The glycemic index is a measure of the blood sugar response to a fixed amount of carbohydrate from a particular food. For example, white bread has a high glycemic index because it raises blood sugar more than another food containing the same amount of carbohydrate, say, lentils. Since chronically elevated blood sugar and its natural partner, insulin resistance, are part of the metabolic syndrome, it made sense that the glycemic index would be a good predictor of the metabolic effect of a food. I believed this myself for a long time.
My faith in the concept began to erode when I learned more about the diets of healthy traditional cultures. For example, the Kitavans get 69% of their calories from high-glycemic index carbohydrates (mostly starchy root vegetables), with little added fat-- that's a lot of fast-digesting carbohydrate! Overweight, elevated insulin and other symptoms of the metabolic syndrome are essentially nonexistent. Throughout Africa, healthy cultures make dishes from grains or starchy tubers that are soaked, pounded, fermented and then cooked. The result is a pile of mush that is very easily absorbed by the digestive tract, which is exactly the point of going through all the trouble.
The more I thought about the glycemic index and its relationship to insulin resistance and the metabolic syndrome, the more I realized there is a disconnect in the logic: elevated post-meal glucose and insulin do not necessarily lead to chronically elevated glucose and insulin. Here's what Dr. Mark Segal from Dr. Johnson's group had to say:
We suggest that the [glycemic index] is better aimed at identifying foods that stimulate insulin secretion rather than foods that stimulate insulin resistance. The underlying concept is based on the principle that it is the ingestion of foods that induce insulin resistance that carries the increased risk for obesity and cardiovascular disease and not eating foods that stimulate insulin secretion.
Well said! I decided to take a look through the literature to see if there had been any trials on the relationship between a diet's glycemic index and its ability to cause satiety (fullness) and affect weight. I found a meta-analysis from 2007. Two things are clear from the paper: 1) in the short term, given an equal amount of carbohydrate, a diet with a low glycemic index is more satiating (filling) than one with a high glycemic index, leading to a lower intake of calories. 2) this effect disappears in the long-term, and the three trials (1, 2, 3) lasting 10 weeks or longer found no consistent effect on caloric intake or weight*. As a matter of fact, the only statistically significant (p less than 0.001) weight difference was a greater weight loss in one of the high-glycemic index groups!
As I've said many times, the body has mechanisms for maintaining weight and caloric intake where they should be in the long term. As long as those mechanisms are working properly, weight and caloric intake will be appropriate. The big question is, how does the modern lifestyle derail those mechanisms?
Dr. Johnson believes fructose is a major contributor. Table sugar, fruit, high-fructose corn syrup and honey are all roughly 50% fructose by calories. Total fructose consumption has increased about 19% in the U.S. since 1970, currently accounting for almost one eighth of our total calorie intake (total sugars account for one quarter!). That's the average, so many people actually consume more.
Fructose, but not starch or its component sugar glucose, causes insulin resistance, elevated serum uric acid (think gout and kidney stones), poorer blood glucose control, increased triglycerides and LDL cholesterol in animal studies and controlled human trials. All of these effects relate to the liver, which clearly does not like excessive fructose (or omega-6 oils). Some of these trials were conducted using doses that are near the average U.S. intake. The effect seems to compound over time both in humans and animals. The overweight, the elderly and the physically unfit are particularly vulnerable. I find this pretty damning.
Drs. Johnson and Segal recommend limiting fructose to 15-40 grams per day, which is the equivalent of about two apples or one soda (choose the apples!). They also recommend temporarily eliminating fructose for two weeks, to allow the body to recover from the negative long-term metabolic adaptation that can persist even when intake is low. I think this makes good sense.
The glycemic index may still be a useful tool for people with poor glucose control, like type II diabetics, but I'm not sure how much it adds to simply restricting carbohydrate. Reducing fructose may be a more effective way to address insulin resistance than eating a low glycemic index diet.
