135: How Glucose Overload Breaks Your Metabolism (And How to Fix It) with Dr. Ben Bikman

Bikman emphasizes that dietary carbohydrate, especially refined sources, is the primary driver of NADH accumulation. Each glucose molecule metabolized through glycolysis generates NADH. When intake is high and constant, the mitochondria cannot keep up, leading to the pseudohypoxic state. By cutting carbs, particularly those in processed foods, you reduce the substrate for glycolysis, allowing the NAD+/NADH ratio to recover. He cites a 2014 study showing low-carb diets improved the ratio in liver and muscle within weeks. He also ties this to blood glucose control: avoiding chronic hyperglycemia prevents the vicious cycle of reductive stress and mitochondrial damage. His personal rule—avoid carbs with a barcode—makes the advice actionable.

Physical activity increases the demand for ATP, which pulls electrons through the mitochondrial electron transport chain, oxidizing NADH back to NAD+. This not only clears the backlog but also stimulates the body's own NAD+ synthesis pathways. He notes that regular exercise is one of the most potent ways to improve NAD+ levels and mitochondrial function, countering the sedentary lifestyle that contributes to a low ratio. Unlike supplements, exercise addresses both NADH clearance and NAD+ production simultaneously.

Fasting periods allow the cell to clear accumulated NADH because glucose influx stops. This restores NAD+ levels and activates sirtuins, particularly SIRT1, which are NAD+-dependent proteins that oversee DNA repair, mitochondrial biogenesis, and fat metabolism. Sirtuins consume NAD+ but also trigger feedback loops that enhance NAD+ synthesis. Thus, intermittent fasting addresses both sides of the equation: reducing NADH production and boosting NAD+ regeneration. Bikman presents this as a practical complement to carbohydrate restriction.

Sleep deprivation disrupts the circadian regulation of NAD+ biosynthesis. The body's internal clocks control enzymes that produce NAD+, so when sleep is short or irregular, NAD+ levels drop. This impairs the NAD+/NADH ratio and contributes to metabolic dysfunction. He presents sleep as a foundational, often overlooked factor that supports the other interventions.

Alcohol metabolism in the liver uses NAD+ as a cofactor, converting it to NADH. This causes a rapid and dramatic shift in the ratio. Chronic consumption depletes hepatic NAD+, impairing fat oxidation and promoting fatty liver disease, which is closely linked to hepatic insulin resistance. Eliminating or reducing alcohol is a straightforward way to protect the NAD+/NADH balance, especially for those already struggling with metabolic health.

Bikman explains that when blood glucose is chronically high, the sheer volume of glucose entering cells overwhelms glycolysis and the mitochondria. NADH is produced faster than it can be oxidized back to NAD+, causing the NAD+/NADH ratio to plummet. This state mimics hypoxia because, even with abundant oxygen, the electron transport chain is backed up, and the cell experiences reductive stress—too many electrons with nowhere to go. This pseudohypoxia inhibits GAPDH, a key glycolytic enzyme, causing upstream metabolites to accumulate and divert into damaging pathways. The result is a self-perpetuating cycle: high glucose → low NAD+/NADH → mitochondrial dysfunction and oxidative stress → insulin resistance → higher blood glucose. This mechanism explains why insulin resistance can develop even before fasting blood glucose looks abnormal, because the cellular energy traffic jam is already underway.

Under normal glucose conditions, the polyol pathway is minimal. But when glucose is chronically elevated, the enzyme aldose reductase converts glucose to sorbitol, consuming NADPH—the cell's antioxidant currency. Then another enzyme converts sorbitol to fructose, generating more NADH. So the pathway delivers a double blow: it depletes antioxidant defenses and adds to the NADH overload. This is particularly damaging in tissues like the eyes, nerves, and kidneys, where aldose reductase is abundant, explaining why diabetic complications often manifest there. Bikman ties this to the broader pseudohypoxia narrative, showing that the polyol pathway is one of the four major damaging routes activated by the altered NAD+/NADH ratio.

Bikman references a landmark 2000 paper that demonstrated all four classic pathways of diabetic complications—polyol pathway activation, protein kinase C stimulation, hexosamine pathway flux, and advanced glycation end-product formation—originate from a single upstream event: mitochondrial overproduction of superoxide radicals due to the skewed NADH/NAD+ ratio. When mitochondria are flooded with NADH, electrons leak and form superoxide, which then triggers each of these damaging cascades. This unifying mechanism underscores that controlling the NAD+/NADH ratio is not just about energy, but about preventing widespread cellular damage. It also explains why simply lowering blood glucose without addressing the underlying mitochondrial redox state may not fully halt complications.

Bikman walks through the human trial data. A 2018 study in obese insulin-resistant men found that 1,000 mg/day of NR for 6 weeks raised blood NAD+ levels by 60% but produced no significant improvements in insulin sensitivity or other metabolic outcomes. A 2019 trial in healthy older adults similarly saw no meaningful metabolic or physical performance benefits. A 2021 NMN study showed a modest improvement in muscle insulin sensitivity only in prediabetic women, with a small effect size. He posits that bioavailability issues, underdosing relative to animal studies, and the failure to address the root cause—chronic NADH accumulation from glucose overload—explain the disconnect. He warns that the supplement industry markets these products aggressively based on mouse data, and that for most people, lifestyle changes are far more effective and evidence-based.