Strange Science: Meat consumption increases risk of Type 2 diabetes
A new meta-analysis concludes that a diet high in meat increases your risk of Type 2 diabetes by 17%. Eating a lot of so-called "red" meat was associated with a slightly higher increase (21%), and a high intake of processed meats increases your risk by a whopping 41%.
Media reports are quick to point out that this is just the latest in "an ever increasing list of bad news for red and processed meat."
In all of these studies, the division of meat into "red" and "white" seems totally arbitrary, as I discussed at length in this post: Meat and mortality: What does color have to do with it?
In this particular case, the authors concede that the apparent association between meat consumption and diabetes risk could be explained by other factors. (So why exactly are we going to press with this result?)
A false association seems even more likely in this case than in the recent associations between meat intake and cancer risk or all-cause mortality. At least there are plausible mechanisms to explain why high meat intake might increase cancer risk. For example, charred meat contains known carcinogens--although I hasten to point out that this has nothing to do with the "color" of the meat.
Diabetes is a disease of disordered carbohydrate metabolism. Meat is made up of protein and fat. How could eating more protein and fat increase the risk of diabetes? Doesn't it seem more likely that there is something else about the lifestyle or dietary habits of people who eat large quantities of meat (especially processed meat) that might increase their diabetes risk? Are they also over-weight? Are they sedentary? What's their consumption of alcohol? Of high-glycemic foods?
I'm keeping an open mind but pending more convincing data, I'm not sure I'm buying it.
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Posted by: greg | Nov 18, 2009 7:19:58 PM
@Adrienne Larocque
I guess my sense was unclear. Yes, your body synthesizes saturated fat. That is why it is not an essential nutrient - your body can make what it needs in the absense of dietary staurated fat.
The only fats that are essential to get in our diet are n-6 and n-3 PUFA because we cannot synthesize fatty acids with double bonds at such late positions.
Posted by: toni | Nov 18, 2009 12:31:31 PM
I think it is simplistic to state that insulin-metabolism problems (from Metabolic Syndrome to Diabetes) are solely a carb problem, therefore not potentially connected to consumption of the fats and proteins in meat. After all, one of the diagnostic symptoms of early-stage insulin resistence, in metabolic syndrome, is elevated triglycerides and an imbablance in cholesterol ratio in terms of a low LDL level. Which makes it obvious that unhealthy blood fat levels ARE connected with how our body is metabolizing carbs. And unhealthy blood fat levels are DEFINITELY impacted by the meat we eat. --Additionally, the hormones in conventiaonally-raised meats can have a huge impact on hormones in the body of all types, potentially affecting insulin resistence from multiple angles. For instance, raising estrogen to unhealthy levels, which could also explain recent studies that link red meat consumption to higher levels of breast cancer...( a link between insulin resistence and estrogen imbablance is shown by the connection between Polycystic Ovarian Syndrome and Metabolic Syndrome...)or research that links xeno-estrogens in non-organic meat and produce to disruption in the apetite-regulating hormones in the body. This could contributing to overeating and diabetes resulting from obesity.
Posted by: Adrienne Larocque | Nov 18, 2009 5:25:09 AM
@ Greg - Your body DOES make saturated fat! Read the following article:
JS Volek, et al. A hypocaloric, very low carbohydrate, ketogenic diet results in a greater reduction in the percent and absolute amount of plasma triglyceride saturated fatty acids compared to a low fat diet. NAASO, Boston, MA, October, 2006.
Posted by: greg | Nov 17, 2009 3:17:29 PM
@Ranjini
Are saturated fats essential for life? Certainly. Are they essential nutrients? Certainly not. If your body needed more than you consumed, it would synthesize them itself. That said, I don’t think anyone really proposes that they be eliminated from a diet as I’m not sure there is a practical way of doing that.
And yes, butter and coconut oil do contain short- and medium-chain SFAs, but they also have longer-chain SFAs: coconut oil is about 25% long-chain SFA and butter is about 50%.
As for comparing the relative healthfulness of these fats to say the MUFAs and PUFAs found in canola and olive oils… you will get a lot of conflicting opinions from posters around here. I’d try to put the point a different way; it’s not so much about SFAs being “harmful when compared to … vegetable oils” rather, it is about moderation in both.
