Fructose: Friend or Foe?

Fructose: Friend or Foe? post image

There has been a lot of talk about sugar, natural sweeteners and artificial sweeteners in the news lately. However, there is a controversy brewing about the safety and benefit of fructose. We all know that fructose is the natural sugar found in fruits. But recent articles and research are indicating that fructose may not be the safe sugar we all thought.

In a previous post about sugar and cancer, I talked about Dr. Robert Lustig’s research with fructose  that was presented in The New York Times Magazine article called “Is Sugar Toxic?”, written by Gary Taubes. Lustig also presents his ideas in a Youtube video which at this point has had almost 2 million views.

Dr. Lustig explains that fructose is metabolized in the liver while the glucose portion of the table sugar molecule (sucrose) is metabolized by all the cells of the body. Because of this difference in metabolism, fructose causes the liver to work harder. This is damaging and is what is thought to be the driving force behind metabolic syndrome.

Metabolic Syndrome

Metabolic Syndrome is the name for a group of risk factors that occur together and increase the risk for coronary artery disease, stroke, and type 2 diabetes. These risk factors include, high blood pressure, high fasting blood sugar or insulin resistance, high triglycerides, high small LDL particles and low HDL. A sign that this may be developing is central obesity or fat around the middle of the body (an apple shape).

People who have metabolic syndrome often have low levels of inflammation throughout the body as well as excess blood clotting. Complications from metabolic syndrome that reach beyond coronary artery disease, stroke, and type 2 diabetes, include, nonalcoholic fatty liver, peripheral artery disease and kidney disease.

Fructose and Diet

When I researched fructose and diet I was pleasantly surprised to see several studies involving just that, with the most recent from Dr. Stephanie Seneff et al. Dr. Seneff is a brilliant scientist with many degrees from MIT in computer science. She shifted her interest to health and nutrition several years ago and has since researched and written a great deal about diet.

Dr. Stephanie Seneff spoke about the benefits of a high fat, high cholesterol diet at the Wise Traditions Conference this past year, emphasizing the dangers of using statin drugs.

She questions the need for lowering cholesterol at all, in fact, she proclaims to go out of her way to eat cholesterol rich foods. You gotta love this woman! At the same time, she supports a moderate to low carbohydrate diet with the emphasis on elimination of sugars.

Is the metabolic syndrome caused by a high fructose, and relatively low fat, low cholesterol diet?

This is the title of her recent research published in the peer reviewed journal, Archives of Medical Science. The abstract clearly states that this is a hypothesis regarding metabolic syndrome:

We have developed a new hypothesis regarding MetS [Metabolic Syndrome] as a consequence of a high intake in carbohydrates and food with a high glycemic index, particularly fructose, and relatively low intake of cholesterol and saturated fat. We support our arguments through animal studies which have shown that exposure of the liver to increased quantities of fructose leads to rapid stimulation of lipogenesis and accumulation of triglycerides… Excess exposure to fructose intake … also leads to increased levels of advanced glycation end products. The macrophages exposed to advanced glycation end products become dysfunctional and, on entry into the artery wall, contribute to plaque formation and thrombosis.

In order to understand some of this important research we need to first talk about advanced glycation end products or AGEs.


Advanced glycation end products (AGEs) are proteins or lipids that become glycated after exposure to sugars. AGEs contribute to a variety of microvascular and macrovascular complications through the formation of cross-links between molecules in the basement membrane of the cell.

A critical property of AGEs is their ability to activate receptors for advanced glycation end products (RAGEs). Due to such interaction, AGEs may stimulate processes linked to inflammation and its consequences and thereby affect a diverse group of diseases, such as diabetes, inflammation, autoimmunity, neurodegeneration, and aging.

How do AGEs form?

Advanced Glycation End products can come from two sources:

  1. Exogenous sources from the food we eat
  2. Endogenous sources from internal production in the body

AGEs in food

AGEs are formed when proteins and sugars are cooked together without water. Water prevents the binding of sugar to the protein molecules. The Maillard reaction results from the browning of proteins like meat and can produce AGEs. However, there are also proteins in vegetables, grains and fruits that may also produce AGEs when exposed to heat. Browning is used in cooking and food processing to give food flavor and color.

