Yang Q, Zhang Z, Gregg EW, Flanders WD, Merritt R, Hu FB. Added sugar intake and cardiovascular diseases mortality among US adults. JAMA Intern Med. 2014. [Epub ahead of print].
This study includes 2 analyses: a trend analysis and an association analysis. The trend analysis estimates added sugar consumption over time in the US population. It relies on data collected in 1988–2010 from a series of cross-sectional surveys known as the National Health and Nutrition Examination Survey (NHANES). The association analysis examines a relationship between sugar consumption and death from cardiovascular disease (CVD). It is based on data from a prospective cohort known as the NHANES III Linked Mortality Cohort. In order to correct for measurement error and confounding variables, both analyses rely on a validated statistical method developed by the National Cancer Institute.
Over 45,000 nonpregnant US adults responded to surveys through NHANES in 1988-2010. After exclusion for history of myocardial infarction, stroke, congestive heart failure, diabetes mellitus, and cancer, surveys from 31,147 participants remained for the trend analysis. Of these, 11,733 participants were followed to collect mortality data.
Primary Outcome Measures
Two primary outcomes were measured: percentage of calories from added sugar and deaths from CVD. An adjusted hazard ratio (HR) was calculated to reflect the relative risk of CVD based on dietary consumption of added sugar.
Study Parameters Assessed
In addition to the primary outcome measures, the following variables were assessed (the final analysis adjusted for all of these): age, sex, race/ethnicity, educational attainment, smoking status, alcohol consumption, physical activity level, antihypertensive medication use, family history of CVD, Healthy Eating Index score, body mass index, systolic blood pressure, total serum cholesterol, and total caloric intake.
Added sugar contributes to at least 10% of total calories for the majority of US adults and at least 25% of total calories for approximately 1/10 of US adults (2005–2010 data). Compared to those who consume less than 10% of their daily calories from added sugar, individuals who consume 10%–24.9% have a fully adjusted HR of 1.30, meaning a 30% greater risk of death from CVD. Those who consume 25% or more of their daily calories from added sugar have a fully adjusted HR of 2.75.
Excessive sugar consumption and heart disease are both modern phenomena. Although sugar has been cultivated for centuries,1 it has become a dietary staple in developed countries only within the last half century. Consider the following trend: In England in 1700, sugar consumption per capita per year was 4 lbs; in 1800 it was 18 lbs;2 and in the United States in 2005, sugar availability per capita per year was 142 lbs.3 Trends in deaths due to cardiovascular disease (CVD) have followed a similar trajectory. The first heart attack was not documented until 1920,4 and now CVD accounts for 1 in every 4 deaths in the United States.5
Although it is interesting that sugar consumption parallels CVD deaths over time, correlation does not prove causation. One benefit of the current study is that it adds credence to the relationship between dietary sugar and death from CVD. After adjusting for several covariates, the results of this study are clear: consumption of added sugar increases the risk of death from CVD exponentially. And when consumption of added sugar reaches 25% or more of total calories, a person becomes almost 3 times more likely to die from CVD.
But sugar consumption is by no means the only risk factor for death from CVD. To date, it is not even included as one of the major modifiable risk factors for CVD. These risk factors, thought to contribute to 75% of all CVD, include the following: high blood pressure, high cholesterol, tobacco use, physical inactivity, obesity, diabetes mellitus, low intake of fruits and vegetables, and high intake of saturated fats.6 It will be interesting to see if, after publication of this study, "high intake of added sugars" will be added to the list.
Despite its absence from the list of risk factors, sugar consumption has not gone unnoticed by the American Heart Association (AHA). The AHA currently recommends that women limit their intake of added sugar to 100 calories per day (6.7 teaspoons) and men limit their intake to 150 calories (10 teaspoons).7 These amounts reflect approximately 5% of daily caloric intake, making the AHA guidelines the most restrictive for added sugar. The World Health Organization recommends less than 10% of calories come from added sugar and the Institute of Medicine recommends less than 25%.8,9 The 2010 Dietary Guidelines for Americans are not precise on sugar restriction, as they combine sugar with solid fats into a single category of foods that should comprise no more than 15% of caloric intake.10
"Added sugar" is defined as any sugar used in processed or prepared foods, but not naturally occurring sugar in fruit or juices. The biggest contributor of added sugar in the American diet is sugar-sweetened beverages, followed by grain-based desserts, fruit drinks, dairy desserts, and candy.11 A person consuming 25% of calories from regular soda, for example, would drink 43 oz a day. In contrast, a person consuming less than 5% of calories from added sugar could add 2 tablespoons of sugar or other sweetener to their otherwise whole-foods diet each day.
The clinical implications of this study are simple, but profound. As naturopathic physicians, the medicines that we give build on a foundation of a well-nourished body. That means that before prescribing coenzyme Q10, resveratrol, and fish oil pills, we must first help patients correct their diets. I suggest that we go back to the basics: Collect a diet diary from every patient; screen those diet diaries to identify patients consuming too much sugar; talk with every patient about the risks of sugar, but especially those at high risk for CVD; and provide materials and resources to help patients maintain a whole-foods diet with little added sugar. If excessive sugar consumption can increase the risk of death substantially (HR=2.75), a prescription to restrict sugar may be the most powerful medicine we can provide.