Experts recommend limiting added sugar to six teaspoons a day to improve health

Experts recommend reducing consumption of added ("free") sugars to around six teaspoons a day and limiting sugar-sweetened drinks to less than one serving a week after a comprehensive evidence review published by The BMJ today.

They found significant harmful associations between sugar consumption and 45 outcomes, including asthma, diabetes, obesity, heart disease, depression, some cancers and death.

It's widely known that excessive sugar intake can have negative effects on health, and this has prompted the World Health Organization (WHO) and others to suggest reducing consumption of free or added sugars to less than 10% of total daily energy intake.

But before developing detailed policies for sugar restriction, the quality of existing evidence must be comprehensively evaluated.

Researchers based in China and the U.S. therefore carried out an umbrella review to assess the quality of evidence, potential biases, and validity of all available studies on dietary sugar consumption and health outcomes.

Umbrella reviews synthesize previous meta-analyses and provide a high-level summary of research on a particular topic.

The review included 73 meta-analyses (67 of observational studies and six of randomized controlled trials) from 8,601 articles covering 83 health outcomes in adults and children.

The researchers assessed the methodological quality of the included articles and graded the evidence for each outcome as high, moderate, low, or very low quality to draw conclusions.

Significant harmful associations were found between dietary sugar consumption and 18 endocrine or metabolic outcomes including diabetes, gout and obesity; 10 cardiovascular outcomes including high blood pressure, heart attack and stroke; seven cancer outcomes including breast, prostate and pancreatic cancer; and 10 other outcomes including asthma, tooth decay, depression and death.

Moderate quality evidence suggested that sugar-sweetened beverage consumption was significantly associated with increased body weight for highest versus lowest consumption, while any versus no added-sugar consumption was associated with increased liver and muscle fat accumulation.

Low-quality evidence indicated that each one serving per week increment of sugar-sweetened beverage consumption was associated with a 4% higher risk of gout, and each 250 mL/day increment of sugar-sweetened beverage consumption was associated with a 17% and 4% higher risk of coronary heart disease and death, respectively.

Low-quality evidence also suggested that every 25 g/day increment of fructose intake was associated with a 22% increased risk of pancreatic cancer.

In general, no reliable evidence showed beneficial associations between dietary sugar consumption and any health outcomes, apart from glioma brain tumors, total cholesterol, type 2 diabetes and cardiovascular disease mortality. However, the researchers say these favorable associations are not supported by strong evidence, and these results should be interpreted with caution.

The researchers acknowledge that existing evidence is mostly observational and of low quality, and stress that evidence for an association between dietary sugar consumption and cancer remains limited but warrants further research.

Nevertheless, they say these findings, combined with WHO, World Cancer Research Fund and American Institute for Cancer Research guidance, suggest reducing the consumption of free sugars or added sugars to below 25 g/day (approximately six teaspoons a day) and limiting the consumption of sugar-sweetened beverages to less than one serving a week (approximately 200-355 mL/week).

To change sugar consumption patterns, especially for children and adolescents, a combination of widespread public health education and policies worldwide is also urgently needed, they add.