Field Notes

Taxing Sugar Content, Not Volume, of Soda More Effective

Taxing sugar-sweetened beverages (SSBs) by the amount of sugar they contain, rather than by the liquid volume of these drinks, as several US cities currently do, could produce even greater health benefits and economic gains, a team of researchers has concluded.

The analysis, by researchers at New York University, Harvard’s T.H. Chan School of Public Health, the Wharton School at the University of Pennsylvania, and the University of California, Berkeley, appears in the journal Science.

Seven US cities tax SSBs by the volume of the beverage—levies that don’t take into account the amount of sugar these drinks contain.

“Despite their different sugar content and resulting different harms, all sugar-sweetened beverages are taxed at the same rate per liter under a volumetric tax,” wrote Harvard’s Anna Grummon, PhD; New York University’s Hunt Allcott, PhD; Wharton’s Benjamin Lockwood, PhD; and the University of California, Berkeley’s Dmitry Taubinsky, PhD. “This tax structure gives consumers no incentive to substitute from high-sugar to low-sugar SSBs, even though the latter are less harmful. Thus, while a volumetric tax reduces consumption of SSBs in general, it does not provide the maximum possible health benefits.”

“A basic economic principle is that such corrective taxes should be proportional to the harm caused,” the authors added. “The harm from sugary drinks comes from the sugar, and SSBs vary substantially in sugar per unit volume.”

The researchers noted, however, that a tax on liquid volume is beneficial. They estimate, for instance, that a 34-cent per liter volumetric tax causes the average US adult to drink 2.9 fewer ounces of SSBs per day, a 22% reduction. This decrease in sugar intake would help the average adult to lose 2.3 lbs. In addition, a nationwide volumetric SSB tax would reduce obesity rates by 2%—a 2.1 million decline in adults with obesity—and would lower the number of new type 2 diabetes cases by 2.3%, or approximately 36,000 new cases per year.

They add that such a tax also would result in economic gains—primarily through savings in health care costs—of about $1.4 billion per year nationwide.

However, in their assessment, a tax on the amount of sugar in SSBs would yield even greater health and economic gains. Such a tax would potentially cause US adults to consume 2.3 fewer grams of sugar per day from SSBs than they would under a volumetric tax, helping the average adult lose an additional 0.7 lbs. Across the United States, a sugar tax instead of a volumetric tax would reduce obesity rates by an additional 630,000 adults and would cut the number of new type 2 diabetes cases by another 0.7%—or approximately 11,000 people per year. Moreover, the additional annual economic gain would be another $400 million.

“Once there is agreement to tax SSBs, it seems natural to tax the harmful sugar, instead of the liquid that comes with the sugar,” the authors concluded. “Our calculations suggest that this idea offers valuable low-hanging fruit for improving public health.”

A previous study by Allcott, Lockwood, and Taubinsky concluded that soda taxes serve as a “net good,” an assessment based on an examination of health benefits and consumer behavior. That analysis, which appeared in the Quarterly Journal of Economics earlier this year, estimated that a nationwide soda tax would yield $7 billion in net benefits to society each year.

— Source: New York University


Healthful Foods More Important Than Diet Type for CVD Risk

Everyone knows that achieving or maintaining a healthy body weight is one key to preventing CVD. But even experts don’t agree on the best way to achieve that goal, with some recommending eliminating carbohydrates and others emphasizing reducing fats to lose weight. Few studies have investigated the effects of these specific macronutrients on cardiovascular health.

In a study published online in the International Journal of Cardiology, researchers at Beth Israel Deaconess Medical Center examined the effects of three healthful diets emphasizing different macronutrients—carbohydrates, proteins, or unsaturated fats—on a biomarker that directly reflects heart injury. Using highly specific tests, the team found that all three diets reduced heart cell damage and inflammation, consistent with improved heart health.

“It’s possible that macronutrients matter less than simply eating healthful foods,” says corresponding author Stephen Juraschek, MD, PhD, an assistant professor of medicine at Beth Israel Deaconess and Harvard Medical School. “Our findings support flexibility in food selection for people attempting to eat a healthier diet and should make it easier. With the average American eating fewer than two servings of fruits and vegetables a day, the typical American diet is quite different from any of these diets, which all included at least four to six servings of fruits and vegetables a day.”

Juraschek and colleagues analyzed stored blood samples from 150 participants of the Optimal MacroNutrient Intake Trial to Prevent Heart Disease (OmniHeart) trial, a two-center, inpatient feeding study conducted in Boston and Baltimore between April 2003 and June 2005. The average age among the study participants was 53.6 years, while 55% were African American and 45% were women. The participants, all of whom had elevated blood pressure but weren’t yet taking medications to control hypertension or cholesterol, were fed each of three diets—emphasizing carbohydrates, protein, or unsaturated fat—for six weeks with feeding periods separated by a washout period.

The diets included a carbohydrate-rich diet similar to the Dietary Approaches to Stop Hypertension (DASH) diet, with sugars, grains, and starches accounting for more than one-half of its calories; a protein-rich diet with 10% of calories from carbohydrates replaced by protein; and an unsaturated fat–rich diet with 10% of calories from carbohydrates replaced by the healthful fats found in avocados, fish, and nuts. All three diets were low in unhealthful saturated fat, cholesterol, and sodium, while providing other nutrients at recommended dietary levels. The research team looked at the effects of each diet on biomarkers measured at the end of each dietary period compared with baseline and compared between diets.

All three healthful diets reduced heart injury and inflammation and acted quickly within a six-week period. However, changing the macronutrients of the diet didn’t provide extra benefits. This is important for two reasons: First, the effects of diet on heart injury are rapid, and cardiac injury can be reduced soon after adopting a healthful diet. Second, it isn’t the type of diet that matters for cardiac injury (eg, high or low fat, high or low carb), but rather the overall healthfulness of the diet.

“There are multiple debates about dietary carbs and fat, but the message from our data is clear: Eating a balanced diet rich in fruits and vegetables, lean meats, and high in fiber that’s restricted in red meats, sugary beverages, and sweets, will not only improve cardiovascular risk factors but also reduce direct injury to the heart,” Juraschek says. “Hopefully, these findings will resonate with adults as they shop in grocery stores and with health practitioners providing counsel in clinics throughout the country.”

— Source: Beth Israel Deaconess Medical Center