by Jason Fung
The purported link between meat and cancer, notably colon cancer, is controversial. The World Health Organization (WHO) recently declared that processed and red meats might cause cancer, though the effect is small. A daily portion of 2 ounces of processed meat or 3.5 ounces of red meat increases the risk of colon cancer from about 5 percent to 6 percent, according to the WHO.20 If true, protein is probably not responsible for the increase because other meats (white meat) have as much or more protein. This association study cannot prove causation. Further, while the risk associated with red meat was marginal and controversial, it is hardly useful to lump processed meats with fresh meat, which has formed part of the human diet since humans came into existence.
Consider fresh meat versus bologna. How are processed meats like bologna made? Well, you take the worst, most horrible cuts of meat (lungs, hooves, noses, and so on), grind them up so that you can’t recognize all the yucky parts, and then shove in lots of sugar, chemicals, and seasonings, including MSG and other stuff, to cover all the terrible flavors. Then you shape it into something that looks vaguely like meat (sausages, sliced meats), package it nicely, and advertise the hell out of it. If you knew how they made hot dogs, you probably wouldn’t eat them.
Ingredient lists on bologna often list “mechanically separated chicken or pork.” What is that? Well, they take the chicken carcass and, after removing all the good meat, they fling the carcass around violently so that any remaining meat flies off the bone. Yes, all the eyeballs, nose hairs, lungs, and intestines are ground up into processed meat. This bologna, which looks appetizingly like sliced turkey or chicken, actually contains corn syrup, sodium lactate, sodium phosphates, autolyzed yeast, sodium dictate, sodium erythorbate (made from sugar), sodium nitrite, dextrose extractives, potassium phosphate, sugar, and potassium chloride. Here’s what you need to know: Corn syrup is sugar. Dextrose extractives are sugar. Sugar is sugar. In other words, some form of sugar shows up three times in the ingredients list. Autolyzed yeast is MSG. It’s all sugar and MSG to make things taste good. Aside from the sugar and MSG, this “meat” includes plenty of chemical preservatives, like nitrates and phosphates, too.
Does it seem reasonable to lump this unholy meat concoction together with grass-fed fresh beef? Hardly. And that’s the point of one of our key messages: Eat real food. Don’t eat processed carbohydrates. Just as importantly, don’t eat processed meat or oil, either. Processed vegetable oils are not the same as natural fats (and we cover this in greater detail in Chapter 11).
Meat supplies a large amount of essential amino acids because it’s higher in leucine and methionine than dairy and eggs. Steak and chicken have about double the leucine and methionine compared to eggs, whereas seafood has only about 50 percent more of these amino acids compared to eggs. Overconsumption of these two amino acids is implicated in aging. Eating more of the amino acid glycine, found in bone broth and collagen, may alleviate methionine toxicity.21
Animal protein in real foods also contains natural fats and other micronutrients like vitamin B12, the long-chain omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) (especially in oceanic seafood and grass-fed or pastured meat), zinc, and iron. Iron can be a double-edged sword, though; it’s good or bad for your health depending on whether you’re malnourished or overnourished. People with iron deficiency anemia were traditionally advised to eat liver because it's a rich source of iron; however, people who have iron overload should avoid it.
BONE BROTH
The standard Western diet is low in the amino acid glycine, which may be responsible for helping to block the harmful cardio-metabolic effects of fructose.22 Glycine mimics methionine restriction, which robustly extends the life span of lab animals. Glycine “pulls” methionine out of the biochemical cycle known as the trans-sulfuration pathway. For both of these reasons, adding glycine-rich foods to your diet is a healthy thing to do. One of the richest sources of glycine is bone broth, which is made by simmering bones for several hours. You can use the resulting broth as a base for soups, sauces, and many other recipes. Hydrolyzed collagen protein is also a great source of glycine, as one-third of the amino acids contained in collagen are glycine.
ANIMAL PROTEIN: TOO MUCH OR TOO LITTLE?
