Why Sugar Is Bad For You–A Summary of the Research

fatty liver on couch watching tv surrounded by empty fructose cans

Type “is fructose bad for you” into your search engine and you’ll get a slew of articles telling you that fructose (aka fruit sugar) can cause diabetes, obesity, gout, fatty liver disease, and even cancer. If you believe the headlines, you might be worried that every time you bite into a banana, you’re hammering a big squishy yellow nail into your future fruity coffin. Yet public health officials, and even pediatric obesity specialist Dr. Robert Lustig, who goes so far as to call fructose a poison, continue to advise us to eat fruit. Confused? In this post, I provide a review of the science and clear, simple answers about the connection between fructose, glucose, and common health problems so that you have the information you need to make smart decisions about your health.

I put all of these diseases in a single blog post not to overwhelm you, but because they belong together. Although these conditions seem very different on the outside, as you’re about to see, they are actually just different faces of the same basic underlying metabolic problem: insulin resistance. You’ll also quickly discover that all kinds of sugar are risky when it comes to your health, and that fructose is probably the least of your worries. [Note: this article is part of a 5-part series on sugar and health. To begin with article one, see Has Fructose Been Framed?]

Ok, so let’s get to the bottom of these, once and for all.

Note: Because fructose malabsorption differs metabolically from the above diseases, I decided to cover it in article four of this series, instead of here as originally planned.

Q:  Does fructose cause TYPE 2 (“adult-onset”) DIABETES?

A:  There’s no evidence that reasonable amounts of fructose increase risk for diabetes more than other sugars do. Excessive intake of sugars of any kind can lead to high blood glucose levels and type 2 diabetes in susceptible people, but glucose raises blood glucose and insulin levels more than fructose does (except at very high doses), so glucose is arguably the more dangerous of the two sugars.

Type 2 diabetes is a disease characterized by “insulin resistance”, which can gradually lead to high insulin levels and high blood glucose levels. Insulin resistance means that your body has become less sensitive to the effects of insulin, a powerful hormone released after meals that tells your body what to do with the calories you eat. For example, after eating a meal, insulin tells muscle and liver cells to soak up excess glucose from your blood stream to keep your blood sugar from going too high. The most powerful trigger for insulin release is glucose (from sugars and starches); fructose does not directly stimulate insulin production.

If you eat too much sugar and/or starch too often, as most people do, your blood glucose will spike frequently and your body will have to release lots of insulin over and over again to deal with those glucose spikes. Eventually your cells can become so accustomed to insulin spikes that they become less responsive to insulin. If your cells become numbed to insulin’s storage signals, they won’t be able absorb extra glucose from the bloodstream very well, and your blood sugar could stay too high for too long after meals. In response, the body releases even more insulin to try to get cells to respond better. One result of this vicious cycle can be type 2 diabetes, a disease marked by high blood sugar and high insulin levels. I highly recommend this wonderful video of Dr. Andreas Eenfeldt interviewing kidney specialist Dr. Jason Fung explaining why it makes no sense to treat type 2 diabetes with insulin. 

Excess consumption of sugars in general is well-established as a major risk factor in the development of insulin resistance, but is there quality evidence to suggest that fructose in particular is any more dangerous than any other sugar in this regard? Does fructose increase fasting insulin, fasting glucose, or insulin resistance more than glucose does?

It depends on who you ask and what kinds of doses we’re talking about.

It turns out that low to moderately high amounts of fructose are no worse than glucose and often are superior to glucose when it comes to these metabolic markers in human studies.1)Livesey G 2009 J Nutr 139(6):1246S-1252S 2)Cozma AI et al 2012 Diabetes Care 35:1611-1620 3)Sievenpiper JL et al 2014 Curr Opin Lipidol 5:8-19 That is to say that fasting insulin, fasting glucose, hemoglobin A1C (a measure of blood sugar over time) and insulin resistance often look better when people consume fructose than when they consume glucose. This makes sense because it is well-known that glucose is a far more powerful trigger of blood sugar and insulin spikes than fructose.

However, at very high doses (more than 100 grams per day) fructose actually starts to look a little worse than glucose.4)Reiser S et al 1979 Am J Clin Nutr 32(11): 2206-16 5)Stanhope 2009 J. Clin. Invest. 119:1322–1334 6)Livesey G 2009 J Nutr 139(6):1246S-1252S The fact that fructose behaves so differently at very high doses is responsible for some of the confusion and disagreement among scientists about whether fructose is worse than glucose for diabetes or not.

