Raw vegan diets are all the rage these days. Advocates claim that a diet composed exclusively of raw plant foods will support optimal health, protect animals, and save the planet.

The raw truth is that raw vegan diets don't support health for most people, for a very simple reason: Humans are not adapted to a raw vegan diet. For that matter, not even our closest primate relative, the chimpanzee, is adapted to a raw vegan diet.

Let's take a critical look at the rationales and effects of raw vegan diets

Raw Rationale

David Wolfe, raw food advocate, wrote a book entitled Nature's First Law (Don't buy it!). In this book, he suggests that the "first law" of nature is that food is raw; if not raw, its not food. He derives this "law" from the observation that no animal other than humans cooks anything before eating it. Thus, humans break the "law."

Let's try more reasoning like Wolfe's:
  • No other animal uses language, therefore humans should not use language.
  • No other animal wears clothes, therefore humans should not wear clothes.
  • No other animal makes violins, therefore humans should not make violins.
  • No other animal writes sonnets, therefore humans should not write sonnets.
These people apparently have not noticed that by their reasoning, we humans probably should not be, well, human.

And, particularly pertinent to the raw food lifestyle, no other animal uses metal knives, blenders, dehydrators, grinders, or juicers, therefore humans should not process foods with any of these items either. Yet raw foodists seem plenty happy to apply the knife, high speed blending, mechanical grinding, and juice extraction to food.

Flimsy Analogies

Wolfe and other raw foodists also are fond of using analogies like this: "If you set fire to your house, it does not improve the house, it destroys it. Therefore, we can conclude that applying fire to food can only destroy, not improve it."

Raw vegan blogger Steve Pavlina states it this way:
"Incidentally, if you want to see what happens to protein when you cook it, pluck a hair off your head and put a flame under it. Cooked protein becomes a sticky mess that doesn't digest well at all. Raw plant foods provide all the protein we need, in the right form for easy assimilation."
Wolfe and Pavlina have constructed straw man arguments against cooking by conflating it with incineration.

Perhaps their starved brains can't see this, but incinerating a house or human hair with a direct flame is, well, not quite the same thing as cooking. Cooks don't light food on fire, they use finesse to capture and employ radiant heat arising from flames to alter the physical properties of the foods. Strictly speaking, it is not the fire that they use, it is the heat.

Does cooking make food less valuable? On the contrary, skillfully applied heat dramatically increases the nutritional value of plant foods.

Hedren et al performed an experiment designed "to develop an in vitro digestion method to assess the impact of heat treatment, particle size and presence of oil on the accessibility (available for absorption) of alpha- and beta-carotene in carrots." Their methods:
"Raw and cooked carrots were either homogenized or cut into pieces similar to chewed items in size. The carrot samples, with or without added cooking oil, were exposed to an in vitro digestion procedure. Adding a pepsin-HCl solution at pH 2.0 simulated the gastric phase. In the subsequent intestinal phase, pH was adjusted to 7.5 and a pancreatin-bile extract mixture was added. Carotenoids released from the carrot matrix during the digestion were extracted and quantified on high-performance liquid chromatography (HPLC)."
Their results:
"Three percent of the total beta-carotene content was released from raw carrots in pieces. When homogenized (pulped) 21% was released. Cooking the pulp increased the accessibility to 27%. Addition of cooking oil to the cooked pulp further increased the released amount to 39%."
Look, although they treated the finely chopped (chewed-simulation) carrots with an HCl solution at pH 2.0, only 3 percent of ß-carotene was released. Don't you think this tells us something? For example, maybe our gut isn't equipped to adequately digest raw plants as they occur in nature?

The human gut can't extract high amounts of anything from raw carrots or similar vegetables for one simple principal reason: our bodies do not produce the enzyme cellulase required to digest and break down the plant cells that contain all the nutrients supplied by fibrous plants.
plant cell structure
© Wikipedia
Almost all of the valuable nutrients in plants occur inside the cells of the plants. These cells have walls composed of cellulose. Lacking any enzyme to break down this cell wall, humans must use other means to open the cells to extract the nutrients. Outside modern industrialized nations, most people apply heat to the food, which causes the juice in the cells to expand and this causes the cells to explode open, making their contents more available for absorption.

