What Is the Forks Over Knives Diet?

| By Alona Pulde, MD and Matthew Lederman, MD

The Forks Over Knives whole-food, plant-based diet is centered on whole, unrefined, or minimally refined plants. It’s a diet based on fruits, vegetables, tubers, whole grains, and legumes; and it excludes or minimizes meat (including chicken and fish), dairy products, and eggs, as well as highly refined foods like bleached flour, refined sugar, and oil.

We know that’s a mouthful! Rest assured, though, that you’ll be eating in a way that people have thrived on for thousands of years. We believe that you will find—as we do—that the diet and foods are very tasty and satisfying. Following are the food categories from which you’ll eat, along with a few examples from each. These include the ingredients you’ll be using to make familiar dishes, such as pizza, mashed potatoes, lasagna, and burritos:

  • Fruit: mangoes, bananas, grapes, strawberries, blueberries, oranges, cherries, etc.
  • Vegetables: lettuce, collard greens, broccoli, cauliflower, kale, carrots, etc.
  • Tubers and starchy vegetables: potatoes, yams, yucca, winter squash, corn, green peas, etc.
  • Whole grains: millet, quinoa, barley, rice, whole wheat, oats, etc.
  • Legumes: kidney beans, chickpeas, lentils, lima beans, cannellini beans, black beans, etc.

Now that you know generally what sorts of foods you’ll be eating, let’s delve further into what the diet is and what it most definitely is not.

A Whole-Food, Plant-Based Diet Is Not a Diet of Vegetables

You may have heard that people living this way eat lots of spinach, kale, and collard greens, and that this is, in fact, the primary basis for many of the meals. You may even think we live only on leafy and raw vegetables. However, nothing could be further from the truth.

While leafy vegetables are an important part of the whole-food, plant-based diet, they are a very poor calorie, i.e., energy, source to be sustainable. We would need to eat almost 16 pounds of cooked kale to get 2,000 calories of food! We certainly don’t eat this way, and we wouldn’t blame you for thinking it sounds crazy—we think so, too! In fact, it is virtually impossible to get enough calories from leafy vegetables alone to form a sustainable diet. Perhaps the most common reason for failure in this lifestyle is that people actually try to live on leafy vegetables alone. If you try to live on these vegetables, you become deficient in calories. Not eating enough calories leads you to feel hungry, which over time may result in decreased energy, feelings of deprivation, cravings, and even binges. These issues are not caused by switching to a plant-based diet—rather, they are all related to not eating enough.

Don’t get us wrong: We certainly recommend you eat generous amounts of leafy vegetables. But these are complementary foods that you eat regularly. They are not the energy source on your food plate.

So if leafy vegetables aren’t the basis of a whole-food, plant-based life- style, what is?

Starch-Based Foods and Fruit Form the Basis of the Whole-Food, Plant-Based Diet

In America most of us are accustomed to building our dinner plate around meat. This will change with your new lifestyle. The center of your plate is now going to be the starch-based comfort foods most of us have always loved, but that have long been relegated to side dishes or stigmatized because of a misperception that they are “unhealthy.” Yet these are the foods that people around the world have thrived on for generations: tubers like potatoes and sweet potatoes; starchy vegetables like corn and peas; whole grains like brown rice, millet, quinoa, and buckwheat; and legumes like chickpeas, black beans, kidney beans, and lima beans.

They may be prepared a bit differently—leaving out oil and dairy, for example—but most of them will nonetheless be familiar. Those that aren’t may become delightful new discoveries you’ll make as part of embarking on your new lifestyle. They come in the form of delicious dishes like Sweet Potato Lasagna, Mashed Potatoes and Gravy, Tuscan White Bean Burgers, Easy Thai Noodles, Lima Bean Soup, Shepherd’s Pot Pie, Black Bean and Rice Burritos, Polenta Curry, and Spicy French Fries. (Recipes for all these dishes can be found in The Forks Over Knives Plan.) In addition to starch-based foods, you can enjoy as much whole fruit as you like.

