Raw Versus Cooked: Which Diet is the Most Nutritious?

A raw, plant-based diet is cleansing, detoxifying, energizing and purifying, if the Internet is anything to go by. You don’t have to look too hard to find impressive lists of the many healing properties of a raw food diet. But you would have to look very hard to find any evidence.

Instead, you’ll find plenty of evidence of the damage that such a diet can cause: malnutrition, infertility, bone loss. But first, a definition.

“Raw” is generally defined as food that has not been chemically processed, or heated above 48C.

It’s a diet based on lots of plant foods. But raw does not necessarily mean vegan — you can eat raw eggs, or fish, or drink unpasteurized milk, for example, but most raw foodists exclude all animal-source foods. Usually, the diet is based on fruits, vegetables, nuts, seeds and sprouted grains and beans.

What they say

An Internet search reveals that among the many claims made for following a raw food diet, the most common include:

• Better heart health
• Cancer prevention
• Clearer skin
• Improved digestion
• Better liver function
• Better chance of swerving most diseases
• Weight loss.

It’s all bunkum — except for the last item. You will almosts certainly lose weight on a raw food diet. That’s because there is a high chance of becoming malnourished. It’s similar to starvation, but more expensive.

The reason you can expect to be malnourished is that the human gut is not built to digest raw plant foods.

You don’t have the guts

There are two types of herbivore, and through evolution they have developed complex digestive systems to manage the large amount of plant matter they consume.

The first type of herbivore is the ruminant, an animal that has a complex, four-chambered stomach to facilitate the breakdown of raw cellulose. This group of herbivore includes cattle, goats and deer. Food is regurgitated and the digestive process is repeated, in a process called chewing the cud.

The second type of herbivore — called the hindgut fermenter –has an enlarged caecum and complex colon, which act like a fermentation “tank” to digest plant material. This group of herbivore includes elephants, horses, rhinos and rabbits.

It also includes gorillas and other primates. It does not include humans.

Even with their specially adapted digestive systems, both these types of plant-eaters have to graze all day in order to consume enough calories to meet their energy requirements.

Humans are simply not equipped with the right gut gear to digest most raw plant material efficiently. You, as an evolved member of the Homo sapiens species, have neither a four-chambered stomach nor an enlarged colon and caecum; instead, you are equipped with a simple stomach and short colon, features that are characteristic of all omnivores.

Creating, not digesting

Being omnivores who don’t have to graze all day, we have lots of spare time to get on with being creative.

We humans may be closely related to gorillas — sharing 98% of our DNA — but the remaining 2% makes a lot of difference. Gorillas must eat up to 40 pounds of plant material a day, to get all the calories they need. They are not very creative though.

Having a simple gut means that, should you still be swayed by the argument that a diet of raw plant foods is the path to purification, and decide to give it a go, you’d almost certainly end up with nutrient deficiencies, including vitamin B12 and the omega-3 fatty acids.

Vitamin B12 is crucial to brain function, so, unsurprisingly, memory problems and slow mental processes are the most commonly reported cognitive problems associated with deficiency of this vitamin. Without supplementation, long term deficiency can lead to irreversible brain damage.

The omega-3 fatty acid, DHA, is also crucial to brain function. Without enough DHA, you could find yourself suffering from depression and anxiety.

Instead of purification and enlightenment, you can expect three major outcomes:

1. Amenorrhoea

This is a common outcome for women. In one study of people regularly consuming a raw food diet, a quarter of 297 women had partial to complete amenorrhoea, the absence of menstruation.

2. Weight loss

Eating a raw food diet is certainly an effective weight loss method, because of its poor absorption rate. The higher the percentage of raw food in the diet, the more weight loss observed, and the lower the BMI.

“Since many raw food dieters exhibited underweight and amenorrhea, a very strict raw food diet cannot be recommended on a long-term basis.” (koebnick et al)

3. Bone loss

Long-term adherence to a raw food diet can result in bone loss, or osteoporosis. One study compared 18 non-smoking raw-foodist volunteers, aged 33–85, with no history of chronic disease, with similar volunteers who ate a typical American diet (which, we can safely assume, is not an especially healthy one). Bone mineral content and density of the lumbar spine and hip area were significantly lower in the raw food group than the typical American diet group.

All this may appear counterintuitive; surely eating raw food is more natural than eating cooked food? Cooking is a form of food processing, after all.

Like our close relatives, the chimp and the gorilla, we humans were also once raw food eaters, with similar digestive systems. Before the Homo genus emerged, around 2.6 million years ago, we were tree dwellers, living mainly on fruit and other raw foods.

