Tuesday, January 27, 2015

Is Meat Unhealthy? Part VII

Looking at individual diseases is informative, but it can cause us to become myopic, making broad health-related decisions based on narrow information.  It can cause us to miss the forest for the trees.  In this case, the "trees" are individual diseases and the "forest" is total mortality: the overall risk of dying from any cause.  Does eating meat increase total mortality, shortening our lifespans?

Non-industrial cultures

Traditionally-living cultures such as hunter-gatherers and non-industrial agriculturalists are not the best way to answer this question, because their mean lifespans tend to be short regardless of diet.  This is due to ~30 percent infant mortality, which drags down the average, as well as a high risk of death in adulthood from infectious disease, accidents, and homicide/warfare.  It can also be difficult to accurately measure the age of such people, although there are reasonably good methods available.

However, there are semi-industrialized cultures that can help us answer this question, because they feature a somewhat traditional diet and lifestyle, combined with modern medicine and the rule of law.  The so-called Blue Zones, areas of exceptional health and longevity, fall into this category.  These include Sardinia, Italy; Okinawa, Japan; Loma Linda, California; Nicoya Peninsula, Costa Rica; and Icaria, Greece.

What do people eat in the Blue Zones?  With the exception of one mostly vegetarian Blue Zone in Loma Linda, California, all of them eat meat, and most eat dairy and eggs.  However, they tend to eat much less meat than people in affluent nations (though not necessarily less dairy and eggs).  Blue Zone diets tend to be starchy, often based on grains, starchy tubers, and legumes.

It's worth keeping in mind that these populations are relatively isolated and may carry genetic variants that promote longevity.  Also, they exhibit a complex of healthy behaviors that extends beyond diet, including regular physical activity and social interaction.  However, these cultures provide us with a dietary template that is, at the very least, compatible with a long, healthy life.

Observational studies

Let's begin again with the Adventist Health Study of vegetarian Seventh-Day Adventists in California.  In the first round of study, male but not female vegetarians had a lower mortality than omnivores (1, 2).  In the second round of study, male and female vegetarians had a 12 percent lower mortality rate than omnivores (3).  However, lacto-ovo vegetarians, vegans, pescetarians, and semi-vegetarians were all approximately tied, which is not consistent with the idea that eliminating meat is necessary for the survival benefit.  In absolute terms, the longest lived were the fish eaters, although the error bars are too large to conclude that the various subgroups are different from one another.  As usual, keep in mind that this is an atypical population with a cluster of healthy behaviors, particularly among the most observant, vegetarian Seventh-Day Adventists.

There have been many other observational studies on vegetarianism and mortality, so I'll rely on meta-analyses that compile and analyze these individual studies.

One of the first meta-analyses was published in 1999 (4).  Although it's older and only included five studies, it's interesting because it reported results for subgroups of vegetarian and semi-vegetarian diets, including vegans and pescetarians.  Overall, being vegetarian was not associated with a survival advantage.  However, subgroup analysis suggested that lacto-ovo vegetarians, semi-vegetarians, and pescetarians had a survival advantage, while vegans had exactly the same mortality risk as omnivores.

Consistent with this early meta-analysis, a recent meta-analysis including seven studies also reported no survival advantage for vegetarians, although there was a modest trend toward lower mortality (5).

What about specific types of meat?  Some studies have shown an association between red and processed meat consumption and higher mortality risk, most notably the large observational studies from the Harvard School of Public Health (6).  A highly publicized study on elderly Americans came to a similar conclusion (7).  The two most recent meta-analyses, which considered a broader swath of studies, arrived at a different conclusion.  Neither one found a significant association between red meat consumption and total mortality, although there was a modest trend toward higher risk (8, 9).  Both confirmed the association between processed meat and mortality.

In general, poultry and fish consumption have neutral or beneficial associations with total mortality (10, 11, 12, 13, 14, 15), and dairy consumption is not associated with mortality (16).

