Sugar and your health: what science has been warning us about for decades

At our clinic we have always insisted that oral health is a mirror of overall health. Sugar, our greatest enemy in the mouth, is equally harmful to the rest of the body. Here we explain why, backed by science.

The Nobel Prize winner who discovered it in 1931

In 1931, German biochemist Otto Warburg was awarded the Nobel Prize in Physiology or Medicine for a discovery that, nearly a century later, remains uncomfortable for many: cancer cells metabolise glucose differently from healthy cells. Instead of using normal aerobic respiration, tumour cells ferment glucose even in the presence of oxygen -- a phenomenon known as the Warburg effect.

What Warburg observed was that cancer cells have an insatiable appetite for sugar. They require large amounts of glucose to sustain their accelerated growth. For a long time this observation was treated as a scientific curiosity, but modern research has turned it into one of the keys to understanding the relationship between diet and cancer.

Today we know the problem extends beyond glucose. Fructose -- found in massive quantities in ultra-processed foods, soft drinks, and industrial fruit juices -- activates specific metabolic pathways that promote tumour growth, fatty liver disease, and metabolic syndrome.

The three enzymes that regulate the process

To understand how sugar influences the development of cancer and metabolic syndrome, you need to know three key molecular players. These three enzymes regulate cell growth, energy metabolism, and the body's response to excess nutrients:

Metformin, the most widely prescribed drug for type 2 diabetes, works precisely by activating AMPK. It is significant that diabetic patients treated with Metformin show a notably lower incidence of cancer than expected. This is no coincidence: by reactivating AMPK, Metformin restores one of the body's natural defence mechanisms against uncontrolled tumour growth.

9 days without fructose: the results

In 2017, a team led by Schwarz et al. published a landmark study in the Journal of the American Association for the Study of Liver Diseases. The design was simple yet powerful: they took a group of obese children with metabolic syndrome and replaced the fructose in their diet with starch for just 9 days, without reducing total calories.

The results were striking:

These changes occurred in just 9 days and without any calorie reduction. The message is clear: not all calories are created equal. Added fructose has a specific metabolic effect that goes far beyond its energy value. And perhaps most importantly: metabolic syndrome is not exclusive to overweight individuals. Up to 40% of people with a normal weight have metabolic abnormalities linked to excess fructose in their diet.

Fructose and breast cancer

Research by Jiang Y et al. (2016), published in Cancer Research, demonstrated that fructose activates the 12-LOX/12-HETE pathway in breast cancer cells, promoting metastasis. This mechanism is independent of glucose -- meaning fructose has its own specific oncological role.

The work of Strober JW et al. (2019) added another piece to the puzzle: chronic fructose excess generates hyperinsulinaemia (persistently elevated insulin levels), which in turn raises IGF-1 (insulin-like growth factor 1), a potent stimulator of tumour growth.

Is the scientific literature on sugar objective?

In 2016, the journal PLOS Medicine published an investigation that shook the foundations of evidence-based nutrition. After analysing decades of studies funded by the sugar industry, the authors found a clear pattern: industry-sponsored studies were five times more likely to conclude that there was no link between sugar and cardiovascular disease.

The story of the Sugar Research Foundation (now the Sugar Association) is particularly revealing. In the 1960s, this foundation funded studies at Harvard University that deliberately shifted attention away from the harmful effects of sugar and towards saturated fats. The result was half a century of misguided nutrition policies that prioritised fat reduction -- often replacing fats with added sugars.

Information that goes unpublished carries the same weight as information that does reach doctors' desks.

Today we have high-quality independent research confirming what those censored studies were trying to show. But the damage is done: entire generations grew up believing fat was the enemy, while sugar entered the Western diet without restraint.

The connection to your dental health

Everything described above does not stay confined to research laboratories -- it has a direct impact on your mouth. The relationship between sugar and dental health is twofold, and runs deeper than most patients realise.

The local attack: tooth decay. Cariogenic bacteria -- especially Streptococcus mutans -- ferment sugars (both glucose and fructose) and produce organic acids that dissolve dental enamel. Every sugar intake triggers an acid attack lasting approximately 20 minutes. If consumption is frequent, the enamel has no time to remineralise, and cavities develop.

The systemic attack: periodontal disease. As we have seen, chronic fructose excess generates hyperinsulinaemia, systemic inflammation, and metabolic disruption. This low-grade inflammation directly worsens periodontal disease: inflamed gums bleed more readily, lose their attachment, and the supporting bone resorbs more easily. Metabolic syndrome and periodontitis are, in fact, frequent comorbidities.

From the perspective of biological dentistry, nutrition is not an afterthought tacked on at the end of an appointment -- it is an integral part of our treatment protocol. There is little point in treating aggressive periodontitis if the patient is consuming 70 grams of added sugars daily. Likewise, optimising nutrition before surgery or implant treatment significantly improves clinical outcomes.

If you want to learn more about how diet affects your teeth and gums, we recommend our article on nutrition and dental health.