The raw food lifestyle has inspired an enthusiastic, soul-stirring movement across the globe and much of this excitement can be credited to Cherie Soria, who instructed and encouraged a host of devoted followers, entrepreneurs, and fledgling chefs.
Fueled by her desire to bring good health, weight loss, energy, and a youthful constitution to millions, Cherie joined with Brenda Davis and Vesanto Melina, both registered dietitians, to lead the way toward a raw food health revolution.
The raw-food movement continues to make converts, thanks to a devoted group of individuals and celebrities who embrace the belief that an all-raw food diet is the best diet. The idea that stirs the most enthusiasm for this diet is the contention that cooking both destroys about fifty percent of the nutrients in food, and destroys all or most of the life promoting enzymes. Raw-food enthusiasts commonly make the claim that “cooked foods are dead foods.”
But, are cooked foods really dead foods?
Many people advocate eating raw food because animals eat raw food and stay healthy, or because raw foods contain a little more of some nutrients. However, the subject is more complex.
We are not like the animals. We think more, we worry, we go to work and do not sleep enough, and most people’s digestion is weak, unlike that of the animals.
Vegetarian animals, in particular, often have very complex or multiple stomachs, such as cows and goats, in order to digest raw vegetables. Human beings lack these.
For hundreds of thousands of years the evolving human race had eaten its food raw, but at some time between the first deliberate use of fire–in Africa in 1,400,000BC or Asia in 500,000BC (depending on which theory happens to be the flavor of the month)-and the appearance of the Neanderthals on the prehistoric scene, cooking was discovered.
Whether or not it came as a gastronomic revelation can only be guessed at, but since heat helps to release protein and carbohydrate as well as break down fiber, cooking increases the nutritive value of many foods and makes edible some that would otherwise be inedible.
Improved health must certainly have been one result of the discovery of cooking, and it has even been argued, by the late Carleton Coon, that cooking was the decisive factor in leading man from a primarily animal existence into one that was more fully human’.
Whatever the case, by all the laws of probability roasting must have been the first method used, its discovery accidental. The concept of roast meat could scarcely have existed without knowledge of cooking, nor the concept of cooking without knowledge of roast meat.
Eating raw food is necessary for good health and is an important feature of a healthy diet. But that does not mean that one’s entire diet has to be raw to be in excellent health. It also does not mean eating an all-raw diet is the healthiest way to eat. It is healthier to expand your nutrient density, your absorption of plant protein and your nutrient diversity with the inclusion of some conservatively cooked food in your diet.
Generally speaking, the larger the mammal, the larger its brain will be. Humans are a bit of an anomaly among primates, however, because we have the largest brain and number of neurons, but not the largest body. Great apes, for instance, have much bigger bodies than humans, yet much smaller brains.
How humans came to be so well endowed in the brain department has long been a mystery – but many theories abound, including the predominant one of access to animal-based omega-3 fats from seafood.
Another theory suggests it may, in fact, be cooking that allowed humans to develop so much brainpower.
Your brain is a major consumer of the calories you consume in a day. Even though it makes up only about 2 percent of your body mass, it uses 20 percent of your calories!
The size and number of neurons in your brain is, therefore, largely dependent on the number of calories you can consume in a day. Ancient humans had to graze constantly to find enough calories to live on, much the way apes and gorillas do today. There are only so many hours in a day, and raw, mostly vegetable, foods do not contain many calories, which together put a metabolic limitation on how big the brain could grow.
Researchers believe that it was the shift to a cooked-food diet that gave humans the extra calories they needed to allow their brains to get bigger.
“Absent the requirement to spend most available hours of the day feeding, the combination of newly freed time and a large number of brain neurons affordable on a cooked diet may thus have been a major positive driving force to the rapid increased in brain size in human evolution,” the researchers noted.
They speculated that gorillas would need to spend another two hours a day eating to gain the extra caloric intake to allow their brains to grow as big as humans’, and pointed out that the cooked foods were likely easier to chew and digest, and may have released more calories in some cases.
In 2008, researchers similarly concluded that human brains “smartened up” – allowing for the use of tools and the creation of art and religion – due to the extra calories that became available when cooked food became widespread.4 Eating cooked meals, they said, would have lessened the energy needs of the human digestive system, thereby freeing up calories for the brain.
Gathered around a blazing fire, our ancient ancestors probably huddled to pass the archaic kebab, munching cooked meat and figuring out how they might share it and plan to get more of it. Eating cooked food allowed these early hominids to spend less time gnawing on raw material and digesting it, providing time–and energy–to do other things instead, like socialize. The strenuous cognitive demands of communicating and socializing forced human ancestors to develop more powerful brains, which required more calories–calories that cooked food provided. Cooking, in other words, allowed us to become human.
A new paper examines the metabolic restrictions of a raw diet, and suggests that our primate cousins are limited by their inability to heat their dinners. It bolsters the cooking hypothesis of Richard Wrangham, a primatologist and professor of biological anthropology at Harvard who believes cooking is our legacy.
