Fruit Is Healthy... Except When It Isn't

Rethinking "Healthy": Why Fruit Isn't Always Your Friend

We've all been taught: 5 a day! Eat at least five servings of fruits and vegetables. It's advice that's literally woven into our food pyramids, MyPlate, and public health campaigns, as part of a balanced diet. Fruit is positioned as a whole food. A guilt-free source of vitamins, fiber, and antioxidants. But what if this universal advice is flawed? What if, for the vast majority of people, certain "healthy" foods are actively hindering their health goals or even harming them?

To figure this out, we first need to redefine what "healthy" means. A food is healthy only if it promotes health in the body that's eating it. If a food contributes to fat accumulation in the liver, elevates damaging blood markers, and worsens a dysfunctional metabolism, it isn't healthy for that person, no matter how many vitamins it contains. The context of an individual's metabolic health matters.

The Fructose Factor: A Different Kind of Sugar

At the heart of this issue is fructose, one of the sugars found in fruit. While it's often lumped in with glucose, your body handles it in a profoundly different way.

Glucose is easy fuel. Nearly every cell in the body can use it for energy. When we consume glucose, it circulates in our bloodstream, and with the help of insulin, it enters cells to be used immediately.

Fructose is a different story. It can't be used by most cells. Instead, it must be processed almost exclusively by the liver. Think of the liver as a busy city's traffic control center. Glucose has many roads it can take, but fructose has only one exit, and it leads directly to the liver.

Inside the liver, fructose metabolism bypasses a key regulatory checkpoint that governs energy production. This allows it to be converted into other substances with alarming efficiency, chief among them being triglycerides (a type of fat). This process is called De Novo Lipogenesis (DNL), which literally means "making new fat." Consuming high amounts of fructose, whether from fruit, table sugar, or high-fructose corn syrup, is like putting your liver's fat-production factory into overdrive, directly contributing to conditions like non-alcoholic fatty liver disease (NAFLD).

And please understand, the liver does not differentiate between the 'natural' fructose from an apple and the fructose from high-fructose corn syrup in a can of soda. The biochemical pathway to creating new fat is identical.

This isn't just a theoretical problem; it has been demonstrated in clinical research. A 2022 randomized controlled trial on patients with NAFLD looked at this exact issue. Researchers found that the participants instructed to eat four or more servings of fruit per day had significantly worse outcomes after six months. Their liver enzymes, cholesterol, and insulin resistance all increased, while their "good" HDL cholesterol decreased. The study concluded that for this group, a high-fruit diet could worsen the very conditions they were trying to fix, confirming that for a metabolically unhealthy person, large amounts of fruit can be actively harmful.

The Body's Own Fructose Factory: The Polyol Pathway

Our body can make its own fructose from glucose. It does this through a biochemical route called the polyol pathway. In a healthy person with normal blood sugar, this pathway is mostly dormant, producing only minuscule amounts of fructose needed for specific functions, such as providing energy for sperm cells.

The pathway works in two steps:

The enzyme aldose reductase converts glucose into a sugar alcohol called sorbitol.

Sorbitol is then converted to fructose by the enzyme Sorbitol Dehydrogenase.

Under normal conditions, this is a slow, controlled process. But when blood glucose levels are chronically high, as they are in pre-diabetes and diabetes, this pathway kicks into high gear. The flood of excess glucose forces aldose reductase to work overtime, producing a flood of sorbitol and, subsequently, fructose, right inside the cells that aren't equipped to handle them.

This internal fructose production is devastating because it happens in tissues that are not designed to process it, leading directly to many of the severe complications associated with diabetes.

Vision (Diabetic Retinopathy): In the lens of the eye, sorbitol accumulates because it can't easily exit the cell. It draws water in through osmosis, causing the lens to swell and become cloudy, forming cataracts. In the retina, the overactive pathway creates oxidative stress, damaging the delicate blood vessels and leading to vision loss.

