Science of Raw Food?

October 5, 2010 7:52 PM

I find the supposed basis and theory of rawism compelling, but would like scientific corroboration and/or analysis. What resources (books, papers, anything reputable and thoughtful) have you encountered that you'd recommend? Thanks in advance!

As I understand it, uncooked food has its enzymes intact, which eases and maximizes nutrient extraction without drawing on finite enzyme stores in the body. In addition, those nutrients themselves are drastically compromised by heat over 118° (I've heard fifth-ed by cooking). These quantitative claims are what I'm really interested in, moreso than "life-force" and associated concepts. I'm sure there are already glaring errors in my understanding by now, so please correct me with cited info.

posted by alexandermatheson to Food & Drink (14 answers total)

As I understand it, uncooked food has its enzymes intact, which eases and maximizes nutrient extraction without drawing on finite enzyme stores in the body.

You will not find scientific corroboration for this because it doesn't make sense. There are lesser arguments about heat related changes to some specific food components which have some evidence, changes to milk proteins for example, but even they are contentious (and none of them say anything about 'finite enzymes' because that is bunk). You will not find reputable research on this area or concept because scientists need some degree of plausibility or reasoning before they spend time and money researching something.

Just as an aside, there are plenty of nutritions which are more bioavailable and digestible after cooking.

I've just finished my PhD looking at how specific food components interact with the body and have a strong background in both nutritional biochemistry and digestive physiology (and have been reading widely in nutrition research for my project). I'm not an expert in nutrition but I have never head of this anywhere in the literature, which I should have if it was real as it's relevant to my research
posted by shelleycat at 8:15 PM on October 5, 2010 [22 favorites]

Best answer: Yeah.

So here's the thing. Raw Foodism doesn't have anything to do with nutritional science. Some of the claims are non-crazy (yes, cooking food does enact chemical change upon it, see Maillard reaction), but the whole thing is too heavily tied up with ionized water and homeopathic dilution style pseudoscience.

What it comes down to is this: Raw vegetables are good for you. Cooked vegetables are also good for you, though often slight less so. But eating just raw vegetables is not good for you.

There's a very short but reference heavy paper you can read here. It's a college paper, but it summarizes nicely. If you want something more detailed, this link from the references seems to be the gem, though I haven't had a chance to read more than the abstract.

But basically, if you're looking for a philosophy to help you reshape your relationship with food, I'd buy a copy of In Defense of Food before buying a copy of Nature's First Law.
posted by 256 at 8:27 PM on October 5, 2010 [4 favorites]

This pubmed search includes a bunch of articles about the effects of a raw food diet. The ones in actual scientific journals aren't very complementary about the diet (to put it nicely), the ones pushing some possible benefits are from journals with 'complementary' in the name - i.e. pseudoscience. It was difficult to find any articles, and it's a very small number compared to pretty much any other kind of nutrition research (also at least two of them are referring to dog food)

This is taken from a very short article in that list (which I can't find a free full text for, but it's so short thre isn't much else in there:

Raw foods diet proponents, however, claim that this temperature keeps enzymes intact and leads to better digestion. The problem with this theory is that the body already makes the enzymes needed to digest and absorb foods, and the enzymes in food are inactivated by the acidity of the stomach.

posted by shelleycat at 8:53 PM on October 5, 2010 [2 favorites]

Oh, I screwed up the link back there. Should be to this: http://www.ncbi.nlm.nih.gov/pubmed/15389429
posted by shelleycat at 9:03 PM on October 5, 2010

I was just reading "Catching Fire: How Cooking Made Us Human" last week. I picked it up out of interest in the evolutionary argument, but it spends a fair bit of time taking the raw food movement apart. About the nicest thing the author has to say about strict raw food diets is that they are a great way to lose weight fast.
posted by richyoung at 9:09 PM on October 5, 2010

As I understand it, uncooked food has its enzymes intact, which eases and maximizes nutrient extraction without drawing on finite enzyme stores in the body.

The amount of enzymes that actually pass intact through your highly acidic stomach environment is not sufficient to significantly influence what goes on in your body. Also, some "prepared" foods, like pickled vegetables of any sort, are far richer in B vitamins – and thus healthier by your definition – than their raw counterparts.
posted by halogen at 9:15 PM on October 5, 2010

Best answer: When it comes to raw eats....well, there is a reason Louis Pasteur has an entire process named after him. Believe me, the slight alteration in milk proteins and potential of damaging any hypothetical 'probiotic' substances is well worth the other stuff you're missing out on. The same goes for juices.

