Is soda bad for your brain?

One of the biggest fears we face – especially if we’re lucky enough to live a long life – is dementia. Despite great efforts to treat Alzheimer's and other dementia forms, there is no cure for this malady. Prevention is crucial.

Important modifiable risk factors for dementia are poor nutrition, binge drinking, lack of physical activity and mental stimulation and smoking.

A new study in the American Journal of Clinical Nutrition looks at a large population of almost 180,000 people in England, with no signs of dementia at the start of the study, and follows them for an average of almost 10 years. The diet of the participants was reported, and their sugary drink consumption tallied. The genetic risk of dementia was assessed for each participant looking at common genetic variants related to the risk of Alzheimer’s disease. 

During follow-up almost 1300 of the participants developed dementia. After adjusting for socioeconomic status, lifestyle factors, such as alcohol intake, smoking, exercise and weight status, and underlying health conditions that may affect dementia risk, the researchers found that those who consumed more than 2 sugary drinks a day had greater odds of developing dementia: their risk rose by some 35 percent. Excessive intake of added sugar was also linked with dementia risk.

The added risk was seen with sugary drinks, but also with artificially sweetened ones. On the other hand, those consuming moderate amounts of fruit juices did not have a higher risk of dementia. These links were not modified by genetic predisposition.

A similar study of almost 3000 people over the age of 60 years showed almost doubling of dementia risk among those with high intake of artificially sweetened drinks, and another study of 1865 people showed greatly increased risk of dementia with an intake of on average 7 sugary drinks a week.

How could sugary drinks impair the brain? It might be that the excessive sugar and rapid rise in insulin impair the brian, and for artificially sweetened drinks the authors suggest that aspartame could disrupt energy production and increase oxidative stress.

Why are sugary drinks singled out?

The western diet contains plenty of added sugar, but while sugar’s added to many foods, most of the added sugar hides in drinks – soda, sports drinks, energy drinks, flavored milks and fruit juices – the sheer amount of sugar in sugary drinks can explain why they are linked so tightly with obesity.

But studies show that there is something distinctive about getting calories in liquid form. Solid sugars suppress hunger somewhat, while liquid sugar – in sugary drinks – doesn’t affect satiety.  Sugary drinks’ calories are just added, and the meals eaten with them will be just as large, if not larger. And several studies have suggested that sugary drinks are an independent risk factor for diabetes and hypertension irrespective of obesity. 

Liquid sugar lends itself to overconsumption, and it might very well be that sugar in liquid form poses an especially tough burden on our body’s metabolism and on our brain’s function.

Dr. Ayala