Soft Drink News | Tufts Health & Nutrition Letter

Exploring the health implications of soft drinks and what you should know.

In a startling revelation earlier this year, a report indicated that diet sodas may pose a higher risk for stroke and heart attack than previously thought. Many soda enthusiasts, believing they chose the healthier option, were shocked by the studies that connected daily consumption of diet soda to a staggering 60% increase in the likelihood of suffering from cardiovascular incidents. This study examined 2,564 individuals with an average age of 69 over a nine-year period, revealing that, even when accounting for other risk factors, diet soda consumers faced a 48% greater risk.

Even more perplexing was the lack of similar risks found among regular soda drinkers, despite numerous health warnings directed at sugary beverages. Many experts have urged caution about interpreting these findings too dramatically. “I am confident that these results will be reversed,” said Tufts’ Irwin H. Rosenberg, MD, editor of the Health & Nutrition Letter. He asserted that traditional sugary sodas have been under-scrutinized when it comes to health impacts.

So, what alternatives exist for health-conscious individuals seeking hydration? Furthermore, what insights do current studies provide on soft drinks?

Examining the Downsides of Diet Drinks
Before considering a complete ban on diet sodas, it’s essential to note that the controversial findings were first presented at the International Stroke Conference and have yet to undergo rigorous peer review. Furthermore, the number of daily diet soda drinkers in the study was relatively small, totaling just 116 participants. It’s possible that those who prefer diet sodas often compensate with unhealthy food choices—perhaps enjoying a diet cola alongside a Mega-Burger and fries.

The crux of the issue, according to Alice Lichtenstein, DSc, the director of Tufts’ HNRCA Cardiovascular Nutrition Laboratory, lies in whether the effects linked to diet soda are genuinely due to the beverage itself or stem from the habits of those who drink it. For instance, an overweight person is more likely to opt for a diet soda, which indicates a predisposition to heart disease, type-2 diabetes, or metabolic syndrome. Much of this potential bias is difficult to adjust for in statistical analysis.

Even lead researcher Hannah Gardener, ScD, from the University of Miami, advised that the findings should not yet inform dietary recommendations.

This isn’t the first time diet sodas have been associated with health issues. Back in 2007, a study featured in Circulation suggested that individuals consuming soft drinks—including diet variations—were 48% more likely to develop metabolic syndrome, known as a precursor to heart disease and type-2 diabetes. These consumers also exhibited a greater likelihood of obesity, high blood pressure, and adverse cholesterol levels.

Consuming excessive cola—diet or otherwise—may also impact bone health. A 2007 Tufts study found a correlation between cola consumption and lower bone-mineral density in women, although this was not the case for men. This conclusion was supported by a later study involving younger women, who were assigned to drink either diet cola or water. Results indicated significantly higher excretion of calcium and phosphorus after consuming diet cola, which suggests a negative calcium balance that can lead to decreased bone-mineral density.

Understanding Sugary Sodas
Given the mixed evidence regarding diet sodas, sugary soft drinks remain the primary concern for health professionals. According to the 2010 Dietary Guidelines for Americans, while these beverages can provide hydration, they often introduce unnecessary calories without essential nutrients. This was a key reason for the Guidelines’ historical recommendation encouraging the consumption of water over sugary drinks. In fact, sodas, energy drinks, and sports drinks rank among the top sources of empty calories for American adults, contributing an average of 112 calories per day.

Moreover, these guidelines noted that sugary drinks are the leading source of added sugars in the American diet, accounting for 30% of overall sugar consumption. Increasing intake of added sugars corresponds with rising body mass index (BMI) rates across various demographics. A 2009 study highlighted that reducing sugary drink consumption could lead to more effective weight loss compared to cutting the same number of calories from solid foods; specifically, eliminating one daily 12-ounce serving of sugary soda correlated with an average weight loss of one pound over six months.

