Health & Nutrition
Miscellaneous diet and health topics
Enzymes in raw foods
There is a widespread belief that the enzymes in raw foods provide important health benefits, and this idea is one of the central concepts of the raw foods movement. The notion has a lot of intuitive appeal - it seems like something that should be true. But when I looked into the issue, I was shocked to discover that it wasn't true. The idea that food enzymes are important is based on the ideas of Edward Howell, and is a testament to the creative power of his imagination since it's not based on science or observation.
There's more to whole foods than their identified essential nutrients, and there are important reasons to offer vegetables and fruit to our birds. For example antioxidants are not considered to be essential nutrients but they appear to serve a useful purpose in the body. There may be other, more subtle chemicals in plants that also serve a useful purpose and would be destroyed by cooking. But plant enzymes are NOT a reason for providing raw veggies in the diet, because in general they're not expected to do anything beneficial.
There are thousands of enzymes and each one is designed to participate in a very specific chemical reaction. A given enzyme isn't a general-purpose nutrient like amino acids or calcium that can be used by just about any organism. Animals (including humans and birds) do use enzymes to digest their food, but these are their own enzymes synthesized in the body for that specific purpose. They don't rely on plant enzymes to do the job for them, because plants don't digest food and therefore don't have enzymes that were designed to help with digestion. The plant enzymes were synthesized for an entirely different purpose and usually can't do anything else. There's a small number of plant enzymes that can coincidentally help out with digestion, but these are an exception to the general rule.
There currently isn't any information on whether birds process plant enzymes differently than humans do, but it's very likely that it works pretty much the same way in both groups; their overall digestive process is similar. The mainstream medical point of view is that humans normally produce all the digestive enzymes they need and food enzymes do little or nothing for us. In any case, most of the enzymes in food are destroyed in the body before they reach the small intestine, which is the point where we could hypothetically begin to make use of them. Enzymes are made of protein, and protein is quickly broken down into its component amino acids in the stomach. As the Huffington Post stated (amusingly but rather awkwardly), "Meaningful health effects of swallowing an enzyme that doesn't survive to see the duodenum are dubious at best."
In addition, the vast majority of food enzymes aren't expected to do anything for the person/animal eating them even if the enzymes did manage to arrive intact in the small intestine. Plant enzymes are synthesized to perform a very specific function in the plant, and in general vertebrates don't have a corresponding function that the enzyme could be used for; e.g. what could a photosynthesis enzyme be expected to do for an animal? The digestive enzymes that we synthesize in our bodies are very different from plant enzymes, because they serve a very different purpose.
Enzymes are often described as "living" or the "life force" of foods, which they certainly are not. They are chemical compounds that don't have any attributes that could reasonably be described as life, and there are a host of other chemical compounds in plants that are just as essential to the plant's survival. We wouldn't describe calcium or carbohydrates as "living", and it doesn't make any more sense to describe enzymes in these terms.
It has been demonstrated that enzymes in raw foods are released into the mouth when food is chewed. Raw foodists have extended this into a claim that these food enzymes interact with other substances in the upper digestive tract to aid in digestion, and this interaction can continue for up to 30 minutes until the raw foods reach the lower stomach where the enzymes are destroyed by digestive juices (Wikipedia). There is no evidence to support this contention.
There are a few specific food enzymes that have an effect on digestion and can be helpful for people with digestive problems. These are called the digestive enzymes and include some uncommon enzymes like bromelain from pineapple and papain from papaya. The most efficient way to supply these enzymes is to buy them in pill form if needed. But people and animals with a properly functioning digestive system aren't expected to need them.
'alternative' sources including Andrew Weil agree with the mainstream view.
They say that supplemental enzymes may be useful for people who have trouble
synthesizing their own, and that's about it.
There are many pro-enzyme websites that apparently accepted Howell's ideas at face value without investigating their accuracy. I couldn't find any websites that analyzed Howell's theory and concluded that it was valid, but I did find some that did an analysis and decided Howell was wrong. They are a mix of 'alternative' and mainstream sources:
Preventive Nutrition Consultants: Raw Food Diets, the Real Raw Truth
A long article that gets very heavy on the science at times, and concludes that the enzyme claims are wrong. This is a defunct site stored on archive.org. Apparently Preventive Nutrition Consultants is or was a research company investigating the benefits of various foods and supplements. Their article on food enzymes is tricky to navigate since the article has seven pages and the links only work up to page 2. There's a page number near the end of each url and you can go to the next page by changing this number manually.
A long article that dissects the enzyme claims and finds them to be unconvincing, as well as analyzing the advantages and disadvantages of raw and cooked foods. It supports the idea of eating a lot of raw foods but does not support the idea of an all-raw diet.
Skeptical Vegan: Raw Veganism
Rejects the enzyme concept while sensibly discussing other pros and cons of cooking.
Frederic Patenaude: Enzymes, are they the key to raw food?
The answer to the title's rhetorical question is "no". The writer is a raw foodist who says "food enzymes are not important at all in the digestive process".
Dr. Fuhrman: Raw vs. Cooked?
An M.D. specializing in nutritional medicine (with a flavor of the alternative) says "sloppy science prevails in the raw-food movement" and discusses several raw-foodist fallacies, including the one about the importance of enzymes.
Medical School of Wisconsin: Herb Blurb, Digestive Enzymes
http://web.archive.org/web/20081026153724/http://healthlink.mcw.edu/article/971119645.html A medical school website that concludes that supplemental enzymes are not harmful, but are also not useful for healthy people. They'll obviously have a mainstream bias, but medical schools normally base their teaching on actual scientific research.
Quackwatch: "Enzyme Deficiency"
http://www.quackwatch.org/01QuackeryRelatedTopics/PhonyAds/mp.html This is an organization that is NOT friendly to 'alternative' ideas and therefore subject to bias. The article talks about the quackery of a specific enzyme pill, but the principles are generally applicable.
LiveScience: The Raw Food Diet, a Raw Deal
A science-news website with an interesting discussion of raw foods versus macrobiotics.
LiveScience: 5 Risks of Raw Vegan Diet
Explains why raw veganism is unnatural and unhealthy.
Family & Consumer Sciences: The Raw Truth About Raw Foods
This article is undistinguished except for one interesting paragraph that says, "It’s true that cooking destroys essential enzymes—essential to the food, that is. The human digestive tract itself contains the enzymes needed for digestion. A greater problem is that moderate heat actually activates some enzymes, allowing them to start destroying delicate nutrients like vitamin C. That’s why you’re advised to have water already boiling before adding food to cook: the higher temperature kills the enzyme before it can attack the nutrients." I never heard this before, and I wonder if it's true. You can't "kill" an enzyme of course because it isn't alive, but you can certainly destroy it.
All this information relates to human digestion, and what's applicable to humans isn't necessarily applicable to birds and other species. Raw-foodists often use the old Pottenger cat study to condemn cooking. The cats on a raw diet did fine and the ones on a cooked diet did poorly. But now we know more about cat nutrition than we did back then, and it's believed that the difference was due to the amino acid taurine which is affected by heat (taurine is NOT an enzyme; it's a different kind of chemical compound). Cats can't synthesize taurine and must get it from their diet. Humans CAN synthesize taurine so these results don't apply to us. At present there are no known differences between bird digestion and human digestion that would make birds require raw food to supply an essential nutrient.
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