Because animal protein generally has a higher biological value than plant protein, most people view animal protein as being better for building muscle. This is true only if the focus is malnourishment, or too little protein, which for much of human history was a significant problem. But not today. Overnutrition is the major concern in the West, and this problem is metastasizing to the rest of the world. Currently, some 70 percent of the American population is overweight or obese, which has led to an epidemic of type 2 diabetes, which in turn increases the risk of other diseases, such as heart disease and cancer. Being overnourished is not the same as being well-nourished because eating highly processed junk food, which is mostly empty calories and is often the cause of being overnourished, does not prevent vitamin deficiencies. In a world where overnutrition is a primary concern, the higher biological value of animal protein may work against it. Paradoxically, animal protein may be too nutritious.
Plant Protein
Plant proteins are harder to digest than animal proteins, as evidenced by their lower biological value. However, plants can still provide a complete amino acid profile with fewer calories because plants have a lower fat content. Ground beef, for example, is 17 percent protein compared to 28 percent protein in lentils and 40 percent in tofu. Plant sources also contain healthy amounts of phytochemicals—popularly known as “antioxidants”—of which animal sources contain none. Phytochemicals, like sulforaphane in cruciferous vegetables (like broccoli and cabbage), can upregulate cancer defense mechanisms such as the Nrf2 system. Plant sources have more fiber, vitamin C, potassium, and magnesium, which are associated with lower blood pressure and lower risk of stroke and death.23
A novel finding of a recent large study of more than 170,000 people spanning several decades was that eating more plant protein was associated with a lower death rate.24 Previous studies had focused on the total amount of protein rather than the source. Animal protein was associated with a higher death rate in only those people with other risk factors, such as smoking, being obese, or being sedentary. Further, only processed and red meats, not fish or poultry, were associated with the risk, and processed meat was the major offender. Substituting plant protein (and perhaps fish or poultry) for processed and red meats could perhaps reduce mortality.
VEGETARIANS AND VEGANS
Vegetarians avoid meat, but some eat eggs and dairy. Vegetarians are generally healthier and live longer than meat eaters, but this benefit may not be related to eating less meat; it could stem from other health-related lifestyle practices. Health-conscious people who do eat meat have death rates similar to the death rates of vegetarians.25 General avoidance of processed and junk foods, more exercise, less smoking and alcohol, and lower body mass index explain most of the difference rather than eating less meat per se.
Vegans go even further than vegetarians, avoiding all animal products completely, including meat, eggs, and dairy. Plants are their sole protein source. To avoid protein deficiency, vegans must combine different types of plants to get the right balance of amino acids. A classic combination is rice and beans; the proteins in these two foods complement each other. Together, these proteins have a higher biological value than when you consume only one. Vegans also can lack other nutrients, such as vitamin B12, carnitine, zinc, vitamin K2, and iron.
Infants fed a vegan diet may develop protein deficiency,26 so it is generally a bad idea to adopt this diet too early in life. Decreased growth rates may lead to shorter stature and delayed puberty.27 For adults, who don’t have any growth requirements, it is a different story because of the trade-off between growth and longevity. Vegan diets, low in essential amino acids, decrease the synthesis of the growth hormone pro-aging IGF-1. The amino acid methionine, a potent stimulus to IGF-1, t
ends to be low in plant proteins such as nuts and legumes. Certain IGF-1-dependent cancers, such as breast and colon cancer, occur less commonly in vegans.
When growth is important, as with children, eating more meat is beneficial. When longevity is more important, eating less meat might be beneficial. Perhaps this is why many children strongly prefer meat and animal proteins, and adults change their preference to vegetables over time. Dr. Fung has noticed this effect personally. As a child, he only ate vegetables when forced, but as he got older, he gravitated toward the salad bar and other vegetables.