There is no good scientific evidence to support the idea that sugar (which is a 50/50 mix of fructose and glucose) is metabolically any worse than starch (glucose) when appropriate amounts are considered.7)Gibson S et al 2013 Crit Rev Food Sci Nutr 53:591-614

However, just because fructose is no worse than glucose does not mean that either one of them is innocent. When it comes to the big picture and common sense recommendations to reduce your risk for diabetes, I wholeheartedly agree with the conclusions reached by Dr. James DiNicolantonio and colleagues in a recent review of the subject:

“There is no need for added fructose or any added sugars in the diet; reducing intake to 5% of total calories (the level now suggested by the World Health Organization) has been shown to improve glucose tolerance in humans and decrease prevalence of diabetes and metabolic derangements that often precede and accompany it.”8)DiNicolantonio JJ et al 2015 Mayo Clin Proc 90(3):372-381


Type 2 diabetes is a disease of insulin resistance, which leads to high fasting insulin and blood sugar levels. Except at very high doses, glucose may actually be worse than fructose when it comes to diabetes risk. However, because much of the fructose we consume turns into glucose (see article one), it is wise to be careful with both of these sugars.

The sad truth is that diabetes is simply your body’s way of telling you that you can’t process carbohydrates anymore. The happy truth is that diabetes is a dietary disease, so it can usually be treated by changing what you eat. In article four I’ll provide lots of helpful advice about how to eat if you want to prevent or reverse diabetes.

Q:  Does fructose cause CANCER?

A:  There’s no evidence that fructose causes cancer, however it may play a role in the spread of the disease. Cancer cells require glucose, not fructose, for energy and survival. High blood glucose and insulin levels set the stage for cancer growth in the body, so individuals with insulin resistance, high blood sugar, and type 2 diabetes are at higher risk. There is some evidence to support the notion that fructose may make it easier for certain kinds of cancer to spread, but no cancer cell can live without glucose.

It is an undisputed fact that cancer cells are addicted to glucose, which is found in virtually all sweet and starchy foods.

Cancer cells need a LOT more glucose than healthy cells because they rely mainly on a process called “anaerobic glycolysis” to fuel their furious growth rate. This means that instead of using oxygen to burn glucose for energy (aerobic glycolysis) like most healthy cells do, they ferment glucose into lactic acid for energy. Fermentation is very inefficient, so cancer cells demand high amounts of glucose to stay alive. [To learn more about how cancer cells operate, please see my series What Causes Cancer?]

Malignant cancer cells display high numbers of glucose transporters on their surfaces; without these special sugar transporters, glucose molecules would not be able to enter cancer cells from the bloodstream.

The more glucose you have in your bloodstream, the happier cancer cells are, so it makes perfect sense that high blood sugar levels would be a strong risk factor for cancer. Insulin resistance makes it hard to process glucose properly, so blood glucose levels rise. To make matters worse, cancer cells love high insulin levels, too, because insulin is a growth hormone that helps cells to grow. People with high insulin levels are at higher risk for cancer and have a worse prognosis once they develop cancer. High blood sugar and insulin levels are seen in people with insulin resistance, type 2 diabetes, and obesity, all of which belong to a group of related conditions collectively known as “metabolic syndrome.”

“Several studies indicate a strong association between MS [metabolic syndrome] and increased risk of cancer. The underlying mechanism of this association is not fully understood but, obesity, hyperglycemia, and hyperinsulinemic states are definitely involved… increased insulin levels in MS may lead not only to cancer initiation but also to its progression.”9)Mendonca FM et al 2015 Metabolism 64(2): 182-189

Okay, so when it comes to cancer, too much glucose in the blood is BAD. But what about fructose and cancer? Do tumor cells eat fructose, too?  Do cancer cells have enough fructose transporters on their surfaces to use fructose as an energy source?

Yes, some cancer cells do eat fructose.