I'll summarize before moving on.  Being vegetarian is not associated with a clear survival advantage, nor is being vegan.  Some studies have suggested that fresh red meat consumption is associated with increased mortality risk, but the overall literature does not strongly support that conclusion.  Processed meat consumption is fairly consistently associated with higher mortality risk.  There is no evidence that eating fish, poultry, or dairy is associated with a higher mortality risk.  In fact, people who eat fish seem to die a bit less often than anyone else.

It's very unlikely that we'll ever have long-term randomized controlled trials to test these questions.

Possible mechanisms

The most obvious mechanisms by which meat might shorten lifespan are by increasing the risk of the primary killers we've already discussed, including cardiovascular disease, diabetes, and cancer.  I won't repeat what I've already written on those topics, except to say that the negative potential of meat appears to be linked specifically to processed and red meat.

Yet there is a larger mechanism that some have suggested may link meat to shorter lifespans, and that is by increasing the activity of an enzyme called mTOR (mammalian target of rapamycin).  mTOR is one of two key sensors of cellular energy status, the other being AMPK (AMP-activated protein kinase).  My own research has touched on mTOR, as my graduate work involved basic aging research (17).

One of the interesting things about mTOR is that it senses more than just energy abundance.  It is also highly sensitive to amino acids, the building blocks of protein.  When the body has abundant energy and amino acids, such as after eating a large steak and potatoes, mTOR activity is high.  When the body has low energy and amino acids, such as during calorie restriction, mTOR activity is low.  As you might predict, when mTOR is activated, it tells the cell to fire on all cylinders because its energy and protein balance sheets are in the black.  This favors anabolic processes such as cell division, RNA and protein synthesis.

This brings us to the big hypothesis: firing on all cylinders effectively accelerates cellular aging.

There is some pretty compelling evidence to support this general biological principle.  In brewer's yeast-- a surprisingly productive organism for aging research-- removing or inhibiting the yeast equivalent of mTOR extends lifespan* (18).  This is thought to be similar to what happens during calorie restriction, which inhibits TOR and extends lifespan in yeast and some other organisms.  One of the ways to inhibit TOR is by using a drug called rapamycin.

What about in mammals?  At least in certain species under specific conditions, we know that calorie restriction can extend lifespan.  Does this relate to lower mTOR activity?  As it turns out, rapamycin can be used in mice, as long as it's administered carefully.  And it does indeed extend lifespan (19).  What else extends lifespan in mice?  Low-protein, high-carbohydrate diets (20).

Together, this suggests that dietary protein may be able to increase mTOR activity and accelerate aging-- at least in rodents under lab conditions.  Meat is the most concentrated, highest-quality source of protein available.  Plant proteins tend to be less concentrated, less completely digested/absorbed, and have a less complete amino acid profile, leading them to be less anabolic.

It's a beautiful theory, but real life is complicated.  Beautiful theories are no substitute for empirical evidence.  What we need is actual evidence that eating meat increases mortality risk-- then we can say that the mTOR theory might explain what we've observed.  Unfortunately (fortunately?), we don't have such evidence.  While there is some hint that red meat intake may shorten lifespan, there is no evidence that poultry, fish, or dairy do the same.  Since these are all concentrated sources of high-quality protein, I believe our hypothesis has run aground.  Perhaps someday it will receive more convincing support, but for the time being it's a little too speculative for my tastes.

Synthesis and conclusions

When we consider individual diseases, specific types of meat appear to have substantial impacts.  However, when we zoom out and consider health as a whole by examining total mortality, the picture becomes quite a bit fuzzier.  If your overall goal is to live a long, healthy life, there appears to be little to gain from avoiding all meat.

Most of the healthiest, longest-lived cultures eat meat in modest quantity, and there is no evidence that poultry or seafood consumption increase overall mortality risk.  There is not strong evidence that red meat intake is associated with mortality, but there is fairly consistent evidence that processed meat does.

