Health

5 drawbacks of the raw, vegan diet

Jan. 15, 2013 at 5:02 PM ET

By Christopher Wanjek, livescience.com#mce_temp_url# 

On the road to good health, there are many forks. Some paths, such as vegetarianism or the Mediterranean diet, have considerable science supporting them. Others, such as the vegan or plant-based diet, which shuns all animal products including eggs and dairy, are winning converts.

And then there's a new offshoot, the raw vegan diet, which deems cooking to be unnatural and unhealthy.

An increasing number of celebrities — most recently, tennis sensation Venus Williams — swear by this diet as the best way to prevent and reverse diseases and to stay young and vital. Testimonials from ordinary folks are endless, boasting advantages along the lines of having more energy, better skin, improved relationships with woodland creatures and so on.

But on your road to good health, the raw vegan diet would likely be a U-turn. If you are already vegan or vegetarian, you have nothing to gain and much to lose by going totally or even mostly raw. Even doctors who prescribe and live by a vegan diet caution their patients against attempting a raw diet.

The reason? You would greatly reduce the types of foods you can eat. And you would do so in vain, because most of the raw vegan principles are based on misconceptions about human nutrition, and work counter to good health. [ 7 Medical Myths Even Doctors Believe ]

This article addresses five such principles that are either half true or completely false.

What is raw veganism?

First, a primer: Raw veganism is a plant-based diet that involves no cooking. No food is heated above 104 degrees Fahrenheit (40 degrees Celsius). Foods are eaten fresh, dehydrated with low heat or fermented.

A core tenet of the diet is that heating food above 104 degrees not only diminishes its nutrients, but also makes the food toxic and less digestible. In raw vegan parlance, cooking is killing. Many raw vegans speak of "live" foods versus "dead" foods, and they aren't talking about sushi, so fresh it still wiggles.

Live or uncooked foods are said to be filled with vital life energy. In this way, raw veganism is an extension of the vegan appreciation for animal welfare, with the added spirituality of a life force, called chi or prana. Dead or cooked foods are said to be depleted of their life energy, as well as most of their nutrients.

Juicing and blending "green smoothies" often are key elements of this diet.

Now for the misconceptions:

Misconception #1: Cooking destroys nutrients

Sure, raw foods can be nutritious. But cooking breaks apart fibers and cellular walls to release nutrients that otherwise would be unavailable from the same raw food. Cooking tomatoes, for example, increases by five-fold the bioavailability of the antioxidant lycopene. Similarly, cooking carrots makes the beta-carotene they contain more available for the body to absorb. Soups are full of nutrients that would not be available in a pot of raw carrots, onions, parsnips and potatoes. [ Science You Can Eat: 10 Interesting Facts About Food ]

Cooking can also reduce certain chemicals in a vegetable that inhibit the absorption of minerals, including important minerals like zinc, iron, calcium and magnesium. Cooking spinach makes more iron and calcium available from its leaves, for example.

Admittedly, some nutrients are lost in cooking, such as vitamin C and certain B vitamins. But "plants are so excess in nutrients that even this breakdown is insignificant in practical terms," said John McDougall, creator of the McDougall Program, a vegan-friendly, starch-based diet.

And by eating both raw and cooked foods, "you get the best of both worlds," said Jennifer Nelson, director of clinical dietetics at the Mayo Clinic and associate professor of nutrition at the Mayo Medical School in Rochester, Minn.

Overcooking and charring can be a problem. Boiling the life out of greens will indeed reduce the nutrient load. And charring meats and vegetables creates cancer-causing chemicals. The solution, however, is not to stop all cooking, but rather to steam, lightly sauté or stir-fry vegetables, and to make more soups.

Fermenting or juicing raw foods also can make some nutrients more available, but that shouldn't deter from the fact that cooking is an ancient craft that makes some foods more digestible and nutritious.

As for the concept of life energy in raw food, this is a spiritual belief beyond the realm of science, so debating its benefit, let alone existence, would be futile.

Misconception #2: Cooking destroys enzymes

This one is absolutely true, but it doesn't matter. Yes, heat destroys enzymes. But humans make their own digestive enzymes to break down large food molecules into smaller ones.

The raw-enzyme logic itself breaks down when you consider that most humans cook food and that most humans are digesting that food reasonably well.

Ironically for the raw vegan, most of the plant enzymes in raw food get destroyed anyway in the acid of the human gut. Only a few make it to the small intestine. Fermented foods such as sauerkraut can carry enzymes into the gut. Their contribution to digestion is not zero, but it does appear to be minimal. "I know of no importance of plant enzymes in human digestion," said McDougall.

The enzyme theory for raw foods dates back to Edward Howell, a physician who published a book on enzymes in the 1940s, primarily citing research from the 1920s and 30s. We now know, however, that almost all nutrients are absorbed in the small intestine and that digestion at that stage relies almost entirely on human-generated bile and pancreatic enzymes.

A corollary myth is that humans have a finite number of enzymes and that, once they are used up, these enzymes are gone. This idea, too, was hatched by Howell. But where would this packet of enzymes reside? Howell never said. But in reality, humans make new enzymes throughout their lifetimes.

Misconception #3: Raw foods are detoxifying

Dietary detoxification is an alternative medicine concept with little scientific credibility. Usually, two organs are cited as needing detoxification: the liver and the colon. In reality, toxins can accumulate anywhere in the body, particularly in fat and fatty tissue, but also in proteins and bone.