No More Eating For Single Nutrients . . . Focus on the “Package” and the Foods You Enjoy

The idea of eating a particular food for one nutrient is pervasive in our culture. We have been led to believe we should eat meat for protein, dairy for calcium, fish for omega-3 fatty acids, and even tomatoes for lycopene, among many others. This sort of thinking is misguided and has caused grave harm to human health. The quest for protein, for example, has steered us toward meat consumption. In this quest, we not only consume protein in excess of our needs, but also many harmful substances like dietary cholesterol that are only present in animal foods.

No food is a single nutrient, and we should never think of foods in that way. Any given food has countless nutrients. What matters most is the overall nutrient profile, i.e., the whole package. Whole, plant-based foods contain all the essential nutrients (with the exception of vitamin B12), and in proportions that are more consistent with human needs than animal-based or processed foods. So our question is really this: Why waste any of what we eat on inferior packages? As long as—over time—we choose a variety of whole, plant-based foods, we will easily meet our nutritional needs.

Even on this diet, people sometimes tend to worry about eating a certain type of green vegetable for calcium, beans for protein, nuts for fat, and so on. We ask you to let go of that kind of thinking. The most important thing in this lifestyle is to choose the whole, plant-based food you enjoy most!

To learn more about the whole-food, plant-based lifestyle, and how to make a successful transition, be sure to check out The Forks Over Knives Plan.

Our Experts Address Common Concerns

You are not alone if you are asking, “Where will I get my protein?” People believe this single nutrient is so important and difficult to get that we must actively pursue foods that contain high amounts of it, even when those foods, such as meat and dairy, in so many ways compromise our health.

We have been led to believe that primarily animal-based foods contain sufficient protein and, furthermore, that we need to eat those foods to avoid becoming protein deficient. The reality is that protein deficiency is almost exclusively seen in people suffering from a calorie deficiency. In these cases, there will be an overall nutrient deficiency, not just protein deficiency, and when this happens the concern should be getting more calories and all nutrients—not just more protein.

As for how much protein you need, the answer is the amount that a diet of whole, plant-based foods provides you. All whole, plant-based foods have protein. We know from our extensive review of the research and our experience in our practice that people thrive on a plant-based diet without ever going out of their way to find “sources” of protein. Indeed, it’s not a mystery that we’ve evolved over millions of years without ever aiming for a “source” of this or any other nutrient. Yet the mistaken notion that we need to go out of our way to consume certain individual nutrients is pervasive, and protein is the nutrient most commonly identified as one you must target to ensure you get enough. But we’re not interested in trying to achieve arbitrary targets; we’re interested in achieving good health. And the best way to achieve good health is by targeting whole plant foods, not numbers of grams of protein.

When you eat a diet based on fruit, vegetables, tubers, whole grains, and legumes about 10% of your total calorie intake will be from protein. We list this percentage only to demonstrate how the diet contains a sufficient amount of this nutrient­—not as any kind of target. In fact, you should not worry about how much protein you’re getting any more than you should worry about the perfect number of breaths you should take in a day. And, if you’re worried that 10% isn’t adequate, note that there’s evidence that consuming too much protein is harmful—especially when it comes from animal sources.

(Read more: Do Vegetarians and Vegans Eat Enough Protein?)

Many believe that it’s important to get enough calcium from certain foods, especially milk and other dairy products, which they perceive to be excellent “sources” of it. It’s easy to interpret this message—that constant vigilance is necessary to make sure we’re getting our calcium—as an implicit warning that we might not otherwise get enough.

Just as with protein it is not difficult to get enough calcium—you just need to eat whole, plant-based foods. Calcium, like iron, magnesium, and copper, is a mineral. It is found in the soil, where it is absorbed into the roots of plants. Animals get their calcium by consuming the mineral-abundant plants and metabolizing that calcium into their bodies. Surprised? That’s because we’ve been so conditioned to think that calcium comes primarily from milk and dairy products that few of us realize it actually comes from the earth and is abundant in all whole foods.

