Re: Science on Raw vs Cooked Foods

January 9, 2008

Thank you , it seems to be an interesting site, it's presented in a

balanced way, and from what I've read so far it gives a fair look at all angles.

Katy Brezger

http://to-reverse-diabetes.blogspot.com/

Be a Blessing, Find ways to be someone's Santa Claus all year 'round. May you be

so richly blessed that you will bless others with what overflows from your cup.

" If people let government decide what foods they eat and what medicines they

take, their bodies will soon be in a sorry state as are the souls of those who

live under tyranny. "

~ Jefferson~

Science on Raw vs Cooked Foods

Just ran across this very lengthy but also very comprehensive

discussion of pluses and minuses associated with raw vs cooked foods:

http://www.beyondveg.com/tu-j-l/raw-cooked/raw-cooked-1a.shtml

Enjoy

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January 11, 2008

--- <oz4caster@...> wrote:

> Just ran across this very lengthy but also very comprehensive

> discussion of pluses and minuses associated with raw vs cooked

> foods:

> http://www.beyondveg.com/tu-j-l/raw-cooked/raw-cooked-1a.shtml

One of the claims made in this paper is that enzymes in food may not

be all that beneficial to our digestion, because most of them are

destroyed in the stomach, whereas most of our food is absorbed in the

small intestines. And it is in the small intestines that our bodies

add enzymes from the pancreas as well as bile for digestion. Below is

a short excerpt.

http://www.beyondveg.com/tu-j-l/raw-cooked/raw-cooked-2b.shtml

===================================================================

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.

===================================================================

The paper was written in 1999 by Jean-Louis Tu. I have seen the

Beyond Vegetarianism web site before, but missed this paper. They

claim to have " reports from veterans of vegetarian and raw-food diets,

veganism, fruitarianism, and instinctive eating, plus new science

from paleolithic diet research and clinical nutrition " .

My guess is that it may depend what kind of enzymes are in a

particular food. If the food has enzymes that can work in the saliva

and/or stomach or can survive to work in the small intestine, then

there may be some benefit. I have to wonder if enzymes such as

phosphatase in raw milk may improve absorption of minerals from the

milk as compared to pasteurized milk - though I haven't been able to

find any studies covering this question. To do so, they would have to

somehow make the minerals more bio-available before leaving the

stomach, or the enzymes would have to survive the stomach in

significant quantities to do their work in the small intestines. It

seems intuitive to me that enzymes in raw milk are there to aid

digestion. Otherwise, why would evolution have put them there? On

the other hand, enzymes present in raw vegetables are not likely to

have evolved to aid our digestion, but rather to serve functions for

the plant.

Another point made in the Raw vs Cooked paper is that heterocylic

amines from burnt meat may not be that harmful at levels normally

consumed by most people.

http://www.beyondveg.com/tu-j-l/raw-cooked/raw-cooked-1e.shtml#HCA%20lab%20vs%20\

r-w

===================================================================

The authors [Augustsson et al.] note that:

" Heterocyclic amines have been shown to be carcinogenic in animals.

This carcinogenic effect is induced by high doses, such as 10-400

mg/kg of body weight. The lack of carcinogenic effect of heterocyclic

amines in our study may be due to the much lower intake in the study

population (median 1 ng/kg of body weight). "

In other words, doses required to induce cancer in laboratory animals

are typically 10 million times higher (or even more) than those

obtained by ordinary cooking.

Extreme cooking times/temperatures may represent the main risk. While

the median HCA intake was less than 100 ng, it was observed that seven

participants had intakes higher than 1,900 ng--and all of them were

cancer cases. A sample of only seven people is certainly too small to

provide statistically significant results, but this finding suggests

that HCAs may induce cancer at the very highest doses that could

conceivably be encountered in food (i.e., in people who consume

well-done, fried/roasted meats very frequently).

