Rick Johnson, M.D.: Metabolic Effects of Fructose (Ep. #87 Rebroadcast)
This episode features a rebroadcast with Rick Johnson, professor of nephrology at the University of Colorado, discussing how fructose profoundly impacts metabolic health, blood pressure, insulin resistance, and obesity, and his clinical approach to these issues.
Deep Dive Analysis
17 Topic Outline
Introduction to Rick Johnson and Fructose Research Origin
Revisiting Salt's Role in High Blood Pressure
Defining Glucose, Fructose, and Sucrose
Ancient Ape Mutation and Human Fructose Sensitivity
Uric Acid: Beyond Gout to Metabolic Disease
Fructose Metabolism: ATP Depletion and the Fat Switch
Why Drinking Sugar is Worse Than Eating It
Fructose, Oxidative Stress, Insulin Resistance, and Diabetes
How Cancer Utilizes Fructose as a Fuel
Fructokinase Inhibitors: A Potential Therapeutic Breakthrough
Clinical Management of High Uric Acid Levels
Salt Intake: Balancing with Water for Health
High Glycemic Carbs and Endogenous Fructose Production
Artificial Sweeteners Versus Real Sugar
Umami, MSG, and Their Role in Metabolic Illness
Fructose Consumption: Acceptable Amounts and Fruit Intake
Managing Children's Sugar Intake
6 Key Concepts
Serum Osmolality
Serum osmolality refers to the concentration of molecules in a set volume of blood. When you eat salty food, if not balanced with water, your serum osmolality and sodium concentration increase, which acutely triggers a rise in blood pressure.
Essential Hypertension
This is a term for high blood pressure without an obvious cause, which accounts for the majority of cases. Recent research suggests it can be linked to an inflammatory and autoimmune response in the kidneys, causing them to retain sodium aberrantly.
Uricase Mutation
An ancient genetic mutation in apes, inherited by humans, that led to a much stronger uric acid response when metabolizing fructose. This mutation enhanced fat storage from fruit, providing a survival advantage during periods of food scarcity, but makes humans more sensitive to sugar's metabolic effects today.
ATP Depletion (Fructose Metabolism)
Unlike glucose, fructose metabolism by fructokinase consumes ATP in an unregulated manner, causing intracellular ATP levels to drop significantly (40-50%). This signals an energy crisis, shifting the body into a state that prioritizes energy storage (fat, glycogen) and reduces metabolic expenditure.
AMPK vs. AMPD Pathway
When ATP breaks down to AMP, the cell can activate one of two opposing pathways. The AMPK pathway promotes energy burning and fat oxidation, while the AMPD pathway, triggered by the intracellular phosphate drop from fructose metabolism, drives fat storage, insulin resistance, and uric acid generation.
Aldose Reductase
This is an enzyme that converts glucose into fructose within the body. It becomes activated by high glucose levels (e.g., from high glycemic diets) and high salt intake, leading to the endogenous production of fructose even when no dietary fructose is consumed.
13 Questions Answered
Salt intake, particularly when consumed without sufficient water, increases serum osmolality and sodium concentration, which acutely raises blood pressure by about six millimeters for a small increase in serum sodium.
While 120/80 is considered optimal, risks for stroke and mortality increase with blood pressure above 140/90, with a significant inflection point around 160-180.
Glucose is the body's primary energy fuel, stored as glycogen. Fructose is a sweeter sugar found in fruit and honey, primarily involved in energy storage (fat). Table sugar (sucrose) and high-fructose corn syrup are combinations of glucose and fructose.
Humans, along with other primates and birds, carry an ancient uricase mutation that leads to a much stronger uric acid response to fructose, enhancing fat storage as a survival mechanism.
Elevated uric acid is a significant risk factor for high blood pressure, kidney disease, pre-diabetes, insulin resistance, and fatty liver, by stimulating oxidative stress in mitochondria and promoting fat storage pathways.