For strong bones and calcium, how much of the nutrient you get isn’t as important as where you get it—and how you lose it. There are two major contributing factors to the leaching of calcium from bones, which leads to their weakening and may increase the risk for osteoporosis: First, consuming a highly acidic diet. Our bodies are alkaline. It is vital that the acidity level of your diet is not so high that your bones must leach calcium to keep your body’s alkaline levels balanced. The levels of acidic compounds are lower in plant foods so they won’t draw the calcium from your bones the way animal foods will. Eating a whole-food, plant-based diet gives your body the acid/alkaline balance it needs for optimal bone health. Second, consuming a high-sodium diet. The diet we recommend is naturally low-sodium, as it relies very little on processed foods, which tend to be very high in salt.

Once a certain threshold for calcium has been met—which you will do eating a whole-food, plant-based diet—the formula for strong bones relies on two other factors entirely: First, that you get sufficient vitamin D from exposure to the sun. Vitamin D is a key factor in calcium absorption, and the sun is the best way for us to meet our requirement. The key is getting sufficient sun exposure on our bare skin without getting burned. (The vitamin D in milk is added to it; we do not recommend getting vitamin D from milk or other fortified foods in which the vitamin does not naturally occur.) Second, that you practice strength training and impact exercise. When you lift weights or do resistance exercises you not only build muscle, you stress your bones—this makes them stronger. Walking, jogging, and running are examples of impact exercises that will also help with bone strength.

As with protein, many organizations will suggest that you need to consume a specific amount of calcium per day for strong bones. We do not make any such recommendations because we know that good bone health has nothing to do with hitting an arbitrary number for calcium intake. Furthermore, we fervently believe that when people are instructed to achieve these subjective targets, it creates a skewed notion of what is good nutrition and leads people to make poor food choices—as is the case with dairy.

(Read more: Getting Clarity About Calcium)

Some fats are necessary in our diet. Consuming oil, fish and processed foods as a means to get these, however, is unnecessary, and even harmful. Every whole plant food has fat, and there’s no evidence that we need any more fat than what occurs naturally in a low-fat, whole-food, plant-based diet. Just as is the case with protein and calcium, we should not target specific foods to get enough of a particular kind of fat.

Omega-3 and omega-6 fatty acids appear to be involved in a variety of important bodily functions, including cell membrane stabilization, nervous system function, immune system function, and blood clotting, as well as impacting triglyceride levels, blood pressure, inflammation, cancer, and heart disease. Although they are both essential (meaning you need to consume them), you have probably heard a lot more often that you need to seek out omega-3. This is not because it is more essential than omega-6. Instead, it is because, in general, these two essential fatty acids should be consumed in a healthy ratio to each other. Studies are not clear exactly what that ratio should be, but we do know that the Standard American Diet is significantly skewed in such a way that we get an excess of omega-6. This excess consumption of omega-6 impairs the absorption of omega-3.1 The answer, however, is not simply that you need to eat more omega-3 fats. The answer is to eliminate or minimize processed and animal-based foods and instead eat a whole-food, plant-based diet, which we know in most cases restores a healthy omega-6 to omega-3 balance and, more important, leads to positive health outcomes. And isn’t that what we care about most?

If 1 to 3 percent of your calories come from the essential fats, you’ll be in great shape. Adequate omega-3 intake specifically is 1.1 g for adult women and 1.6 g for adult men.2 That’s 1⁄4 to 1⁄3 teaspoon per day. If you meet all your caloric needs with a low-fat, whole-foods diet full of fruits, vegetables, whole grains, and legumes, you will easily consume enough essential fatty acids and those fatty acids will be in good balance to each other. Note that while walnuts and flax- and chia seeds are whole plant foods with higher concentrations of essential fatty acids, there’s no evidence that you actually need to eat these foods to get the proper amount of any kind of fat. Most whole plant foods have small amounts of essential fats. Over the course of a day full of these foods you will achieve the needed amounts—which aren’t that much to begin with. In fact, it is significantly more important to worry about not consuming excess fat than it is to worry about consuming sufficient omega-3.

1Philip C. Calder, “N-3 Polyunsaturated Fatty Acids, Inflammation, and Inflammatory Diseases,” American Journal of Clinical Nutrition 83 (June 2006): 1505S–19S.
2Jennifer J. Otten, Jennifer Pitzi Hellwig, and Linda D. Meyers, eds., DRI: Dietary Reference Intakes: The Essential Guide to Nutrient Requirements (Washington, DC: National Academies Press, c. 2006), http://www.nal.usda.gov/fnic/DRI/Essential _Guide/DRIEssentialGuideNutReq.pdf.


