Greger eats mushrooms daily, with porcini a favorite, for ergothioneine and spermidine, micronutrients hard to obtain elsewhere. If his Daily Dozen were a baker’s dozen, he said, mushrooms would be the thirteenth.

Breakfast: berries, whole grains, lentils. The two men discovered they eat nearly the same breakfast. Greger uses a rolled mix of oat, barley, purple barley, and rye groats with lentils, topped with wild blueberries, blackberries, fresh pomegranate in season, pumpkin seeds, walnuts, and his flax and wheat-germ mixture. Fuhrman cooks black lentils, mixes them with grain, and adds wild blueberries with pomegranate from his freezer.

Green tea. Both men drink green tea for its catechins, chiefly EGCG. Fuhrman recalled a study of Chinese women in which those who ate mushrooms daily and also drank green tea had about 90 percent lower breast-cancer risk (see note 6). He asked what a drug with that effect would be worth. Greger answered that one drug is approaching that kind of market already: Ozempic, a trillion-dollar class of medication that mimics some effects of a good diet. Fuhrman doubted that it truly does what food does, and Greger conceded the point.

Prevention and Treatment Are One Continuum

The conversation’s most important idea is that the line between preventing cancer and treating it is artificial. The American Institute for Cancer Research and the World Cancer Research Fund recommend the same diet for both, and Greger explained why. The common epithelial cancers of the breast, colon, prostate, and ovary take decades to grow. An ovarian cancer diagnosed at 70 may have begun at 50. The patient says, “I was healthy yesterday, and today I have cancer,” but in fact the cancer was present for twenty years before it grew large enough to detect.

Autopsy studies confirm how common hidden cancer is. Women in their thirties and forties who die in accidents are frequently found to have microscopic breast cancers, and microscopic prostate and thyroid tumors are similarly common in people who never knew they had them (see note 7). The body is constantly suppressing budding tumors. So a person who eats well in midlife, believing he is preventing cancer, is often already treating one: slowing its growth so that it never reaches a size that matters in his lifetime. Fuhrman added the best outcome of all: a cancer that is never diagnosed because it never grows. The practical conclusion is that it is never too early and never too late to begin.

Diet During and After Treatment

Fuhrman’s sharpest criticism was aimed at what happens after diagnosis. Patients with slow-growing cancers, such as ordinary estrogen-receptor-positive breast cancer or indolent prostate cancer, undergo radiation, chemotherapy, and hormone therapy while giving no attention to diet. In his judgment the food portfolio is more effective than those treatments at extending life.

Greger framed the point so that it holds whatever a patient decides about conventional treatment. Diet is never an either-or choice. A patient who chooses full chemotherapy and radiation has even more reason to eat well, both to counter the side effects of treatment and to give his body its best chance.

Fuhrman explained the mechanism behind recurrence. Chemotherapy does not kill every cancer cell; stray cells scattered through the body survive and can later regrow. The body has its own means of finding and destroying individual cells, including triggering programmed cell death (apoptosis). In his decades of clinical practice with cancer patients, nutritional excellence has been strikingly effective at preventing recurrence.

Greger supplied a concrete example: soy. Studies following thousands of breast-cancer survivors, about half a dozen of them, have found that women who eat soy have significantly lower risk of recurrence and significantly lower all-cause mortality than survivors who do not (see note 8). This contradicts a fear many women still hold, that soy feeds breast cancer.

Supplements, Spices, and the Diversity of Fiber

Fuhrman plans to give patients a written prescription: the diet plus a conservative set of supplements. When Greger asked which supplements, Fuhrman named turmeric, green-tea EGCG, and possibly extracts from a wide variety of mushrooms. He added culinary herbs and spices such as sage, rosemary, and thyme, all as ways of widening our exposure to the protective compounds of the plant kingdom.

Fuhrman noted a shift in thinking over the past five years. Where people once ate yogurt or kimchi or took a probiotic to get the right bacteria, the evidence now points to the variety of fibers and phytochemicals across many plants as what builds the healthiest gut and immune system. Greger agreed. “Fiber” is a catch-all word for thousands of different indigestible carbohydrates, each of which may feed a different population of beneficial bacteria. A single fiber supplement cannot match fifty different plant foods in a week.

Greger was skeptical of probiotic pills for the same reason. If a person’s beneficial bacteria have died off, it is because he created a gut environment that killed them, and swallowed bacteria will die there too. The remedy is to keep sending down a wide variety of prebiotic foods, so the good bacteria can multiply on their own.

Why the Case Stands, and the Portfolio in Practice

I stand with Fuhrman and Greger: a diet built deliberately from protective foods is the most powerful and most neglected anti-cancer measure available to ordinary people. The areas of uncertainty are real. Most single-food evidence is observational; trials such as the flaxseed study measure tumor markers rather than survival; and no trial has tested a thirty-food portfolio against cancer outcomes. None of these uncertainties weakens the central claim, for four reasons.