LEGUMES
Legumes are seeds and include beans, chickpeas, lentils, and peas. They are a great source of plant protein and contain significant amounts of dietary fiber and polyphenols. For those who follow a vegetarian diet, legumes provide a significant portion of daily protein needs. Large-scale studies show that a diet high in beans may provide a small cardio-protective effect (4 to 9 percent) and perhaps a small weight loss effect as well.28 A meta-analysis of twenty-one studies estimated that 1 cup of legumes per day reduced weight by 0.34 kilogram (0.75 pound), which is a small but potentially beneficial amount.
Beans and lentils are high in protein, and they contain healthy amounts of calcium and potassium. These foods might be particularly effective for weight loss because they provide enough protein to meet requirements and supply fiber, which creates a sense of fullness.
GO NUTS!
Aside from eating more legumes and seeds, eating more nuts increases the potassium-containing, buffering bases that fight against an acidic bodily environment.29 By emphasizing plant protein rather than animal protein, you can still meet your overall protein requirements, which is very important for the elderly and infirm, yet protect yourself against latent acidosis that’s caused by the modern Western diet.
Nuts contain lots of protein, and they’re a good plant source of healthy fats. Walnuts contain healthy omega-3 fats, which are seriously lacking in most Western diets. Almonds are high in fiber and calcium. Tree nuts (not peanuts) might protect against weight gain,30 metabolic syndrome,31 and heart disease.32 People who eat nuts daily have about a 20 percent lower death rate than those who do not.33 Studies on the health habits of Seventh-Day Adventists, who live around seven years longer than the average person, find that nut consumption is a huge factor; only non-smoking and low body mass index are more significant factors.34 These results are only associations, but eating nuts in place of other foods, whether animal-derived or carbohydrate-dense, may very well offer protection against obesity and early death.
PROTEIN BARS
A great plant protein bar is IQ BAR (www.eatiqbar.com), which is a plant protein bar that comes in three flavors: Cacao Almond Sea Salt, Blueberry Lemon Sunflower, and Matcha Chai Hazelnut. The main ingredients include almonds, blueberries, sunflower seeds, and hazelnuts. IQ BARs are “real food” plant protein bars that provide 35 percent to 40 percent of the daily value for magnesium (a mineral that nearly 80 percent of the general population may be deficient in).
Advantages of IQ BAR (www.eatiqbar.com)
Plant protein
Ingredients that are real whole foods
Contains 35 to 40 percent of the daily value for magnesium
High in fiber
Comparing Plant and Animal Proteins
This section discusses the advantages and disadvantages of plant protein in comparison to animal protein. At the end of this section, we provide a summary table that compares the two types.
ANABOLIC RESPONSE
Different proteins provoke different anabolic (growth) responses. Consuming an adequate amount of protein is important for athletes and bodybuilders who are building strength but also for older people who need to maintain other lean tissues (including muscle and bone), which is robustly associated with good health.35 If you are eating adequate protein, then the source makes little difference. Vegetarian and meat-containing diets were equally good at building muscle36 when matched for total protein intake.37
Due to anabolic resistance, there is some data to suggest that in older people, eating only the recommended daily allowance (RDA) of protein (0.8 gram per kilogram per day) leads to muscle loss.38 Taking more protein, whether plant or animal, can be useful. Plant protein doesn’t have the excess leucine and methionine (which are pro-aging) that’s in meat, but these two amino acids may help maximize muscle growth. You have to find a balance between growth and longevity.
Strength training supplemented by whey or pea protein can increase muscular growth. Pea protein contains amounts of leucine comparable to whey, but only half the methionine, which makes it a useful alternative.39 Rice protein supplementation works, too, but you have to supplement with a fairly large amount (48 grams).40
HIGH-PROTEIN AND LOW-CARBOHYDRATE DIETS
A protein-rich diet that has a balance of plant and animal sources can lower blood pressure, improve lipid profiles, and reduce estimated cardiovascular risk.41 From an evolutionary standpoint, our ancestors are estimated to have consumed about 50 percent protein from plants and 50 percent from animals.
