Diet soda linked to higher heart disease risk: study

[blog editors note] Pharmacists inducing their customers to drink cheap pop -- please take note.

Written by: SHERYL UBELACKER

TORONTO (CP) - For those who drink diet pops in the belief that sugar-free beverages are healthier than regular soft drinks, new research suggests they should think again.

A huge U.S. study of middle-aged adults has found that drinking more than one soft drink a day - even a sugar-free diet brand - may be associated with an elevated risk for metabolic syndrome, a cluster of factors that significantly boosts the chance of having a heart attack or stroke and developing diabetes.

"We found that one or more sodas per day increases your risk of new-onset metabolic syndrome by about 45 per cent, and it did not seem to matter if it was regular or diet," Dr. Ramachandran Vasan, senior investigator for the Framingham Heart Study, said Monday from Boston.

Because the corn syrup that sweetens most regular soft drinks can cause weight gain and lead to insulin resistance and diabetes, "you would expect to see an association with regular soft drinks - but not diet soft drinks," he said. "Our findings suggest that this is not the case."

"That for me is striking."

Metabolic syndrome is associated with five specific health indicators: excess abdominal fat; high blood sugar; high triglycerides; low levels of the good cholesterol HDL; and elevated blood pressure.

"And other than high blood pressure, the other four . . . all were associated with drinking one or more sodas per day," said Vasan, a professor of medicine at Boston University.

The study included nearly 9,000 observations of middle-aged men and women over four years at three different times. The study looked at how many 355-millilitre cans of cola or other soft drinks a participant consumed each day.

The researchers found that compared to those who drank less than one can per day, subjects who downed one or more soft drinks daily had a:

-31 per cent greater risk of becoming obese (with a body mass index of 30 or more).

-30 per cent increased risk of adding on belly fat.

-25 per cent higher risk of developing high blood triglycerides or high blood sugar.

-32 per cent higher risk of having low HDL levels.

But Vasan and his colleagues, whose study was published Monday in Circulation: Journal of the American Heart Association, are unsure what it is about soft drinks that ratchets up the risk of metabolic syndrome.

"We really don't know," he said. "This soda consumption may be a marker for a particular dietary pattern or lifestyle. Individuals who drink one or more sodas per day tend to be people who have greater caloric intake. They tend to have more of saturated fats and trans fats in their diet, they tend to be more sedentary, they seem to have lower consumption of fibre."

"And we tried to adjust for all of these in our analysis . . . but it's very difficult to completely adjust away lifestyle."

While soft drink consumption is declining in Canada, statistics from 2006 showed that Canadians overall still gulp down an average of 85 litres each per year.

Dr. David Jenkins, director of the Risk Factor Modification Centre at St. Michael's Hospital in Toronto, said previous studies have suggested that diet pops did not have the same effects on weight and health as do naturally sweetened soft drinks.

"The unusual thing that needs comment is they (the study authors) say that the diet colas are the same as the calorically sweetened colas," said Jenkins. "So I think that is the piece that they've put into this puzzle . . . I think we need a lot more scrutiny of that."

Jenkins said he believes that high consumption of soft drinks likely goes along with eating a high-calorie diet.

"I think the disappointing thing is if you thought you were doing (yourself) a major service . . . by taking diet drinks, this is not helping you," he said. "Before we were saying take the diet (drink) and you're OK. Now we're saying: 'Watch it."'

The study findings also beg the question whether there is some ingredient in soft drinks - both regular and diet - that may encourage metabolic syndrome.

Caramel, used to colour colas, is an ingredient that goes through a chemical reaction that has been shown in studies to "be quite toxic," said Jenkins. "It's possible that (such products) increase insulin resistance and cause oxidative stress and damage and all the other things we don't want."

Dr. Arya Sharma, chair of cardiovascular obesity research at McMaster University, said one explanation for the link between diet drinks and metabolic syndrome is that their just-as-sugary taste may condition consumers to crave other foods that bring sweetness to the palate.

"So people who drink diet pop may be eating other sweets, whether that comes in the form of dessert or other things, I don't know," Sharma said Monday from Hamilton. "It may be that people who are drinking diet pop - and we have this effect often with people who go on diets or when people go running or whatever - that you do a little bit of something that you think is good, and then you overcompensate by doing more of something that is bad."

"The idea could be because I'm drinking diet pop, I can afford to splurge on dessert."

Vasan said he cannot out-and-out recommend that people stop drinking pop based on this study, because the findings are based on association, not clear cause and effect. More research is needed, he said.

"The simple message is eat healthy, exercise regularly and everything should be done in moderation," he said. "If you're a regular soda drinker you should be aware that this study adds to the evidence that regular soda may be associated with metabolic consequences."

"If you're a diet soda drinker, stay tuned for additional research to confirm or refute these findings."