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(Looking at the Science on Raw vs. Cooked Foods--continued, Part 2B)

Do "food enzymes" significantly enhance
digestive efficiency and longevity?

The references discussed here include, first:

The food enzyme theory in a nutshell

Howell's theory of "food enzymes" as discussed in the above two books basically proposes the following:

In a nutshell, those are the primary elements of Howell's "food enzyme" theory. It is basically a hybrid two-part theory, part hypothetical science, part mystical theory. The first three bullet points above put forward the physiological elements of the theory; the fourth bullet proposes a mystical element that is, ultimately, unverifiable by experimental method, thus unscientific. In one sense, if the principle of Occam's Razor were to be employed, the fourth bullet could be pared away from the theory as entirely unnecessary, since it is essentially a redundant duplication (one restated in mystical terminology) of the physiology proposed in bullet point number three.

Reference sources for theory are outdated. Although both Howell books proposing the food-enzyme theory are dated, they are still among the most often-cited references in raw-food circles. In the 1946 book, for example, most scientific references cited are from the 1920s and 1930s. (By the way, isn't it startling that three major raw-foodist references are more than 50 years old--leukocytosis, Pottenger's cats, and Howell's 1946 book?) As we proceed, we'll see several examples where Howell's claims are based on such outdated science (which is still harked back to by his proponents today) as to completely invalidate a claim by that very fact, let alone the logical problems which also riddle much of Howell's theory.

Example of diversionary tactics that may be engaged in by present-day promoters of Howell's theories

Just as relevant to our discussion of Howell's "food enzymes" theory besides Howell's own writings, though, are the flavor of the arguments made by raw-foodists who promote Howell's theories today. To begin our discussion, let's take as one example a debate over Howell's enzyme theories that occurred on the Veg-Raw email list (currently defunct) in May and June of 1998, to give an up-to-date illustration.

Two commonly encountered logical fallacies. In this debate, the supporters of Howell's theories engaged in two major logical fallacies that typify the kind of reasoning commonly offered in defense of his theories. First, when asked for credible evidence for the claims of Howell, his proponents asserted that such proof was in fact provided in the unabridged (rare, perhaps privately published) 700+ page version of Enzyme Nutrition, quotes and/or evidence from which no one was able to produce because no one had actually seen a copy. One might as well claim that the unabridged version has credible proof that the earth is flat, i.e., such claims are pure speculation. Claims that aspire to be scientific (including the enzyme theories of Howell) require credible scientific evidence, not "vaporware" proofs based on evidence that advocates themselves admit they have not yet seen, or can produce, even at the very same time they claim it exists.

Second, the supporters of Howell's theories made the common rawist error of adopting an unproven theory, and then aggressively demanding that others disprove it. By all logical standards of evidence, the burden of proof rests on those who propose a theory to provide evidence for it; a burden the rawists here would apparently have preferred to be able to reverse or escape. Thus, those who advocate speculative claims, such as the ones Howell put forward, are logically required to provide reasonable proof, and as we shall see below, the proof provided is not adequate.

(Note: If any reader has a copy of the unabridged, 700+ page version of Enzyme Nutrition--assuming it exists--please contact one of the site editors. We would be interested in examining a copy.)

Assessing the main arguments and corollaries of Howell's theory of food enzymes

With that as preface, let's now look at the main arguments by Howell "proving" that food enzymes are important for human health, and the weaknesses of these arguments. It will appear that, in fact, "food enzymes" (meaning enzymes present in foods before they are eaten, as opposed to digestive enzymes produced by the body) play a very minor role in our health, if any.

CLAIM: Enzymes are not merely catalysts. They contain the "life force," which is subtle and unmeasurable. Once the body's enzyme potential has been used up, we die. Therefore, preserving our enzyme potential will ensure longevity.

COMMENT: First let's note that, in the form it's asserted, the above claim constitutes assuming to be true what insteads needs to be demonstrated/proven via evidence (and not simply assumed). That there is an "enzyme potential" needs to be shown by evidence, yet here it is instead assumed at the beginning without proof. This is unfortunately a common logical fallacy in much of rawist thinking.

That enzymes are held to be the "life force" is mystical, not scientific. If the author starts with these particular assumptions, one must question the scientific value of their reasonings. One of the most fundamental axioms in science is that the components of a theory must be at least in principle "falsifiable" to qualify as science in the first place. (That is, the components have to be capable of being observed and in principle testable for truth or falsity by physical observation or measurement.)

If one cannot physically observe or measure something, then it is not amenable to scientific testing, and advocates can basically affirm anything they want with regard to it, no matter what experimental results are gotten, since there is no scientific way to confirm or disconfirm something allegedly immaterial. Therefore, if one claims that enzymes contain a "life force" that transcends their measurable physical characteristics, then it is by definition a mystical assertion and not a scientific hypothesis.

Enzymes ARE catalysts, in the broad sense (i.e., they speed up a chemical reaction, or allow a barrier of potential to be crossed, and are left unchanged after the reaction has occurred). The mode of action of various enzymes has been described by scientists--there is nothing mysterious. Anyone not convinced by the last statement is invited to check out a textbook about enzymes in any university library.

