(RxWiki News) The issue of soft drink regulation has heated up across the country, especially in New York City with their super-size drink ban. But what does the evidence say about soda and obesity?
Researchers have been publishing more and more evidence about sugar-sweetened drinks and obesity risk.
The link between the two has been clear for years, but it's not clear whether people who are obese simply drink more soda in addition to eating too much other unhealthy food.
A recent study has found the first evidence that drinking sugar-sweetened drinks, such as soft drinks and fruit drinks, is linked to a higher likelihood of obesity in a person's genes.
"Drink less sugary drinks."
The study, led by Qibin Qi, PhD, from the Department of Nutrition at Harvard School of Public Health, used data from three very large established study groups.
The three groups included 6,934 women from the Nurses' Health Study, 4,423 men from the Health Professionals Follow-up Study and 21, 740 women in the Women's Genome Health Study.
The men and women selected were those of European ancestry whose generic genetic profiles were available.
The researchers divided all the participants into four groups:
- those who had less than one serving of sugar-sweetened beverages per month
- those who had 1 to 4 servings per month
- those who had 2 to 6 servings per week
- those who had one or more servings per day
"Sugar-sweetened beverages" on the questionnaire included both caffeinated and caffeine-free colas, carbonated soft drinks that are not colas and non-carbonated sugar-sweetened drinks such as fruit punches, lemonades or other fruit drinks.
The questionnaire also asked participants about their intake of artificially sweetened drinks, whether caffeinated, caffeine-free or non-carbonated.
Only participants who were not obese four years ago were included in the study's analysis so that the drink intake questions accurately related to recent weight gain.
Then the researchers analyzed whether each person was more likely to be obese based on a score calculated from their genetics.
To calculate the score, the researchers analyzed 32 specific parts of the participants' DNA called "single-nucleotide polymorphisms" that are linked to obesity.
These are variations in the genetic code of the person which play a role in their body mass index, which is a ratio of a person's weight to height.
The researchers found that the individuals who drank one or more sugar-sweetened drinks a day had twice as much influence from their genes on their risk of obesity than those who had less than one sugar-sweetened drink per month.
In other words, genetic code differences in the people who drank a lot of sugar-sweetened drinks had twice as much impact on those individuals' body weight than genetics had for the people who drank very few sugar-sweetened drinks.
In a release about the study, senior author Lu Qi pointed out that the study's results can be reproduced and confirmed.
"Our study for the first time provides reproducible evidence from three prospective cohorts to show genetic and dietary factors—sugar-sweetened beverages—may mutually influence their effects on body weight and obesity risk," said Dr. Qi, MD, PhD, an assistant professor in the Department of Nutrition at Harvard School of Public Health.
"The findings may motivate further research on interactions between genomic variation and environmental factors regarding human health," Dr. Qi said.
Co-author Frank Hu, MD, PhD, made a statement in the same release that contradicts what soft drink companies have been saying for years.
"Sugar-sweetened beverages are one of the driving forces behind the obesity epidemic," said Dr. Hu, also a professor of nutrition and epidemiology at Harvard School of Public Health. "The implication of our study is that the genetic effects of obesity can be offset by healthier food and beverage choices."
Soft drinks company and soft drink lobby representatives have continued to state that no one factor is responsible for the obesity epidemic, denying that their drinks play a large part. This study appears to provide strong evidence to the contrary.
The study did note that those who drank a higher amount of sugar-sweetened drinks were more likely to be younger and were less likely to drink as much alcohol, to be physically active, to eat healthily or to drink artificially sweetened drinks. They also tended to consume more calories overall.
However, when the researchers adjusted for these differences, the higher genetic risk for obesity was still linked to consumption of sugar-sweetened beverages.
In other words, even after making calculations to even out the differences in diet and lifestyle, the people who drank many more sugar-sweetened drinks were much more likely to have a higher genetic predisposition toward obesity.
The study could not establish that drinking sugar-sweetened beverages caused the greater genetic effect on weight. It also cannot show that the greater genetic impact on obesity causes those individuals to drink more sugar-sweetened drinks.
It shows that individuals who drink a lot of sugar-sweetened beverages are also more likely for their genes to contribute to obesity.
The study was published online September 21 in the New England Journal of Medicine. The research was funded by the National Institutes of Health and Merck Research Laboratories.
Dr. Hu has received consulting fees from Novo Nordisk and grant money from Merck and the California Walnut Commission. Dr. L. Qi has received lecture fees from Kellogg.
Another author, Dr. Ridker, has received consulting fees from Genzyme, Isis Pharmaceuticals, Vascular Biogenics, Merck and Abbott, as well as grants from Novartis and Astra-Zeneca.