Thus, carrots cooked to a soft texture deliver 9 times as much ß-carotene as chewed raw carrots. This experiment explains why raw foodists love and need their blenders and juicers. Let's say some raw food person eschews machinery. Here's the data:

  • One hundred grams of raw carrot contains 16, 706 potential IU of potential vitamin A activity in the form of carotenes.
  • A human requires about 1000 mcg daily of retinol equivalent (RE) activity from food.
  • If only chewing the carrots, a human will extract about 3% of the carotenes, or 501 IU.
  • 10 IU of ß-carotene from plant foods provides one RE.
From this we can conclude that 100 g of raw carrot provides only 50 RE. Since a human requires about 1000 RE daily, he would have to eat 20 x 100 g, or 2 kg/4.4 pounds of carrots daily to even have a chance of meeting his vitamin A needs.

Since the typical person eats only 3-5 pounds of food daily, he would have to eat nothing but carrots. Two kilos of carrots supplies only 820 calories, assuming that we can extract 100% of available calories from raw plants, or only about 24 calories if we extract calories from chewed carrots at the same 3% rate that we extract ß-carotene (the safer assumption, since all the sugars in carrots are also locked up in the indigestible cells).

So this guy better be up for spending a lot more time eating to meet his 2500 calorie daily requirement. How about at least 6 kilos of carrots daily, and possibly 200 kilos daily, to meet your energy requirements?

So the raw fooders fall back on their blenders, which will increase the nutrient delivery by about 7 times. Now you only need a mere 600 g/1.3 lbs. of carrots to get enough ß-carotene to have a chance at adequate vitamin A production. The caloric delivery soars to 84 calories per kilo. Now we're making some progress.

Perhaps you can begin to see why some people rave about weight loss achieved when they gorge on raw foods. The caloric delivery can be so low, you may as well be fasting.

Back to the vitamin A, all of that assumes that he was not one of the approximately 45% of people who don't convert carotenoids to vitamin A at all. It appears that in the course of human evolution, the activity of ß-carotene 15,15'-dioxygenase (needed to convert ß-carotene to retinol) has declined substantially, such that up to 45% of people do not convert ß-carotene to retinol vitamin A. Hickenbottom et al found that 45% of 11 men tested did not convert ß-carotene to vitamin A (retinol). Lin et al found the same in women. Leung et al identified gene polymorphisms contributing to this variability in carotene conversion capacity.

Now apply this to calcium. Take a raw vegetable with a fairly high calcium content, such as collards, which may contain up to 250 mg calcium per 100 g. Like the ß-carotene in carrots, this mineral lies inside the cells of the collards, surrounded by cellulose that we can't digest. This means that we might extract only 3% of the calcium from raw collards, i.e. 7.5 mg per 100 g raw. A human requires about 750 mg calcium daily, so he'd have to eat 10 kilos of raw collards daily to get adequate calcium. Let's get chewing!

Actually, one might rightly question whether we can rightly call a food that has gone through a juice extractor, blender, or grinder of any sort "raw," "uncooked," or even "unheated."

All of these devices treat the food with friction, and friction always generates heat, the key element of the "cooking" that raw foodists so passionately attack. One might call the products minimally heated, but they are heated nonetheless.

Moreover, no other animal has to use blenders to get adequate nutrition from its raw food diet. If you vegan raw fooders discard cooking because "no other animal does it," shouldn't you also discard blenders and juicers for the same reason? Perhaps your starved brains can't comprehend contradiction?

If your raw food diet only works if you use a blender, I have to wonder what you think your raw food ancestors did without those blenders, only invented in the 20th century. So far as I know, no archaeological dig has found blenders or juicers in early human tool kits. Can you imagine stone age women trying to juice carrots by grinding them against rocks? Not quite optimal foraging.

I've a few more things to say about the delusions of vegan raw fooders. Until next time, have a steak.