Limited evidence suggests that vegans do not share the modest survival advantage that lacto-ovo vegetarians and pescetarians have over the general omnivorous population.  There are no examples of long-lived vegan cultures to reassure us that this dietary pattern sustains long-term health and longevity.  So while a vegan diet may protect against specific diseases such as cardiovascular disease, it may not be the safest strategy for overall health and longevity.


*It's surprisingly complicated to measure lifespan in yeast.  The best way is to measure "replicative lifespan", or how many times a cell can bud (divide) before becoming senescent (too "old" to bud).  Genes that affect replicative lifespan in yeast often seem to relate to lifespan (or lifespan-related factors such as diseases of aging) in mammals as well.  mTOR (TOR1/2 in yeast), AMPK (SNF1 in yeast), and SirT1 (Sir2 in yeast) are good examples of this.  It's pretty remarkable that a single-celled fungus we use to brew beer, which is separated from us by a 600+ million year evolutionary chasm, has such similar pathways for sensing cellular energy status and regulating lifespan.  Evolution doesn't fix what isn't broken.

33 comments:

elbatrofmoc said...

Great series. Thank you for these very informative articles and for giving them for free. I greatly appreciate the time and effort you have put into writing them.

The bottom line
The good: poultry, seafood
The bad: processed red meat
The unknown: fresh red meat (although some evidence suggests it may fall into "the bad" category)

Also, eat meat in moderation if you have to. If you don't have to, you should be fine without it.

I hope I didn't misrepresent the views presented in the article.

Sunny Sattva said...

Thank you Stephan. This article suggests to me what I have strongly suspected, which is that for whatever reason, small amounts of animal products in the diet may be favourable to overall health. This puts one at odds with many in the plant based community, who are dogmatically attached to 100% adherence to a plant based regime. I suggest that 100% may work for some long term, and is superlative as a short term therapeutic strategy, particularly when the food is consumed close to its natural state. I regret the 'all or nothing' attitude that the human mind loves to express. As a more truthful reality may be more nuanced. So we may not be able to say absolutely that meat/fish/poultry are 'bad'. I appreciate a calmer debate, with open minds who are not merely seeking to uphold their preferred version of truth. For myself, I'll be staying with a very modest amount of wild seafood (approx 5% diet by calories) as I find this overall to be beneficial.

Stylooke said...

Excellent post Stephan!

The good news is, I think, that there are many different strategies to excellent health. I think it makes sense that vegans don't tend to live longer due to the highly restrictive nature of the diet (i.e. B12 being absent).

You however never mentioned methionine (I think). Calorie restriction is also thought to contribute to life extension by reducing homocysteine levels (which in rodents is also mimiced by restricting methionine or supplementing glycine). Are problems caused by high red meat caused by excess methionine/relative glycine deficiency?

Chuck Steak said...

Great post, although I can't help but feel exasperated with all this. Nutrition science has got to be the most useless science ever spawned. Meat is good, no it's not good, no it's good but moderately, actually forget about red meat, but did you hear about this magic tribe of warriors that eat 30 kg of meat a day? Fat is bad, err no, specific types are bad, at least we can all agree that Omega 3s are good. Oh wait, turns out they raise your chances of cancer. Carbs? Depends on whose dogmatic opinion you ask. How much, what kind, GI, GL, fast vs. slow?
All recent literature I've read is a bunch of confused researchers saying: "meh, just eat whole foods i guess, and hope for the best." I might as well ask a voodoo priest for answers. Sorry for the rant.

Ultra Monk said...

Do your studies count meat eating mortality minus any drugs taken for diseases?

Gretchen said...

I sometimes wonder if the stress of focusing on mortality causes as much disease as various dietary patterns.

Sure, it would be nice to live to be 110 . . . if one were happy and healthy and still had friends alive. But simply extending life isn't enough. We need to think of the quality of our lives.

IMHO, if you enjoy a high-carb, low-carb, vegan, or mixed diet, as long as it doesn't result in obesity and metabolic diseases, you should follow that diet that makes you happy. Living an extra 3 years isn't my goal in life, and a lot of these studies show statistical benefits, but not benefits large enough to warrant a lifetime on some diet that makes you miserable.