We are baffled that certain oils are presented as “health” foods. Olive oil is not a health food. Neither is coconut, grape seed, flaxseed, or any other oil you’ve heard you must endeavor to add to your diet because it’s good for you. Sure, if you replace some or all of the butter in your diet with vegetable oil, some of your cholesterol numbers may look a little bit better, but that’s not at all the same as doing well. Oil is a bad idea because it is highly refined and its nutritional package is inadequate.

How is it that we know that processed sugars are junk foods, yet we’ve allowed ourselves to be convinced that certain oils are somehow good for us? Oil follows essentially the same model as processed sugar, which is also pressed from plants. Think about what oil is: fat—and nothing but fat. All the nutrients, including protein, carbohydrates, vitamins, minerals, fiber, and water, have been thrown away. Oil of any kind has more calories per gram than any other food we know. And without any fiber or water in it, oil lacks the bulk to convey to your senses how many calories you have eaten; this virtually guarantees you will consume more calories at the meal than you need. So we ask you: Why would you waste calories on something that has no nutrients in it other than fat? And why would anyone believe that highly concentrated fat is healthy?

So let’s look at where the “good oil” hype came from. Its origins lay in data collected in the 1960s that showed the people on the island of Crete. At the time these people had the lowest all-cause mortality rates over twenty years when compared to people in other Mediterranean countries. A main contributing factor was their diet, which included some animal products and a little bit of olive oil, but otherwise consisted primarily of fruits, vegetables, and whole grains.1 In the years since then, unfortunately, the phrase “Mediterranean diet” has become synonymous primarily with olive oil. What subsequent researchers—and marketers—took from those early studies was that olive oil was the Holy Grail. But it never was.

All oils have a negative impact on blood vessels and promote heart disease.2 Furthermore, they may also lead to increased bleeding through thinning of the blood; negative effects on lung function and oxygen exchange; suppression of certain immune system functions; and increased risk of cancer.3 Not to mention that excess calories from fat get stored as fat, no matter what type of fat calories you consume.

(Read more: Is Coconut Oil Healthy or Hazardous?)

(Read more: Why Olive Oil Isn’t a Health Food)

