Sugar gains notoriety in the recent decade as research begins to reveal the underlying harms to human health. Prominent scientists call the substance a "poison", while policymakers keep themselves busy developing guidelines on sugar consumption. Some even went as far as to levy a "sugar tax" on the sweet confectionary.

Pure, White and Deadly” was how Professor John Yudkin, a prominent British nutritionist, described sugar. Now, the sweet nectar may have become deadlier, as the latest research suggests an intimate correlation between sugar and cancer.

The “Warburg effect”: Correlation between sugar and cancer is nothing new

The postulation where consumption of sugar may lead to cancer has been around for almost a decade. The hypothesis was first proposed by the Nobel laureate Dr Otto Heinrich Warburg, in the 1920s.

In his lecture delivered to the Nobel laureates on 30 June 1966, titled "The prime cause and prevention of cancer", Dr Warburg argued that "cancer, above all other diseases, has countless secondary causes. Almost anything can cause cancer. But, even for cancer, there is only one prime cause. The prime cause of cancer is the replacement of the respiration of oxygen in normal body cells by fermentation of sugar."

The hypothesis was derived from the observation that cancer cells largely obtain energy from the process of fermentation, as contrast to normal body cells which generate energy from the “respiration of oxygen” in the presence of fully functioning mitochondria. In Dr Warburg’s words, all normal body cells are obligate aerobes while all cancer cells are partial anaerobes.

A substantial body of evidence was generated especially in the past ten years, which attempted to explain the phenomenon now known as the “Warburg effect”.

Abundant conflicting empirical evidence

One of the latest pieces of evidence that supports the correlation between sugar and cancer comes from a nine-year joint research project from Belgium scientists from several institutions. The group clarified how the Warburg effect stimulated tumour growth; thus, providing the much-needed empirical evidence to support a positive correlation between sugar intake and cancer.

Professor Johan Thevelein, one of the lead researchers, stated that “Our research reveals how the hyperactive sugar consumption of cancerous cells leads to a vicious cycle of continued stimulation of cancer development and growth. Thus, it is able to explain the correlation between the strength of the Warburg effect and tumour aggressiveness.”

However, he was careful to say that “The findings are not sufficient to identify the primary cause of the Warburg effect. Further research is needed to find out whether this primary cause is also conserved in yeast cells.”

Not all studies also point to the same conclusion. In fact, many research projects found conflicting, if not outright confusing, results pertaining to the relationship between different types of sugar and a myriad of cancer subtypes. For example, a large-scale eight-year multi-ethnic cohort study found no association between high sugar intake with pancreatic cancer.

A significant association was also found with fruit and juices intake, but not observed with soda intake. The peculiar observation where fruit intake posed greater risk warrant further scrutiny, and serves as a reminder that the underlying correlation is highly complex.

Similar findings were found in other cancer types. Consumption of sugary beverages was associated with higher odds of developing oestrogen-receptor positive breast cancer; but, such effects were confounded by the ethnicity and menopausal status of the subjects.

Sugar-coat decisions for now

So, is the evidence presented to the medical community sufficient to warrant a sugar-free diet for all cancer patients?

Not necessarily. It is imperative to differentiate a breakthrough in research and that in medicine. An important research finding does not always translate into successful medical practice.

The results presented by Professor Thevelein's group may form the foundation for novel cancer treatment in the future, but to implement sugar-free diets in all cancer patients now may prove to be an impetuous decision - reckless even.

There is robust scientific literature that shows being overweight or obese markedly increase the risk of many different types of cancer – high sugar intake can cause weight gain. It may be prudent to advise against the excessive consumption of added sugar such as sugary drinks, cakes and other confectionaries rather than complete abstinence of all sugar and carbohydrates. MIMS

Read more:

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UK officials warn toast and roast potatoes cause cancer – despite lack of evidence
Nutritional studies: Often overly sensationalised – lead to confusing, conflicting messages in the end