David L said...

Stephan,

I wonder if you could give the magnitude of the different mortality rates that you suggest. For example, I'm not likely to be convinced to drop bacon if the lifespan without it 67.5 and the lifespan with is 67.3. How does this compare to the differences created by modest exercise, for example?

Gary Katch said...

"In fact, people who eat fish seem to die a bit less often than anyone else. "


Well, I certainly wouldn't mind dying less often!

Reijo said...

It's interesting that vegan diet is not unanimously associated with reduced mortality albeit both high fiber intake and high fruit consumption are associated with reduced mortality in recent meta-analyses. In any case, processed and possibly red meat seem to be the only animal protein sources that are associated with mortality.

It's difficult to find meta-analysis that would show mortality advantage for red meat, but in Asian cultures red meat might be inversely associated with mortality, a meta-analysis by Lee et al. (AJCN) suggested a year ago. In Asian cultures red meat consumption is still low compared to Western countries.

Exhaustive analysis of 304 systematic reviews from 1950 until 2013 paint pretty similar picture on red meat what you have depicted. It concluded results in all diet-related chronic diseases. It was hard to find meta-analyses that support high intake of red/processed meat in prevention or treatment of chronic diseases. At the other end, there are plenty with either neutral or negative results. Actually sweetened beverages and red/processed meat stood out as the worst ones in the analysis. It's unfortunate that red and processed meat were lumped together, no separate analyses were done.

Fardet and Boirie. Nutrition review 2014;72:741-762.

jreiser said...

I like grassfed meat as I can be sure-ish that it ate a reasonable diet. Your comments about red meat are causing me to question my strategy. Were the tests that view red meat in a negative light done with CAFO meat? Do they translate to grassfed meat? Would you advise a family member to avoid red meat even if it is grass fed?

Gretchen said...

"Well, I certainly wouldn't mind dying less often!"

Gary, Thanks for the laugh.

We need more laughter.

Zahc said...

Stephan you stated: "The two most recent meta-analyses, which considered a broader swath of studies, arrived at somewhat different conclusions. One found a significant association between fresh red meat consumption and total mortality, while the other did not"

The first stated that "Unprocessed red meat consumption was not significantly associated with all-cause mortality" - http://www.ncbi.nlm.nih.gov/pubmed/24148709

The second stated that "In the meta-analysis combining the risk estimates for the highest v. the lowest consumption category, the consumption of processed meat but not of total, red and white meats was found to be positively associated with all-cause mortality" - http://www.ncbi.nlm.nih.gov/pubmed/24932617

Where is the significant association you are talking about? Also, the effect sizes are so weak that I cannot take any of these associations seriously (even for processed meat).

You may also be interested in the most recent analysis of vegetarians where it was concluded that "the reduction in IHD and all-cause mortality with vegetarian diet stems mainly from the Adventist studies, and there is much less convincing evidence from studies conducted in other populations. Once the SDA studies have been excluded, the results are either less significant or with a lesser magnitude of benefit, and this raises the concern that the non-dietary factors (confounders) in SDA lifestyle may be responsible for the risk reduction among the vegetarian studies. In addition, among men there appears to be greater benefit of vegetarian diet compared to women. In view of these inconsistent findings, we conclude that the benefits of vegetarian diet for reducing death and vascular events remain unproven." - http://www.ncbi.nlm.nih.gov/pubmed/25149402

George Henderson said...

I noticed in the vegan and vegetarian studies that women in these groups have significantly lower parity.
Not having too many kids should extend life. You get to keep more of your income, sleep better, work more reasonable hours, cook better meals, get more education, and childbirth itself is a risk factor for women.
No-one has yet taken this difference into account.

Stephan Guyenet said...

Hi Sunny,

Good thoughts. I believe the health views of some people in the plant-based diet community are clouded by other considerations such as ethical and environmental concerns. There is some value to their views on health, but the all-or-nothing approach is unnecessary.

