Comprehensive evidence review uncovers detrimental links between excessive sugar consumption and 45 health outcomes, such as diabetes, depression, obesity, and heart disease
In a thorough evidence review published by The BMJ, experts suggest limiting the intake of added (or “free”) sugars to approximately six teaspoons per day, and restricting sugar-sweetened beverages to less than one serving per week. The review found substantial harmful connections between sugar consumption and 45 health outcomes, including asthma, diabetes, obesity, heart disease, depression, certain cancers, and even death.
The World Health Organization (WHO) and other entities have previously acknowledged the adverse effects of excessive sugar intake on health and recommended reducing the consumption of free or added sugars to less than 10% of total daily energy intake. However, before implementing detailed policies on sugar restrictions, a comprehensive evaluation of the existing evidence is necessary.
To address this, researchers from China and the United States conducted 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 offer a high-level summary of research on a specific topic.
The review encompassed 73 meta-analyses (67 observational studies and six randomized controlled trials) from 8,601 articles, covering 83 health outcomes in both adults and children. The researchers evaluated the methodological quality of the included articles and graded the evidence for each outcome as high, moderate, low, or very low quality before drawing conclusions.
Significant detrimental associations were discovered between dietary sugar consumption and 18 endocrine or metabolic outcomes, such as diabetes, gout, and obesity; 10 cardiovascular outcomes, including high blood pressure, heart attack, and stroke; seven cancer outcomes, such as breast, prostate, and pancreatic cancer; and 10 additional outcomes, including asthma, tooth decay, depression, and death.
Moderate-quality evidence revealed that consuming sugar-sweetened beverages was significantly linked to increased body weight when comparing the highest and lowest consumption levels. Similarly, any added sugar consumption was associated with increased liver and muscle fat accumulation.
Low-quality evidence suggested that each additional serving per week of sugar-sweetened beverages was linked to a 4% higher risk of gout, while each 250 mL/day increment of sugar-sweetened beverage consumption was associated with a 17% and 4% increased risk of coronary heart disease and death, respectively.
Furthermore, low-quality evidence indicated that every 25 g/day increase in fructose intake was connected to a 22% heightened risk of pancreatic cancer.
In general, there was no reliable evidence to demonstrate beneficial associations between dietary sugar consumption and health outcomes, except for glioma brain tumors, total cholesterol, type 2 diabetes, and cardiovascular disease mortality. However, the researchers caution that these favorable associations are not supported by strong evidence and should be interpreted carefully.
The researchers acknowledged that most of the existing evidence is observational and of low quality. They emphasized that evidence for an association between dietary sugar consumption and cancer remains limited, but further research is warranted.
Nonetheless, they argue that their findings, along with guidance from the WHO, World Cancer Research Fund, and American Institute for Cancer Research, support reducing free or added sugar consumption to below 25 g/day (approximately six teaspoons a day) and limiting sugar-sweetened beverage intake to less than one serving a week (approximately 200-355 mL/week).
To alter sugar consumption patterns, particularly among children and adolescents, the researchers stress the urgent need for a combination of extensive public health education and global policies.
Types of Sugar
There are several types of sugar, which can be broadly categorized into two groups: natural sugars and added sugars. While consuming sugar in moderation is generally safe, excessive consumption of added sugars is associated with various health issues.
- Natural sugars: These sugars are found naturally in foods, such as fruits and dairy products. The two main types of natural sugars are:
a. Fructose: This sugar is found in fruits, honey, and some vegetables. Consuming fructose in moderate amounts through whole fruits is considered healthy, as fruits also provide essential vitamins, minerals, and fiber.
b. Lactose: This sugar is present in dairy products like milk, yogurt, and cheese. Lactose is a healthy source of energy when consumed as part of a balanced diet, providing nutrients like calcium, protein, and vitamins.