High Blood Pressure from Sodas?
Alongside weight gain, sugary sodas may also contribute to elevated blood pressure levels. Recent findings published in Hypertension show that individuals who consume greater quantities of sugar-sweetened beverages tend to have higher blood pressure. In a comprehensive study involving 2,696 participants from the U.S. and U.K., each additional sugary beverage consumed per day was found to correspond with an increase of 1.6 mm Hg in systolic blood pressure, with similar results for diastolic pressure. No comparable correlation was found for diet sodas.

The researchers suggested several explanations for these links. One possibility is that calories derived from sugary drinks replace those from more nutritious foods. Another theory posits that fructose, a simple sugar prevalent in table sugar and high-fructose corn syrup, may elevate uric acid production in the body, which in turn reduces nitric oxide levels—a critical compound that helps keep blood vessels dilated.

A separate study conducted in 2010 analyzed fructose consumption and its relationship with hypertension through national nutrition survey data involving 4,528 adults. Consuming at least 74 grams of fructose daily—equivalent to the quantity found in two and a half regular sodas—was tied to a significantly heightened risk of developing various hypertension thresholds. While fructose was the only sugar assessed, its consumption was connected to raised systolic blood pressure, but not diastolic readings.

Conversely, reducing sugary beverage intake appears to lower blood pressure. In another 2010 study published in Circulation, participants who cut back on just one sugary drink per day experienced significant blood pressure reductions over 18 months. The study analyzed 810 adults, primarily with borderline high blood pressure or stage 1 hypertension, and found an average drop of 1.8 mm Hg in systolic pressure and 1.1 mm Hg in diastolic pressure.

Concerns About Cancer and More
Emerging studies are revealing additional motives to limit sugary drink consumption. Although the incidence of pancreatic cancer has stabilized in the U.S., rates in Asia are still on the rise, largely attributed to a shift toward a Westernized diet, including increased soft drink consumption. A 14-year study following 60,524 adults in Singapore indicated that those who consumed two or more soft drinks weekly had an 82% increased risk of developing pancreatic cancer.

Participants provided information about their diet through a 146-question survey, then results were cross-referenced with records of pancreatic cancer fatalities. The investigation, published in Cancer Biomarkers, Epidemiology and Prevention, accounted for known risk factors like smoking. Moreover, three-quarters of similar U.S. studies have also linked sugary soda consumption to pancreatic cancer risks. Researchers theorize that excessive sugar intake might influence insulin levels in a manner conducive to cancer cell proliferation.

Additionally, diets high in sugary beverages may signal potential liver health issues. A 2009 Israeli study in the Journal of Hepatology found that individuals with non-alcoholic fatty liver disease (NAFLD) consumed five times the amount of carbohydrates from soft drinks compared to those without the condition. In a study of 90 participants, 80% of those with NAFLD consumed excessive amounts of soft drinks, defined as more than about 17 ounces a day. The relationship suggests a strong correlation between soft drink consumption and fatty liver risk, although causation cannot be definitively established.

Furthermore, soft drink consumption may play a role in the rising incidences of gout—an inflammatory arthritis condition. An analysis of nearly 80,000 women over 22 years from the Nurses Health Study indicated an association between sweetened soft drink and orange juice intake and gout. The results revealed that women with the highest fructose consumption had a 62% increased risk of gout compared to those with lower intake. Those who averaged one soda daily experienced a 74% higher risk, while those who consumed two or more saw an alarming 240% increase. However, given that only 778 women were diagnosed with gout during the investigation, the overall impact on the population is likely minimal.

As Lichtenstein reminds us, it’s crucial to consider the broader lifestyle choices of those consuming sugary drinks. Those who favor these beverages often exhibit poor dietary habits and a lack of physical activity.

Nonetheless, Lichtenstein emphasizes that there are no significant benefits to drinking sugary beverages. When feeling thirsty, it’s all too easy to consume a large quantity of unnecessary calories in a short span. Instead, reaching for a glass of tap water can save both calories and money, providing the opportunity to invest in healthier lifestyle choices, such as a good pair of walking shoes.