The long-chain SFAs have been implicated in heart disease and diabetes. PUFAs are helpful for reducing heart disease risk but perhaps only up to a point, hence the need for moderation. Traditionally people have used animal fats as their main source of fats so dietary authorities talk in terms of substituting PUFAs for SFAs. The World Health Organization suggests that we try to keep SFAs below 10% of our calories, substituting with PUFAs when we can but keeping PUFAs below 10% of our calories as well. The remainder of our fat should come from MUFAs. I’d guess that if a larger than typical percentage of your SFAs are coming from short- and medium-chain SFAs then the 10% of energy mark may be conservative – at least based on what we know today. On the other hand, many experts would encourage you to keep your SFAs as low as practical so having the short-chain SFAs in lieu of long-chain would be a bonus but they would still encourage the 10% overall limit.
Posted by: Ranjini | Nov 17, 2009 1:58:34 AM
Can we totally do away with saturated fat consumption in daily life? Are they not essential?Fats like butter, ghee &coconut oil containing short /medium chain f.acids get digested with gatric lipase & used by the mitochondria for power generation & are not stored I suppose.How are they harmful when compared to other vegetable oils?
Posted by: greg | Nov 17, 2009 1:15:34 AM
@Dave
Thanks for the link. I am sure you are aware nowhere in that study is there a finding that Indian vegetarians “experience higher rates of Type II diabetes than Indian non-vegetarians.” What it does point out is that Indians seem to be genetically predisposed to develop diabetes. You are surely correct that vegetarianism does not guarantee protection from diabetes (or other chronic illness), but I would not agree that there do not seem to be real benefits from the dietary pattern and with respect to diabetes we have some good ideas of what those might be at the biochemical level.
PS – full disclosure, in my own search I did find one reference to a study conducted in the 60s(?) which suggested vegetarians did have higher rates of diabetes in India. However, 1) it was only a reference to a study and I could not access the original, 2) at that time diabetes prevalence was only ~2% and fully a quarter of diabetes in India was thought to be malnutrition-related which really is a totally different pathology, and 3) the authors of the study that sited the earlier work drew no dietary conclusions from it with regard to the current epidemic of Type II diabetes in India.
@ Icarus
First, please note you are changing my quote substantially when I write "Certainly “eating large quantities of carbohydrates” have not been shown to be causal" and you re-write this as “a high refined carbohydrate diet” – those of course are not the same thing.
Second, you seem to be confusing different types of diabetes. You write, “Diabetics cannot produce enough insulin to handle the carbohydrate in their blood.” That is true of Type I diabetics, but Type I really has nothing to do with diet is an autoimmune disease where the body attacks the pancreas so it no longer secretes insulin. On the other hand, Type II diabetics (what we are writing about) have no problem creating insulin (at least at first). A Type II diabetic's cells have become insulin resistant so they can no longer regulate serum glucose even with plenty of insulin.
This difference is crucial and is why your intuition that it is “absurdly obvious” that carbs should cause this disorder is in fact wrong: it need not be so simple. WD Stark has pointed you on the correct path. Sorry to be redundant but I’ll re-post Monica’s earlier discussion which was on point
http://blog.nutritiondata.com/ndblog/2009/09/can-a-high-fat-diet-increase-insulin-resistance.html
As for your request for example studies, the literature on diabetes is large and if you spend any time with it you quickly find all the studies you care to read. Rather than my trying to wade through it all on this blog and prove the negative (not easily done) please do some research yourself and you will find that the studies of the impact of carbohydrates are ambiguous at best. If you find a smoking gun study that says “eating large quantities of carbohydrates” causes diabetes, please post again but I am highly confident that no such finding has been made.
As for what we do know about diabetes, the largest risk factors are 1) genetic, 2) overweight/obesity, 3) lack of exercise. The World Health Organization identifies what it terms “convincing” evidence that both 1) dietary saturated fat and 2) lack of dietary fiber as contributing to diabetes, but does not consider either as proven. After that, the evidence of causality from other sources is weak.