When sugar-containing liquids are consumed quickly, the high concentration of fructose rapidly reaches the liver, causing a significant ATP depletion that triggers metabolic effects more dramatically than eating the same amount of fructose with fiber or other foods.
Fructose metabolism depletes intracellular ATP and phosphate, activating the AMPD pathway which promotes fat storage, reduces fat burning, induces insulin resistance, and increases hunger and thirst, shunting calories towards fat and glycogen.
Many cancer cells thrive in low-oxygen environments and preferentially use fructose as fuel because it helps them switch from oxygen-dependent mitochondrial metabolism to glycolysis, a process that doesn't require oxygen.
Yes, drugs that block fructokinase (the enzyme metabolizing fructose) are being developed, with one showing success in treating fatty liver in phase two trials, suggesting they could be powerful in reversing metabolic syndrome.
While labs often flag high uric acid above 6.5 or 7.5, risks for pre-diabetes, insulin resistance, hypertension, and kidney disease begin to increase when serum uric acid is over 5.5 mg/dL.
Yes, high glucose intake (from high glycemic carbs like bread, potatoes, rice) can induce the enzyme aldose reductase in the liver, converting glucose into fructose endogenously, which then drives fatty liver, insulin resistance, and diabetes.
Artificial sweeteners are generally considered the lesser of two evils compared to real sugar because they don't have the same peripheral metabolic effects that drive fat storage and insulin resistance, even if they activate sweet taste receptors.
While liquid forms of sugar/fructose should be avoided, whole fruits contain beneficial compounds that can mitigate fructose's negative effects. Small to moderate amounts of low-fructose fruits (like berries, kiwi, lemon) are generally fine, but large quantities of high-fructose fruits (like grapes, large apples) can still trigger metabolic pathways.
18 Actionable Insights
1. Strictly Avoid Liquid Fructose
Draw a hard line against consuming any liquids containing added sugar, fructose, or high fructose corn syrup, as rapid consumption leads to high fructose concentration in the liver, significantly triggering metabolic issues like obesity and insulin resistance.
2. Minimize Fructose Intake
Reduce overall fructose consumption to prevent rapid ATP depletion in cells, which triggers a ‘survival mode’ that reduces metabolism, increases hunger, and shunts calories towards fat and glycogen storage, contributing to obesity, insulin resistance, and high blood pressure.
3. Reduce High Glycemic Carbohydrates
Limit intake of high glycemic carbohydrates (e.g., bread, potatoes, chips, rice), especially if overweight or metabolically compromised, as high glucose levels can induce an enzyme in the liver to convert glucose into fructose, driving metabolic disease even without dietary fructose.
4. Pair Salt Intake with Water
Always drink plenty of water when consuming salty foods to prevent a rise in serum sodium, which can trigger endogenous fructose production, acute blood pressure spikes, and other metabolic effects.
5. Maintain Adequate Hydration
Drink plenty of water (or zero-osmolarity beverages like diet soda, tea, or coffee) daily to help suppress the negative metabolic effects of fructose, prevent endogenous fructose production from dehydration, and potentially slow the progression of kidney disease.
6. Consider Uric Acid Management
Discuss with your doctor the potential benefits and risks of taking allopurinol if your serum uric acid levels are consistently above 5.5 mg/dL, especially if they are 8 mg/dL or higher, or if you have kidney disease, as high uric acid is linked to high blood pressure, insulin resistance, and fatty liver.
7. Limit Beer Consumption
Reduce beer intake, as its brewer’s yeast content and umami components can significantly raise uric acid, contributing to abdominal obesity, fatty liver, high blood pressure, and metabolic syndrome (the ‘beer belly syndrome’).
8. Be Mindful of Umami-Rich Foods
Be cautious with high umami foods, especially those rich in purines (e.g., shrimp, Parmesan cheese), as they may raise uric acid levels and contribute to metabolic risk, potentially bypassing the sugar pathway.
9. Consume Whole Fruits Judiciously
Eat whole fruits in moderation, prioritizing berries (blueberries, raspberries, strawberries) which are generally safe in larger quantities, and limiting high-fructose fruits like grapes and large apples to avoid overwhelming the body’s metabolic pathways.