Hi Gretchen,

I agree that lifespan isn't the best metric for all people. I think most people are more concerned about living a good life and performing at a high level than living a few more years. I'll address that concept in the next post.

Hi David,

They hover around the 10 percent range. IOW, someone who eats a lot of red meat has a 10% higher risk of dying at any given time than someone who doesn't. It would take some math to figure out how that relates to absolute life expectancy but I'll leave that to you.

Hi Reijo,

Thanks. There were also one or two European studies suggesting that the "optimal" red meat intake was above zero (but that a high intake was also bad). Perhaps it's healthy, or at least neutral, in small quantities.

Hi jreiser,

The studies in this series represent almost exclusively CAFO red meat I'm sure. There's no way to be certain that the results would apply to grass-fed, yet we also don't have specific reasons to believe they wouldn't apply. You asked me what I'd advise a family member. I would say go ahead and eat grass-fed red meat, but in modest quantities.

Hi Zahc,

You are correct-- I misread the abstract of the second meta-analysis. They found an association with cardiovascular disease but not total mortality. Thanks for pointing that out; I'll have to modify the post. Also, thanks for the meta-analysis; I missed that one.

Hi George,

That's a great point. Some vegetarian studies have found higher breast cancer risk, possibly related to lower parity. I think that illustrates just how hard it is to tease apart different lifestyle and diet characteristics in these studies.

rantyscientist said...

The difficult thing with studies comparing omnivores to vegans is that they don't really assess the quality of the diets. The majority of vegans are vegan for ethical reasons. I personally know many of these people and I must say their diets are terrible. Lots of processed foods, fake meats, junk food and restaurant food. Therefore, I take anything these studies say with a grain of salt.

The one consistent thing we see in nutrition studies is that the more whole plant foods that are consumed (specifically vegetables, fruits, legumes), the lower the mortality.

Perhaps the exclusion of whole plant foods is more detrimental than the inclusion of animal ones...

WilliamS said...

My opinion: all this low quality evidence doesn't amount to better evidence. Meta-analyzing it adds nothing. Observational epidemiology with massive confounding and small effect sizes is not real evidence, no matter how many times you do it. The biology is so poorly understood, and the healthy subject effect so profound, that no amount of statistical "correction" can make a silk purse of a sow's ear.

To me all we really know is that as a traditional food meat (at least traditionally raised meat) is obviously consistent with almost complete avoidance of the diseases of civilization (including some cultures that eat vast amounts of the stuff). It's a core part of our ancestral diet. It can't be toxic per se. In its industrial form, and as part of larger modern diets with vegetable oils, industrial carbs, etc., no one knows what all its effects may be. Anyone who thinks they do know is simply stating opinion. It's not science, at least none that deserves the name.

To me any scare-mongering about meat is ill advised considering how little is actually known and how long healthy populations have been consuming it. A great deal of humility and skepticism are in order. We may not have come very far since, decades ago, leading academics begged the McGovern committee to avoid demonizing animal fat before real evidence existed.

jreiser said...

Thanks for the reply Stephan.
I was probably overdoing the beef as I overdid liver (I have hypervitaminosis A). I probably eat a hockey puck size amount of beef 2-3 times a day. Based on your comment I will probably go with beef one-three times per week. Do you think that is modest? I had thought 3 lbs of liver was modest but was quite wrong. Again I appreciate your responses.

John Myers said...

Instead of looking at "Blue Zones" why not look at the CIA fact book list of longest life expectancy? In years past Andorra has been in the top spot or at least in the top 10. Traditionally they've relied heavily on cured (processed) meat. They raise sheep and grow tobacco.
Monaco

Rok Osterman said...

Most if not all (!) diet trials are flawed from the start because they generalize food, e.g. "every red meat is the same". Using pastured-only meat or not-seen-the-sun meat would yield totally different results.

Stella B. said...