Brazilian biomedical scientists Karina Fonseca-Azevedo and Suzana Herculano-Houzel note that the largest primates do not have the largest brains, a perplexing question. Encephalization (a larger brain size per body size than you’d expect) has long been thought to be a key feature setting humans apart from other primates, and mammals as a whole, but there is no consensus on how or why this happened.
“We consider this disparity to be a clue that, in primate evolution, developing a very large body and a very large brain have been mutually excluding strategies, probably because of metabolic reasons,” the authors write. They’re the first to try and quantify these limits.
“You would think, ‘Surely people have thought about this stuff before,’” Wrangham said in an interview. “But nobody has ever thought about the fact that cooking gives you more energy.”
This is a central thesis of Wrangham’s 2009 book, “Catching Fire.” He argues that the control of fire allowed early hominids to not only cook their food, but obtain warmth, allowing them to shed body hair and in turn run faster without overheating; to develop calmer personalities, enabling social structures around the hearth; and even to form relationships among men and women–in short, to become human.
“My day job is studying chimpanzees in the wild, and I have often studied feeding behavior. I have tried to survive on what chimps eat,” he said.
“If I don’t have any food with me, I just eat what they eat. And that told me that what they eat is totally unsatisfying,” he continued. “I thought about what would happen if humans had to live like chimps. And that took me very rapidly to the conclusion, within a few minutes, that as long as we’ve been human, it’s hard to imagine how we could live on raw food.”
Wrangham’s ideas follow the expensive-tissue hypothesis. That concept predicts an inverse relationship between brain size and gut size–to accommodate a large, human-sized brain; our guts shrank relative to our primate cousins. Imagine the potbelly of a gorilla, Wrangham notes. This paper doesn’t even address gut size, just the requirements of our hungry brains.
“In order to be able to apply a sufficient number of calories to the brain, you have to be able to cook your food,” Wrangham said. “You can only afford to have a brain if you can supply a lot of energy to it.”
The idea is that raw food just doesn’t provide enough calories. You have to get out more than you put in, and raw food takes a lot more work (meaning calories) for your muscles and organs to chew and digest, resulting in a net decrease in the amount of calories available for the rest of your cells.
But you can only spend so many hours of the day eating–there must be time to sleep, forage and procreate, too. This limits the amount of calories you can get per day, and it turns out this is directly related to how many neurons you can grow, according to Fonseca-Azevedo and Herculano-Houzel.
The duo crunched numbers to figure out the metabolic costs of a human-sized brain, which is the third most energy-expensive organ in the human body, ranking below only skeletal muscle and the liver in terms of metabolic needs. The more neurons the brain has, the more energy it needs.
If we ate an only-raw diet, to maintain the body size we humans possess, as well as the number of neurons our brains possess, people would have to eat for more than 9 hours per day, they found.
Cooking does some of the work of digestion for us, as Wrangham puts it.
“Molecules are moving faster under the influence of heat; they are breaking up or shaking apart from each other, and that’s essentially what happens in digestion, the denaturating of proteins,” he said. “They lose their structure, and become more accessible.”
As an example, he and others have investigated the effects of cooking on starch molecules and humans’ ability to digest cooked versus raw grains. Simply cooking starchy foods increases the net energy gain by 30 percent, he said.
“The grains themselves represent long chains of glucose, which are very difficult to digest until they have been gelatinized; you are opening up these chains,” he said.
Take, for example, a simple white sauce of flour and butter. You have to stir constantly over even heat, letting the water in the butter invade the starch molecules in the grain. “Then you get this change in consistency, where the whole thing becomes a continuous colloid, and the starch grains have become gelatinized. The result is that it will be easier to digest,” Wrangham said. “Our body pays fewer calories for the digestion.”
Certainly, there are benefits to consuming plenty of raw fruits and vegetables. These foods supply us with high nutrient levels and are generally low in calories too. Eating lots of raw foods is a key feature of an anti-cancer diet style and a long life. But are there advantages to eating a diet of all raw foods and excluding all cooked foods?
The answer is a resounding “No”.
In fact, eating an exclusively raw-food diet is a disadvantage. Excluding all steamed vegetables and vegetable soups from your diet narrows your nutrient diversity and has a tendency to reduce the percentage of calories from vegetables in favor of nuts and fruits which are lower in nutrients per calorie.
Raw vegetables are dramatically low in calories and we probably only absorb about 50 calories a pound from raw vegetables. Our caloric needs cannot be met on a raw food diet without consuming large amounts of fruits, avocado, nuts and seeds.
Unfortunately, sloppy science prevails in the raw-food movement. Raw food advocates mistakenly conclude that since many cooked foods are not healthy for us, then all cooked foods are bad. This is not true.
The idea that stirs the most enthusiasm for this diet is the contention that cooking both destroys about fifty percent of the nutrients in food, and destroys all or most of the life promoting enzymes. It is true that when food is baked at high temperatures—and especially when it is fried or barbecued—toxic compounds are formed and most important nutrients are lost.