10. Avoid Dried Fruit
Steer clear of dried fruit, as it is a concentrated source of fructose with many of the beneficial components of whole fruit lost during processing, making it metabolically less favorable.
11. Choose Diet Over Regular Soda
If choosing between regular sugar-sweetened beverages and diet versions, opt for diet drinks as they are the lesser of two evils compared to the significant metabolic harms of regular sugar.
12. Educate Children on Sugar
Teach children (e.g., 4th-6th grade) how to read food labels to understand sugar content and demonstrate the high amount of sugar in beverages like soft drinks to foster healthier eating habits.
13. Critically Evaluate Sugar Studies
Be critical of studies on sugar and weight gain that control for caloric intake, as they may not reflect real-world effects where sugar consumption can lead to increased overall food intake due to leptin resistance.
14. Contextualize High-Energy Foods
Consume high-energy foods like trail mix and sports drinks only when contextually appropriate (e.g., intense physical activity, mountaineering) rather than as general snacks or beverages, due to their high sugar content.
15. Target Optimal Blood Pressure
Aim for a blood pressure around 120/80 mmHg, as this is considered optimal and is associated with a lower risk of heart failure, stroke, and other cardiovascular diseases.
16. Understand Allopurinol Risks
If prescribed allopurinol, be aware of the risk of allergic reactions (e.g., rashes), particularly if you are of Asian or African-American descent, and stop the drug and contact your doctor immediately if a rash develops.
17. Use Sugar Substitutes for Baking
When baking at home, use sugar substitutes like Splenda to reduce sugar intake, especially for children, while still allowing for occasional treats.
18. Limit Purine-Rich Foods for Gout
To reduce the risk of gout, limit consumption of purine-rich foods like anchovies, small fish with high cellular density, and beer (due to brewer’s yeast), as these increase uric acid levels.
6 Key Quotes
When you eat fructose, the energy in the cell falls before it goes up. It's the only nutrient that lowers energy in the cell.
Rick Johnson
Humans are much more sensitive to sugar than most animals. And it's because of this mutation.
Rick Johnson
If you live in the Western world and you just have to go down to the grocery store, no. I think living without fructokinase would probably solve a lot of the world's health problems.
Rick Johnson
Regular Coke is more dangerous than a Diet Coke.
Rick Johnson
The old wives tale that drinking six glasses of water a day is good to help keep you skinny is true. It turns out that water suppresses some of the effects of fructose.
Rick Johnson
What I usually say is the big four are bread, potatoes, chips, and rice. Those four are the foods that you should reduce a little bit.
Rick Johnson
2 Protocols
Rick Johnson's Clinical Approach to High Uric Acid Levels
Rick Johnson- Measure the patient's serum uric acid level.
- If the serum uric acid is 8 mg/dL or higher, start allopurinol after discussing the pros and cons, including the risk of rash (Stevens-Johnson syndrome).
- If the serum uric acid is between 5.5 mg/dL and 8 mg/dL, discuss the pros and cons of treatment with the patient. Consider starting allopurinol, especially for patients with kidney disease (e.g., at 6.5 mg/dL).
- Instruct the patient to stop the drug immediately and call if any rash develops.
General Dietary Advice for Reducing Metabolic Disease
Rick Johnson- Avoid drinking any liquids that contain added sugar, fructose, or high-fructose corn syrup.
- When consuming salt, ensure adequate water intake to prevent acute rises in serum sodium and osmolality.
- Reduce the intake of high glycemic carbohydrates, specifically 'the big four': bread, potatoes, chips, and rice, as they can induce endogenous fructose production.
- Be mindful of umami-rich foods, especially in liquid form or those high in purines (e.g., beer), as they may activate metabolic pathways similar to sugar.
- Limit consumption of high-fructose fruits and dried fruits. Prioritize low-fructose whole fruits like berries, kiwi, and lemon in moderation.