In humans, certain types of cancer cells are capable of sporting significant numbers of fructose transporters on their surfaces (in addition to the required high number of glucose receptors): certain kidney cancer cells,10)Medina VV et al 2011 Oncol Rep 25(2):215-323 breast cancer cells, and certain brain cancer cells (gliomas).11)Calvo MB et al 2010 Int J Endocrinol 205357

The most recent review of the possible role of fructose in cancer was written by scientists at the University of Maryland and Boston University in 2012 and is quite good.12)Port AM et al 2012. Curr Opin Endocrinol Diabetes Obes 19(5):367-74

The authors of this review emphasize that it is well established that cancer cells love glucose and that excess glucose fuels cancer growth. However, they believe that fructose may be even more dangerous than glucose under certain circumstances. Almost all of the evidence used to support their argument against fructose comes either from epidemiological studies or from laboratory studies of specialized cell cultures under extreme conditions, but there are important exceptions that make their conclusions worth our attention:

  • Interestingly, there is an autopsy study showing that lung cancer tumor cells that had metastasized (spread) to the liver displayed higher numbers of fructose transporters than the primary (original) lung tumor cells that hadn’t left the lung.
  • Certain kidney cancer cells (clear cell renal carcinoma cells) display significant numbers of fructose transporters on their surfaces and have certain features that could make them more likely to metastasize (spread).
  • In the laboratory, if you put cancer cells in Petri dishes and feed them fructose instead of glucose, they grow much more slowly than they do on glucose, but they also produce smaller amounts of self-destructive lactic acid, and produce more protein (via the pentose phosphate pathway—see article one). The thinking is this: if a cancer cell can use fructose in addition to glucose, it might be able to survive better because it produces less lactic acid, and its ability to crank out proteins may make it easier for it to break free and travel (metastasize).

“Fructose appears to be a superior precursor for protein synthesis over glucose by enhancing flux through biosynthetic pathways. Together, glucose and fructose may act synergistically to support malignant growth. . . . Fructose may also promote a more aggressive phenotype in cancer cells and increase the likelihood of metastasis. Further research into the specific effects of fructose, together with glucose, at physiologic levels on malignant growth is warranted.”13)Port AM et al 2012. Curr Opin Endocrinol Diabetes Obes 19(5):367-74

Keep in mind that, unless you are in the habit of consuming high doses of fructose, most cancer cells are unlikely to be able to get much fructose out of your bloodstream, because remember that the liver sops up the vast majority of the fructose we absorb from foods and beverages before it has a chance to circulate (see article one), as long as the amount you consume is not too high. The only theoretical exception to this rule might be cancers of the digestive tract, which could be exposed to any fructose that you can’t absorb (we’ll look at fructose absorption problems in part four). Regardless, it appears that some cancer cells have come up with ways to exploit whatever fructose might be floating around and use it to their advantage.


Glucose is your bad boy when it comes to cancer because cancer cells require high amounts of glucose and insulin to take hold, grow, and thrive. This is why people with insulin resistance (high blood sugar and high insulin levels) are at higher risk for cancer and have a worse prognosis. However, some cancers, including breast, and certain brain and kidney cancers, may be able to use fructose to supplement their glucose habit and improve their ability to spread.

If I had cancer, I wouldn’t touch a carbohydrate with a ten-foot pole.

To learn more about cancer and nutrition, please see my series What Causes Cancer? or take a look at the new book Tripping Over the Truth: The Return of the Metabolic Theory of Cancer Illuminates a New and Hopeful Path to a Cure by Travis Christofferson.

To read my critique of the World Health Organization’s 2015 report claiming that red and processed meats cause cancer: WHO Says Meat Causes Cancer?

Q:  Does fructose cause OBESITY?

A:  There’s no evidence that reasonable amounts of fructose cause more weight gain than other sugars. However, too many sugary calories (of any kind) can absolutely cause weight gain, especially in people with insulin resistance.

An excellent 2012 review of human studies funded by the Canadian Institutes of Health Research14)Sievenpiper JL et al 2012 Ann Intern Med 156: 291-304 concludes convincingly that fructose does NOT cause weight gain compared to other sugars unless people are fed extra calories.

Yet, when high doses of fructose that add lots of extra calories to the diet are given to people, yes, some studies do show weight gain.