*Here was the author's way of putting it in the abstract: "Because of the increasing number of confounding variables in the available long-term studies, it is not possible to conclude that low-glycaemic diets mediate a health benefit based on body weight regulation. The difficulty of demonstrating the long-term health benefit of a satietogenic food or diet may constitute an obstacle to the recognition of associated claims." In other words, the data not supporting our favorite hypothesis is an obstacle to its recognition. You don't say?
53 comments:
I really enjoyed reading this post! It's something I've been thinking a lot too.
Thanks!
Another great post!
I've been eating less fruit ever since I've learned that much of the fruit available to us now has been genetically modified for higher fructose content.
I don't each very much table sugar. However, the little I use I've been replacing with erythritol - which I tolerate well compared with other sugar alcohols, tastes great, and apparently it has no/low effect on insulin. Anyone know whether erythritol has any effect on insulin sensitivity??
Great post!
The glycemic index is notoriously inaccurate for people with diabetes. It is measured in people without diabetes who can usually disperse slow metabolizing carbohdyrates without seeing a spike since they have functional second phase insulin releases.
People with diabetes have failing insulin release--so their response to a food containing slow digesting carbohydrates will vary greatly from person to person. The less insulin they produce the more irrelevant the glycemic index value of the food in predicting its blood sugar impact.
People with diabetes who want to learn which carbohydrate-containing foods are safe for them, personally to eat would do better to follow the testing strategy outlined in my "Blood Sugar 101" flyer:
How to Lower Blood Sugar
Fructose is a separate issue. It doesn't appear on blood glucose tests. Instead, it goes to the liver and turns directly into fat. It is not possible to measure its impact on your body in a direct way the way you can measure glucose and we do NOT have research studies for fructose quantifying it's impact on diabetic complications the way we do for glucose.
Cutting out sugary drinks: fruit juices, spritzers, smoothies, lattes, and soda would probably would go a long way to helping otherwise normal people avoid the negative effects of fructose in the diet. That's where much of the fructose comes in.
Never trusted that glycemic index. But not my honey! Is wildflower honey less fructose than clover? Or.. just give it up already. At least I'm not one of the poor people steered toward agave! ugh.
Excellent post.
Jenny
That link didn't work for me
Our primate ancestors seem to have eaten a LOT of fruit. That makes it hard for me to believe that fruit is bad for us (GMO fruit aside -- I had not heard about that before).
I kept expecting as I was reading along for you to say something to the effect that fructose ingested "in [natural] context" is healthful, and it is only the "pure" form that is problematic.
Any thoughts along that line?
Jenny's link had a typo. Take out the t in flyter. Should have been flyer, I'm quite sure.
Super topic and post, Stephan! Now how about we all chip in for a TV spot to air right after those insane ads suggesting HFCS is just fine to consume? :-)
John,
Didn't mean GMO - I mean that old variety fruits (apples for example) were smaller and far less sweet. Almost all modern fruit has been bred to be larger, sweeter, etc.
John, there's a theory that since we've cultivated many fruits to be a lot sweeter and larger than they'd be in their original forms, we're getting more sugar from them now than our ancestors would have. Personally, I think it depends on the fruit and the region, and I'd be curious to know more.
My question is whether fructose that's bonded with glucose in a sucrose molecule affects us differently than fructose does in monosaccharide form.
Debs
Food Is Love/Seattle Local Food
Micawber,
I don't know about erythritol specifically, but I'm generally suspicious about unnatural foods.
Jenny,
Nice to see you on the blog!
Mess Talker,
I think honey and fruit are OK in moderation. Small amounts of fructose may actually be better then none at all.
John,
Some primates do eat a lot of fruit. That was a long time ago though, as our last common ancestor with chimps was 4-5 million years ago. The Homo genus branched off about 2 MYA, corresponding with a shift to more meat eating. Our closest recent relatives, the neanderthals, were carnivores.
I think the best indication of what diet we're "built for" is what modern hunter-gatherers eat. Many HGs do eat a fair amount of fruit. But they don't typically get as many calories form sugar as modern humans, and it's often seasonal.
