Vegan For Life
by Jack Norris, RD &
Ginny Messina, MPH, RD
Raw Food Vegan Diets
(Last updated July, 2010.)
- I was a Twenty-Something Raw Foodist
- History of Cooking Foods
- Is Cooked Food Toxic?
- Is Raw Foodism Healthy?
- Becoming Raw
Raw foodism is the philosophy that most or all of one's diet should be uncooked foods. Raw foods diets are usually vegan and vegan raw foodism will be the focus of this article. As I understand it, the trend in raw foodist circles in recent years has been to emphasize eating at least 80% of your food (by volume) as raw, rather than 100%.
In 1993, I became interested in raw foodism. I had been getting cavities in my teeth fairly regularly for the previous few years and one of my co-workers at a natural foods cooperative distribution warehouse told me it was due to eating my food in an unnatural state. He pointed out that wild animals do not cook their food and they don't get cavities.
At about the same time, I met a couple who were into raw foodism and they introduced me to a lot of literature and gave me moral support. They, like me, were animal advocates, and were also quite vibrant and active, so they served as enticing role models.
From the fall of 1993 until 1995 I ate about 90% of my foods raw. I also read any and every book and article on raw foodism that I could get my hands on. They contained story after story of people curing their heart disease, diabetes, cancer, and other diseases through raw foods.
The diet simply made sense. Since humans are the only animals who cook their food, we'd have to be better off eating a more natural diet of raw foods...wouldn't we?
It didn't go so well for me. I had low body fat to begin with, and on the raw foods diet my weight dropped ten pounds. As a regular weightlifter, I noticed my strength decline considerably. I got frequent colds (some say this is the body detoxifying; a more likely explanation is that I wasn't eating enough protein to prevent infections). I was obsessed with food and wanting to eat cooked food. The couple who mentored me were also struggling with the diet.
Eventually I had to admit that it wasn't working and I slowly weaned myself back onto cooked foods. Though I tried to resist, my diet became more cooked all the time. Since 1997 I've eaten most of my food cooked.
The experience turned me to science, relying more on published scientific research and much less on popular theories and anecdotal reports. As I read more mainstream nutrition science, it became clear that many of the claims made by raw foodists were not true.
Some raw foodists say that humans have only cooked food for a relatively short period of our history. In their 2003 article, Cooking as a Biological Trait, Harvard University anthropologists Richard Wrangham and Nancy Lou Conklin-Brittain cite research that indicates, in their words, "Cooking is therefore widely accepted back to at least 250,000 years ago." (3) Some evidence points to 1.6 million years ago. They also argue that it takes only 5,000 years or less for the human body to adapt to different methods of eating. The implication is that humans have been cooking long enough to have adapted to a diet of cooked foods. This could explain why many people who try raw foodism fail to thrive.
Richard Wrangham's theory that cooking food is what allowed early ancestors of humans to grow large brains is discussed in the June 15, 2007 issue of Science (Food for Thought: Did the first cooked meals help fuel the dramatic evolutionary expansion of the human brain?). By cooking food, we were able to make it more digestible (by breaking down plant fiber and muscle tissue) and therefore eat more calories with less digestive effort, resulting in a smaller digestive tract and more energy for developing our brains.
A 2010 article Chew on this: thank cooking for your big brain, also discusses Wrangham's work. They suggest that the smaller molar teeth in Homo erectus and Homo sapiens might be a result of cooking food.
Some raw foodists claim that cooked food is toxic or poisonous. A good article examining this question is, Is Cooked Food Poison?, by Jean-Louis Tu, which concludes:
Cooking creates some toxins, neutralizes others. All plants contain at least some amount of "nature's pesticides." There is no such thing as a toxin-free diet. Within a normal range of consumption, toxins resulting from conservative cooking techniques can be safely handled by the body's normal mechanisms, and do not seem to increase the incidence of degenerative diseases.
Cooking has both negative and positive effects. Cooking, especially for long periods, can damage some vitamins. Boiling and steaming causes some vitamins and minerals to seep out of the food. Chemicals thought to cause cancer are formed when food is burned or oils are heated above the point at which they smoke. Deep-frying foods causes trans fats to form.
On the plus side, cooking can break down food components that would otherwise bind minerals and prevent their absorption. It can soften fiber, which allows more food to be eaten. Cooking liberates some nutrients, such as beta-carotene and other antioxidants, for easier absorption. It denatures proteins, essentially flattening them out, which can aid digestion. Cooking destabilizes toxic components of some foods, such as goiter-promoting properties of broccoli. It makes many foods more edible. Cooking can reduce the allergic reactions caused by certain foods (5).
While fiber is a good thing, and most Americans should eat more of it, some vegan diets can be too high in fiber. Fiber provides very little energy while filling you up, and vegans with high energy needs might benefit from having a high percentage of cooked foods. On the other hand, people who want to lose weight could help themselves by increasing their intake of high-fiber, raw foods.