Given that only a tiny fraction of pure fructose is turned into fat (see article one), it’s unlikely that fructose on its own could be responsible for the obesity epidemic. HOWEVER, in real life, fructose and glucose are almost always eaten together. Fructose itself doesn’t cause much of an insulin response, but glucose certainly does, so when fructose and glucose are eaten together, insulin will spike and turn on fat building in the liver.  So it should be no surprise that big doses of fructose, when eaten with glucose, can make people fat.

But it’s important to point out that eating a big dose of glucose can make people just as fat.

A good example of a study that illustrates this point compared the effects of glucose drinks to fructose drinks on older overweight men and women. The sweetened drinks provided 25% of daily caloric intake (for a 2000 calorie/day diet, that would be 500 calories worth of fructose or glucose per day). Despite the fact that this study uses high doses of these sugars, it is interesting to note that, after 8 weeks, both glucose and fructose had caused the same amount of weight gain–more than 3 pounds,15)Stanhope KL et al 2009 J Clin Invest 119:1322-1334 suggesting that overeating either type of sugar can make you fat.

If you tend to gain weight around your middle, like an apple, you probably have insulin resistance

There is a consensus building that “central obesity” is a disease of insulin resistance.16)Booth A et al 2014 Horm Mol Biol Clin Investig 1:13-27 This means that if you tend to gain weight around your middle, like an apple, you probably have insulin resistance and therefore your body will tend to turn sugars and starches into fat very easily and have a harder time burning it for energy. [Take my quiz: How Carbohydrate Sensitive Are You?]

Fructose is no worse than glucose when it comes to weight gain. Overeating either of these sugars can make susceptible people fat. Sugars and starches raise insulin levels, which turns fat burning OFF and turns fat storage ON. It’s awfully hard to lose fat when carbs are literally telling your body to make more fat! It is not dietary fat that makes us fat. It is excess carbohydrate that can make us fat, because carbs turn on insulin and insulin tells our body what to do with the calories we eat. To read more about how carbohydrates make us fat, please see my carbohydrates page. I also recommend Gary Taubes’ book Why We Get Fat and What To Do About It.

Q:  Does fructose cause GOUT?

A:  There’s no evidence that reasonable amounts of fructose raise uric acid levels, let alone cause gout. High doses of fructose do raise uric acid levels more than glucose does, but high uric acid levels alone are not enough to cause gout.

Gout is a special type of arthritis marked by painful deposits of uric acid crystals in joints. Uric acid is a normal by-product of everyday cellular activity, so we all have uric acid in our blood all the time, whether we eat fructose or not, but some people have more uric acid floating around in their bloodstream than others do. High uric acid levels alone are not enough to cause gout—most people with high uric acid levels will never develop gout. It is unclear why some people are more prone to gout, but we do know that people with insulin resistance are at higher risk.17)Li C et al 2013 Curr Opin Rheumatol 25(2):210-216 This is partly because high insulin levels tell the kidney to hold on to extra uric acid instead of excreting it in the urine, the way it normally would.

Studies consistently show that very high doses of fructose do raise uric acid levels more than glucose does (see article one). However, when studies use a normal number of calories, fructose does not raise uric acid more than other sugars do.18)Wang Wang DD et al 2012 J. Nutr. 142: 916–923, Angelopolous TJ et al 2015 J Clin Hypertens 17:87-94 For more information about diet and gout, please see my post Got Gout But Love Meat?

Fructose doesn’t cause gout, but improving your insulin sensitivity could be very helpful in allowing your body to eliminate uric acid more efficiently, as well as reduce your tendency to develop inflammation. You’ll see how to improve insulin sensitivity in article four.

Q:  Does fructose cause FATTY LIVER DISEASE?

A:  There’s no evidence that reasonable amounts of fructose lead to fatty changes in the liver. However, excessive intake of sugar of any kind can leady to fatty changes in the liver.

Non-alcoholic fatty liver disease (NAFLD) affects 30% of Americans [wow!]. It is characterized by insulin resistance and fatty deposits in the liver, which can lead to liver damage over time.

A recent review of all available controlled feeding studies in humans concluded that there is no evidence that fructose at ordinary doses can cause fatty liver changes in healthy people19)Chiu S et al 2014 Eur J Clin Nutr 68:416-423.