I'm being pedantic again, but as far as I know all American beef is "grass-fed". It's just not "grass-finished", receiving instead feed lot grain in confined quarters for the last six weeks or so to build up fat. It would be prohibitively expensive to raise cattle on grain for its entire lifecycle and I've never heard of cattle being raised indoors. The members of my family who raise "CAFO" cattle certainly raise it on the wide open range; grazing in the summer and supplemental hay in the winter (if you want to know anything about hay and cattle, I've got an uncle who will tell you in detail...lots and lots and lots of detail.) The idea that grass feeding somehow obviates any risk from red meat consumption is analogous to the people who claim they don't have to worry about smoking risks because they only smoke organic tobacco. Wishful thinking.

Hafthor Bjornssen said...

We are all pretty much taking risks regarding our dietary choices- vegans, Atkins, Paleolithic Diets etc.

These studies only measuring effects will not tell us much of anything. Medicine and nutrition are very often guilty of such things- measuring effects with zero explanation or mechanism .

As Paul Lutus and David Deutsch note, science needs very deep explanations. We need demonstrable or at least highly plausible mechanisms or underlying physical principles as to how meat specifically is unhealthful - if it is so.Without the explanations we have very little.

Take blood pressure, for instance. In this situation the correlation with stroke and coronary artery disease is VERY important because there is an underlying physical principle which explains the correlations. This can be demonstrated even in a hose. The artery is more flexible but eventually it can only take so much beating.

On the other hand the number of movies Nicolas cage has appeared in from 1999 to 2009 is highly correlated with people drowning in a swimming pool. Obviously no connection here.

Explanation is extremely critical in science.

So, until we understand how cells work FAR better and understand how nutrients affect the cell, we will be mostly groping in the dark.

Diane in Flagstaff said...

I don't see that overall mortality rate is a good outcome variable to rest your conclusions on because many people actually live longer today because of medicine, but not because they are healthier. Moreover, there is a huge difference in the quality of life for people, even at the same age. These data don't take into account the higher risk of so many disease associated with meat.

glib said...

somewhat slanted post due to the poor quality of the source. I am familiar with the old saridinian diet and

1) the fat of choice was lard, not olive oil. yes, the current generation does prefer OO (no doubt due to all the medical establishment propaganda), but the centenarians were raised on lard

2) Okinawans fat of choice is also lard

3) the Barbaricini (sardinians from Barbagia) are in fact quite carnivorous. In fact, if you bother to read the Blue Zone book, the interviewer arrives at a farm to interview the super-active 75-yrs old farmer, and finds him in the process of gutting a steer. They eat pork, lamb, chickens, and beef, and eat all offal. Importantly, they eat a lot of broth.

This post, plus the recent sacrilegious post on ribs, remind me that the nutritional analysis biases are in fact deep. Of course meat alone can have some negative effects, due to processing but also due to excess methionine and lack of fats accompanying the lean meat.

I think the best meat (or the best diet) is high in low-temperature fat and collagen/glycin. Make the ketchup yourself from scratch, if you wish, but eat near the bone, fatty meat that has been baked or boiled.

Hafthor Bjornssen said...

Hi WilliamS, :)

I just saw your comment and you make truly excellent points. Fabulous insight.

I could not have said it better. Obesity and nutrition are going to be enormous mysteries for a long time. We do not even understand how a SINGLE cell works completely-nowhere near completely. That is why the 30 Bananas A Day people and all other salesman of any dietary philosophy are making stuff up to sell product.

This is not to say we know "nothing." We know some stuff and some progress has been made. But what we do not know dwarfs what we know. This is true in all fields of science.

Physics ( one of the most mature sciences other than astronomy) itself is significantly uncertain. It is very likely tings will be modified in the future and plenty fo undiscovered physicist remain.Our instruments cannot even probe the Planck scale.

On another note, Stephan is highly creative and perceptive . I do not think I could have posted a different rewarding food for over a year straight. each post tops the next. That fried chicken hot dog made me LOL !!!!!