I do think fruit is better than table sugar and HFCS, but it's more because of the vitamins and minerals than anything.
Nice speculations, but experiment is in order.
Fructarians tend to be skinny! Google around for "raw food diet" and you'll find lots of pictures of skinny people -- too skinny.
Back in grad school I had tried going high-starch as per the recommendations of Robert Hass (Eat to Win), in order to boost my endurance. I got fat for the first time since being a toddler. Admittedly, I did eat more fat than Haas recommended.
After getting fat and feeling crappy on such a diet, I discovered Anopsology -- eating by instinct. I went on a nearly all raw diet; the only food I cooked was meat. In other words I eliminated all cooked starches and ate a truly huge amount of fruit.
Lost 30 pounds in about a month. I got ripped, but I was too skinny. Finding raw foods which were satiating was impossible, and the social and economic costs were too high, so I quit. Also, I did start to get some blood sugar bouncing near the end.
----
In nature, most sugar is associated with acid, honey being an exception. Based purely upon my subjective response to sugar, I'd say that consuming acid makes a huge difference. My response to cakes or cookies vs. sugar in fruit very different.
I second deb's question! It's something I've been curious about. If stephan you don't know, does anybody else?
Debs and Scott,
I don't know if it affects us differently, but both forms are found naturally. Fruit typically contains fructose, glucose and sucrose (50% fructose, 50% glucose). Honey is mostly monomers, table sugar is sucrose.
Some people have a hard time digesting sucrose, so honey would be better for them. Digesting sucrose requires the sucrase enzyme, which some people don't secrete much of. This can be genetic or due to intestinal damage (celiac).
Some fruitarians may be skinny, but not all. The only people I know who would come close to being "fruitarians" are overfat people who eat an enormous amount of fruit, some veggies, very little or no animal fat or animal products, and primarily tofu or processed soy juice for protein.
One is male and he is the most overfat (quite obese actually), though he is quite active and seems relatively fit. His wife eats similarly, has gained weight in the past few years and suffers from a lot of menopause hot flashes.
The others I know are all female somewhat overfat (love that term) but not yet obese and they all exercise a lot and go on and on about how great it is to eat so much fruit and that everyone should eat that way. Hmmm.
CSM,
The experiments have already been done. In humans, fructose feeding increases insulin resistance, fasting uric acid and triglycerides in a matter of weeks. I'm not convinced it causes weight gain, at least in the short term, although some animal studies suggest it does.
You could make the argument that fruit is different, which is possible. It would be interesting to see the trials repeated with fruit. I think the controlled trials are still useful because they are directly relevant to the form of fructose most people consume: refined (in the form of sucrose or HFCS).
Personally, too much sugar in any form makes me feel exhausted, whether it comes from fruit or candy.
Isn't a high fructose diet the standard protocol for inducing insulin resistance > diabetes in lab rats?
Hi Micawber,
Fructose feeding causes insulin resistance and liver damage in rats, but I don't believe it reliably causes diabetes. Rats are pretty hard to make diabetic. Typically researchers use genetic mutants like the Zucker rat or drugs.
Anna: are the "fructarians" you know raw fructarians or do they cook their fruit?
The raw foodists that I have met personally ranged from thin to scary thin. Granted, these were not fructarians, but fruit was a significant part of their diet. Juiced vegetables tend to be big among raw foodists these days.
Have a look at the picture here:
http://genefitnutrition.com/about.html to see the raw foodist look. (These writers are attempting a pre-paleo diet, if you will.)
----
Stephen: experiments feeding fructose are a better simulation of the soft drink diet, agreed. But a high fructose diet in the form of lots of raw fruits and a few raw veggies is very much conducive to weight loss. Maybe some of the sugar stays caught in cell membranes or some such, but I think fruit acids play a large role.
Anna: are the "fructarians" you know raw fructarians or do they cook their fruit?
I've only seen them eat on "their turf" and it was raw fruit and raw veggies (I've eaten a number of times in their homes). Everything was delish and very nicely prepared.