It is important to point out that when certain people (typically people with insulin resistance) overeat sugars of any kind, the liver can start to become fatty, because insulin orchestrates the movement, usage, and storage of sugars and fats throughout the body. If insulin signaling isn’t working properly, fats can end up in the wrong places. In one study, when overweight men drank 25% of their daily calories as either glucose or fructose, after two weeks BOTH groups exhibited the kinds of changes that can lead to fatty liver, not just the fructose group.20)Johnston RD et al 2013 Gastroenterology 145:1016-1025

Fructose does not raise your risk for fatty liver any more than other sugars can. Since fatty liver disease is an insulin-resistant condition, improving your insulin sensitivity could be the most effective way to reduce fat buildup in the liver. I’ll show you ways to improve insulin sensitivity in article four.

Q:  Does fructose raise your blood pressure, cholesterol and triglyceride levels, increasing your risk for HEART DISEASE?

A:  Fructose is no worse than glucose for your overall cardiovascular health, and may even have some advantages over glucose when it comes to blood pressure.

An excellent review about this topic21)Sievenpiper JL et al 2014 Curr Opin Lipidol 5:8-19 summarizes what is currently known about the effects of fructose on various heart health markers. Unfortunately most of the human evidence comes from studies using too many calories, but nevertheless, even when high doses of fructose are compared to equally high doses of glucose, some differences do appear:

Cholesterol levels (fasting):  There are no differences between fructose and glucose when it comes to LDL (so-called “bad cholesterol”) or HDL (so-called “good cholesterol”). However, fructose does raise total cholesterol in some people more than glucose does, but, total cholesterol levels do not tell us anything about our risk for heart disease. When it comes to standard cholesterol test results, HDL is the only number worth paying attention to in estimating heart disease risk. (For more information about what cholesterol is, how carbohydrates raise cholesterol and how to interpret cholesterol test results, please see my cholesterol page, Jimmy Moore & Dr Eric Westman’s excellent book Cholesterol Clarity, and Dr. Peter Attia’s comprehensive series The Straight Dope on Cholesterol.

Triglyceride levels: Fructose temporarily raises triglycerides (blood fats) after eating more than glucose does, but does not affect fasting triglyceride levels any differently than glucose does, and it is fasting triglycerides that are used to help predict heart attack risk. If you already read article one, you saw that pure fructose has almost no effect on fat production in the liver, so you may wonder how fructose can raise blood fats, even temporarily. If fructose is eaten in combination with glucose (which is almost always the case in the real world and in human experiments), then glucose will trigger an insulin spike, and insulin will tell the liver to build fat (triglycerides). Fructose also temporarily slows down the removal of triglycerides from the blood, so the level can appear to rise even if the liver isn’t making any more triglycerides than usual.22)Tappy L 2012 BMC Biology 10:42

Blood pressure: Diets high in sugars in general can raise blood pressure,23)Morenga LT et al 2014 Am J Clin Nutr 081521 at least partly because sugar can raise adrenaline levels.24)DiNicolantonio JJ and Lucan SC 2014 Open Heart 1:e000167 However, glucose raises blood pressure more than fructose in some people.25)Sievenpiper JL et al 2014 Curr Opin Lipidol 5:8-19 This makes sense because hypertension is known to be an insulin-resistant condition,26)Ferrannini E et al 1987 N Engl J Med 317(6):350-357 and it is high levels of glucose that overtax insulin.

Fructose is no worse than glucose when it comes to increasing your chances for heart attacks, and may even be safer than glucose when it comes to blood pressure. Excess sugars in general should be your target when it comes to preventing high blood pressure and reducing your risk for heart disease.

So, Is Fructose Bad for You?

It turns out that excess GLUCOSE, the source of most of the sugar in our diet, is just as risky, and often riskier than fructose when it comes to these health conditions, primarily because of how glucose affects insulin and blood sugar. However, fructose at very high doses, or in people with cancer, poses health risks as well, so both of these sugars are worth minimizing.

Each and every single one of these health problems—type 2 diabetes, cancer, obesity, gout, fatty liver disease, and heart disease—is an insulin-resistant condition. Insulin resistance, which leads to high blood glucose and high insulin levels, is the scourge of our time.

Any lifestyle change you can make to improve insulin resistance, lower insulin levels and lower blood sugar, is well worth making, and will go a long way toward protecting and perhaps even completely restoring your good health. I can think of no better target, no better use of your time and energy.

