Try This: How Fructose Damages the Brain and Increases Our Risk for Alzheimer’s

Did you know that regularly consuming highly concentrated sources of fructose can potentially harm the brain?

Today we’re talking about the link between fructose and Alzheimer’s, inspired by Dr. Richard Johnson’s groundbreaking new hypothesis.

I want to be clear that we’re talking about highly concentrated sources of fructose, like high fructose corn syrup and frequent consumption of fruit juice, not the natural fructose in whole fruit. We’re not trying to instill any fruit phobia here!

How Our Evolutionary Foraging Response Is Backfiring Today

Fructose has been a part of our diet forever. When our ancestors foraged for fruit, a survival mechanism would kick in and tell the brain to keep eating. In our first interview, Dr. Johnson explains why this benefited human survival. He says that large amounts of fructose increase uric acid production, which tells the liver to turn any excess into fat.

This mechanism helped our ancestors avoid starvation, but today, with 10 percent or more of the average person’s calories coming from fructose, it has backfired, resulting in metabolic disaster. And as Dr. Johnson’s hypothesis suggests, this metabolic devastation is not limited to the body. It takes a massive toll on our brain health as well.

The Effects of Fructose on Mitochondrial Function

In addition to revving up fat production, uric acid damages the mitochondria and creates oxidative stress. When this happens, our energy levels drop, which increases cravings for carbs and sugar.

The Brain’s Response to Excessive Fructose Intake

When we consume significant quantities of fructose, our bodies receive a signal to direct blood flow toward the brain regions responsible for foraging behavior. Consequently, our ancestors were likely motivated to continue eating fruit whenever it was accessible. However, this preference came with a trade-off: the reduction of blood flow to less vital brain regions, such as those involved in memory.

This was a fair deal at the time. But now, in a world where sugar is always at our fingertips, it has caused oxidative stress, mitochondrial damage, and the deterioration of our brain’s memory center.

Why High Sugar Loads Are Problematic Today

While we’re primarily focusing on fructose today, Dr. Johnson also says that the brain and body can convert concentrated sources of glucose into fructose. This conversion of glucose into fructose creates oxidative stress and amyloid beta plaque, a precursor to Alzheimer’s disease.

Moreover, high salt concentrations in ultra-processed foods expedite the conversion of glucose into fructose. According to Dr. Johnson’s work in mice, this helps convert glucose and fructose into fat. Evolutionarily, this was beneficial because salt has a dehydrating effect. So, in times of famine, we could rely on our fat stores for energy and water. Pretty cool, right?

Try This:

Do these five things to reduce the amount of concentrated fructose in your diet to protect your mitochondria from damage and your brain from oxidative stress and Alzheimer’s disease.

1. Dramatically reduce high fructose corn syrup in your diet. The primary sources of high fructose corn syrup are soda and ultra-processed foods. If you’re unsure whether or not an item contains high fructose corn syrup, read the ingredient label.

2. Lower your intake of concentrated fructose. Soda and ultra-processed foods are the biggest offenders, but there are other sneaky sources of fructose to watch out for, such as large amounts of dried fruit and fruit juice.

Fruit juice contains concentrated sources of fructose that would otherwise be difficult to consume from fruit in its whole-food form. Regular consumption of large amounts of fruit juice can increase the overall fructose burden on the body.

Dr. Johnson is most concerned about high fructose corn syrup and liquid fructose and not about natural fructose in whole fruit because it contains fiber, polyphenols, and other nutrients that benefit gut health.

If you’re eating ultra-processed food, starchy carbs, or dried fruit or drinking soda or fruit juice regularly, start here:

  • Aim to cut your added sugar intake in half. This will help to lower your fructose and glucose load. In my interview with Dr. Robert Lustig, he discusses what to expect after dramatically cutting back on sugary foods and drinks.

Then, after cutting back by half…

  • Aim for no more than 25 grams of added sugar per day.

3. Treat sugar as a dessert. Sugar is not the enemy. When we eat it for breakfast, lunch, and dinner, though, we start to run into problems. The big challenge with added sugar is that Big Food mixes it into everyday foods like salad dressings, pasta sauces, bread, and protein bars. Look for the added sugars on packaged food ingredient labels to lower your exposure.

4. Utilize the power of hydration. Dr. Richard Johnson’s core research into hypertension helped me understand that extremely salty foods can increase the conversion of glucose to fructose to fat.

Ensuring you are properly hydrated, especially if you plan to consume processed, salty foods, can help halt this conversion. As a reminder, the problem with salt isn’t the salt we add to foods we cook at home. The problem with salt, like added sugar, is that it’s in everything ultra-processed!

Dr. Johnson uses French fries as a classic example of this. As a high-glycemic carb coated in salt, they’re especially fattening—the salt causes a dehydration-like state that encourages the conversion of starch into fructose. That doesn’t mean you can never eat fries again. According to Dr. Johnson, simply having a large glass of water beforehand can help minimize the impact.

5. Increase lean muscle mass. Lean muscle helps soak up glucose and improves glycemic control. I saw this firsthand in my journey. When I doubled down on strength training, I had more freedom to incorporate starchy foods into my diet without crazy blood sugar swings, and my fasting insulin stayed in the optimal range.

Final Thoughts

I want to hammer this point home one last time! We’re not worried about the fructose from whole fruit or the occasional glass of juice.

I’ll also add that I’m not worried about some added sugar here and there as long as we do not have pharmacological doses of it every day—which is what most Americans are doing.

The truth is, if you are getting most of your calories from whole foods, generally staying away from ultra-processed foods and soda, and focusing on the basics like hydration, adequate protein, and strength training, then you are doing better than 99 percent of people.

And as a bonus, your body can get away with having more carbs and sugar because you’re more metabolically flexible.

Here’s to your health,
Dhru Purohit

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