I spent an entire weekend with one of the women, who is experiencing some weight gain and hot flash issues, while we attended an out of town workshop and stayed at a place owned by her relatives; while I had no problem with the fresh fruit and veggies she preferred and provided (I resisted the tofu and soymilk), I really, really missed eating proteins and fats, and was really hungry the whole weekend. I wish I had known in advance to pack provisions. The only relief was when we took a lunch break during the second day of the workshop; I headed out to a nearby restaurant for sustenance.
On fructose and diabetes.
Glucose promotes fat storage indirectly through insulin and by inhibiting fat oxidation.
Fructose does not need insulin to promote fat storage.
Fructose is implicated in IBD which sets the body up for inflammation and worsens digestion.
Fructose may increase hunger.
Excess Omega 6 compounds the situation by promoting oxidative stress, inflammation, and pushes insulin into a blocked loop.
This link is thought provoking and seems to make sense.
http://www.second-opinions.co.uk/fructose-diabetes.html
Robert Brown
Author Omega Six The Devils Fat
Good post, as usual.
I mostly eliminated fructose from my diet several years ago, initially because fructose is the sugar that makes you fat. Since then, in my ongoing readings, I've learned of many of the other ill-effects of fructose. Here's a good summary:
http://www.thorne.com/altmedrev/.fulltext/10/4/294.pdf
One of the worst features of fructose consumption is that it leads to greatly accelerated advanced glycation end-products. Perhaps this plays a role is insulin resistance, but seriously degrading cellular function.
Anna, perhaps the weight gain is due to the soy she consumes? Soy depresses thyroid? She's menopausal too.
The raw fruit eaters would be depleting their muscle mass. So their skinniness is due to low calories causing fat loss and wasting of muscle so they look smaller.
I agree with everyone - this is an excellent post! I've been coming to the same conclusions also. In my experience, sweets were quite addicting and I wonder if it may be mainly the fructose component that fosters addiction? I guess I'll have to add some dextrose to my food for a week and see if I get addicted again :)
Thanks to Peter (Hyperlipid) for providing the link that allowed me to find your excellent blog. Maybe I can retire from blogging now :)
Great thought provoking post. I am glad I dropped my fruit intake down to ~1 serving per day.
Scott,
Thanks for the article, that was interesting.
Bryan,
Retire from blogging? You just got started! I checked out your blog and it looks good.
I wonder if something has changed how we react to fructose?
Scott, my guess is that our metabolism of fructose has not changed much over time, but the availability of fructose has changed radically with the advent of refined sugars. I'm also guessing that fructose has addicting qualities that plants have exploited to attract animals to eat their fruit and disperse their seeds. Most people seem become addicted to sweets containing fructose, and very often, these are the ones who become overweight.
Oddly, however, I still eat small amounts of fruit but don't feel addicted. Whereas, for many years I was addicted to sweets with refined sugar, as indicated by regular cravings for sweets ... until I broke my addiction not quite three years ago. I no longer crave any sweets, but eat bananas and grapefruit mainly to get some natural vitamin C and potassium (though I'm not entirely convinced this is necessary for optimal health).
Thoughts are percolating.
Stephan, your blog is the most interesting, most consistently informative and thought provoking blog. I am always excited when a new post shows up.
Your reference to the Kitavans and their non-low-carb but very healthy culture is consistently interesting.
I know that starches break down into sugars in your digestive system. I wonder if different starches break down into different sugars? Or, do they break down into different sugars based on the cooking method?
EG roasting a sweet potato
vs boiling a russet potato
Are some dietary starches better than others, related to fructose load?
Count me as another big fan and also as a third person who's interested in whether there is a difference in consuming fructose directly or metabolizing it from sucrose. Stephen, if you learn any more about this, I'd appreciate a post expanding on your answer above
This reminds me, Stephan, to ask how those of us who enjoy and learn so much from your blog can "pay back" a bit, perhaps with a contribution to your website costs?
I think you should seriously consider a Paypal donor button! I'd contribute!