1Antonia Trichopoulou, Tina Costacou, Christina Bamia, and Dimitrios Trichopoulo, “Adherence to Mediterranean Diet and Survival in a Greek Population,” New England Journal of Medicine 348 (June 26, 2003): 2599–608.
2Robert A. Vogel, Mary C. Corretti, and Gary D. Plotnick, “The Postprandial Effect of Components of the Mediterranean Diet on Endothelial Function,” Journal of the American College of Cardiology 36 (November 1, 2000): 1455–60.  AND Blankenhorn DH1, Johnson RL, Mack WJ, el Zein HA, Vailas LI. The influence of diet on the appearance of new lesions in human coronary arteries. JAMA. 1990 Mar 23-30;263(12):1646-52
2D. C. E. Nordström, C. Friman, Y. T. Konttinen, V. E. A. Honkanen, Y. Nasu, and E. Antila, “Alpha-Linolenic Acid in the Treatment of Rheumatoid Arthritis. A Double-Blind, Placebo-Controlled and Randomized Study: Flaxseed vs. Safflower Seed,” Rheumatology International 14 (1995): 231–34; M. A. Allman, M. M. Pena, and D. Pang, “Supplementation with Flaxseed Oil Versus Sunflowerseed Oil in Healthy Young Men Consuming a Low-Fat Diet: Effects on Platelet Composition and Function,” European Journal of Clinical Nutrition 49 (March 1995): 169–78; M. R. Namazi, “The Beneficial and Detrimental Effects of Linoleic Acid on Autoimmune Disorders,” Autoimmunity 37 (February 2004): 73–75; P. Purasiri, A. McKechnie, S. D. Heys, and O. Eremin, “Modulation in Vitro of Human Natural Cytotoxicity, Lymphocyte Proliferative Response to Mitogens and Cytokine Production by Essential Fatty Acids,” Immunology 92 (October 1997): 166–72; D. Hazlett, “Dietary Fats Appear to Reduce Lung Function,” Journal of the American Medical Association 223, no. 1 (1973): 15–16; Clifford W. Welsch, “Relationship Between Dietary Fat and Experimental Mammary Tumorigenesis: A Review and Critique,” Cancer Research 52 (April 1992): 2040S–48S; Patrizia Griffini, Olav Fehres, Lars Klieverik, et al., “Dietary Omega-3 Polyunsaturated Fatty Acids Promote Colon Carcinoma Metastasis in Rat Liver,” Cancer Research 58 (August 1, 1998): 3312–19; Lars Klieverik, Olav Fehres, Patrizia Griffini, Cornelis J. F. Van Noorden, and Wilma M. Frederiks, “Promotion of Colon Cancer Metastases in Rat Liver by Fish Oil Diet Is Not Due to Reduced Stroma Formation,” Clinical & Experimental Metastasis 18 (September 2000): 371–77; Kenneth K. Karroll, “Experimental Evidence of Dietary Factors and Hormone-Dependent Cancers,” Cancer Research 35 (November 1975): 3374–83; J. H. Weisburger, “Worldwide Prevention of Cancer and Other Chronic Diseases Based on Knowledge of Mechanisms,” Mutation Research 402 (June 18, 1998): 331–37; Leonard A. Sauer, David E. Blask, and Robert T. Bauchey, “Dietary Factors and Growth and Metabolism in Experimental Tumors,” Journal of Nutritional Biochemistry 18 (October 2007): 637–49; Clement Ip, “Review of the Effects of Trans Fatty Acids, Oleic Acid, N-3 Polyunsaturated Fatty Acids, and Conjugated Linoleic Acid on Mammary Carcinogenesis in Animals,” American Journal of Clinical Nutrition 66 (December 1997): 1523S–29S.
3N. F. Chu, D. Spiegelman, J. Yu, N. Rifai, G. S. Hotamisligil, and E. B. Rimm, “Plasma Leptin Concentrations and Four-Year Weight Gain Among US Men,” International Journal of Obesity and Related Metabolic Disorders 25 (March 2001): 346–53; N. F. Chu, M. J. Stampfer, D. Spiegelman, N. Rifai, G. S. Hotamisligil, and E. B. Rimm, “Dietary and Lifestyle Factors in Relation to Plasma Leptin Concentrations Among Normal Weight and Overweight Men,” International Journal of Obesity and Related Metabolic Disorders 25 (January 2001): 106–14; Motonaka Kuroda, Masanori Ohta, Tatsuya Okufuji, et al., “Frequency of Soup Intake and Amount of Dietary Fiber Intake Are Inversely Associated with Plasma Leptin Concentrations in Japanese Adults,” Appetite 54, no. 3 (June 2010): 538–43.

The relationship between whole food and the human body is very intricate and has come about as a result of millions of years of evolution. There are countless nutrients and substances in food that lead to thousands of metabolic reactions when they are consumed. As T. Colin Campbell, PhD, describes it, when it comes to nutrition, the whole is greater than the sum of the individual parts. The nutrients in whole food work together much like a symphony; extract and consume those nutrients apart from the whole, and all bets are off as to their effects.

The complex, harmonious relationship between our bodies and the whole food we eat might explain why the hardworking supplement industry has not been able to produce beneficial products, despite decades of effort and billions of dollars. Consequently, we do not recommend our patients take supplements—with the notable and important exception of vitamin B12— unless a specific deficiency arises that cannot be corrected with whole, plant-based foods. Putting aside the bluster of consumer marketing, the research on multivitamin supplements is consistent: They do not demonstrate benefit and may cause harm.1 A review of twenty-four randomized controlled trials showed “no consistent evidence that the included [vitamin and mineral] supplements affected CVD [cardiovascular disease], cancer, or all-cause mortality in healthy individuals.”2 Single-vitamin supplements have shown similar negative results. In fact, the harm caused by some of them is dramatic. For example, vitamin A, beta-carotene, and vitamin E—while all healthy when consumed in food—have been shown to significantly increase death when consumed as supplements.3

The problems with supplements shouldn’t come as a surprise. The fact that we need a particular nutrient doesn’t mean we need a megadose of it, nor should we consume it in isolation from all the other nutrients and substances it’s designed to work with. It may run counter to what we’ve been taught, but when we think about nutrition, we should think about getting the right amount of nutrients; this means obtaining neither too little nor too much of them—and being sure they are packaged in the right proportions. We should not think for a moment that we are “playing it safe” by taking supplements; the only true way to play it safe is to not take those supplements—and to look instead to whole, plant-based foods for the nutrition we need.

