Dr. Robert H. Lustig is a pediatric endocrinologist, an expert on obesity in children and a very talented speaker. He’s also the guy who brought the dangers of fructose into mainstream attention.
His presentation above, Sugar: The Bitter Truth, is a 90 minute lecture that delves deep into the science and biochemistry behind fructose consumption, with 3 million views.
This video is a must watch… I’ve seen it 3 times already and it is about as entertaining as a movie in my opinion. He published a book on sugar in December. I haven’t read it yet but I’m planning to.
Why is Fructose Bad For You? Some Important Points
Sugar (sucrose) and High Fructose Corn Syrup both supply a significant portion of the total calories in a standard western diet.
They both consist of two simple sugars… glucose and fructose.
Glucose also comes from starches like potatoes, our bodies produce it and every cell on the face of the earth has glucose in it. Glucose is a molecule absolutely vital to life.
Fructose however, is not. Humans don’t produce fructose and throughout evolutionary history have never consumed it except seasonally when fruit were ripe.
Glucose and fructose are metabolized very differently by the body.
The key thing to realize, is that while every cell in the body can use glucose, the liver is the only organ that can metabolize fructose in significant amounts.
When people eat a diet that is high in calories and high in fructose, the liver gets overloaded and starts turning the fructose into fat.
Lustig and other scientists believe that excess fructose consumption may be a key driver of many of the most serious diseases of today, including: obesity, type II diabetes, heart disease and even cancer.
The Harmful Effects of Excess Fructose
Eating a lot of fructose in the form of added sugars may:
- Make your liver synthesize fats, which are exported as VLDL cholesterol, which leads to dyslipidemia (blood tryglicerides and cholesterol), fat around the organs and ultimately, heart disease (1, 2).
- Increase blood levels of uric acid, leading to gout and elevated blood pressure (3, 4).
- Cause deposition of fat in the liver, potentially leading to non-alcoholic fatty liver disease (5, 6).
- Cause insulin resistance, which ultimately leads to obesity and type II diabetes (7, 8).
- Insulin resistance leads to elevated insulin and insulin like growth factor (IGF-1) in the entire body, which may ultimately cause cancer (9, 10).
- Fructose doesn’t affect satiety in the same way as glucose, making you eat more total calories automatically if your fructose intake is high (11).
- Excess fructose consumption may cause leptin resistance, throwing body fat regulation out of whack and contributing to obesity (12, 13).
- Sugar may be downright addictive (14).
Leptin resistance, elevated insulin and vicious addictive cycles of cravings and binge eating are a recipe for fat gain disaster.
If potentially leading to obesity, cancer, heart disease and diabetes isn’t reason enough to stop eating added sugars, I don’t know what is.
Be aware that not all of this has been proven beyond a shadow of a doubt in controlled trials, but the evidence is still very strong and more studies will paint a clearer picture in the coming years and decades.
Fructose From Added Sugars is Bad For You, Fruit is NOT
It’s important to realize that all of this does NOT apply to fruit.
Fruits aren’t just watery bags of fructose, they are real foods with a low energy density and lots of fiber.
They’re hard to overeat on and you’d have to eat ridiculous amounts to reach harmful levels of fructose. In general, fruit is a minor source of fructose in the diet compared to added sugars.
The harmful effects of fructose apply to a western diet supplying excess calories and added sugars. It does NOT apply to the natural sugars found in fruits and vegetables. Period.
Kris,
I couldn’t agree more that all excess sugar does is lead to obesity and disease. Best to cut all that stuff out.
Alykhan
Wonderful lecture, I really enjoyed it. Thanks Kris.
What about coconut sugar? There has been a lot of claims recently on choosing coconut sugar over other types of sweeteners for diabetic or pre-diabetic patients. According to studies, coconut sugar has about 35% fructose in it. Is coconut sugar good or bad?
I haven’t done any research on it. It’s probably less bad than sugar, but personally I think diabetics shouldn’t be eating any sugars at all.