Ed,
Thanks. Anything made from starch will ultimately digest into glucose. I don't think the cooking method affects that.
Starch is made of 100% glucose polymers. The corresponding fructose polymer is inulin, found in sunchokes, burdock and other things related to sunflowers. It's not well digested in humans, so it tends to produce gas.
In general, if it doesn't taste sweet, it doesn't contain fructose. The only exception I'm aware of is vegetables that contain inulin, but there aren't too many.
Susan,
Blood fructose spikes higher with fructose monomers than with sucrose (given the same amount of total fructose), but it may stay elevated longer with sucrose. I think sucrose just slows down digestion a bit because it requires an extra enzymatic step. That's under lab conditions though; who knows if the differences would be meaningful in the context of a meal. There's a nice graph in the link Scott posted.
My feeling is, it's probably best to get fructose in the context it was meant to be delivered: fruit or honey. We've been eating them for a long time, but we just started drinking soda!
Anna,
Thank you very much, that's kind of you. I'll consider it. I'm enjoying having the blog be a community service right now, but I am keeping in mind the possibility of having something related to this be part of my employment/revenue someday. I doubt I'll ever make it pay-only, because I'd like to keep the info as accessible as possible. I don't know how my career will develop, but it would be great to have something like this be a part of it. The blog has been really rewarding.
Just a quick look at Wikipedia shows a rat study where rats with a diet of 1/3 sucrose first saw elevated blood levels of triglycerides, which induced visceral fat and ultimately resulted in insulin resistance.
http://www.ncbi.nlm.nih.gov/pubmed/15157941?dopt=AbstractPlus
Brock,
That looks like a very interesting study. I think I'll read the full text.
Thanks Stephan.
I'm T2 since 2005,trying to understand what is hapening.I find it very reassuring that you as a doctoral candidate in neurobiology can find the time to put such a lot of good information on the internet :) I came to exactly the same conclusion as you, correct me if I'm wrong.In short : we ingest too many calories because a mechanism beyond our control makes us eat.This results in obesity.The obesity causes all kind of trouble.
The human body is a survival machine and food intake is far too important to leave it to the conscious mind.A zillion signals from hormones, transcription factors, nerve signals from the stomag and intestine are all integrated in the Hypothalamus, our lizard brain.The hypothalamus can be regarded as a "local" firm-ware programmed processor.It also has it's own setpoints.Our conscious brain, the neocortex, has no control over it.If you say to someone : "you should stop eating" then you are not talking to the man in charge...You are talking to the neocortex, not to the hypothalamus.I know very intelligent but fat people.They know that they won't die from hunger.They know that they will get in trouble.They still keep eating.I know an endocrinologist who smokes.People eat because they are hungry all the time.The wrong hunger signal should be treated by the dokter.The wrong hunger signal is just as bad luck as a broken leg.This will not be an easy task for science because the energy homeostasis system is very complicated.I saw articles where the wrong hunger signal was attributed too polution by bis-phenol-A.Here is one where fructose directly blunts the leptin signal to the hypothalamus.The man in charge....Both bis-phenol-A and fructose (from high corn fructose, and we are up to our noses in high corn fructose) increased in our environment during the obesity tsunami.
http://www.ncbi.nlm.nih.gov/pubmed/18703413?dopt=Citation
Am J Physiol Regul Integr Comp Physiol. 2008 Nov;295(5):R1370-5. Epub 2008 Aug 13.Related Articles, Links
Fructose-induced leptin resistance exacerbates weight gain in response to subsequent high-fat feeding.