We also had much bigger guts, teeth and jaws back then. You need them, to break down all that cellulose. Unfortunately, we also had much smaller brains. You can’t have everything.

All change

All that changed when we started to explore terra firma, and began scavenging for meat, and consuming shellfish.

Then we discovered how to light a fire.

Richard Wrangham is a professor of biological anthropology at Harvard University, and author of the book Catching Fire: How Cooking Made Us Human. In it, he argues that cooking helped shape our destiny and changed our physiology.

Wrangham explores how, when we came down from our tree dwellings, stood on two feet and went a-hunting for food, fire gave us the protection from predators that we needed.

We also learned how to cook.

We know that for at least 500,000 years humans have been cooking their food. According to Wrangham, it’s probably a lot longer — as long as 1.8 million years. That’s when Homo erectus showed up, with smaller teeth and guts (and bigger brains) than their tree-dwelling ancestors.

Cooking not only makes food more palatable, it makes it more nutritious. When plant food is cooked, the indigestible cellulose portion is broken down and the nutrients within are released for absorption. Even though some nutrients are lost in the cooking process, cooked food still provides much higher levels of bioavailable nutrients than raw.

Some plant chemicals in food, such as the carotenoid lycopene in tomatoes, only become available for absorption if food is cooked. Otherwise, they pass right through you, like a missed opportunity.

Cooking meat makes it more nutritious, because heating tenderizes the meat, a process that releases the nutrients and reduces the need for prolonged chewing (and big teeth and jaws).

“All studies of human raw foodists, and many comparisons of domestic or wild animals on cooked versus raw diets, lead to the same conclusion: the more cooked food in the diet, the greater the net energy gain.” (Wrangham & Carmody)

There are exceptions. Some plant foods, for example fruit, consist mainly of water and simple sugars, so are easy to digest, making cooking unnecessary as well as undesirable.

The changes to the way we ate brought changes to our bodies: cooking changed our jaws and teeth, and eliminated the need for a long, complex digestive tract. Cooking food reduces toughness and therefore the need for larger teeth for chewing.

Between approximately 100,000 and 10,000 years ago, human tooth size started to shrink at a rate of 1% every 2,000 years, a phenomenon that has been attributed to cooking.

“Small guts probably explain why modern humans fare poorly on raw diets and why no human societies live without cooking.” (Wobber et al)

If we compare ourselves to raw food-eating primates of similar size, our guts are about 60% smaller.

Nor do we need to eat so much, as cooked food has much greater calorific value than raw. We humans are not grazing beasts that need to have their noses to the trough all day.

Cooking — it’s in your genes

The upshot of all this is that we are now genetically adapted to eating cooked food.

Wrangham proposes that because of this genetic adaptation, any efforts to live on raw food alone is detrimental to our health — indeed we could not survive. Hunger, malnutrition and infertility would have meant inevitable extinction.

Despite the evidence, the case for raw foodism is supported by plenty of pseudoscience. The benefits are attributed to the “live” enzymes present in raw foods, enzymes that are destroyed by cooking.

Yet the stomach is a highly acidic environment, as it must be, in order to digest proteins. Any live enzymes — which are proteins — are thoroughly metabolised and despatched in the way of all proteins. That’s why we produce our own enzymes.

When you cook your food, you destroy many harmful pathogens, including bacteria such as E.coli, Salmonella and Listeria.

Cooking also destroys lectins, “anti-nutrients” that interfere with nutrient absorption and damage the gut lining. They are most abundant in seeds but are also found in roots, leaves, and bulbs.

These lectins do serve a purpose as far as the plant is concerned — they provide protection against insect attack.

It comes down to taste

Cooked food on the whole tastes better than raw food, with the exception of some foods such as fruit and salads. I think we can safely assume that our early ancestors didn’t cook their food because they wanted more nutrients or bigger brains. They preferred the taste.

They’re not the only ones. In 2008 scientists reported the results of an experiment on great apes to see whether they would select raw or cooked foods, when given the choice, and found that they almost always preferred their food cooked.

Across the planet, no human population has ever been found living on a raw food diet.

Hot cooked food provides the perfect antidote to cold winter nights, like a warm embrace. It makes the dark season bearable, when the thought of cold raw food chills the bones.

Food is the new religion, the cult of the secular. Be careful what you choose to believe. Don’t be persuaded that a sprouted mung bean is delicious, when your instinct tells you otherwise. Cook real food and enjoy it, knowing that it is nourishing you in a uniquely human way.