In article four of this series: How to Diagnose, Prevent, and Treat Insulin Resistance, we finally crawl out of the test tube and back into reality. I’ll show you which of your favorite foods and beverages contain the most glucose and fructose and share with you strategies you can use to improve your insulin sensitivity (including some recommendations that may surprise you). But first, we’ll take a quick detour and look at the one health problem that is absolutely caused by fructose and not glucose: fructose malabsorption! Until then, how about you?

What do you think about the connection between fructose and these common diseases? Are you any more or less afraid of fructose than you were before? Have you tried a low-fructose, low-sugar, or low-carbohydrate diet for diabetes, gout, weight loss, fatty liver, high blood pressure, or even cancer? What has your experience been?

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References   [ + ]

  • TedHutchinson


    In reply-Fructose as a Driver of Diabetes: An Incomplete View of the Evidence. DiNicolantonio JJ
    There are some comments in this article that may interest those who have read the post above.

    • erdoke

      I was looking for exactly that discussion, so thank you Ted for providing the link. I tend to side with the ‘fructose is worse’ opinion in this case. Both because of the results referenced in that reply and due to the recent accumulation of new information about biochemical pathways specific to fructose. It seems that the more fructose reaches the liver (and sometimes even overflowing to other organs) the more harm is done. This dose dependent behavior is not completely straightforward though, since there are marked differences in how fructose is absorbed and converted to glucose in different conditions. Most likely there is individual variation as well, not to mention differences in susceptibility to its effects on insulin resistance, liver fat accumulation, etc.
      The recent fructose vs. heart study is also very telling.

  • Harry

    So how much fruit a day is safe?

    • Hello, Harry

      Good question! In article four we’ll cover specific recommendations, but the short answer is: it depends on who you are. If you have a relatively healthy metabolism (meaning that you are not overweight and do not have any metabolic problems already such as those mentioned in today’s article), and especially if metabolic problems don’t run in your family, you may be able to safely consume whole fruits and starchy vegetables to your satisfaction, just as our healthy ancestors were able to do for hundreds of thousands of years. However, those with metabolic issues may have to limit intake of all carbohydrates, even fruit and veggie sources. Nobody knows what the safe consumption limit is for most of these conditions, and it likely varies from person to person.

  • R. Cartocci

    I conclude, from reading these excellent articles, that 1-3 servings of organic, whole, raw fruit per day is prudent. (Total carbs of which do not exceed 15 grams.)

    • Dear R

      I’ll go over specific recommendations in the next and final article, but generally speaking, I agree with you. I personally eat a ketogenic diet and limit my daily carbohydrate to less than 30 grams per day, ideally not more than 10 to 15 grams at a time, and most often from low glycemic fruits such as berries, or low-carbohydrate “fruit vegetables” such as zucchini. We each vary in our ability to tolerate carbohydrate, so some may be able to get away with more than others (please also see conversation with Harry, below).

  • R. Cartocci

    Thank you for the reply. I am looking forward to the next article. On your ketogenic diet, have you found that LDL-P has increased? If so, is this a temporary result, and, if not, is it troubling?

    • When I first embarked on a ketogenic diet a couple of years ago, I had a variety of metabolic numbers tested but did not get a fractionated LDL. I haven’t had them checked this year yet. I generally don’t worry about cholesterol especially if all my other numbers look good. I looked up my numbers from 2013, after I’d been on a ketogenic diet for a month (labeled KD below) and compared them to numbers from 2012 when I had been eating a low-carb Paleo diet (labeled LCHF below). For whatever it’s worth here they are:

      Fasting blood glucose: Ketogenic=56, LCHF=90

      Hemoglobin A1C (normal range 4.8-5.6): KD=5.2; LCHF=5.5

      Fasting insulin (normal range 3 – 25): KD=1.6, LCHF=7.3

      Fasting leptin (normal range 8-38.9): KD =5.2 (no value for LCHF)

      Highly sensitive CRP: KD=0.9 (estimated risk for cardiovascular disease = “low”) LCHF regular CRP (not highly sensitive)= 0.67

      Uric acid (normal range 2.5-7.1): KD=5.5; LCHF=2.9

      Total cholesterol: KD=260; LCHF=263

      HDL: KD=70; LCHF=91

      LDL: KD=170; LCHF=160

      Triglycerides: KD=99; LCHF=61

  • TedHutchinson
  • TedHutchinson

    A dose-response study of consuming high-fructose corn syrup-sweetened beverages on lipid/lipoprotein risk factors for cardiovascular disease in young adults.