How does one break the sugar addiction? I know it’s bad but I am addicted
That’s a tough one, the only thing that has worked for me is complete abstinence. Haven’t touched added sugar or gluten in over 4 months.
I’m writing an e-book about food addiction, plan on releasing it in February.
Looking forward to it.
When you say you haven’t touched sugar in 4 months… do you mean ADDED sugar? (not fruit itself) Just want to clarify!
Yes, added sugar. I eat fruit occasionally.
Just wanted to chime in to say that something that can help with breaking a sugar addiction is to find awesome recipes for “desserts” that are free of added sugars. That way your mind doesn’t feel deprived at least.
Brilliant video, thanks for posting. The science really made me think a great deal about how careful I have to be when buying any sauces/dips where the sugar lurks. Ive been low carb/no gluten/no sugar and eating fats for a month now and I feel great. Just have to get some recipes for my own sauces to go with my food.
Thanks for the comment, you can easily find lots if you google “low carb sauces” and “paleo sauces” – many blogs and even entire cookbooks are dedicated to this way of eating.
Kris, thanks for the newsletters. They keep me on track, latest from my new eating habits is a weight loss of 17lbs in 4 weeks and blood pressure down from 148/90 to 120/61 last week. My doctor was amazed and so was I.
Many thanks,
Sarah
That’s incredible, congrats.
What about organic honey? Should that be cut out as well?
Honey is 38% fructose so I think the same would apply to honey as it is a more concentrated form of fructose that you would usually find. I would limit my honey intake for that reason.
I was wondering about comments made about CVD. My understanding is that plaques start from a macrophage responding to inflammation, then adsorbing LDL to make a foam cell. This to some extent is why CRP can be used as an indicator for heart disease. The foam cell then sends out all kinds of crazy signals, generating more inflammation, and then eventually more macrophages engage at the site and adsorb LDL. I hadn’t considered that fructose interacts with JUNC-1. So, is it necessarily that fructose leads to LDL and thus CVD, or could it be that fructose leads to inflammation, which leads to more active macrophages and more LDL to convert them to foam cells?
I’m definitely no expert on the pathophysiology of heart disease, but my understanding is that it is a little bit of both.
I didnt watch all the video, but from my understanding, high blood glucose damages blood vessels, which initiates atherosclerosis. This damage to the blood vessels then triggers the cascade response of LDL and increase in plaque. So, without excess sugars in the blood, there wouldnt be a cascade in the first place. But once the damage begins, the LDL in blood and immune response make it worse. Hope this helps a bit.
You harp on fructose so much, but how often does anyone consume solely fructose? Fructose is almost always found in a ratio close to 50/50 with glucose. The same ratio exists in fruit, honey, table sugar, and (heaven forbid) high fructose corn syrup. As long as fructose is ingested with equal amounts of glucose there is no real problem.
All the studies that like to point out how evil fructose is are performed using ONLY fructose. (Which, yeah, when consumed by itself does exhibit different effects than a nice 50/50 blend of glucose/fructose such as decreased satiety.) Its the amount of sugar people consume that leads to all your scare tactic points in your above thoughts. Not the form so much. So quit bagging on poor fructose so bad. The country has had enough skewed information.
On Glucose, it is needed throughout the body, but I think that in the bitter truth, they say it is as bad as fructose, once the body has received it’s fill, and the waste path for it is as bad as for fructose. That part wasn’t completely clear to me in one watching. But it is an important point one way or another, because in the US diet overconsumption of sugar is a problem. The people who get the memo on fructose, one thing they do is search out stuff like pop made with cane sugar, etc… but when the channels are maxed out, that may not be a solution. Not to mention the calorie load.
So, what is the sugar found in fruits? I was always under the impression that it is called Fructose. How can fructose be bad for you, but it is in fruit and you say that fruit sugar is good for you? I am probably over thinking, just want to be sure. Nice article.
Fruits have fructose, but also fiber and lots of water. It is very hard to eat too much fructose if you only get it from fruits.
I wouldn’t worry about fruit, but avoid added sugars.