For those who enjoy diet soda, recent reports linking these drinks to a higher stroke risk may be concerning. However, a closer look at the studies behind the headlines suggests a more nuanced understanding is needed.
Understanding the Studies
News stories have tended to focus on the health problems that were identified in the research. The findings come from what are known as “observational studies.” This is a type of study in which researchers gather and analyze information about the effects of a certain behavior, treatment, diagnostic test, environment or risk factor. They do not intervene in any way. The goal of an observational study is to uncover statistical patterns or trends. The data for observational studies is typically drawn from a variety of public health records and from large population studies.
One study included 2,888 people ages 45 and older from the long-running Framingham Heart Study. Participants filled out diet questionnaires up to three times over a seven-year period. The study was co-authored by Shirley Beresford, senior associate dean and professor of epidemiology at the University of Washington School of Public Health. Another study was led by Yasmin Mossavar-Rahmani and Sylvia Wasserheil-Smoller from the Albert Einstein College of Medicine.
Key Findings and Considerations
People who said they drank at least one artificially sweetened soda a day were about twice as likely to have a stroke over the following decade when compared to those who drank less than one a week. In the AHA study, researchers analyzed data on 81,714 postmenopausal women between the ages of 50 and 79. Researchers found that women who reported drinking more than one diet soda or other artificially sweetened drink a day had a higher risk of stroke caused by a blood clot. Additionally, women who drank two or more artificially sweetened beverages a day but had no history of heart disease or diabetes were 2.44 times more likely to have a stroke caused by blood clot than those who didn’t. In women with no prior history of cardiovascular disease or diabetes, high intake of diet drinks more than doubled their risk of small artery occlusion, a specific type of ischemic stroke that occurs when blood flow is blocked to a very small arterial vessel. Woman who consumed two or more diet drinks a day were also 23 percent more likely to have all strokes, 29 percent more likely to develop coronary heart disease and 16 percent more likely to die from any cause.
However, it’s crucial to remember that these types of studies can't prove cause and effect, only an association. Also, only 97 people (3%) had strokes during the follow-up, which means only two or three of those strokes could possibly be attributed to drinking diet soda.
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Observational Studies: A Closer Look
Specific research linking frequent diet soda consumption to adverse cardiovascular effects includes an analysis of seven large studies, with a total of 308,420 participants, conducted by scientists in Great Britain. A link to an increased risk of long-term weight gain was found when analyzing data from the San Antonio Heart Study, a 10-year study with 5,000 participants. A study that found evidence tying diet beverage consumption to an increased risk of stroke was conducted by researchers at Albert Einstein College of Medicine in New York.
It is important to note that these studies are observational. A famous example of the latter is the Nurses’ Health Study series, which is still ongoing. Established in 1976, these studies have analyzed detailed health, environmental and behavioral data gathered from more than 100,000 female registered nurses between the ages of 30 and 55. This research uncovered early links between tobacco use and heart disease, the role of diet in cancer risk and that being obese or sedentary can raise the risk of developing Type 2 diabetes.
Survival Bias and Reverse Causation
Although the latest study didn't detect a higher stroke risk from sugary beverages, that certainly doesn't suggest they are a better choice than diet sodas. In fact, one possible explanation why sugary beverages weren't linked to stroke in the recent study might be a phenomenon known as survival bias. Conversely, diet beverages may have shown a link to stroke because of a different issue, called reverse causation.
In an attempt to be healthier, people who are overweight or have diabetes may be more likely to choose diet drinks over sugary ones. Their heightened stroke risk may result from their health problems rather than their beverage choice. "We might just be measuring the residual impact of obesity and diabetes".
The Artificial Sweetener Conundrum
Another conundrum: researchers don't have any plausible explanation for why artificial sweeteners might increase stroke risk.
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If you use artificial sweeteners to control your weight, you should know that the support for that strategy is pretty shaky. Some evidence suggests that artificial sweeteners make people crave sugary, high-calorie foods, thereby negating the sweetener's potential to cut your overall calorie intake. And some experts believe that people who use these high-intensity sweeteners (which are hundreds of times sweeter than sugar) may come to find naturally sweet foods, such as fruit, less appealing and less-sweet foods, such as vegetables, downright unpalatable.
The Body's Response to Artificial Sweeteners
The problem is when the body doesn’t get what it’s expecting, it becomes confused on how to respond. In essence, your pancreas produces insulin to deal with anticipated sugar. But when no sugar arrives, the metabolic process is disrupted. As a result, when you actually do consume sugar, your body isn’t sure what to do. It’s been fooled too many times.
Alternative Perspectives
"I encourage my patients to eliminate regular soda and other sugar-sweetened drinks to avoid empty calories,". "But if someone says they can't do without a Coke in the morning to wake up, I'll encourage them to switch to coffee or diet Coke." Water is an even better choice, however. "There are a lot of ways to make it more appealing, both visually and taste-wise," she adds.
Erring on the Side of Caution
When it comes to drinking diet soda, it’s wise to err on the side of caution. Rather than consume it daily, save it for an occasional treat. Many people find that it’s the bubbles as much as the sweet taste that they crave.
Moderation is Key
“The key here - like it is with just about anything - is moderation. Sure, it’s not the fun answer, but we just need to be smart about how much of anything we eat or drink".
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