For about a century, raw foods have been foundational "health foods”.
And since the advent of electric juicers, fresh produce juices have led the raw food movement.
Hard-core raw foodists rely entirely on fruits and vegetables (fresh or fermented) but may eat sprouted beans and grains and unpasteurized dairy (raw milk, yogurt, cheeses).
The popularity of raw foods grew fast in the 1970's and ‘80's, fueled by inescapable "Juiceman” TV ads and rational fears over refined/processed foods.
There's no way to know the size of the "raw foods” movement, but juicing is a fast-growing, $5 billion dollar industry.
Advocates assert the superiority of raw foods and inferiority, and even the toxicity of cooked foods.
Clearly, some people thrive while eating little or no cooked foods.
And it's true that inflammation-related medical conditions (e.g., arthritis and allergies) sometimes respond well to raw food diets.
But is that because patients consume raw veggies, or because people on such diets are cutting out proven inflammation-promoters, like sugars and refined starches?
Is there good evidence that raw plant foods are superior to cooked, or that raw food juices trump whole raw plant foods?
Let's take a close look at the claims.
Plant foods: The whole and the raw
The whole foods aspect of the raw-foods movement is laudable, given the overwhelming evidence in favor of whole foods diets.
And that evidence makes sense, because humans and our primate predecessors evolved eating whole foods.
Whole plant foods provide essential vitamins and minerals, many of which occur in animal foods.
Critically, only whole plant foods abound in fibers and diverse "nutrigenomic” antioxidants, which exert broadly beneficial effects on our genes.
(Wild salmon, krill, and shrimp are rare exceptions among animal foods, because they provide the highly beneficial carotenoid-class orange pigment called astaxanthin … which, thanks to their shrimp-y diet, is also what makes Flamingo feathers pink.)
Thousands of published studies show that fruits, vegetables, herbs, spices, cocoa, tea, and coffee exert indirect antioxidant, anti-inflammatory, anti-cancer, and other beneficial nutrigenomic effects.
Raw food-ism: The leap from whole to raw
Whole food diets are clearly essential to minimal and optimal health … but raw-food advocates take things a step further.
They make two controversial claims for diets based heavily on uncooked plant foods:
Humans are better adapted to primarily raw-food diets than to diets containing substantial proportions of cooked foods.
The "food enzymes” in raw (and very lightly cooked) foods help our bodies digest these foods, easing the body's workload and conferring significant health benefits in the body.
These ideas sound good, but there's little evidence behind them … and an exclusively or primarily raw-food diet may have some drawbacks.
Raw food folks accurately say that cooking certain foods in certain ways (e.g., grilling and browning) can degrade their nutritional value and/or generate carcinogenic, oxidizing, and/or pro-inflammatory chemicals.
On the other hand, cooking makes many plant foods more digestible and enjoyable, and renders their nutrients more available and absorbable.
Cooking plant foods:
No nutrition trade offs
What proportion of nutrients are lost when we cook food?
Cooking seems to do little harm, and some good.
Because cooking breaks down plant cell walls, more of a plant food's nutrients become available for absorption and use.
Fresh is best, but frozen vegetables are quick-frozen right after picking, which preserves their nutrients for months
The USDA tested 290 foods
to measure the effects of various cooking methods on the levels of 16 vitamins and eight minerals.
The tests showed that most minerals were unaffected by cooking.
Vitamin C, folate, and thiamine were the nutrients most commonly reduced by cooking, but levels rarely dropped by as much as half.
In addition to taking multivitamins, loss of those three nutrients can be offset by foods not normally or necessarily cooked:
- Folate - leafy green vegetables, avocados, and fortified breads
- Thiamine - Legumes (beans, lentils), beef and pork, Brewer's yeast, whole-grain breads and cereals, oatmeal, enriched pastas, rice bran and wheat germ, milk, nuts, seeds and oranges and because of fortification, so too is bread.
Vitamin C – Tomato, citrus fruits, apples, asparagus, berries, broccoli, cabbage, melon, cauliflower, kiwi, fortified foods (breads, grains, cereal), dark leafy greens, red bell peppers, potato.
And an exclusively plant foods diet (raw or cooked) will lack the most beneficial kinds of omega-3 fat (DHA and EPA), found only in seafood.
Raw foodism and food enzymes:
Dr. Howell's persistent hypothesis
Advocates for heavily raw-food diets often claim digestive and overall health benefits accrue from the enzymes in raw foods.
Many raw foodists are vegetarian, but some include raw dairy and fish, and meats and fish cured at low temperatures, in their raw regimens.
Raw-foodists also believe that the enzymes in a raw food assist in its own absorption and digestion.
Enzymes are a special class of proteins, needed for many critical bodily processes at the molecular level. Heating food above 140° F (60° C) inactivates (denatures) most enzymes in food, while some denature at about 113° F (45°C).