People who espouse natural/natural-state foods uncritically--which you are not doing, you are asking questions and trying to figure things out, which is great--often forget that on the whole 'nature' is not looking out for your well-being. A significant part of the natural world not only doesn't care, its other inhabitants will kill you to ensure its own survival. There's no moral decision involved. Your death=another's survival? Done and done. I'm not even thinking animals or pathogens--I'm thinking 'plants.' Natural remedies discovered in various plants and such were not put in the juicy, tasty, vital parts for our benefit--a good number of those remedies were evolved to kill us or to kill some other, similar threat to those juicy, delicious, vital parts. Cooking can be an end-run around those defenses.

on preview: Bromelain is an excellent example of a 'natural' enzyme that is good to inactivate, because it's not like you can tell it when to start doing its thing. Bromelain is a nice little molecule found in the stalk and center of pineapple, and it's good at breaking proteins down. You know what it likes to break down? The inside of your mouth and surface of your tongue. That's why you aren't supposed to eat the center of a pineapple, and why raw pineapple in general can make your mouth sore. Your food is eating you back. And it's not even technically poisonous or that harmful overall. It just digests you on the way down, before the stomach inactivates it. Canning and cooking inactivate it as well. No sore mouth.
posted by Uniformitarianism Now! at 9:30 PM on October 5, 2010 [6 favorites]

All of which goes to show that sometimes things that seem to make sense don't actually make sense.

Rawism comes from the same school as food combining and intestinal mucous, neither of which - in spite of how much sense they seemed to make and how very much I wished to believe in them! - survived any scientific inquiry whatsoever.
posted by goblinbox at 9:55 PM on October 5, 2010

Response by poster: Thank you for the detailed and thoughtful responses! You've provided me a good deal to investigate and ponder through.

Upon reviewing the PubMed articles, most actually seemed positive; problems arose, as they would in any diet, from nutritional insufficiencies surmountable within the regime.

That the stomach is too acidic an environment for external enzymes to work intrigues me. Does the HCl deactivate those enzymes, or actually destroy them? I ask because they might become active (and helpful) in the lower intestine.

Goblinbox describes the experience of wanting to believe something that certainly seems both satisfying and credible enough well—as one can probably tell, I'm still clinging to hope. Nonetheless, I certainly put evidence and efficacy far above anecdotal praise.

To richyoung: is the "evolutionary argument" to which you refer essentially that humans thrived on uncooked food for the vast majority of our existence, so perhaps it would follow that we'd be more efficient at digesting uncooked food? Not that I recognize that as more than a theory, albeit a intriguing one.

Lastly—if you'll continue to indulge my curiousity!—are enzyme stores finite?

Best!
posted by alexandermatheson at 11:37 AM on October 6, 2010

Response by poster: Arrgh, scratch my claim about the PubMed articles. Impression was formed from few-and-far-between summaries, as I can't access the articles themselves.
posted by alexandermatheson at 11:43 AM on October 6, 2010

I have read most of the articles, they're not positive at all. Particularly not when you're used to reading nutrition articles. Generally you'd see a whole bunch about how it supports normal health then some specific benefits and some problems. These are all this goes wrong, that goes wrong, and the main general benefits I'd see from any diet aren't even mentioned. No 'good' diet has bone density loss, B12 deficiency, and being severely underweight as a standard side effect, not even a rare side effect, and it's also telling that it's pretty much always studied only as a case of an extreme diet with serious issues. Less controversial diets with known negative effects, like the Atkins diet for example, have a shit load more research being done, was more articles published, and a lot more positive evidence. This diet is a fringe case at best.

The HCl and proteases destroys the enzymes just like it destroys pretty much all proteins you eat. This is a necessary and normal part of digestion. Also, of course 'enzyme stores' are not finite, I said that in my first comment. They aren't even stored, we make them on demand quite happily. All the claims about enzymes being made by the rawism people are bunk, pure and simple

Every time you see the paleo argument remember that the average life span in the 'cave men' days was less than half what it is now. It's not some idyll we want to return to. (there is more to this too, but no point going into the rest of the science about why it doesn't work because of this right here)

There really, seriously is no science here. To anyone with even a small amount of knowledge about digestion or nutrition none of this makes sense, or is plausible, or reasonable. It only seems to make sense to you because you have no understanding about the processes involved.