It has been suggested that increased fructose intake is associated with obesity. We hypothesized that chronic fructose consumption causes leptin resistance, which subsequently may promote the development of obesity in response to a high-fat diet. Sprague-Dawley rats were fed a fructose-free control or 60% fructose diet for 6 mo and then tested for leptin resistance. Half of the rats in each group were then switched to high-fat diet for 2 wk, while the other half continued on their respective diets. Chronic fructose consumption caused leptin resistance, while serum leptin levels, weight, and adiposity were the same as in control rats that were leptin responsive. Intraperitoneal leptin injections reduced 24-h food intake in the fructose-free group (73.7 +/- 6.3 vs. 58.1 +/- 8 kcal, P = 0.02) but had no effect in fructose-fed rats (71.2 +/- 6.6 vs. 72.4 +/- 6.4 kcal, P = 0.9). Absence of anorexic response to intraperitoneal leptin injection was associated with 25.7% decrease in hypothalamic signal transducer and activator of transcription 3 phosphorylation in the high-fructose-fed rats compared with controls (P = 0.015). Subsequent exposure of the fructose-mediated, leptin-resistant rats to a high-fat diet led to exacerbated weight gain (50.2 +/- 2 g) compared with correspondingly fed leptin-responsive animals that were pretreated with the fructose-free diet (30.4 +/- 5.8 g, P = 0.012). Our data indicate that chronic fructose consumption induces leptin resistance prior to body weight, adiposity, serum leptin, insulin, or glucose increases, and this fructose-induced leptin resistance accelerates high-fat induced obesity.
PMID: 18703413
Thx again for sharin
Gys
Hi Gys,
That's the basic idea. I agree the conscious mind is not really the "man in charge" of caloric intake, expenditure etc, barring a heroic effort on the part of the conscious.
One other point I'll add is that the body shuts down its metabolic rate at the same time as it seeks more calories, in response to the modern lifestyle. We've flipped the switch to put ourselves in "storage mode".
Have you seen the "paleolithic diet" trial by Staffan Lindeberg where he essentially saw a diabetes reversal in 100% of subjects? Might be something to think about. I posted a series on it a while back called "paleolithic diet clinical trials".
Hi Stephan,
I agree.I shall speak for myself.I was in a constant "overfed state" and thus in a constant "storage mode".The store was never used.My mitochondria forgot how to burn fat.I trained them again, I think, by less calories and more exercise.Fasting now and then means that my glycogen store is empty.Exercise in that condition means that my body has no other choise than burning fat... :) I know both Lindeberg and Cordain.I tried to apply the consequences of this theory to myself and for me it works : lower insulin resistance, better cholesterol values, lower fasting blood glucose.Here is one by Cordain :
Mayo Clin Proc. 2004 Jan;79(1):101-8.
Cardiovascular disease resulting from a diet and lifestyle at odds with our Paleolithic genome: how to become a 21st-century hunter-gatherer.
O'Keefe JH Jr, Cordain L.
Our genetic make-up, shaped through millions of years of evolution, determines our nutritional and activity needs. Although the human genome has remained primarily unchanged since the agricultural revolution 10,000 years ago, our diet and lifestyle have become progressively more divergent from those of our ancient ancestors. Accumulating evidence suggests that this mismatch between our modern diet and lifestyle and our Paleolithic genome is playing a substantial role in the ongoing epidemics of obesity, hypertension, diabetes, and atherosclerotic cardiovascular disease. Until 500 generations ago, all humans consumed only wild and unprocessed food foraged and hunted from their environment. These circumstances provided a diet high in lean protein, polyunsaturated fats (especially omega-3 [omega-3] fatty acids), monounsaturated fats, fiber, vitamins, minerals, antioxidants, and other beneficial phytochemicals. Historical and anthropological studies show hunter-gatherers generally to be healthy, fit, and largely free of the degenerative cardiovascular diseases common in modern societies. This review outlines the essence of our hunter-gatherer genetic legacy and suggests practical steps to re-align our modern milieu with our ancient genome in an effort to improve cardiovascular health.
PMID: 14708953
Thanks for sharing
Gys
I recently read a british article that said to get 125g of fructose from fruit it would require that you eat 4 kg of strawberries, 1.5 kg of apples or 2.3 kg of cherries.
http://www3.interscience.wiley.com/journal/121517110/abstract?CRETRY=1&SRETR
kinds of puts it into perspective.
eat fruit no pop!