AGEs in the body

A small proportion of the sugar in your bloodstream is glycated, while the rest goes to other metabolic reactions. If a person’s blood sugar runs high, there will be more opportunities for this circulating sugar to be glycated, which can lead to other consequences.

Importantly, fructose and galactose are said to undergo glycation at about 10 times the rate as glucose (I could not find a study referencing this, but it seems to be all over the internet. I do not know how true it is). With the dramatic increase in sugar consumption over the past several decades, (at least  50% as fructose and high fructose corn syrup), it is no surprise that we’re seeing rising rates of heart disease, arthritis, autoimmunity and other inflammatory diseases of aging.

Is the Jury In?

In their hypothesis, Dr. Seneff, Glyn Wainwright, and Luca Mascitelli set about providing proof from animals studies that Metabolic Syndrome is linked to high intake of fructose coupled with a low intake of cholesterol and saturated fats.

In this paper, we developed a theory accounting for all the features of MetS [Metabolic Syndrome], which involves a cascade of events brought on by gross dietary imbalances. We argue that this syndrome has reached epidemic proportions due to misguided advice regarding a “healthy” lifestyle, leading to reduced dietary intake of fats and cholesterol and excessive sun avoidance. The increasingly widespread availability of highly processed foods, particularly the practice of substituting fructose [HFCS] for glucose as a sweetener due to economic considerations, has been an equally damaging contributing factor. Calcium and vitamin D deficiency play a role as well.

Fructose is a highly reactive reducing agent and must be aggressively removed from the bloodstream by the liver to prevent it from damaging serum lipids and proteins via fructation. In the presence of a high carbohydrate diet, the sugars enters the bloodstream rapidly due to the lack of buffering in the intestine by dietary fats.

Excessive sugars (fructose and glucose) cause glycated proteins or AGEs and play a critical role in the damage to vascular tissue, collagen tissue, albumen, cholesterol and LDL.

Fatty liver and cholesterol deficiency in the cell membranes

The scientists explain how fructose, in the presence of a low fat, low cholesterol diet may lead to damage to the cell membranes and increased oxidation of fats, which is of concern.

After a meal, the liver rapidly processes the fructose to basic building blocks that can later be converted to fat, but it can neither safely store the fat nor release it within newly synthesized lipoproteins. This is the key factor that leads to both fatty liver and liver insulin resistance, early indicators of the metabolic syndrome…

Cholesterol deficiency becomes a problem for cells throughout the body, with dire consequences. One consequence will be the increased susceptibility of the fats in cell membranes to oxidation.

In conclusion, we would urge medical practitioners to encourage individuals exhibiting MetS to strongly limit the consumption of dietary fructose and other high-glycemic-index carbohydrates, and to stop discouraging them from consuming foods rich in cholesterol.

How to protect yourself from AGEs

  • Lower your intake of sugar, especially fructose. Over the last 20 years the average yearly sugar consumption per person in the United States has gone from 26 pounds to 135 pounds.  Surprisingly, the American Dietetic Association and the American Diabetic Association both agree that sugar consumption is one of the 3 major causes of degenerative diseases in America.
  • Stabilize your blood sugar levels by balancing meals with protein and good fats.
  • Eat vegetables and fruits raw, boiled, or steamed.  Water prevents sugars from binding to protein molecules.  By eating fruits and vegetables raw or by cooking them in water or with steam prevents AGEs from forming.
  • Learn how to braise (cook in water) and slow cook meats. Crock pot cooking is a form of low and slow cooking and it is also good because it braises the food in water.
  • These methods not only cook foods with a lower amount of heat, but they create more moisture during the cooking process.
  • Cooking with water prevents these sugars from binding to the protein and fat molecules.
  • Marinating foods in cider vinegar, lemon juice, and dry wines can also help.
  • Eating rare or medium-rare meats will contain fewer AGEs than well-done.
  • Include more fresh foods in your diet like low glycemic fruits, green vegetables, raw seeds or nuts, and other unprocessed, raw foods.
  • Limit your consumption of processed and browned foods. Even in home cooked foods, these techniques directly increase the number of Advanced Glycation End products.
  • Avoid high fructose corn syrup.  Avoid processed foods in general.
  • Drink lots of water and only water. Ditch the soft drinks — whether they have sugar or artificial sweeteners they are bad!
  • Don’t smoke. Recent research has clearly shown a significantly higher level of serum AGEs in smokers and especially diabetic smokers.