Posted by: WD Stark | Nov 16, 2009 6:34:41 PM
The answer to this question lies in understanding what the fats do to the cells that prohibits the glucose from being able to be metabolized and causes it to stay in the blood stream. There are actually several good studies out there that show what the correlation is and how quickly it can be brought on and also how quickly it can be reversed by dietary changes in the area of fat intake. A good book would include "The China Study" if you would like more info on this problem. Please note that there has been an 800% increase in type II diabetes in the last 20 years alone and then look at our dietary habits. You will find many interesting facts, such as most of the 3rd world countries have little to no diabetes, and when you look at their diet, they use meat as more of a condiment to flavor rather than the large consumption that we see in our country.
Posted by: Icarus | Nov 16, 2009 4:37:51 PM
"Certainly “eating large quantities of carbohydrates” have not been shown to be causal."
Um, has this even been investigated? i.e. has anyone bothered looking at the effect of ingestion of refined carbohydrates on the development of diabetes in randomized, controlled trials? If you can show me any studies that have done that, and yet have not found any effect, I'd be shocked. Diabetics cannot produce enough insulin to handle the carbohydrate in their blood; it seems to me to be absurdly obvious that a high refined carbohydrate diet would cause this disorder.
Posted by: Mike Watkins | Nov 16, 2009 4:25:31 PM
I'm glad to see a little common sense about the results of this report. Factors affecting the incidence of diabetes isn't as simple as many would like to make it, and I would agree that linking meat as a cause not good science. My take is that it may well be agenda driven.
Posted by: Nancy | Nov 16, 2009 4:20:24 PM
As usual it's the poor press understanding of observational studies. These studies are horribly skewed by the "Healthy User Effect".
People who don't eat red meat probably don't do so because they're concerned about their health. They also do (and don't do) other things like smoke, eat a lot of sweets, abuse drugs or alcohol. They just take better care of themselves than the run-of-the-mill sort who disregards all the latest health warnings.
Gary Taubes, who is a REAL science journalist wrote about the problems with these observational studies in http://www.nytimes.com/2007/09/16/magazine/16epidemiology-t.html?_r=2&ref=magazine&oref=slogin (Do we really know what makes us healthy?)
Posted by: Dave | Nov 16, 2009 11:49:46 AM
On Indian vegetarians and Type II diabetes:
http://www.ajcn.org/cgi/reprint/46/6/955.pdf
Somewhat related:
Posted by: greg | Nov 2, 2009 12:01:33 PM
@Monica,
Your point is well taken. Not one poster here has come up with a reason that red meat intake would cause diabetes other than through saturated fat.
As you point out, the authors did allow that "the possibility that residual confounding could explain this association cannot be excluded." I can't tell from reading the abstract whether or not the authors controlled for saturated fat intake - an obvious potential "residual confounder" - or to Dave's point for carb intake.
If they found an association independent of saturated fat intake and other known risk factors, that would be more interesting and tell us to look harder for new potential causes... Does this come out in the body of the paper? (I'm too cheap to pay for it and figure that out ;)
Posted by: Monica Reinagel | Nov 2, 2009 10:22:48 AM
Good conversation re: saturated fat and insulin resistance, but if this is the most likely mechanism, why aren't various types of meat divided into higher and lower saturated fat content, rather than "red" and "white"? If myoglobin were the putative mechanism, this might make sense.
Posted by: Denise | Nov 2, 2009 2:16:37 AM
If you want a truly lean meat, eat goat meat. It does not marble - any fat is stored in globs by organs. "Goat meat is 50%-65% lower in fat than similarly prepared beef, but has a similar protein content. The US department of Agriculture also has reported that saturated fat in cooked goat meat is 40% less than that of chicken, even with the skin removed." from:
http://www.jackmauldin.com/cooking_with_goat.htm
.
Posted by: Greg | Nov 1, 2009 5:43:31 PM
@Dave
You may have missed my question – do you have a source for the claim that vegetarian Indians have a higher rate of Type II diabetes than non-vege? I’d be curious to see a serious study that had such a finding.