I saw this on the mayo Wellness site regarding HFCS:
"High-fructose corn syrup is a common sweetener and preservative. High-fructose corn syrup is made by changing the sugar (glucose) in cornstarch to fructose — another form of sugar. The end product is a combination of fructose and glucose. Because it extends the shelf life of processed foods and is cheaper than sugar, high-fructose corn syrup has become a popular ingredient in many sodas, fruit-flavored drinks and other processed foods.
So far, research has yielded conflicting results about the effects of high-fructose corn syrup. For example, various early studies showed an association between increased consumption of sweetened beverages (many of which contained high-fructose corn syrup) and obesity. But recent research — some of which is supported by the beverage industry — suggests that high-fructose corn syrup isn't intrinsically less healthy than other sweeteners, nor is it the root cause of obesity.
While research continues, moderation remains important. Many beverages and other processed foods made with high-fructose corn syrup and other sweeteners are high in calories and low in nutritional value. Regularly including these products in your diet has the potential to promote obesity — which, in turn, promotes conditions such as type 2 diabetes, high blood pressure and coronary artery disease."
Yet one poster on your site has a link to Mayo clinical research indicating that it indeed has negative consequences overall for health.
Besides the disclaimer that some of the HFCS research was paid for by the industry, I find it interesting that it is used to extend the shelf-life of food, much like hydrogenated oils. that by itself is a red flag to me.
Looks like the line of thinking that "it's not the carbs, it's the fructose" might be older than we thought.
Here's a study from 2005:
http://www.nutritionandmetabolism.com/content/2/1/5
It's the first google result for fructose metabolism
Quote from the abstract:
An important but not well-appreciated dietary change has been the substantial increase in the amount of dietary fructose consumption from high intake of sucrose and high fructose corn syrup, a common sweetener used in the food industry. A high flux of fructose to the liver, the main organ capable of metabolizing this simple carbohydrate, perturbs glucose metabolism and glucose uptake pathways, and leads to a significantly enhanced rate of de novo lipogenesis and triglyceride (TG) synthesis, driven by the high flux of glycerol and acyl portions of TG molecules from fructose catabolism. These metabolic disturbances appear to underlie the induction of insulin resistance commonly observed with high fructose feeding in both humans and animal models. Fructose-induced insulin resistant states are commonly characterized by a profound metabolic dyslipidemia, which appears to result from hepatic and intestinal overproduction of atherogenic lipoprotein particles. Thus, emerging evidence from recent epidemiological and biochemical studies clearly suggests that the high dietary intake of fructose has rapidly become an important causative factor in the development of the metabolic syndrome.
Ed,
Looks like an interesting article. I think the idea has been around for a while.
Have there been any studies to show that a high amount of fruit consumption (whole fruits, not juices) can cause insulin resistance and diabetes? I eat a lot of fruit. It is common for me to eat a pint of strawberries, a peach, a nectarine, an orange, an apple, a banana, and a couple plums, and that's my food for the work day, along with water. Somtimes I also eat raw celery, zucchini, carrots, and/or a whole avocado (all by itself) during the workday, instead of some of those fruits. Then in the evening I eat whatever, maybe some Indian food or Greek food or Japanese food (all vegan), but generally I go home and make my favorite dinner, which is: tortillas with grapeseed oil vegenaise and stuffed with fresh raw cabbage, leafy greens like spinach, romaine, and red lettuce, hemp nuts, alfalfa sprouts, etc. Plus some tortilla chips and spicy salsa. And maybe some hummus. And lots of water. I don't drink anything besides water.
Well, that's my typical diet. I'm 34 years old, I run and walk several miles a day, and I dance in the evenings, so I'm pretty active. I'm concerned about diabetes because it runs in my family, and my fasting blood sugar is 89. Isn't that kind of high for someone my age? Here is my cholesterol panel.
CHOLESTEROL 167
TRIGLYCERIDE 59
HDL 54
LDL CALCULATED 101
Do you think that all the fresh fruit I'm eating could be causing me to have insulin resistance and potentially I could be on the way to diabetes? I love eating fruit, and I feel great, but I'm worried about my blood glucose level being kind of high.