Enzymes are proteins that work to speed up or “catalyze” chemical reactions. Every living cell makes enzymes for its own activities. Human cells are no exception. Our glands secrete enzymes into the digestive tract to aid in the digestion of food.
However, after they are ingested, the enzymes contained in plants do not function as enhancements or replacements for human digestive enzymes. These molecules exist to serve the plant’s purpose, not ours. The plant enzymes get digested by our own digestive juices along with the rest of the food and are absorbed and utilized as nutrients.
Contrary to what many raw-food web sites claim, the enzymes contained in the plants we eat do not catalyze chemical reactions that occur in humans. The plant enzymes merely are broken down into simpler molecules by our own powerful digestive juices. Even when the food is consumed raw, plant enzymes do not aid in their own digestion inside the human body. It is not true that eating raw food demands less enzyme production by your body, and dietary enzymes inactivated by cooking have an insignificant effect on your health and your body’s enzymes.
Plant foods do not supply enzymes that aid in their digestion when consumed by animals. Our body supplies exactly the precise amount of enzymes needed for digestion; we are not ill equipped to digest normal food. The plant enzymes are broken down into simpler molecules by our own powerful digestive juices and even those that are absorbed as peptide size pieces (or with some biologic function) do not function to catalyze human functions.
So it is not true that eating raw food demands less enzyme production by your body. A healthy body produces the precise amount of enzymes needed to digest the ingested food appropriately and the enzymes our body uses for other processes are unique to our human needs and are not present in plants. We make what we need from the proper materials.
Recent studies confirm that the body absorbs much more of the beneficial anti-cancer compounds (carotenoids and phytochemicals—especially lutein and lycopene) from cooked vegetables compared with raw. Scientists speculate that the increase in absorption of antioxidants after cooking may be attributed to the destruction of the cell matrix (connective bands) to which the valuable compounds are bound.
In many cases, cooking actually destroys some of the harmful anti-nutrients that bind minerals in the gut and interfere with the utilization of nutrients. Destruction of these anti-nutrients increases absorption. Steaming vegetables and making vegetable soups breaks down cellulose and alters the plants’ cell structures so that fewer of your own enzymes are needed to digest the food, not more. On the other hand, the roasting of nuts and the baking of cereals does reduce availability and absorbability of protein.
Only small amounts of nutrients are lost with conservative cooking like making a soup, but many more nutrients are made more absorbable. These nutrients would have been lost if those vegetables had been consumed raw. When we heat, soften and moisturize the vegetables and beans we dramatically increase the potential digestibility and absorption of many beneficial and nutritious compounds.
Many vitamins are water-soluble, and a significant percent can be lost with cooking, especially overcooking. Similarly, many plant enzymes function as phytochemical nutrients in our body and are useful to maximize health. They, too, can be destroyed by overcooking. However, we cannot paint with this brush of negativity over every form of cooking.
When food is steamed or made into a soup, the temperature is fixed at 100 degrees Celsius or 212 Fahrenheit—the temperature of boiling water. This moisture-based cooking prevents food from browning and forming toxic compounds. Acrylamides, the most generally recognized of the heat-created toxins, are not formed with boiling or steaming. They are formed only with dry cooking. Most essential nutrients in vegetables are made more absorbable after being cooked in a soup and water-soluble nutrients are not lost because we eat the liquid portion of the soup too.
We also increase the plant proteins in the diet, especially important for those eating a plant-based diet with limited or no animal products.
Multiple studies have demonstrated that the beneficial antioxidant activity of cooked tomatoes is significantly higher than from uncooked tomatoes. Scientists speculate that the increase in absorption of antioxidants after cooking may be attributed to the destruction of the cell matrix (connective bands) to which the valuable compounds are bound.
It is true that vitamin C, folate, B vitamins, and certain minerals are water-soluble and can be destroyed by cooking; but vitamin C contributes less than one percent to the total antioxidant activity of fruits and vegetables. For example, the main antioxidant activity in apples is provided by classes of chemicals called phenolics and flavonoids, both of which are made more available by cooking.
If you compare raw broccoli to steamed or frozen broccoli, about 25 percent of the vitamin C and about 20 percent of the selenium is lost during cooking, but the other 20 commonly measured nutrients show only an insignificant change. Raw-food advocates are not accurate when they claim that 50 percent of nutrients are lost with steaming. A closer estimate would be 10 percent.
Cooking corn also has been shown to significantly boost its antioxidant activity, despite reduction in vitamin C. When the ability to quench free radicals was measured, cooked corn outperformed raw corn by between 25 to 50 percent. Cooking corn releases a compound called ferulic acid, which provides anti-cancer health benefits. Ferulic acid, a phytochemical, is unique in that it is found only in very low amounts in fruits and vegetables, but is found in very high amounts in corn. The availability to the body of ferulic acid can be increased 500 to 900 percent by cooking the corn.
In conclusion, eating lots of raw foods is only a feature of a healthy diet. Like most things in life, most who practice the raw food diet did so with blind faith, thinking it was the end all and be all.
This is NOT true.
Live and Learn. We All Do.
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