- Added sugars: These sugars are added to foods and beverages during processing, preparation, or at the table. Added sugars are not inherently unhealthy, but excessive consumption can lead to health problems. Some common types of added sugars include:
a. Sucrose: Also known as table sugar, sucrose is derived from sugar cane or sugar beet. It is used in various foods and beverages as a sweetener.
b. High-fructose corn syrup (HFCS): This sweetener is produced from cornstarch and is commonly used in processed foods and beverages like soda, candy, and baked goods.
c. Glucose: Glucose is a simple sugar used as a sweetener and is also produced by the body as a primary source of energy.
d. Agave nectar, maple syrup, and honey: While these sweeteners are natural, they are often used as added sugars in various food products.
Excessive consumption of added sugars can contribute to weight gain, obesity, type 2 diabetes, heart disease, tooth decay, and other health issues. It is essential to limit the intake of added sugars and maintain a balanced diet rich in whole foods, including fruits, vegetables, whole grains, lean proteins, and healthy fats. The World Health Organization (WHO) recommends that adults and children reduce their daily intake of free sugars (including added sugars) to less than 10% of their total energy intake, and further reducing it to below 5% for additional health benefits.
History of Sugar
Sugar has a fascinating history and has played a significant role in shaping global trade, politics, and culture. One interesting fact about sugar is that, during the 16th to 19th centuries, it was a luxury commodity known as “white gold.”
Before the widespread cultivation of sugar cane and sugar beet, sugar was a rare and expensive product, available only to the wealthy. European explorers and traders discovered sugar cane in Southeast Asia, and its popularity spread rapidly across the globe.
As demand for sugar grew, European powers established sugar cane plantations in their colonies, particularly in the Caribbean and South America. The production of sugar was labor-intensive, and tragically, the sugar trade became intertwined with the transatlantic slave trade. Enslaved people were forcibly brought from Africa to work on the plantations, and their exploitation played a significant role in the sugar industry’s growth.
The high value and demand for sugar led to the development of new technologies, such as the sugar mill, to improve production efficiency. As sugar became more accessible and affordable, its consumption skyrocketed, and it became a staple ingredient in everyday diets.
Today, sugar is a ubiquitous and inexpensive ingredient, but its historical significance as “white gold” illustrates the dramatic transformation of its social, economic, and political roles over the centuries.
There are adverse health effects associated with excessive sugar consumption. Other research:
- Yang, Q., Zhang, Z., Gregg, E. W., Flanders, W. D., Merritt, R., & Hu, F. B. (2014) explored the association between added sugar intake and cardiovascular disease (CVD) mortality. The study found that higher consumption of added sugar was significantly associated with an increased risk of CVD mortality.
- Te Morenga, L., Mallard, S., & Mann, J. (2013) conducted a meta-analysis of randomized controlled trials and cohort studies that investigated the relationship between dietary sugars and body weight. Their findings revealed that reducing the intake of free sugars was associated with a decrease in body weight, while increasing sugar consumption was linked to weight gain.
- Malik, V. S., Pan, A., Willett, W. C., & Hu, F. B. (2013) examined the role of sugar-sweetened beverages in the development of obesity and related chronic diseases, such as type 2 diabetes and heart disease. The study concluded that higher consumption of sugar-sweetened beverages increased the risk of obesity and related health problems.
- Aune, D., Giovannucci, E., Boffetta, P., Fadnes, L. T., Keum, N., Norat, T., … & Tonstad, S. (2017) conducted a meta-analysis on the association between intake of sugar-sweetened beverages and the risk of cancer. The analysis found a positive association between sugar-sweetened beverage consumption and the risk of developing several types of cancer, such as breast, endometrial, and colorectal cancer.
These studies provide consistent evidence supporting the need to reduce added sugar consumption in order to minimize the risk of various health issues, including obesity, diabetes, heart disease, and certain types of cancer. They emphasize the importance of public health education and policy initiatives aimed at promoting healthier dietary choices and reducing the intake of added sugars, particularly from sugar-sweetened beverages.