In the 1920's, Edward Howell, M.D., asserted his idea that the enzymes in raw foods help us to break down these same foods and reduce the need to produced enzymes internally.
Further, he claimed that the normal, continuous, internal manufacture of enzymes by the body taxes its limited energy stores.
But healthy people have no difficulty synthesizing enzymes, provided the body gets enough protein and other essential nutrients.
And healthy people normally experience no shortage of digestive enzymes, or any difficulty digesting frozen or cooked foods.
(Cooking animal foods at temperatures in excess of the boiling point (212° F / 100° C) renders their proteins somewhat harder to absorb.)
Nor is there any evidence for Dr. Howell's claim that diets high in cooked foods tax the body's digestion or overall metabolism, promote disease, or accelerate aging.
In brief, we can find little or no persuasive evidence for Dr. Howell's core claims, which were largely based on limited, unpersuasive research conducted in the 1920's and 1930's.
Raw-food proponents point to enzyme-related research conducted in recent years.
But very little of it has proven any more persuasive than Howell's own … as the Beyond Vegetarianism
Web site mentioned below documents.
Food enzyme advocates lack persuasive evidence
There are several major problems with Dr. Howell's hypothesis.
First, the enzymes present in food are not equipped to act as digestive enzymes.
Second, almost all of the enzymes present in raw foods are broken down into their components (amino acids) by our own digestive processes.
Last, the healthy human body has no shortage of the amino acids and proteins needed to construct enzymes internally.
Voluntary contributors to a remarkable Web site called Beyond Vegetarianism
present a detailed scientific critique of Dr. Howell's claims.
The site's founders and chief contributors present scientifically sound information on various raw, vegetarian, or otherwise restricted diets (e.g., Paleo diet pioneer Professor Loren Cordain, Ph.D., and Steven Bratman, M.D., editor of the Natural Pharmacist book series and e-encyclopedia).
Did early humans eat it raw?
Let's test the credibility of the idea that early humans and their ancestors evolved on largely raw-food diets.
If true, this would lend support to the idea that raw-food diets are the healthiest choices for modern humans.
Some raw food advocates say that humans adapt very slowly to diet changes, and that human cooking dates back no more than 50,000 years ... therefore, humans are not adapted to cooked foods.
What about juicing?
Juicing is promoted as a tactic for weight loss and general health enhancement.
It takes several pieces of produce to make an average-size juice portion, so a glass of juice made from them will deliver a pretty big load of the "antioxidants” and other nutrigenomic phytonutrients in those pieces.
But juicing whole produce also concentrates its sugar and calorie content into a single glass.
One of the benefits of eating whole plant foods is that their fiber and bulk make you feel "full” fast, and which enhances overall satisfaction.
Juice contains far less fiber than whole fruits and vegetables do, and sharply decreases the fiber-related benefits and feeling of fullness gained by eating them.
The sugar and calorie content of juice is much greater than the sugar content of whole fruit and vegetables, and it takes several pieces of produce to make an average-size juice portion.
Importantly, the most successful weight-control diets are those that can be sustained, and for many juicing is an expensive experiment that proves rather unsatisfying on that score.
There are two problems with this claim.
First, most archaeologists date widespread human use of cooking to about 250,000 years ago, when hearths, earth ovens, burnt animal bones, and flint appeared across Europe and the Middle East.
There is also evidence that early humans cooked tubers, which turns some of these plants' near-indigestible starches into sugars and other digestible carbohydrates.
Finally, Paleo-anthropological research proves that major evolutionary adaptations – notably, lactose tolerance among cow-herding cultures in Northern Europe – have occurred within periods as brief as 1,200 years.
The most conservative estimates – which some raw foodists cite – place the earliest provable date for the beginning of cooking by humans at about 50,000 BC.
But even if we use that relatively recent date, the example (among others) of northern European cow-herders' rapid, 1,200-year-long adaptation to dietary lactose suggests that it is reasonable to hypothesize that modern people are by now well adapted to routine consumption of cooked foods.
It is worth quoting here from an evidence review by anthropologists from Harvard University (Wrangham R, Conklin-Brittain N 2003):
- "No human foragers have been recorded as living without cooking, and people who choose a 'raw-foodist' life-style experience low energy and impaired reproductive function. This suggests that cooking may be obligatory for humans.”
- "The possibility that cooking is obligatory is supported by calculations suggesting that a diet of raw food could not supply sufficient calories for a normal hunter-gatherer lifestyle. In particular, many plant foods are too fiber-rich when raw, while most raw meat appears too tough to allow easy chewing.”
- "If cooking is indeed obligatory for humans but not for other apes, this means that human biology must have adapted to the ingestion of cooked food (i.e. food that is tender and low in fiber) in ways that no longer allow efficient processing of raw foods. Cooking has been practiced for ample time to allow the evolution of such adaptations.”
