With all the studies coming out linking diet soda with a bevy of health issues -- including increased stroke and heart attack risks, and even weight gain -- one may wonder whether it's actually the drink that is causing the health problems, or if it's that people who are already unhealthy tend to drink diet soda.
Well, a new study is trying to clear that up by looking not only at the diet soda-drinking habits of people, but also the diets of people who regularly consume those drinks.
Researchers from the University of North Carolina at Chapel Hill found that people in their study who ate the more unhealthy, "western" diets of pizza, fast food and meat were also the ones most likely to have heart disease -- and it didn't matter whether they were diet beverage drinkers or not.
Meanwhile, people who ate a "prudent" diet -- meaning, lots of whole grains, fish, milk and fruit -- and didn't drink any diet drinks were the ones with the lowest risk of metabolic syndrome. Metabolic syndrome is comprised of a group of conditions, including excess body fat, high cholesterol and increase blood pressure or blood sugar levels, according to the Mayo Clinic.
The group that had the second lowest risk of metabolic syndrome was comprised of people who ate the "prudent" diet but also drank diet drinks.
The study included 827 people who were followed over a 20-year period, Reuters reported. The research was published in the American Journal of Clinical Nutrition.
"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," study researcher Kiyah Duffey, Ph.D., research assistant professor of nutrition at the UNC Gillings School of Global Public Health, said in a statement.
However, Duffey did note that the people who drank the diet drinks -- even when they had the "prudent" diet -- had a higher risk of metabolic syndrome compared to those who didn't drink any diet drinks. For a look at all the potential health conditions linked with soda consumption -- both the sugary and diet kinds -- click through the slideshow:
This week, researchers from the Harvard School of Public Health found that drinking just one sugar-sweetened beverage a day was associated with a 20 percent bump in a man's risk of having a heart attack over a 22-year period. What's more, that risk increased along with the amount of sugary drinks consumed -- even after researchers controlled for other factors like family history, tobacco use and BMI. Reported NBC: And while link doesn't absolutely prove that sugary drinks increase the risk of heart disease, there is evidence from other studies showing that these beverages have an impact on risk factors, [lead author Lawrence] de Koning said. In one study, for example, volunteers who decreased sugary soda consumption experienced a reduction in blood pressure levels, he added. The researchers used data from the longitudinal Health Professionals Follow-up study -- a long-term research project that tracked the health behaviors of 42,883 men over 22 years. Of the entire cohort, a total 3,683 had either fatal or non-fatal heart attacks. Previous analysis of long-term research, such as data from the Nurses' Health Study, show that sugary soda consumption has been individually linked to overall heart disease rates for women as well. But before you consider switching to diet soda, research has shown that it, too, has a negative effect on heart attack and stroke: a separate study of 2,600 adults found that those who drank diet soda regularly were 40 percent more likely to have a heart attack or stroke.
Even if it doesn't cause weight gain, sugary soda may be damaging your cardiovascular health -- especially if you're a woman. That's because women who drink sugar sweetened beverages are more likely to develop high levels of triglycerides -- a fat found in the blood stream that can indicate metabolic syndrome at high levels. In a review of data from a large, long-term study of the heart health of both men and women, the Multi-Ethnic Study of Atherosclerosis, researchers found that women who drank at least two sugary drinks per week were four times as likely to have dangerously high trigylceride levels as those who drank only one sugary drink. How does it work? The excess sugar from soda and other drinks is converted in the body to fat. But unlike the subcutaneous fat that's visible under the skin, much of this sugar transforms into either triglycerides or fatty tissue that surrounds organs, like the liver. And both metabolic syndrome and fatty liver disease can contribute to higher risk of coronary heart disease, Type 2 diabetes and stroke.
Naturally, consuming extra calories from added sugar will lead to weight gain. But even diet soda may lead to unhealthy pounds. While the research is not yet conclusive, recent data demonstrated an association between regularly drinking diet soda and larger waist lines. Wrote HuffPost Healthy Living's own Amanda L. Chan: A study presented at an American Diabetes Association meeting this week shows that drinking diet soda is associated with a wider waist in humans. And a second study shows that aspartame -- an artificial sweetener in diet soda -- actually raises blood sugar in mice prone to diabetes. "Data from this and other prospective studies suggest that the promotion of diet sodas and artificial sweeteners as healthy alternatives may be ill-advised," study researcher Helen P. Hazuda, Ph.D., a professor and chief of clinical epidemiology at the University of Texas Health Science Center San Antonio's School of Medicine, said in a statement. "They may be free of calories but not of consequences." An observational study and an experiment in rodents does not make for a lock-tight association, but it's enough to raise cause for concern.
An ingredient in cola could be leaching calcium from your bones. One study from Tufts University researchers found that women who reported drinking just three colas a week had an average 4 percent more bone loss at important sites in the hips than women who drank any other beverage -- including non-cola, sugary drinks and sodas. But why? Both diet and full-sugar cola contain the flavoring phosphoric acid. According to the study's lead author, Kathleen Tucker, that causes greater acidity in the blood. "At that point, your body's first priority is to restore a balance, so it leaches some calcium out of your bones to neutralize the acid," she told The Daily Beast.
Diabetes goes hand-in-hand with obesity and heightened sugar consumption, so it's no surprise that drinking full-sugar soda is associated with the disease. The Nurse Health Study data on 90,000 adult women revealed that those who drank one or more sugary soft drinks (such as soda or juice) were also twice as likely to develop Type 2 diabetes. And a separate study reveals why: sugary drinks increase the level of fasting glucose and insulin resistance -- two signs of pre-diabetes. Initial studies in mice even find that heightened consumption of the aspartame in diet soda can have an ill effect on fasting glucose levels, though that research is not yet conclusive.
About half of Americans who participated in a study done as part of Gallup’s annual Consumption Habits poll claimed that they drink at least one glass of soda per day. Even though soda drinks have no nutritional value and are choc full of sugar and sodium, the same number of non-soda drinkers, about 4 out of 10, said that they are overweight compared to the same number of people who drink soda daily.