1Jaakko Mursu, Kim Robien, Lisa J. Harnack, Kyong Park, and David R. Jacobs, “Dietary Supplements and Mortality Rate in Older Women. The Iowa Women’s Health Study,” Archives of Internal Medicine 171 (October 10, 2011): 1625–33.
2Stephen P. Fortmann, Brittany U. Burda, Caitlyn A. Senger, Jennifer S. Lin, and Evelyn P. Whitlock, “Vitamin and Mineral Supplements in the Primary Prevention of Cardiovascular Disease and Cancer: An Updated Systematic Evidence Review for the U.S. Preventive Services Task Force,” Annals of Internal Medicine 159 (December 17, 2013): 824–34.
3Goran Bjelakovic, Dimitrinka Nikolova, Lise Lotte Gluud, Rosa G. Simonetti, and Christian Gluud, “Mortality in Randomized Trials of Antioxidant Supplements for Primary and Secondary Prevention: Systematic Review and Meta-Analysis,” Journal of the American Medical Association 297 (February 28, 2007): 842–57.

Vitamin B12 is important for the development and protection of nerve cells and red blood cells and helps in the production of DNA. Insufficient B12 can lead to many health issues, including weakness, fatigue, difficulty concentrating, increased irritability, gastrointestinal distress, anemia, and nervous system dysfunction. B12 is the one nutrient that cannot be obtained sufficiently from today’s plant-based diet. This is not because we need to eat animal products to obtain it. In fact, animal products themselves don’t always contain enough B12.1 The reason for this is that neither plants nor animals naturally synthesize B12. It is made from bacteria. Animals consume dirt, which is full of bacteria, through the unwashed plants and non-chlorinated water they consume. B12 accumulates in the animals’ tissues, which becomes a source of the vitamin for humans when we eat the animal.

We humans, on the other hand, rarely eat anything unwashed. In our quest to be clean, we remove the dirt that contains B12-producing bacteria from our foods. This sanitary approach certainly has its benefits, as it has decreased our exposure to parasites and other pathogens. As a result, we believe that when you eat a whole-food, plant-based diet, taking a B12 supplement is the best way to ensure adequate amounts of the nutrient. There is enough research about supplementing B12 that, when taken appropriately, we trust it is beneficial.

1Marijke van Dusseldorp, Jorn Schneede, Helga Refsum, et al., “Risk of Persistent Cobalamin Deficiency in Adolescents Fed a Macrobiotic Diet in Early Life,” American Journal of Clinical Nutrition 69 (April 1999): 664–71.

While some people prefer to eat only organic, fresh food, this is not absolutely necessary from a health perspective. Most modern diseases that afflict people are not the result of the difference between organic and conventional produce, fresh and frozen broccoli, or canned and dried beans. Whether our diets lead to health or sickness is determined mainly by the significant difference between whole, plant-based foods on the one side and animal-based and highly processed foods on the other. We should not let our need for convenient, affordable food—including shortcuts, such as canned and frozen as well as less expensive conventional produce—deter us from consuming the whole, plant-based foods that will stave off disease.

The nutrient makeup of animal foods (for example, high in fat and cholesterol; low in fiber and antioxidants) is the main reason why consuming these foods will increase your chances of getting chronic diseases like heart disease and type 2 diabetes. This nutrient profile exists whether animal foods are organic or not, or whether they are grass-fed or not. Replacing animal foods with whole plant-based foods is a significant change that will greatly improve your chances of achieving good health, whereas the change between organic and conventional animal foods is relatively small and therefore unlikely to make much of a difference.