===================================================================

So maybe those of us who enjoy crispy bacon or barbecue won't suffer

too badly as long as we don't over-do it

January 12, 2008

On 1/11/08, <oz4caster@...> wrote:

> 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.

The enzymes still can offer support in the small intestine if they

survive stomach acid.

> 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.

I don't see how the extent of absorption in the small intestine

affects the argument. Oral pancreatic enzymes are effective without

enteric coating. Noel s told me he did research showing that

lactase survives digestion. In pre-term infants, pasteurized or

boiled milk produces 1/3 less fat absorption and growth than raw milk;

the authors suggested this was because of the heat-sensitive lipase:

on, et al. Effect of heat treatment on absorption of

nitrogen, fat, sodium, calcium and phosphorus by preterm infants.

Arch Dis Child. 1978;53(7):555-63.

Maybe it is more significant in people whose digestion is compromised,

but it is perfectly plausible that food enzymes are of some value and

the exact situations in which they are or are not meaningful have not

been researched yet to my knowledge.

[snip]

> Another point made in the Raw vs Cooked paper is that heterocylic

> amines from burnt meat may not be that harmful at levels normally

> consumed by most people.

Some of the epidemiological research looking at how meat is cooked

would refute that. For example, one study found that women who ate

their meat cooked well done had almost five times the breast cancer

risk as women who ate it medium or less.

======

http://www.ncbi.nlm.nih.gov/pubmed/9827527?ordinalpos=2 & itool=EntrezSystem2.PEnt\

rez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

Women who consumed these three meats consistently very well done had a

4.62 times higher risk (95% CI=1.36-15.70) than that of women who

consumed the meats rare or medium done.

=======

That suggests that at least the level found in well done meat is harmful.

Chris

January 12, 2008

--- Masterjohn <chrismasterjohn@...> wrote:

> Some of the epidemiological research looking at how meat is cooked

> would refute that. For example, one study found that women who ate

> their meat cooked well done had almost five times the breast cancer

> risk as women who ate it medium or less.

> ======

>http://www.ncbi.nlm.nih.gov/pubmed/9827527?ordinalpos=2 & itool=EntrezSystem2.PEn\

trez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

> Women who consumed these three meats consistently very well done had

> a 4.62 times higher risk (95% CI=1.36-15.70) than that of women who

> consumed the meats rare or medium done.

> =======

> That suggests that at least the level found in well done meat is

> harmful.

what percentage of women in the study ate meat very well done

and did not get breast cancer? How well did they eliminate

confounding factors like dietary refined sugar or omega-6 fat?

I think it might be more accurate to say that the level of HCA found

in well done meat could potentially be harmful in some dietary situations.

January 12, 2008

On 1/12/08, <oz4caster@...> wrote:

> what percentage of women in the study ate meat very well done

> and did not get breast cancer?

It was a case-control study, so you can't really answer that question,

because they deliberately chose a set number of people with and

without breast cancer. However, I don't consider that relevant to

whether elements in cooked meat contribute to breast cancer causally

within the levels consumed -- that would be an important indicator of

how important the effect is and how worth it it is to cook meat less,

but not an important indicator of causality.

> How well did they eliminate

> confounding factors like dietary refined sugar or omega-6 fat?

From a quick scan (been a while since I read this study) it doesn't

seem like they adjust for either. However, it seems quite unlikely

that doneness would correlate with omega-6 or sugar consumption.

> I think it might be more accurate to say that the level of HCA found

> in well done meat could potentially be harmful in some dietary situations.

Naturally. But if that big of an effect seems present, and if these

compounds are known carcinogens, it would seem more prudent to believe

that they probably cause cancer in overcooked meat, even though there

may well be situations in which they don't. Also, I'm pretty sure

there's a study showing that when they feed doses of these found in

meat to humans, they result in immediate DNA damage in their

intestinal cells, but I can't find it at the moment. If you look on

pubnmed, though, there's a lot of stuff on beer being protective of

their effects.

Chris

January 12, 2008