I’d agree that looking at western vegetarians will tend to have a selection bias for more heath conscious individuals. An exception to that would be the Adventists who are vegetarian for religious reasons; studies of them have revealed they too have lower rates of diabetes which is a stronger evidence for the healthfulness of vegetarian lifestyle. Hence a study amongst Indians that found the opposite would be interesting.
I would not be too quick to dismiss the link between saturated fat contributing to Type II diabetes. It certainly would fit with the epidemiological data as well as the clinical success of treating Type II diabetes with a vegan diet. In animal model we have gone a long way to tying insulin resistance to ceramide synthesis which is mediated by dietary saturated fat (specifically palmitic acid.)
@Mara Dolan & @ Dave,
Is it a closed case that saturated fat is to blame for diabetes? No; we have a lot more to learn. I just don't think we can discount it out of hand as Dave seems to. Similarly, Dave’s hypothesis that “Problems should only occur if some environmental stimulus drives insulin outside of the normal range” is certainly NOT demonstrated. The cause of type II diabetes is unknown. The primary risk factors are genetic, obesity, and lack of exercise – not exactly “environmental stimulus.” Certainly “eating large quantities of carbohydrates” have not been shown to be causal. I think Monica’s recent post is on point:
http://blog.nutritiondata.com/ndblog/2009/09/can-a-high-fat-diet-increase-insulin-resistance.html
PS @Dave - I think it is almost certainly not true that hominids ate a high-fat diet for millions of years… but that would take us far afield from the topic at hand.
Posted by: Dr Larsen | Nov 1, 2009 2:20:47 PM
have you ever read studies that show that saturated fat increases insulin resistance? That could be one reason why high intakes of meat could be corrlated to diabetes.
Posted by: Denise | Oct 31, 2009 5:41:35 PM
Perhaps the association with red meat is due to the animal fat accumulation of persistent organic pollutants, which are also associated with insuline resistance and type 2 diabetes.
excerpt below is from: http://en.wikipedia.org/wiki/Persistent_organic_pollutant
A study published in 2006 indicated a link between blood serum levels of POPs and diabetes.[4] Individuals with elevated levels of persistent organic pollutants (DDT, dioxins, PCBs and Chlordane, among others) in their body were found to be up to 38 times more likely to be insulin resistant than individuals with low levels of these pollutants, though the study did not demonstrate a cause and effect relationship.[4] As most exposure to POPs is through consumption of animal fats, study participants with high levels of serum POPs are also very likely to be consumers of high amounts of animal fats, and thus the consumption of the fats themselves, or other associated factors may be responsible for the observed increase in insulin resistance. Another possibility is that insulin resistance causes increased accumulation of POPs. Among study participants, obesity was associated with diabetes only in people who tested high for these pollutants. These pollutants are accumulated in animal fats, so minimizing consumption of animal fats may reduce the risk of diabetes.[5] According to the US Department of Veterans Affairs, type 2 diabetes is on the list of presumptive diseases associated with exposure to Agent Orange (which contained 2,3,7,8-tetrachlorodibenzodioxin) in the Vietnam War.[4]
----------------------------
The study referenced in the above article is here: http://care.diabetesjournals.org/content/29/7/1638.full
A Strong Dose-Response Relation Between Serum Concentrations of Persistent Organic Pollutants and Diabetes
---------------------------
One more reason to eat organic meat!
Monica's Response: very interesting! But, again, wouldn't it make more sense to divide the meat into "fatty" and "lean" rather than "red" and "white"?
.
.
Posted by: Ron | Oct 31, 2009 2:28:54 AM
Monica and other professionals, you can get continuing education credit for learning about a vegan approach to diabetes--which has been shown in clinical studies to reverse it.
Posted by: Ron | Oct 31, 2009 1:42:17 AM
Here's some info about the effectiveness of a vegan diet in reversing type 2 diabetes:
Posted by: Dave | Oct 30, 2009 2:34:47 PM
@Mara Dolan,
All fat amplifies the insulin response when consumed with either protein or carbohydrate. This is physiologically normal, and should not cause cravings. Insulin by itself acts on the brain to suppress appetite.