High-protein diets, such as the Atkins diet, reduce refined carbohydrates and sugar, which is likely beneficial. A person who follows one of these diets may replace carbohydrates and sugar with more protein, but the protein is mostly from animal sources, and this substitution may not be optimal for health. Low-carbohydrate diets high in animal protein are associated with higher death rates from cardiovascular disease and cancer.42 However, low-carbohydrate diets with more vegetable protein are associated with a lower death rate, particularly from cardiovascular disease.
The problem is not that meat is not nutritious. Instead, meat is too nutritious, which is not good in diseases of overnutrition and too much growth. Animal proteins stimulate more of the nutrient sensors insulin and mTOR than plant proteins do, and therefore animal proteins promote growth more. This effect is beneficial for malnourished people, which is why cavemen often hunted animals to extinction. But, in people suffering diseases of too much growth, the effect is not beneficial. In this situation, plant protein might be a better choice.
High-animal-protein diets may activate more IGF-1, which is implicated in the promotion of cancer. Lower levels of IGF-1 appear to protect centenarians against cancer—one reason they live that long.43
Eating less refined carbohydrates and sugar (less insulin), as well as targeted amounts of protein derived from animal sources (less mTOR), might be the best-case scenario. Eating less flour and sugar doesn’t necessarily mean you must eat more meat and dairy. The Eco-Atkins diet encourages protein sources such as gluten, soy, nuts, vegetables, and grains, and it has been shown to improve lipid levels better than a low-fat diet that contains animal products.44
ACID LOAD
Animal protein is generally more acidic than plants, so our bodies must neutralize the acid load to avoid serious health implications, including osteoporosis, muscle loss (sarcopenia), kidney disease, and diabetes.45 Ancestral diets are characterized by lots of animal protein, but they usually are balanced by equally large amounts of plant foods, which are often mildly alkaline.46 Paleolithic (ancestral) diets are estimated to contain between 35 percent and 65 percent plants (by weight), which is close to our earlier estimate that humans likely evolved on a diet of approximately 50 percent animal and 50 percent plant foods, varying from season to season and geographic location. Even the Inuit in northern Canada consumed berries, seaweed, wild plants, and other plant material from the stomachs of their kill, thus maintaining long-term acid-base balance.
Modern diets generally contain less than half the amount of animal protein compared to ancestral diets and only about one-third the amount of natural plant foods. Instead, contemporary human diets are loaded with refined carbohydrates and sugars derived from grains but deficient in fiber, potassium, magnesium, and calcium. Certain grains—such as barley, oats, and quinoa—are mildly acidic or even alkaline, but, unfortunately, the most common grain we eat—wheat—is hig
hly acidic.
Eating a typical Western diet with plenty of meat, grains, and sugar produces a lot of acid, which may deplete the body’s buffering system. This depletion forces the body to rely on the minerals in bone and the amino acids, particularly glutamine (which is found in muscle), as a buffering system of last resort. Depletion can lead to osteoporosis and sarcopenia.
A study in women from thirty-three countries found that eating a lower ratio of vegetable to animal protein was associated with a significantly greater risk of hip fractures.47 Germany had the highest risk for hip fracture incidence, followed by the Scandinavian countries, other European nations, and the United States. Countries such as China and Nigeria had a negligible rate of hip fractures.48
Osteoporosis often is believed to be caused by a lack of dietary calcium, but the evidence does not bear this out. Women in Japan and China eat less than one-third of the calcium of American women, but they have a much lower risk of osteoporosis. Neither is genetics a large factor. When Japanese women move to the United States, their risk of osteoporosis also moves up. Large-scale, randomized, controlled trials of calcium supplementation show no benefit in the reduction of fracture risk.49
The high-animal-protein Atkins diet increases net acid and calcium excretion. This result suggests that metabolic acidosis has increased and that bone might become calcium depleted.50 Eating more plant proteins and fewer animal proteins may decrease the risk of osteoporosis and aging. Supplementation with bicarbonate or eating more fruits and vegetables to neutralize the acid is useful in select patient populations to improve mineral balance, bone resorption, bone formation, and kidney function.51