Thank you for maintaining this thoughtful blog on nutrition and medicine. Thanks in advance for your input!
Just curious, brightstar. How are your teeth and gums?
Hi Brightstar,
I'm not aware of any studies showing that eating a lot of fruit causes insulin resistance and diabetes. I don't think it's been tested. My feeling is that when it comes to metabolic effects, sugar is sugar, and eating too much in any form probably isn't good. But I don't have any data to back that up so it's just speculation.
If I can guess based on your cholesterol values, you are not insulin resistant. You also have low triglycerides, which is not what I would expect in someone who's suffering the adverse effects of eating too much sugar.
A fasting glucose of 89 is no problem. But fasting glucose is the last thing to deteriorate if you're becoming diabetic. Better to get a glucose challenge done or buy a glucose meter and see what your post-meal values are if you're concerned. My guess is that you will have normal values.
Hi, I've just come across your blog - fabulous - and did a quick search for fructose content of foods.
Here's a link to the GoogleBooks section of The Sugar Fix By Richard J Johnson, Timothy Gower with pretty good tables.
http://books.google.com/books?id=4AGnJI-9yqcC&pg=PT372&lpg=PT372&dq=fructose+content+of+foods&source=bl&ots=yqBXkTgkLN&sig=N2shQfZI0trC1qTiKItGSuyeX9k&hl=en&ei=mrFkSp6_DZTeMe2NjfgB&sa=X&oi=book_result&ct=result&resnum=2
Just wondering how you would go about eliminating fructose for two weeks, as most veggies also have it; would I mostly be eating protein and fats?
Just wondering how you would go about eliminating fructose for two weeks, as most veggies also have it; would I mostly be eating protein and fats?
I stumbled across a paper on sugars and AGEs (advanced glycation endproducts) a few months ago. Fructose and galactose were indicated as being much more likely to damage proteins in cooking and in the body. It's a pretty interesting read. He asserts that AGEs can be linked to a number of chronic and age-related diseases.
http://andersonclan.us/andersonclan_top/ages.html
The editorial that provoked this post is available in full.
http://www.ajcn.org/cgi/content/full/88/5/1189?etoc
Stephen, might want to update your post with the full text link?
I just printed it out, I'm taking it to my farmer's market, there's a guy there marketing sweets saying they're safe for diabetics because they're made with agave. Yikes.
Is this true? I guess it depends on the person's preference.
Low Glycemic
Great post.
I had the privilege of hearing Dr Richard Johnson speak at a conference in the UK in September 2009. The conference was called "Fructose: the lipogenic carbohydrate".
The clear message I took away was - fructose (uniquely as a sugar) goes to the liver to be metabolised, where it can be turned to fat. The glucose/fructose combination that is table sugar and/or HFCS is a particularly efficient fat storing combination, as the fructose goes to the liver to be turned to fat and the glucose induced rise in insulin enables the fat to be stored.
I have done a couple of articles in the UK national newspapers on the myth of 5-a-day and you would have felt the shock waves in the USA! General outrage that anyone should dare suggest fruit is less than the best thing since sliced bread (ha ha). It's fine to eat if you want a fatty liver and a fatty body - meat from animals grazing on fast growing grass for me please!
Keep up the great work - I often see your posts - just the first one I've commented on.
Zoe Harcombe
I watched this video which shows the terrible effects of fructose on our bodies: http://www.youtube.com/watch?v=dBnniua6-oM
The video does come to mention that fructose found in fruits is acceptable because of the nutrients and fiber that come packaged with the fructose.
However, fructose should be consumed in moderation even from natural sources because it is a toxin.
You have to consider that our ancestors got much less fruit than we do now due to growing climates and regions. Fruit was not always in season, did not grow as large and plentiful as it does now with modern farming techniques and GMO.
Avoid fructose! Aim for the 15-40g per day that mentioned and no more. The video blew my mind when it came to fructose.
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