The study – published in the American Journal of Clinical Nutrition – reveals that diet soft drinks have a complicated relationship with health, especially when the wider context of a person’s dietary habits are considered.
The problem, say the researchers, is that there is still very little concrete evidence to say whether such diet soft drinks are good, or bad, for you. Led by Dr Kiyah Duffey from the University of North Carolina at Chapel Hill, USA, the research team noted that a number of recent studies have implicated diet beverage consumption as a possible cause of cardiovascular disease. However, others they explain have long suggested such drinks may be a viable aid for weight management.
Either way, they noted that most previous research has tended to focus either on people's drinking patterns and preferences, or their overall dietary habits – in other words, Duffey argues that most studies until now have failed to tease apart how those two aspects interact to affect people's health.
To address this, Duffey and her team examined not only people's beverage consumption patterns but also the diets of those who consume diet and sugar-sweetened beverages – finding that people who consumed diet beverages tended to be less healthy than people who did not consume them.
The team said their findings suggest that overall diet is more important than certain food or beverage choice and that to make broad health improvements individuals need to consider the bigger picture.
"There was an important interplay between overall diet and what people drink," said Duffey. "It is important that people consider the entirety of their diet before they consider switching to or adding diet beverages, because without doing so they may not realize the health benefits they were hoping to see."
The researchers studied data collected over 20 years from more than 4,000 young adults who participated in the Coronary Artery Risk Development in Young Adults (CARDIA) study.
They found that 827 study participants developed metabolic syndrome — a cluster of risk factors for heart problems and diabetes including extra weight around the waist, unhealthy cholesterol levels, high blood pressure and elevated blood sugar. Duffey also revealed that young adults who drank diet beverages were more likely than those who didn’t to develop metabolic syndrome over the next 20 years.
However, their results showed that other nutritional choices also may play a role, noting that the lowest risk of metabolic syndrome was seen among people who drank no diet beverages and stuck to a ‘prudent’ diet that was rich in foods like fruits, vegetables, whole grains and fish.
People who also ate a prudent diet but did drink diet beverages had a higher rate of metabolic syndrome, however this was not a great increase, they reported.
Duffey said participants with the highest rate of metabolic syndrome (32%) were those who drank diet soda and consumed a typical ‘Western diet’ that includes high amounts of meat, processed foods and sugar.
The team found that individuals who consumed a ‘”Western diet’ also had increased risk of heart disease – regardless of whether or not they drank diet beverages.
"Our study confirms the recommendations of the American Diabetes Association and many weight-loss programs, which suggest people drink these beverages as a way to cut calories and lose or control weight, but only in the context of the whole diet,” said Duffey.