Clearly, AGEs and their consequences should be taken into consideration when reviewing dietary choices. If the USDA recommended the above guidelines, instead of catering to the Big Ag lobbyists, perhaps Americans would not be in the the sad state they are today. Stay tuned for Part 2 when I talk about other influences on fructose and how much is safe to eat.

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Leave a Comment

  • Patti February 22, 2012, 7:30 am

    I read Dr. Seneff’s article regarding cholesterol in Well Being Journal. My husband is currently on Crestor , which concerns me, but unfortunately, I can’t convince him to completely change his diet. I have made many changes at home, which I hope will help. Now if we could just find a good family doctor in our area, that does more than prescribe drugs.

  • Solveig February 22, 2012, 12:43 pm

    Why does Sally Fallon, in her book “Nourishing Traditions” when making beef bone broth, she tells you to “brown” your broth bones by roasting them in the oven before placing them in the slow cooker. I believe the book says it gives the broth a nice flavor and brown color

    I believe you ascribe to her books and that of the WAPF. Doesn’t “browning” beef bones for bone broth go 180 degrees in the opposite direction of the tenets of Sally’s book?

    • Jill February 22, 2012, 2:15 pm

      Hi Solveig,
      That is a good question. I also like to brown meat before I braise it and I don’t know how “bad” that is. Traditional recipes do call for browning of meats and bones for a better flavor. I think the worst thing to do is to char meat on a grill. I don’t think we have any studies yet specifically about browning potted meat. Hope this helps!

  • Jacob A February 22, 2012, 6:18 pm

    Great article! Just being aware of AGEs and what’s going on in the processes by which they are formed is enough to spark some change in the way we view our food and its preparations. Will I charbroil a steak on the Barbeque ever again? Oh, yes. I will. But will I do it as much, now that I know what’s going on? Nope. No way. This is all great education. Most of what we eat in our house falls to the spectrum of “barely” cooked. But after reading this piece, I can assure you that we will be mindfully diligent to cook as much as possible in water. Awesome information here. Thank you so much.

  • Natalia February 23, 2012, 9:12 am

    I am a bit confused now. Is it better to limit the consumption of fruits?

    • Jill February 23, 2012, 9:49 am

      Hi Natalia,
      I will have more to say about this tomorrow!

  • Jennifer February 27, 2012, 11:58 am

    A really nice piece, well researched. A study quoted in Nutrition Action Healthletter pointed out that if we were to meet all of our nutrition needs from the food we eat, we would only have enough room for about 6 tsp of added sugar for the typical female before we started exceeding our necessary calorie intake and gained weight. This alone is a good reason to cut back on sugar. Just to remind people, common table sugar is a disaccharide (sucrose) that is 50% glucose and 50% fructose. I do think there is a big difference between eating fructose from a piece of raw fruit (which we and our ape ancestors have been doing for going on a million years) and drinking a soda with 14 tsp of added sugar a couple of times a day.

    Have you read “Catching Fire, How Cooking Made Us Human” by Richard Wrangham? He points out that we are the only species on the planet that eats cooked foods, and the advantages that has given us. Google his name for video talks. Often, animal diet studies that feed cooked food are an apples and oranges comparison, in my opinion, because we are the only animal that has evolved with cooked food metabolism for going on 200,000 years. I’ve always wondered about how this comes into play with the warning to stay away from “maillard reaction” foods. We’ve been eating seared meats for hundreds of thousands of years. Not saying the AGE issue isn’t real, but seems strange that we would not have evolved a mechanism for dealing with this.

    • Jill February 27, 2012, 5:01 pm

      Hi Jennifer,
      Thank for your kind words. There probably are people who can handle seared meats — those with healthy gut flora. Healthy gut flora takes care of a lot of toxins for us.

  • April @ 21st Century Housewife February 29, 2012, 1:18 pm

    This is a very interesting post. Thank you for sharing it with Hearth and Soul.

  • Rebecca @ Natural Mothers Network March 3, 2012, 5:48 am

    I found this fascinating- it’s obvious we still have so much to learn on the subject.