Are All Sugars Equally Bad? Fructose vs. Glucose Decoded

This fascinating episode goes deep into sugar – especially fructose. We dig into world class research conducted by Dr. Rick Johnson and team that really lays a lot of the blame behind modern diseases on fructose instead of glucose.

This conversation between Dr. Rick Johnson and Faraz Khan is split up into two parts.

Part 1: We discuss the different types of sugars, fructose vs glucose metabolism, and which may be the worse sugar to eat.

Part 2: We will discuss fructose, high fructose corn syrup, fruits and fruit juices, salt and how to eat to beat the metabolic disorders associated with fructose.

Richard J. Johnson, M.D. is the Tomas Berl Professor of Medicine and was the Chief of the Renal Division and Hypertension at the University of Colorado until recently. His research, which has been funded by the National Institutes of Health (NIH), has focused on the role of sugar, and especially fructose, in driving obesity, diabetes, high blood pressure and kidney disease.

Much of this work has explored the role of fructose metabolism, especially the generation of uric acid, in driving this phenotype, and his work has included studies ranging from molecular biology, integrative physiology, and evolutionary biology.

He is the author of The Sugar Fix) which introduced the first low fructose diet, and also The Fat Switch which explores the role of fructose in driving the obesity epidemic. He has lectured in over 40 countries.

Dr. Rick Johnson’s Background

• Medical doctor and sees patients
• Doing medical research since 1980’s
• Specialist in kidney disease, general medicine and infectious diseases
• Got to high blood pressure, obesity and metabolic syndrome
• Sugar is really important in diabetes and obesity
• Studied hibernating bears, natives in Venezuela, animal experiments and evolution

What Is Sugar? Let’s Simply Explain The Terms

• Two simple sugars: glucose and fructose
• Sucrose is table sugar – contains both glucose and fructose equally
• Glucose comes from starch – it’s one of the principal fuels in body. Also known as dextrose.
• Fructose is sugar in fruits and honey
• High fructose corn syrup – corn is treated to convert some glucose to fructose. People prefer more fructose in taste tests.
• HFCS is used in desserts in sweets, soft drinks.
• Blood sugar means glucose

What Are Added Sugars vs. Natural Sugars

• Sucrose and HFCS are readily added to foods
• Sugar is added to ketchup, crackers, 75-80% of processed foods, 75% of drinks, even added to fruit punch
• About 15% of our average diet comes from added sugars. Some people are reaching 25% of caloric intake with sugar.
• Glucose is not as sweet as fructose.
• Animals such as mice like both glucose and fructose.

Sugar’s Response In The Brain

• Glucose stimulates some dopamine (pleasure), also increases brain activity
• Improves performance in athletes and school children – if blood glucose levels don’t get too high
• Once levels go high – then performance reduces
• In fructose, people get decreased cortical brain activity which reduces willpower
• Fructose induces a hunger state which leads people to eat bad foods (while also reducing willpower)

Side Story – How Gatorade Was Invented

• Rick was friends with Bob Cade who invented Gatorade
• Cade found that athletes were losing up to 10 pounds in one workout in Florida heat
• Scientists had discovered that adding glucose allowed people to get more salt in the diet
• So Cade added water to salt along with a little glucose and gave it to the B-team. That weekend, the B-team beat the A-team
• Then Cade added 1-2% fructose to make it a bit sweeter
• Fructose accelerates glucose absorption in the body

Metabolism of Fructose vs Glucose

• Rick learned that fructose could cause metabolic syndrome in animals
• All foods are used to create energy, but you need some energy to convert the food into more energy
• If during food breakdown – energy levels start to fall inside cells, glucose has a feedback system that stops the reactions until energy levels recover
• But with fructose, your energy drops while trying to make more energy. Energy levels can drop rapidly in the liver – up to 20-30%.
• This causes an alarm inside the cell – the body thinks you may be starving.
• Your body stimulates hunger, thirst, fat production, food foraging and insulin resistance.

Insulin Resistance is a Survival Pathway In Your Body

• When you eat glucose, it stimulates insulin which drives glucose into muscle and liver
• But the brain also uses lots of glucose – it needs the energy
• When there is an alarm signal that the body may be starving, the body acts to save glucose supplies for the brain
• Your body becomes insulin resistant, which saves glucose from muscle and instead spares it for the brain to use
• The brain does not require insulin to make energy
• Insulin resistance is found in animals that are starving, or when trying to store fat before hibernation
• When fructose causes energy drop in your liver, this energy stays low for a while
• This shifts your body to make more fat – and ATP levels stay low even while eating
• So the fat is increased and stored
• When you’re starving, insulin resistance is part of a survival response.

So What’s Wrong With The Survival Switch?

• When you continue to feed the survival switch, this starts to overflow the system
• Insulin resistance turns into diabetes
• Elevated blood pressure drives hypertension, and your brain starts to develop alzheimers
• Chronic fructose feeding and activation of this pathway causes lots of problems

What Causes Insulin Resistance?

• Fructose drops energy in liver cells, causes body to think it’s going in starvation and turns on fat storage
• This is how fructose causes insulin resistance
• Rick’s team started to believe that the danger of sugar was not glucose but fructose
• Fructose does not raise insulin like glucose does
• In lab mice, Rick’s team showed that fructose caused obesity and regular starch (glucose) did not do so
• Rick’s team believed that high fructose was the problem much more so than high glucose

Can We Make Fructose?

• Humans can make fructose from glucose, but only when glucose levels are high
• Lab mice given just glucose still got fat (which perplexed Rick)
• So Rick thought he was wrong, but the high glucose was being converted to fructose
• Then Rick’s team gave the same diet to animals that were engineered to not metabolize fructose – and these rats did not get fat.
• These animals had no fatty liver and insulin resistance
• Thus in the presence of high glucose (high starch foods), your body makes fructose which causes harm

Different Ways Your Body Gets/Makes Fructose

• You can directly eat fructose in the form of excess fruit, fruit juice, added sugars
• You can eat processed foods that have added fructose corn syrup
• Eating a high carb meal can also cause your body to make fructose.

In part 2 of this episode, we will finish the fructose story. Rick will share tips on how to avoid the dangerous side effects of excess fructose. He will share food and lifestyle tips.