Interestingly, a team from Harvard and Germany's Max Planck Institute found that in general, great apes prefer cooked over raw foods (Wobber V et al. 2008).
Another of their studies, published last year, indicates that eating cooked foods takes less energy than eating raw foods… a small but possibly significant survival advantage in terms of calorie conservation (Boback SM et al. 2007).
Modern hunter-gatherers combine raw and cooked foods to healthful effect Studies of modern hunter-gatherer societies indicate two things:
- They cook about half their food, which invariably includes some animal foods (meat, fish, insects), albeit much less meat than Americans and Europeans eat.
- They enjoy low rates of the chronic degenerative diseases that plague Western countries and are rising among developing countries as well: cancer, diabetes, heart disease, and dementia.
Together, these findings suggest that the prevalence of cooked versus raw foods probably plays a minor part in people's overall health and their risk of developing the major degenerative diseases associated with Western civilization.
The negative impact of diets rich in fatty red meats is another matter. Epidemiological evidence suggests that diets high in processed red meats may raise the risk of cancer, heart disease, and dementia.
However, these risks do not appear to apply to hunter-gatherer diets that feature lean meats, as explained by Australian anthropologists from RMIT University in Melbourne:
- "A study of human and pre-human diet history shows that for a period of at least 2 million years the human ancestral line had been consuming increasing quantities of meat… This meat was wild game meat, low in total and saturated fat and relatively rich in polyunsaturated fatty acids...”
- "In our own studies, we have shown evidence that diets high in lean red meat can actually lower [blood] cholesterol [levels], contribute significantly to tissue omega-3 fatty acid [levels] and provide a good source of iron, zinc and vitamin B12.”
Yes to fermented raw foods
Fermented (bacterially colonized) "live” foods can greatly enhance people's intestinal flora and contribute bacteria-produced nutritional factors, including B vitamins.
However, there's little evidence that the enzymes in fermented foods – which produce beneficial changes in them – offer significant benefits to their consumers.
While lactobacilli and other food-fermenting bacteria produce enzymes that digest foods such as milk and cabbage, these enzymes are broken into amino acids in the human digestive tract.
People certainly can survive and thrive eating only raw foods … albeit with a bit more planning and care than required for folks who observe a more conventional diet.
The devil, as always, lies in the details.
There is credible evidence that certain cooking methods degrade the healthfulness of certain foods.
But cooking also enhances the availability of nutirents in some foods, and the biomedical literature contains no evidence that cooked foods are unhealthful.
For now, it seems wise to keep cooking food – while also savoring raw salads, veggies, fruits, and sushi as part of the culinary mix.
Boback SM, Cox CL, Ott BD, Carmody R, Wrangham RW, Secor SM. Cooking and grinding reduces the cost of meat digestion. Comp Biochem Physiol A Mol Integr Physiol. 2007 Nov;148(3):651-6. Epub 2007 Aug 16.
Borenstein S. Life was a beach for early humans: Archaeologists see signs of clambake and makeup from 164,000 years ago. Associated Press. Oct. 17, 2007. Accessed online May 27, 2008 at http://www.msnbc.msn.com/id/21347464/
Cavalli-Sforza LL; Menozzi P; Piazza A (1994) The History and Geography of Human Genes. Princeton, New Jersey: Princeton University Press.
Coursey DG (1975) "The origins and domestication of yams in Africa.” In: Arnott, Margaret L. (ed.), Gastronomy: The Anthropology of Food and Food Habits. The Hague: Mouton Publishers. Distributed in U.S. by Aldine Publishing Co., Chicago, Illinois. (pp. 187-212)
Larsen CS. Animal source foods and human health during evolution. J Nutr. 2003 Nov;133(11 Suppl 2):3893S-3897S. Review.
Mann N. Dietary lean red meat and human evolution. Eur J Nutr. 2000 Apr;39(2):71-9. Review. Milton K. The critical role played by animal source foods in human (Homo) evolution. J Nutr. 2003 Nov;133(11 Suppl 2):3886S-3892S. Review.
Nestle M. Animal v. plant foods in human diets and health: is the historical record unequivocal? Proc Nutr Soc. 1999 May;58(2):211-8. Review.
Pennisi E. Did cooked tubers spur the evolution of big brains? Science. 1999 Mar 26;283(5410):2004-5. Pennisi E. Paleoecology. Fossils help figure out food webs old and new. Science. 2008 May 2;320(5876):598-9.
Roberfroid MB. Inulin-type fructans: functional food ingredients. J Nutr. 2007 Nov;137(11 Suppl):2493S-2502S. Review.
Wobber V, Hare B, Wrangham R. Great apes prefer cooked food. J Hum Evol. 2008 May 15. [Epub ahead of print]
Wrangham R, Conklin-Brittain N. Cooking as a biological trait. Comp Biochem Physiol A Mol Integr Physiol. 2003 Sep;136(1):35-46. Review.