You're being fed a line. Don't cling to hope and don't be sucked in.
posted by shelleycat at 1:21 PM on October 6, 2010

To the OP: no, sorry, I was unclear. The "evolutionary argument" I was referencing was the book's central claim that cooking is the thing that made us human - that the use of fire to extract greater energy from our food was the fundamental advantage proto-humanity had over all other animals. I'm kinda interested in human evolution in general and it was a provocative thesis.

So I meant that I didn't read the book out of interest in raw foodism (of which I have none, because I love me some cooked food, and also because I agree with everyone else here that there's no scientific basis for raw foodist claims). But the author began the book by looking at raw food diets very critically, and summarized a number of studies that showed how humans have severe difficulty thriving on raw diets. You might find the first few chapters of the book helpful for that reason.
posted by richyoung at 2:04 PM on October 6, 2010

Response by poster: The proteases themselves are enzymes, made effective by the highly acidic environment the HCl creates, right? However, as I understand you, all other proteins are dismantled, including external enzymes. That makes sense to me (if I crave specifics, which I can hardly ask you to provide—everyone's already been generous).

To shelleycat: Firstoff, I appreciate you sharing that review of the articles. I did indeed notice your refutation of the "finite enzyme" idea the first time around, and phrased my follow-up clumsily: I was actually hoping for extrapolation before. No enzyme "stores," got it: they're made as required—but does production tends to wane? Irrelevant, I recognize, as food enzymes are destroyed anyways, but such a concept would make sense within the flawed logic of the rawist theory I've encountered.

To summarize what I've learned, in the hopes that I can be confident of my accuracy:

Enzymes in raw food: broken down before they can do anything. No advantage over cooked food.

Nutrition: varies by food. Nutrient bioavailability and levels can rise or fall with heat, depending on the food in question. In addition, cooking can dismantle indigestible or undesirable compounds (i.e. bromelain—which, fittingly, it itself a protease).

Takeaway: you cook some, you eat some raw. Strict observance to raw doctrine is certain to cause psychological strain (inherently labor-intensive!), if perhaps physical strain as well.

This has all been vastly informative for me, and I'm grateful.

Peace be, and be well.
posted by alexandermatheson at 2:46 PM on October 6, 2010

Best answer: but does production tends to wane?

Nope. It increases or decreases as needed based on what you're eating (a process called homeostasis). The cool part is that your body breaks down the proteins in the food you eat (including 'food enzymes') into pieces (amino acids) then builds them back up again into the proteins you need (including digestive enzymes), as and when you need them. The only thing that would make the supply finite is if you never ate any protein and your body wasted away to the point that there was no protein left to cannibalise, and even then I think you'd probably die before you stopped making digestive enzymes. Homeostasis works on pretty much every process within your body and there are all kinds of mechanisms in place to keep it working. I have no idea where the rawist people came up with their enzyme stuff, there isn't even a seed of meaning there.

And yeah, proteases are the form of enzyme that breaks down protein specifically. Some proteases in food are also relatively resistant to your stomach acid - e.g. actinidin in kiwifruit (very similar to bromelain) - which is extra fun because those proteins often cause allergies as well as being kind of harsh. As an aside, proteases such as bromelian or actinidin shouldn't do any damage beyond your mouth because the entire digestive tract is lined with a protective layer of mucous, when they hurt going down it's usually an allergy not proteolysis. Anyway, these proteins just get broken down further along the digestive process, and anything that's not gets excreted (whole proteins can not be absorbed by your body).

Cooking is also very important in that it kills food borne pathogens, and food safety is a big issue with the raw diet. That's probably a key reason why cooking food gave an evolutionary advantage and became widespread, rather than nutrition per se.

I think you have a good attitude by the way. Finding something interesting and instead of just blindly going along with it, trying to fill in the details with some facts. This is pretty much what I do as an actual scientist too. I just have the advantage of a higher amount of background understanding so I can better screen what is worth looking into. Which doesn't make me special either, just stupid enough to spend many years learning about this specific thing (there's all kinds of subject areas where I am totally ignorant). It's the recognising that you don't know enough yet to judge and the desire to find out more that is admirable and I wish everyone would do the same.

Takeaway: you cook some, you eat some raw. Strict observance to raw doctrine is certain to cause psychological strain (inherently labor-intensive!), if perhaps physical strain as well.

That sounds like a good summary. Just add in that the raw doctrine provides no benefit. That's kind of key because it might be worth trying to balance the good with the bad and get it right if you got something out of it, but there is no reason at all for eating this way.
posted by shelleycat at 7:18 PM on October 6, 2010 [2 favorites]