Palmitic acid induces some level of insulin resistance. This is probably true of all fats as well, but palmitic acid has gotten studied. Again, this is a normal physiological response.
Problems should only occur if some environmental stimulus (or disease, like insulinoma) drives insulin outside of the normal range. Eating large quantities of refined carbohydrates appear to do this. Carbohydrate cravings should only be manifested in a situation where the brain perceives glucose levels as too low.
We have multiple examples of people eating both high-fat (Inuit) and high-carb (Kitavans), but low glycemic. Neither population suffers from metabolic issues *until* they adopt the Western diet.
Posted by: Rosmerta | Oct 30, 2009 1:42:11 PM
@TTC
The timeline was a bit condensed - I went vegan on the advice of my doctor when first diagnosed with high cholesterol a number of years ago. It didn't help, so I went omnivore again.
I was diagnosed with diabetes in 2005 and was doing well on diet (basically Mediterranean, definitely including red meat) and exercise, but had a really rough 6 months healthwise and started drinking soda as a comfort food - 8-12 oz. per day, for about 6-8 weeks. My glucose, which had been under good control, went up, and after a month of avoiding soda my blood glucose is still high and carbs send it up much higher than before my binge. I am about to start metformin, which I was trying to avoid through strict control.
I do understand nutrition more than most - have dealt with multiple shifting food allergies/intolerances for years and changed my diet according to changing circumstances, not fad diets but healthful changes. However, after coming back from acute kidney failure, physical rehabilitation from an acute fibromyalgia flare, a shoulder injury and the development of inflammatory osteoarthritis all within 6 months, I just needed that comfort of caffeine-free soda for a few weeks. When I woke up to what it was doing to me I stopped. But my point was that given the sequence of events, it's very hard for me to believe that meat, red or otherwise, had anything to do with the development of my Type 2 or its worsening.
Posted by: Mara Dolan | Oct 30, 2009 1:08:05 PM
Red meat is high in saturated fat. Saturated fat raises insulin.
Elevated levels of insulin cause food cravings which lead to increased consumption of high glycemic foods.
High glycemic diets cause type 2 diabetes.
Posted by: Dave | Oct 30, 2009 10:28:40 AM
@Greg,
I don't know if I've seen specific human studies on omega-6 and insulin resistance, though I believe it's coupled to insulin via delta-6-desaturase. The epidemiological association between excess dietary omega-6 and diseases of insulin resistance is pretty consistent as well (see e.g. http://www.ncbi.nlm.nih.gov/pubmed/18804984).
Western vegetarians probably do have lower Type II diabetes rates. They also tend to be much more health conscious than those eating the SAD, eat less refined foods across the board, exercise more, etc. (a great example of the adherer effect). My point was that at the biochemical level it probably matters little whether or not you're a vegetarian. You can induce high blood sugar and high triglycerides either way (something I know from personal experience with vegetarianism).
One other point is that "insulin resistance" has become something of a 4-letter word. But the insulin resistance in response to high blood levels of fat is normal physiological response. In a healthy individual, elevated fatty acids indicates you haven't had a dietary source of glucose in awhile (like while you're sleeping) and that your body is burning fat. "Insulin resistance" in this case just means your cells that can (most of them) are using fat and sparing glucose for those cells (like some types of brain cells) which require glucose.
Several hours after eating a meal with high glycemic load, you liver converts excess glucose to saturated fat. Maybe not a big deal, unless you follow that meal with another high glycemic load in the face of the resulting insulin resistance. Now you need more insulin to clean up the mess, are generating even more fats from the sugar (since your glucose stores would still be topped off), and away you go.
Suppose, on the other hand, that you eat high-fat and low-glycemic (as hominids did for a few million years before getting "civilized"). Then you'd *want* that insulin resistance to keep your blood sugar stable. In this case, without constant glucose challenges, insulin resistance is the healthy state (and of course this level of insulin resistance is small compared to someone with Type II diabetes, which represents and extreme endpoint).