Stephan is a good guy and a solid scientist. I wish more people in his field and the field of nutrition were more like him and guys in other fields like the late Richard Feynman, Paul Lutus, David Deutsch etc. Nutrition is a different beast. There will always be enormous confounders even in randomized clinical trials that are double blinded. Enormous confounding variables. Humans came with them.

Many pontificating salesman gurus miss this out there in the Blogosphere. They are easily identifiable. They rpofess absolute certitude as to what causes obesity , they dabble in musing the conservation principles,and they think they know how to eat better than anybody.

In real live humans, tons and tons of variables always exist. No way around it. Much of the "science" is just garbage. We MUST look into how the cell works in tremendous detail and we MUST have biologists heavily communicating with the physicists. David Gross notes this, too.

I need to get my regular account back. Sorry :)

Best wishes to all,
Raz

Oliver Magoo said...

In the Adventists, nut consumption had a far greater impact on longevity than did animal consumption.

http://archinte.jamanetwork.com/data/Journals/INTEMED/11988/ioi00635.pdf

Walkitout said...

@ Glib.

Have you actually looked at the amounts of pork and pork fat through the 70's and 80's?

It seem to be an an extremely minuscule amount. The Perfect Health Diet people are obviously trying to mislead and confuse people by scraping together and distorting extremely weak "evidence" they think they have.
One of their main references came from some obscure old magazine article written by a tourist that claimed their diets were "greasy" and they eat nose to tail. Well of course they do because the don't have the luxury of just cutting off the pork fatty pork chops and discarding the rest like we do in some countries.

Richard Nikoley said...

You should be very righteously proud of this series, Stephan. This rivals your 10-Part Tokelauan series that I've linked to a "million" times.

I've always loved how you operate, since about day one. I can't even begin to account for all the ways you've steered me.

Thanks.

"This brings us to the big hypothesis: firing on all cylinders effectively accelerates cellular aging."

It's pretty Occam intuitive. A candle burning twice as bright burns half as long. It's why I kinda laf at the idea of all those people in the gym every day trying to burn a bright candle at both ends, supplementing with concentrated protein in order to fuel the—shorter burning—fire.

You really should do a serious series on fasting, because it seems to me to tie in with the Yin-Yang of protein. To put it another way: animal protein is so concentrated and powerful and nutritionally dense, it's dose dependent.

It all ties in with IGF-1 too. I've recently come full circle with intermittent fasting. One way to look at it is that you can have your plate of ribs, but the payment is no protein for 2 days of the week.

http://freetheanimal.com/2015/02/intermittent-profound-shortcut.html

Colin Macdonald said...

I wonder what exercise might tell us about the idea that cell division reduces life span.

As far as I know, exercise is a form of hormesis. It's an activity that promotes a lot of metabolic activity, oxidation, and the destruction and replacement of cells.

But I think it's also generally accepted that regular exercise lengthens life, not shortens it.

If this theory were true, wouldn't people who get regular, vigorous exercise have shorter (though perhaps still healthier) lives?

mumania said...

In the Food Combining concept, meat can be consumed with vegetables, and it would be worse if it is consumed with carbohydrate..does it mean meat is safe for the daily meal?

Alex said...

Colin - great. I can't eat fat, carbs, protein and exercise will hasten my death.

Someone make me my cyborg body already!

RIF said...

From the Darwinian aspect there are two different paths. The primary one is reproductive fitness and the secondary one is longevity. They are not synonymous and may account for gender difference in protein consumption and longevity. Males build muscle in early competition for females in mammalian species. The losers tend to die younger. It's possible that with males in particular, good reproductive fitness via higher protein consumption is bought at the price of longevity.

As culture develops, longevity and the ability to pass on the culture as opposed to just genes, becomes increasingly important.

Edward Brisson said...

I know this study has been criticized but the "China Study" by T Colin Campbell does seem to indicate that lower animal food consumption leads to less disease, especially heart disease and cancer.

Jenx said...

I have just read the complete series and greatly appreciate your sharing of your knowledge and experience in such an even-handed and careful way. We need more ecumenists and less totalising believers.