Digestive enzymes aid in breaking the molecular bonds in food. Some raw foodists claim that eating raw foods will extend lifespan because raw foods contain digestive enzymes that digest the food and prevent the body from using energy to create its own digestive enzymes. Some say that the body has a limited capacity to produce enzymes and once that capacity has been used up, you will die.
Stomach acid destroys most of the enzymes in raw food before it can do much to digest the food. For more details about enzymes and raw foods, see Do "Food Enzymes" Significantly Enhance Digestive Efficiency and Longevity?.
Rather than saying people will die from a lack of digestive enzymes, it's probably more accurate to say that their ability to digest food will diminish over time as their ability to produce digestive enzymes decreases. At the link in the paragraph above, the author mentions that there are other physiological processes that have more to do with the body aging than a lack of enzyme production.
Not much research has looked at what proportion of raw foods will prevent the most disease, and there have been no studies measuring the disease rates of raw foodists.
Many people who try raw foods diets, such as myself, fail to thrive while others appear much healthier, such as bodybuilder Giacomo Marchese.
Vegan raw foodists should pay attention to the recommendations for all vegan diets, which are summarized in the table, Daily Recommendations for Vegan Adults.
Raw foodists should make sure they get enough vitamin B12, and not rely on natural sources such as seaweed or fermented foods. Studies showing raw foodists to have poor vitamin B12 status can be read about in the section Raw Foodist Vegans of Vitamin B12: Are You Getting It?.
A significant concern about raw foods diets is regarding bone health. The most important study to date on vegan bone health found vegans to have a higher rate of fracture if they did not consume at least 525 mg of calcium per day (see here). I highly recommend that vegans, including raw foodists, get at least 700 mg of calcium per day (the DRI is 1,000 mg for adults under 50; 1,300 mg for adults older than 50). In a 2005 study, raw foodists were eating an average of 579 mg of calcium per day and they had a lower average bone mineral density than a control group of non-vegetarians (2).
In addition to calcium intake possibly being an issue for bones, raw foodist women often have such low body fat that they do not produce enough estrogen to continue menstruating, a condition associated with poor bone health. A 1999 study showed that 30% of raw foodist women in their study had partial to complete amenorrhea (1). Raw foodist women should make sure they are eating enough calories to prevent amenorrhea.
Protein might be an issue for many raw foodists. The amino acid lysine is quite limited in plant foods other than legumes and legumes are generally not eaten in large amounts in raw foods diets. The idea that protein is important is often scoffed at in vegan and raw foodist circles, but long-term, mild protein deficiency could have an impact on bones and possibly other important tissues. If you are a raw foods vegan who eats less than 100% raw foods, you might want to include plenty of legumes as your cooked food.
Finally, the reason I originally became interested in raw foodism, to prevent cavities, turned out to be without much merit - a 1999 study found that raw foodists had significantly more dental erosions than did a control group (4). By not eating extreme amounts of dried or citrus fruit, and paying careful attention to dental hygiene, this problem could possibly be prevented.
Orthorexia is a concern for people who consider cooked and/or processed foods to be toxic. Orthorexia is a term coined by Steven Bratman, MD, to describe an eating disorder characterized by excessive focus on eating healthy foods. In rare cases, it can lead to severe malnutrition or even death. Here are two clips from a 20/20 story on orthorexia that should be viewed by anyone considering raw foodism or even a 100% whole foods diet.
For more information, BeyondVeg.com (a site providing a critique of raw food vegan dogma) has created a list of peer-reviewed studies and abstracts about raw foods diets.
For people who want to be raw foodists, an excellent source of information is Becoming Raw by Brenda Davis, RD and Vesanto Melina, MS RD.
1. Koebnick C, Strassner C, Hoffmann I, Leitzmann C. Consequences of a long-term raw food diet on body weight and menstruation: results of a questionnaire survey. Ann Nutr Metab. 1999;43(2):69-79. PubMed PMID: 10436305. (Abstract)
2. Fontana L, Shew JL, Holloszy JO, Villareal DT. Low bone mass in subjects on a long-term raw vegetarian diet. Arch Intern Med. 2005 Mar 28;165(6):684-9. PubMed PMID: 15795346.
3. Wrangham R, Conklin-Brittain N. Cooking as a biological trait. Comp Biochem Physiol A Mol Integr Physiol. 2003 Sep;136(1):35-46. Review. PubMed PMID: 14527628.
4. Ganss C, Schlechtriemen M, Klimek J. Dental erosions in subjects living on a raw food diet. Caries Res. 1999;33(1):74-80. PubMed PMID: 9831783. (Abstract)
5. Verma AK, Kumar S, Das M, Dwivedi PD. Impact of Thermal Processing on Legume Allergens. Plant Foods Hum Nutr. 2012 Dec 7. (Abstract) | link