    • Thank you for this article, Ted.

      Yes, I completely agree that high-fructose corn syrup-sweetened beverages increase risk for cardiovascular disease. As will be covered in the next post, HFCS is essentially no different than white sugar from a metabolic standpoint. Given that it is 55% fructose and 45% glucose, it’s hard to know which component is more responsible for the increase in risk in this study, or if both of them are, but yes, drinking sugar is clearly not good for us:)

  • Valerie Doyle

    I am wondering if high fructose corn syrup poses any problems that regular fructose does not.

    • Hello, Valerie

      Good question–the next and final article in this series will be all about foods, beverages, and sweeteners, including high fructose corn syrup, but the short answer to your question is that high fructose corn syrup is virtually identical to plain white sugar in its effects on the body, so you can think of it as the same as white sugar. Pure fructose is something we don’t typically consume, which is one reason why so many of the research studies don’t apply to real life. More fun facts to come soon, including helpful tips and tables of the fructose/glucose content of foods and drinks in article four!

      • Valerie Doyle

        Thank you. I look forward to that article.

  • I discovered you from a link someone posted for your “Freshness Counts: Histamine Intolerance” article in a Keto Forum group comment on Facebook. Of course, I then wanted to read some of your other great articles…and sign up for your updates, too!

    I found it interesting that you are following a keto diet and had earlier followed a LCHF diet. Your KD and LCHF numbers are interesting to see.

    During the past few months, I have been reviewing all of the information I could find for ketogenic diets and nutritional ketosis, and I have been very impressed. Early on, for about 10 days, I tried to follow a ketogenic diet without really being prepared or even as informed as I should have been, so it was a complete failure. I was unable to consume enough fat. (I guess I was still with the mindset from the years of the AMA recommending a low fat, high carb diet.) I was probably starving myself, and I really didn’t need to lose weight. That wasn’t the way I wanted to reach ketosis.

    In the near future I will be trying a new product, which includes a drink with ketone salts that will allow your body to reach nutritional ketosis within 1 – 4 hours. There are other components which provide daily nutritional support and satiety, and you prepare your own dinners with a protein, fats, and green vegetables. Others are having great success with weight loss and more. I’m hoping to use it as a means of resetting my body and healing any inflammation. I’ll let you know how this works out for me.

    • Welcome, Cyndi!

      Thank you for telling us about your endeavours–I’m looking forward to hearing more along the way. Good luck!

  • Tim H

    You have not discussed the glycating power of fructose nor the oxidative power. On both, I understand that fructose is 10X or more of glucose.

    • Hello, Tim

      Good points! I had not looked into either of those questions in preparation for this post, because I thought we wouldn’t need to worry about these issues, given that our blood concentration of fructose is almost always very low. However, I just did a quick search on PubMed and discovered this information from
      Schalkwijk et al Diabetes Metab Res Rev 2004:

      “Despite its approximately eightfold higher reactivity, the contribution of extracellular glycation by fructose is considerably less than that by glucose, because of the low plasma concentration of fructose (5 mmol/L glucose vs 35 micro mol/L fructose). Intracellularly, fructose is elevated in a number of tissues of diabetic patients in which the polyol pathway is active. In the cells of these tissues, the concentrations of fructose and glucose are of the same magnitude. Although direct evidence is not yet available, it is likely that the high reactivity of fructose and its metabolites may substantially contribute to the formation of intracellular AGEs and may contribute to alterations of cellular proteins, dysfunction of cells and, subsequently, to vascular complications.”

      Thus it appears rising fructose levels within cells of people with diabetes can be a concern, however, this fructose is generated from within the cell when blood glucose levels are high, and does not come from fructose in the diet.

      Very interesting questions; thanks for asking!