First, the evidence runs in one direction across many lines: population studies, survivor cohorts, randomized marker trials, and laboratory mechanisms. Second, the cost of acting is close to zero. These foods are cheap, safe, and protective against heart disease and diabetes as well, so the portfolio wins even if its cancer effect were smaller than hoped. Third, the comparison is not between diet and a proven alternative. For most screening programs, the trials do not show fewer deaths overall, and the benefit of many routine drugs is far smaller than patients believe. Fourth, the reason this message is underrepresented is plain: as Greger put it, there is no big flax industry. No one profits enough from broccoli sprouts to fund their advertising, while drugs, devices, and screening programs have well-funded advocates.

The foods and practices named in the conversation:

Food or practice	How Greger or Fuhrman uses it	Key compounds named
Ground flaxseed	1 tbsp daily (Greger), mixed with wheat germ; on oats with chia (Fuhrman)	Lignans, alpha-linolenic acid
Chia and hemp seeds	Mixed with flax for variety	Omega-3s, soluble fiber, some lignan
Raw wheat germ	Mixed 1:1 with flax	Spermidine
Cruciferous vegetables	~2 lb daily, chopped, held 45 min, then lightly steamed	Glucosinolates, sulforaphane
Broccoli sprouts and raw salad greens	Raw, chewed well	Sulforaphane
Raw onions and scallions	In salads	Allium compounds
Mushrooms	Daily, porcini favored	Ergothioneine, spermidine
Berries and pomegranate	Daily at breakfast	Polyphenols
Whole-grain groats and lentils (incl. black lentils)	Breakfast base	Fiber, prebiotics
Walnuts and pumpkin seeds	At breakfast	Omega-3s, minerals
Green tea	Daily	Catechins (EGCG)
Soy foods	Regularly, including after breast cancer	Isoflavones
Herbs and spices	Turmeric, sage, rosemary, thyme	Polyphenols
Supplements (Fuhrman, conservatively)	Turmeric, green-tea EGCG, mixed mushroom extracts	—
Plant variety	Many different plant foods each week	Diverse fibers for gut bacteria

The conversation’s final counsel was simple: begin now. It is never too early, and it is never too late.

Notes

Citations below are from the editor’s knowledge and were not re-verified online for this draft; confirm before publishing.

1. Screening and all-cause mortality. Cochrane reviews of the mammography trials (Gøtzsche and Jørgensen, 2013) and of PSA screening (Ilić et al., 2013; updated in BMJ, 2018) found no reduction in all-cause mortality. These trials were not designed to detect small all-cause effects, so the finding is best stated as no demonstrated reduction.
2. Breast self-examination. The large Shanghai trial (Thomas et al., J Natl Cancer Inst, 2002) found no reduction in breast-cancer deaths and roughly twice as many benign biopsies among women taught self-examination.
3. German skin-cancer screening. This was not a randomized trial but a statewide program in Schleswig-Holstein (SCREEN, 2003–2004), later extended nationally. Melanoma deaths fell in the region at first and later returned to prior levels, while diagnoses rose, a pattern consistent with overdiagnosis.
4. Flaxseed muffin trial. Thompson et al., Clin Cancer Res, 2005. Postmenopausal women with newly diagnosed breast cancer ate a muffin with 25 g flaxseed or a placebo muffin daily for about five weeks (roughly 32–39 days) between biopsy and surgery, not six months. The flax group showed reduced tumor cell proliferation (Ki-67), increased apoptosis, and reduced c-erbB2 (HER2) expression.
5. Lignan content of chia. Published lignan values vary widely with method and sample. Most food-composition data place flaxseed far above every other seed. Fuhrman’s figure that chia carries about a third of flax’s lignan should be checked against current data before it is relied on.
6. Mushrooms and green tea. Zhang et al., Int J Cancer, 2009. This was a case-control study of women in southeast China, not a 20-year follow-up. Women with high daily mushroom intake who also drank green tea had roughly 89 percent lower odds of breast cancer than women who consumed neither.
7. Autopsy studies. Nielsen et al. (Br J Cancer, 1987) found in situ breast cancers in a substantial share of Danish women who died of other causes. Hidden prostate and thyroid cancers are likewise common at autopsy, rising with age.
8. Soy after breast cancer. A pooled analysis of U.S. and Chinese cohorts (Nechuta et al., Am J Clin Nutr, 2012; about 9,500 survivors) found about 25 percent lower recurrence with higher soy isoflavone intake.
9. Names. The guest’s name is Michael Greger, and his site is NutritionFacts.org (not “Nutritional Facts”).