The colon is surprisingly low in toxins, however. As for the liver, the confusion is that this organ "filters" toxins and must therefore, the reasoning goes, be loaded with toxins. But the liver is more of a chemical-processing plant than a filter; it breaks down toxins as they pass through. That is, the liver doesn't have extra toxins by virtue of it being the body's natural toxin-neutralizer. [ Wishful Thinking: 6 'Magic Bullet' Cures That Don't Exist ]

Another argument is that burning fat — in this case, on a raw vegan diet — would release toxins from the body. But fat cells don't burn up, as if into ashes, liberating their contents. Fats cells merely get bigger or smaller, depending on the amount of fat within the cell that's used.

It is unclear how much of a toxin, if any, would be set free if the fat molecule it is attached to is burned. The toxin is now free to attach to other fat molecules. If it does mobilize with other recently liberated toxins, in the case of extreme starvation, then the toxin could become toxic and overwhelm the liver.

In short, there are no foods or herbs that can magically bind and pull toxins from your blood or organs. The same would be true for cows or for any "vegan" animals that accumulate toxins in their fat; they don't cleanse themselves with their raw, plant-based diet.

At best, detoxification schemes (juicing, fasting) can help by virtue of not placing more toxins in our body for a day or two. And a healthful, plant-rich diet with plenty of water can, in general, help your liver and kidneys process and remove toxins more effectively, McDougall said.

Misconception #4: Raw veganism is healthful

Healthfulness when eating a raw, vegan diet is a challenge; it's not inherent. Many on the diet do lose weight by consuming fewer calories. But weight loss should not be the ultimate goal.

The most apparent problems are nutritional deficiencies, particularly for vitamins B12 and D, selenium, zinc, iron and two omega-3 fatty acids, DHA and EPA. Without taking supplements in pill form, it would be very difficult (and, for B12, impossible) to obtain a sufficient amount of these nutrients from raw, plant-based foods. [ 5 Key Nutrients Women Need as They Age ]

Also, without access to a variety of foods year-round that can be eaten raw, one tends to rely on single-food sources.

"The problem with the raw food diet is where do you get your energy food?" asked Caldwell Esselstyn of the Cleveland Clinic, the doctor who convinced Bill Clinton to adopt a plant-based diet. "You get it from pouring down nuts," he said, and these are high in fat and not healthful when eaten in excess.

If it's not nuts, then it's bananas, which are healthful perhaps at a level of one or two per day, but not when providing the majority of your calories. Some people on a raw food diet rely so much on fruit that their teeth begin to erode: from acids in the fruits that wear down the tooth enamel, from sugar promoting decay, from dried fruit (another raw vegan staple) sticking to the teeth and further promoting decay, and from a general mineral deficiency.

The raw diet could be more healthful than the so-called S.A.D. ("standard American diet") of processed foods. But there is no evidence that, even given the resources to prepare a variety of raw foods daily, the raw vegan diet would be more healthful than the plant-based diets promoted by McDougall or Esselstyn, or than the diets that allow modest amounts of animal products.

Vegans would have to ask themselves what the added benefit would be from going raw if the raw diet offers no additional moral satisfaction, other than a reduced use of cooking fuel.

Misconception #5: Raw-only foods are natural

"No other animal cooks food," many a raw vegan has stated. One can just as well say that no other animal combines their kale and clover with tropical bananas in a high-speed blender to make the foods more palatable and digestible. Or, that no other animal plays chess.

Judging what is natural is a slippery slope. Humans around the world live to relatively similar ages on a multitude of different diets. Most of the reasonable diets that consist of grains, vegetables and meats will get you to at least age 70 if an accident or infectious disease doesn't kill you first. A traditional, animal-based diet eaten by natives of Siberia is just as natural as a traditional diet eaten by unnamed tribes in the Amazon.

That said, no known human culture has ever attempted to survive solely on raw plant foods. It is the raw-only diet that is unnatural, because it is impossible to survive on this diet without modern conveniences such as refrigerators, storage devices and easy access to packaged foods — such as the aforementioned shelled nuts.

In fact, a child raised on a raw, vegan diet without proper supplementation would likely develop severe neurological and growth problems due to a lack of vitamin B12 and other nutrients. Adults who have eaten animal products for more than 20 years, by contrast, have the benefit of relying on bodily stores of certain key nutrients.

In a natural setting, without electricity, anyone located outside of a narrow belt of land near the equators, which have year-round growth potential, would need to dedicate their entire day to growing, gathering, preserving and storing food. Even around the tropics, where vegetation is plentiful, humans have been cooking as long as humans have been human — at least 200,000 years and likely longer in our hominid form.

Most scientists are in agreement that a combination of, first, eating meat and then cooking food enabled the development of the human brain. Cooking in particular opened up a new world of calories and nutrients. The human brain, after all, requires a lot of energy. [ Eating Meat Made Us Human, Study Suggests ]

Our raw-vegan cousin, the gorilla, has three times the body size of humans, but one-third the brain cells; it grew muscular on plants, but not smarter. According to a study published in October 2012, the gorilla would have needed to eat raw plants for more than 12 hours a day to consume enough calories to evolve a humanlike brain.

This myth busting is not intended to belittle the much-maligned raw vegan, but rather to inform rawists of the realities of this challenging diet.

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