Soft Drinks: Too Much of a Bad Thing?

Sugar-sweetened sodas and fruit punch, already considered notorious contributors to childhood obesity, can also lead to serious health problems in adults -- and may even indicate an overall unhealthy lifestyle, suggests new research.

The study shows that women who increased their intake of sugar-sweetened soft drinks or fruit punch from one can per week to one per day gained more weight and doubled their risk of type 2 diabetes compared with women who did not increase their intake. Diet soft drinks were not associated with increased risks.

What's more, these women usually live a less healthy lifestyle and get more calories overall.

Meanwhile, those who increased their intake of fruit juice also experienced weight gain but no increased risk of type 2 diabetes.

The women in the study were from the ongoing Nurses Health Study and were practicing nurses between ages 24 and 44 during the study period. The study appears in this week's Journal of the American Medical Association.

Researcher JoAnn E. Manson, MD, chief of preventive medicine at Brigham and Women's Hospital and professor of medicine at Harvard Medical School, says her team expected to find a significant weight gain among the study participants consuming the most sugar-sweetened soft drinks. "These drinks are pretty much liquid candy -- just sugar and water," she tells WebMD.

"But we didn't think it would lead to this great an increase in type 2 diabetes risk. It's pretty substantial, an 83% increased risk among women having one can of soda a day and a doubling among those having fruit punch daily."

Doctors Should Ask About Soda Intake

These findings prompted one expert to call upon doctors to specifically ask their patients, whether children or adults, about their intake of sugar-sweetened soft drinks -- just as they do about other factors known to cause health problems.

"They should be asking this if they are interested in helping their patients lose weight," says Caroline M. Apovian, MD, of Boston University School of Medicine, who was not involved in the study but wrote an accompanying editorial to it. "They may not be doing that now, but I think this study is going to change that."

Apovian tells WebMD that some of the study's findings are consistent with her own research, expected to be published in coming months.

"My group is looking at food patterns and overall health, and we're finding that soda consumption is indeed a marker for a general non-healthy lifestyle," she says.

While more study is needed to determine exactly why people who frequently drink these "junk beverages" are more likely to smoke and less likely to eat healthfully and exercise regularly, it's clear how these drinks can hurt health on their own.

Empty Calories Don't Satisfy Hunger

A 12 ounce can of non-diet soda contains about 150 calories and between 40 and 50 grams of sugar. If someone drinks one can a day without cutting back on other calories, that alone can lead to a 15-pound weight gain in only one year, says Apovian, a diabetes and nutrition specialist. Generally, each pound of weight gain results from an intake of an additional 3,500 calories not burned off with exercise.

Past studies have also suggested that the odds of becoming obese increase 1.6 times for each additional sugar-sweetened beverage consumed each day. Sugar-sweetened sodas, but not diet varieties, also have a high glycemic value, triggering an immediate spike in blood sugar levels that may boost diabetes risk.

In addition to those extra "empty" calories offering no nutritional value, Manson tells WebMD past research shows that unlike milk and other beverages, sweetened beverages such as soda and fruit punch don't satisfy hunger, so people don't eat less; if anything, they cause people to eat more.

In her study, women who increased their sugar-sweetened soda intake consumed nearly 360 more calories each day. Conversely, those who reduced sugar-sweetened soda consumption also reduced their overall calories by about 320 a day.

Women who increased the number of sugar-sweetened sodas they drank gained an average of 10 pounds, while those having one or fewer cans per week gained about 4 pounds.

"If you look at soft drink trends over the last 20 years, there's been a 60% increase in consumption among adults and a doubling among children. That pretty much parallels the [rate of] epidemics in obesity and type 2 diabetes during that period," Manson says. "It doesn't mean that obesity and type 2 diabetes are due directly to these soft drinks, but there is that ecological association that should be considered."

"The human body does not process some liquid calories the same way as it does calories from food," says Apovian. "It seems that the brain doesn't register that you just drank 150 calories in a can of soda, so you would still eat as much as if you hadn't had it. There seems to be something about sugar mixed with water that causes this."

Time to Abandon Soda, Fruit Juice?

"Americans love their sweet tea, soda, and fruit juices. There is no reason to believe that these sweetened beverages cannot fit into a healthy diet," Kathleen Zelman, MPH, RD/LD, tells WebMD. The trick, she says, is to control how many calories you get.

"There is no disputing the fact that eating extra calories, in any form, can lead to weight gain, which in turn can increase your risk of developing type 2 diabetes. However, you can continue to enjoy sweetened beverages in moderation (1-2 per day) as long as they do not replace more nutritious foods and your diet is balanced in total calories."

Zelman recommends quenching your thirst with water, sparkling soda with a splash of fruit juice or zest of citrus, or an occasional diet soda.