Kidneys (Diabetic Nephropathy): The same process occurs in the kidneys. Sorbitol and fructose buildup cause osmotic stress and cellular damage, impairing the kidneys' ability to filter blood and eventually leading to kidney failure.

Nerves (Diabetic Neuropathy): Nerve cells are incredibly vulnerable. The accumulation of sorbitol damages both the nerves themselves and the Schwann cells that form their protective myelin sheath. This leads to the classic symptoms of neuropathy: pain, burning, tingling, and numbness, especially in the hands and feet.

This isn't an external attack; it's a form of self-sabotage, triggered entirely by chronically elevated blood sugar.

Why 'Good Control' Can Still Cause Damage

Consider the official guidelines. The American Diabetes Association (ADA) regards a hemoglobin A1c of 7% as a target for "good control."

However, an A1c of 7% doesn't mean your glucose is normal. It translates to an estimated average blood glucose of 154 mg/dL (8.5 mmol/L). A level far above the threshold required to activate the polyol pathway continuously. At this "controlled" level, the damaging conversion of glucose to sorbitol and fructose is constantly occurring inside your cells.

This leads to a tragic and frustratingly common conversation in clinics everywhere. A patient asks, “But my A1c is well-controlled at 7%, so why am I losing my eyesight?” The circular answer they often receive is, “Well, that's a complication of diabetes.”

The truth is, these complications aren't a mysterious part of the disease; they are the predictable biochemical consequence of living with blood sugar levels that are still high enough to inflict damage, even when labeled as "controlled."

The Scary Scale of Our Metabolic Crisis

You might think these issues only affect a small number of people. The reality is terrifying. A groundbreaking 2019 study from the University of North Carolina at Chapel Hill revealed that only 12% of American adults were considered metabolically healthy. A more recent analysis suggests this number may have dropped to less than 7%.

This isn't a vague assessment. Optimal metabolic health is measured by having ideal levels in five specific markers, all without the help of medication:

• Waist Circumference: Less than 40 inches for men, 35 for women.
• Blood Glucose: A fasting level under 100 mg/dL.
• Blood Pressure: Systolic below 120 and diastolic below 80 mm Hg.
• Blood Triglycerides: Below 150 mg/dL.
• HDL Cholesterol (the "good" kind): Above 40 mg/dL for men, 50 for women.

Failing even one of these markers means you are not in optimal metabolic health. With over 93% of the population in this category, it means the vast majority of us have a metabolism that is already dysfunctional, making us highly susceptible to the dangers of fructose, whether from a soda or a fruit smoothie.

Building a Nutrient-Dense Diet

So, what is the solution? It's not about being afraid of food; it's about being informed. A healthy diet prioritizes nutrient density without triggering metabolic chaos. This means building your meals around:

• High-Quality Protein: Meat, poultry, fish, and eggs.
• Healthy Fats: Tallow, butter, olive oil, and avocado.
• Nutrient-Rich Vegetables: Leafy greens and other non-starchy vegetables.

Notice what's not on the list? Fruit. While fruits contain vitamins, every single essential nutrient found in fruit can be obtained from animal foods and vegetables, often in a more bioavailable form and without the damaging fructose load.

One apple is not the enemy

Does this mean nobody should ever eat fruit again? Of course not. A single peach or a handful of berries is not the problem. What is misleading is the idea that fruit is a universal health food with no limits. For many people, especially those already struggling with metabolic health, more is not better.

Small amounts of low-sugar fruit can be fine, especially when paired with protein or fat. Berries with cream, for example, are very different from a glass of orange juice or a smoothie packed with bananas and mango. If you do choose to eat fruit, stick to low-sugar options like blackberries, raspberries, and strawberries in small quantities. Your liver and your future self will thank you.

Final Thoughts:

Fructose is not an essential nutrient; the tiny amount the body needs, it can make itself, and too much, whether from fruit or internal pathways, causes damage.

Good health comes from understanding how foods impact your body.

Eat like it matters
–Coach Roxana

Written by Roxana Soetebeer, MPHC, NNP, MHP, PFC
Published September 7th, 2025

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