In episode 122 of his video series, Dr. Larson discusses:

When I am discussing diets and dietary items with my patients, there are a lot of things that can be up for negotiation. But some things are not. And at the top of that list of things that are bad for you and non-negotiable is high fructose corn syrup or really high fructose anything. It is really bad for the body. A study that recently came out that was put together by researchers from the Joslin Diabetes Center and published in the journal Cell Metabolism looked at something that I haven’t seen in the past. They asked the question, “Why is high fructose syrup so bad for you?”. And why do you think that diabetes researchers are interested in fructose?

There is a major condition that is plaguing our society, metabolic syndrome. And metabolic syndrome is a precursor to diabetes. Metabolic syndrome is defined by having three of five different health markers. The five markers are an increased waist circumference, which for women is generally 35 inches or more, and for men, it is 40 inches or more, an elevated blood pressure, elevated blood sugar, elevated triglycerides, and low HDL-C levels. Metabolic syndrome is not just a precursor to diabetes; it is also a risk factor for certain types of cancers, heart disease, and obesity. But what does that have to do with high fructose? Fructose is a type of sugar that comes from fruit. But we are not suggesting that fruit is bad for you. In fact, when you eat fruit, whatever sugar you get from it is overridden by the nutrients that it provides.

But when you extract the fructose and concentrate it, it makes it extremely high in fructose, which is very bad for you. Just go into any fast food restaurant, and what you will find is a plethora of things that are loaded with high fructose syrup. The researchers in this study wanted to see what the effects of high fructose syrup are on the liver. Fructose is not used in the body like other sugars. Remember, table sugar is half glucose and half fructose. Glucose has a different effect because it can be used throughout the body. The process is that insulin goes up when you ingest glucose, and then insulin helps the cells use glucose for energy throughout the body. Fructose isn’t like that. Only the liver can metabolize fructose and only when it is kept to a small amount. So when you eat fruit, it isn’t a big deal. When you have concentrated fructose, it is a big deal.

High fructose causes nonalcoholic fatty liver disease or NAFLD. NAFLD causes the accumulation of fat around the liver, which is associated with metabolic syndrome. But up until now, we really didn’t understand why fructose has this problem with the liver. The study looked at all sorts of technical pathways and found that fructose shuts off certain genes that lead to fat metabolism by the liver. Not only does it cause more fat accumulation, but it locks down the liver’s ability to burn that excess fat. And it also causes malfunction to the structure and the shape of the mitochondria. The mitochondria are the powerhouses of the cell. When there’s a problem with the mitochondria; it is going to affect the normal function of the liver.


Biology 101 teaches us that structure determines function. So if there is damage to the mitochondria, it is not going to work properly to burn fat as fuel. Fructose blocks the pathway that the liver has to burn fat for fuel, and, therefore, it blunts the liver’s ability to do its job. When the liver becomes fatty, it will often spill over into the rest of the body. Once a person has fatty liver disease, it affects the pancreas, often leading to fatty pancreas disease. And since the pancreas is where insulin is produced, the pancreas doesn’t function normally. So if the pancreas and the liver aren’t working, it will lead to other organ dysfunction, causing a cascade that eventually leads to chronic illness.



High fructose syrup is a major problem. When you eat at a fast-food restaurant, you probably order a soda that is loaded with high fructose syrup. And then you follow it up with ultra-processed grain products and low-quality animal fat loaded with excess bad fat. The high fructose syrup causes the liver not to burn all the additional fat that you are consuming. And that just puts the body into a downward spiral leading to us all getting fattier and fattier. It is this scenario that is at the heart of the American diet. After this study, we have a bit more information about how high fructose syrup works in the body, and also how it contributes to metabolic syndrome. It is all these little details that hopefully, you are starting to piece together to get a full picture of what goes on with the foods you eat. I hope these connections are helping you to make better food choices, which will reduce your risk of chronic disease and illness.


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