The consumption of sugary drinks has increased worldwide by over 40 per cent from 1990 to 2016. Sugary drink consumption was one of the behavioural risks that contributed to the increase in global attributable death because of lifestyle diseases. Such drinks are associated with obesity, a strong risk factor for many cancers.
A French study, to find a specific association between sugar and cancer, suggests drinks such as colas, lemonade and energy drinks show strong association between sugar induced obesity and cancer. The researchers suggest that there could also be other reasons sugar could trigger cancer. It was found that an increase in sugary drink consumption was positively associated with the risk of cancer. On splitting a group of sugary drinks into 100 fruit juices and other sugary drinks, consumption of both was linked with a higher risk of cancer.
The link might be partly explained by their effect on onset of obesity. Excess weight has a strong risk factor for mouth, larynx, pharynx, esophageal, breast, ovarian, endometrial, gallbladder, stomach, pancreatic, liver, colorectal, prostate, and kidney cancers. It suggests that weight gain might not be the only driver. More specifically, it has been suggested that sugary drinks might promote gains in visceral adiposity independent of body weight. Other two randomised trials also support the hypothesis. Tumorigenesis might be promoted by Visceral adiposity through alterations in cell signaling pathways and adipokine secretion.
Another pathway could be the high glycemic index of sugary drinks. Glycemic index is associated with hyperinsulinemia and type2 diabetes. Both potentially increase the risk of breast cancer. Glycemic load is associated with increased proinflammatory markers, such as C reactive protein (CRP) and systemic inflammation. Also, high glycemic index is associated with diabetes-related carcinomas.
In several such drinks, presence of advanced glycation end products suggested impairment of endothelial function in patients with and without diabetes. Daily consumption of sugar from such drinks was positively linked with cancer. Alteration for sugar from the drinks cancelled this link. These results suggest that the relation was strongly driven by sugar content. Even drinks that had lower sugar content were linked to cancer in the study, probably because they were consumed in higher amounts. In contrast, unsweetened tea and coffee and water were not associated with cancer.
This does not imply that nobody should drink them. As usual with nutrition, the idea is not to overdo anything. Several public health agencies recommend consuming less than one drink per day. Fruit juices are considered a little better because they contain some vitamins and fiber.
Epidemiological literature on sugary drinks and risk of cancer is still limited. As these studies are observational, it is not possible for researchers to state that sugar is a definitive cause. There are some biological mechanisms, such as the effect of sugar on the visceral fat stored around vital organs like liver and pancreas, increased blood sugar levels and inflammatory markers, that are linked to increased cancer risk.
Cutting down on sugary drinks, together with increase in sugar taxes and restrictions on marketing of these products, might help to reduce the global cancer burden.
Niranjan Naik, Director, breast & gastro-intestinal (GI) onco-surgery, FMRI