Posted by: Georgie Fear RD | Oct 30, 2009 10:04:13 AM
Thanks Monica for the interesting topic. From the research I've reviewed, it is my opinion that the amount and glycemic quality of carbohydrates in the diet are most influential in the development of type 2 diabetes. Thus I agree with your reservations about this red meat/white meat dichotomy in terms of T2DM risk. Its tempting to think that other factors must be at work, but I havent read the study to see what was controlled for. (yet)
I also believe that secondary to carbohydrate intake, bodyweight and obesity have a lot to do with the development of chronic inflammation, oxidative stress, insulin resistance, and progression to T2DM.
So perhaps "white meat eaters" are consuming fewer calories overall or maintaining lower body weights. Do you know if the study controlled for obesity?
Georgie Fear RD
www.askgeorgie.com
Posted by: TTC | Oct 29, 2009 9:22:04 PM
@Rosmerta - I don't mean to be rude, but if you went vegan in an attempt to lower cholesterol (and presumably improve your overall health), why did you include hefty amounts of soda in your diet? What made you think that soda would lower your cholesterol/make you healthier etc?
Posted by: greg | Oct 29, 2009 6:51:50 PM
@Dave
Have you found human studies that suggest dietary omega-6 contributes to insulin resistence?
While there are lots of studies identifying saturated fats, including SFA palmitic acid, as contributing significantly to insulin resistance, from what I have seen, PUFAs, n-6 and n-3, are thought to improve it.
I can't speak to this study (because I'm not going to pay to read the whole thing and it is not clear from the abstract/free preview) but there certainly have been multivariate studies that have found that SFAs increase insulin resistance independent of carbs. That said, maybe if you take your SFAs but don't take carbs you'll be ok?...
Where do you find data suggesting that vegetarian Indians have a higher rate of Type II diabetes?
I'd be curious to look at that. Every study I've seen on western vegetarians shows them as having lower rates of diabetes than non-vegetarians.
FYI - South Indians also have a lot of saturated fat in their diet in the form of ghee (butter) and cheese (mattar paneer - peas and cheese - is my fav!) to go along with low-fiber, hi-GI carbs. Not a good combination...
Posted by: Joseph Gentzel | Oct 29, 2009 5:08:05 PM
Thanks Monica
Some good logic in an area that the media loves to bash.
I join you in eating red or any color meat; using good sense and moderation as the key, but is that not true for everything?
Posted by: Rosmerta | Oct 29, 2009 4:44:54 PM
What seems to have propelled me into developing Type 2 diabetes is not eating a lot of meat, but being vegan for 2 years and drinking lots of HCFS-sweetened soda. I recently went off the rails for about 6 weeks and had a soda a day, and my BG numbers are way higher even after a month of penance. Meat consumption was obviously nil during the 2 vegan years (an attempt to get cholesterol down), and moderate to low thereafter. Metabolism is a strange and complex thing, but I wouldn't rush to blame red or white or the other white meat for type 2 diabetes. Otherwise there would have been a whole heck of a lot more of it in the 50s and 60s when meat was at the center of the dinner plate.
Posted by: Monica Reinagel | Oct 29, 2009 3:29:38 PM
@Darya,
so, is meat just a marker for saturated fat? If that's the case, it would make more sense to divide meats into "fatty" and "lean" than into "red" and "white" wouldn't it?
Posted by: Dave | Oct 29, 2009 2:11:30 PM
I'll take a crack at explaining this association.
Most people in Western societies eat a lot of carbohydrates with their meat.
The meat is generally grain fed, and higher in fat, particularly palmitic acid and omega-6. Both of these appear to increase insulin resistance. Add to that the high carbohydrate load, probably including a lot of fructose (which makes the liver insulin resistant), and I suspect you have a recipe for inducing a vicious cycle of increasing insulin resistance.
The same thing *could* probably be accomplished on a vegetarian diet, if one ate a lot of high-glycemic foods, as the excess blood sugar also gets converted to palmitic acid. Most high-glycemic foods are highly processed, and also contain high fructose corn syrup and vegetable oil. Apparently vegetarians in India eat both high on the glycemic index and use a lot of vegetable oil (I don't know about fructose), and experience higher rates of Type II diabetes than Indian non-vegetarians.
"Meta-analysis" is a synonym for what comes out of the back end of a cow, whether you feed it grass or grain :-)