  • Dear Peggy

    Thank you for bringing up this important study. Dr. Lustig continues to provide tremendous public health value by raising concerns about sugar intake. I read the methods section of this new Lustig study and find an important shortcoming that sheds doubt on its findings. Unfortunately, the researchers only measured and controlled what the children were eating during the nine day intervention period. Prior to the onset of the study, they used questionnaires to estimate what the children had been eating, and those questionnaires are notoriously unreliable. Therefore we don’t know exactly how much fructose or glucose the children were eating before their diets were changed:

    “Participants filled in food frequency questionnaires (FFQ) and were inter-viewed by a dietitian, from which their baseline macronutrient pro-files (percent of calories as fat, protein, and carbohydrate; and fibercontent as g/1000 kcal) were identified.”

    I wish this study had consisted of a controlled pre-intervention period so that we could glean real information from the results.

  • Dear Peggy

    This study does show a small difference between fructose and glucose but is just one example of many studies which suffer from the problem of overdosage. It is definitely true, as I mention in my series about fructose, that fructose in excessive amounts is a little worse than glucose in excessive amounts, but at reasonable amounts glucose is worse. What we are seeing in this study is a dosage effect.

    People were asked to consume 25% of their calories as fructose (or glucose), which means that for a 2000 calorie/day diet, 500 of those calories would be consumed as sugar (either fructose or glucose). It would be unusual for most people to consume that much fructose, but yes, if they did, it would be a little worse than glucose. Experiments conducted using reasonable amounts find either no difference or that glucose is worse than fructose.

    What would have been even more interesting is if this study had been conducted with a 2-week run-in phase containing no sugar-sweetened beverages of any type, then to add the SSB’s to show how much the glucose-sweetened beverages worsen metabolism compared to baseline. That would have put the slight differences between the two in perspective. But yes, I completely agree, at high doses, fructose can be worse than glucose.

  • Tammy Georgine

    I’m confused….it seems simple on paper but I don’t understand what happened to my body…I am extremely discipline…have not been eating junk food for a long long time…I was not eating any sugar or carbs recommended by a doctor to clear up any fungal issues in the gut…then all of a sudden it hits me…now my blood sugar is all over the place. It would appear I have hypoglycemia based on the glucose readings, however I have lots of symptoms of diabetes….???? sweating, thirst, burning, numb, circulation issues in extremities…I’m totally confused and miserable, very thin not overweight, never have been….too many conflictions about diet, I’m not sure what to do. I’m now eating fruit…when I haven’t for a while…because eating like I was, no sugar at all I was feeling like I was walking in a fog and not feeling well. but not sure if the sugar is going to work either

    • Hi Tammy

      It is unfortunately not possible to know what the underlying problem is without having a complete medical and nutritional evaluation, so I hope you will see your physician right away to help you figure out what is going on. There are many possibilities, most of which have nothing to do with blood sugar that need to be assessed.

  • Vasternorrladn_4ever

    We know historically that glucose does not cause type 2 diabetes. Nor
    does it cause heart issues. We humans have eaten a lot of glucose for
    thousands of years and very rarly they got those disesases. But when
    fructose become a staple food in our diet the raise in those metabolic
    diseases rose.

    • Hello, Vasternorrladn_4ever,

      I agree that eating glucose in the form of whole plant foods seems not to have been a significant cause of modern metabolic diseases. However, all sweet plant foods contain plenty of fructose, so whole food sources of fructose were also never a major problem for our species either. It is excess glucose, primarily from refined foods, most likely, that seems to be the most likely culprit here. You may find Ian Spreadbury’s hypothesis about acellular carbohydrates interesting and relevant to this very question: https://www.youtube.com/watch?v=-BQg9wkPmVw

  • Inga Schubert Geb. Baasner

    I know I´m a little late 😉
    But I´m wondering – not as I had read every singel comment, but quite a few – why there is not named one of the most important thing in the glucose vs. fructose debate (ell me, if I´m wrong, PLEASE!):
    Glucose is energy for every single cell in the body and can metabolized from every single cell (of course, if the carbohydrate-storages fully, the more glucose stores as fat).
    Fructose has no meaning to even one cell at all. It´s useless for the body. So, it´s getting metabolizet in the liver to fat. To near 100% (Remember: glucose only that part, which cannot be used, because the ch-storage are fully).
    So, if that was right, I think it´s obvious, that fructose is much worse than glucose. And: Because all of fructose is metabolized in the liver, it overolads the liver much faster than the not-used-glucose.
    Is that right? Dit I misunderstand something?
    Greetings from Danmark!