Enzymes are not the "life force," and the idea that we have a certain "quantity of life force" at birth, and that by eating "living foods" we can increase our life potential (or at least preserve it) is naive and unproven. No one has ever measured any enzyme potential (in the sense that Howell understands it); and, according to modern theories of aging, such processes as cumulative oxidative damage to tissue, the decreasing length of telomeres with each cell division, and other known processes currently under investigation, rather than enzymes, are the most likely reasons for the process of aging.

Howell postpones his proof of an "enzyme potential." It should be added that the logical organization of Howell's books suffers greatly from the fact that he postpones the "proof" that the body has a limited enzyme potential, and some arguments in the first chapters rely on that assumption. Since, as we shall see, his proof of the existence of an enzyme potential is seriously flawed, these arguments become invalidated.

Side note in regard to Kirlian photos. Raw advocates often cite Kirlian photos that compare cooked and raw foods as evidence of the "life force" in raw foods. Kirlian photos do show something, but there is no evidence that they are somehow photos of a (subtle and/or mystical) "life force."

The logical, plausible explanation for Kirlian photos is that they show the effects of a type of corona discharge (the same phenomenon that produces lightning). The power of such a discharge will depend on moisture content (which in humans may vary with stress, e.g., sweating) and other relevant physical factors.

A corona discharge effect depends on ionized gases that result when a small electric current is applied to the object being photographed. Cooked foods have been heated, and heating can cause a loss of ions via steam and compounds dissolving into the water used in cooking (and the cooking water is usually discarded). Hence one would expect Kirlian photos of raw foods to have a stronger corona discharge than similar cooked foods.

Even more telling, if Kirlian photos were actually the "life force" instead of a corona discharge effect, one would expect there to be no difference between Kirlian photos taken in a vacuum (where there are no ionized gases to create the corona discharge effect), and photos taken in normal atmospheric conditions. However, Kirlian photos taken of an object in a vacuum show no "aura." Thus we conclude that Kirlian photos do not show the "life force" or "aura," and are not credible evidence in comparing raw and cooked foods.

Readers interested in Kirlian photos should check out the links and (Note that the information on Kirlian photography in the second link occurs about halfway down on the page linked to.)

CLAIM: Food enzymes act in the mouth and in the upper stomach, before our own enzymes have begun to digest the food. A few enzymes are left undestroyed by the stomach acids and are absorbed by the intestine. Thus, eating raw food will preserve the enzyme potential.

COMMENT: The impact of pre-digestion by salivary enzymes is small. Tortora and Anagostakos [1981, p. 628] note:

Even though the action of salivary amylase may continue in the stomach, few polysaccharides [carbohydrates] are reduced to disaccharides by the time chyle [the mass of food and digestive fluids in the stomach] leaves the stomach.

Also, Tortora and Anagostakos [1981, p. 629] report that 90% of all nutrients are absorbed in the small intestine. Further, digestion in the small intestine relies on bile and pancreatic enzymes, as a large part (but not 100%) of the food enzymes are destroyed in the stomach prior to the food reaching the small intestine. The above quote, coupled with the 90% absorption figure, suggests by extension that enzymes in raw food are of very limited nutritional significance.

Certainly cooking destroys enzymes in food, but may improve digestibility for other reasons. Indeed, as we saw earlier, cooking sometimes alters the cell structure so that the nutrients become more accessible to our own body's digestive enzymes (such as by gelatinizing starch), or destroys anti-amylases or anti-proteases. Thus, in many cases, cooked food actually requires less enzymes for digestion than raw food.

Digestive enzymes, like any catalyst, are reused/recycled multiple times. Thus, any supposed "savings" (of energy, or of a proposed "life force") in the production of digestive enzymes to make up for food enzymes lost to cooking (assuming the latter are of much use to digestion in the first place) would be very small and mostly illusory given that enzymes are reused during digestion anyway. (Note: Tortora and Anagostakos [1981, pp. 46-47] discusses reuse of enzymes.)

Instances of decreased digestibility from cooking are primarily due to reasons besides enzymes. It should be added that, when cooking does decrease digestibility, it's often not because food enzymes have been destroyed. There are many examples (see above) of foods whose protein digestibility decreases only at temperatures much higher than 100°C (212°F). But obviously, enzymes are already destroyed at 100°C. Also, protein availability may decrease (slightly) because of the Maillard reaction, which has nothing to do with enzyme denaturation. So it is not true that cooking necessarily demands more enzyme production by the body, and it's also not true that, in the cases where cooked food is less digestible, the effect can be attributed to enzyme destruction.

Finally and more importantly, the idea that the body has a limited enzyme potential is, to say the least, dubious. Digestive enzymes in food are just what they are: a possible help in digestion. Obviously enzymes do indeed help--inside or outside the body: ripening of fruits, sprouting of seeds, legumes and grains, and aging of meat are examples of important actions of enzymes that occur prior to consumption. But some types of food processing can also improve digestion, including cooking in some cases.


(Assessing the Arguments & Corollaries of the Theory of "Food Enzymes," cont.)

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GO TO PART 1 - Is Cooked Food "Toxic"?

GO TO PART 2 - Does Cooked Food Contain Less Nutrition?

GO TO PART 3 - Discussion: 100% Raw vs. Predominantly Raw

Back to Research-Based Appraisals of Alternative Diet Lore

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