Researchers analyze previous research to determine the effects of sugar on risk factors of heart disease.
When you consider risk factors for the development of disease, you may think of high cholesterol, high blood pressure, or an unhealthy diet. However, if we zoom into the root of these risk factors, we may notice one that we often overlook: sugar.
Sugar: A Central Risk Factor
In the last five years, sugar has become a central risk factor in the development of non-communicable diseases. Non-communicable diseases are those that are non-infectious and cannot be passed on among people, like diabetes and heart disease.
Among the types of sugars, past studies have found fructose to be particularly responsible for sugar’s effects on obesity and type 2 diabetes. Previous research has also suggested that sugar may have effects on blood pressure and lipid biomarkers of heart disease. Because of this, the World Health Organization (WHO) recommended that people reduce their daily sugar intake to less than 10% of their total energy intake, and that a reduction to less than 5% may provide additional health benefits. However, researchers remain uncertain on whether sugar’s detrimental effects are caused by the intake of sugar itself or an excess of calories.
Free Sugars and Complex Carbohydrates
To distinguish whether the harmful effects of sugar are caused by sugar intake or an excess of calories, researchers analyzed past studies that substituted free sugars for complex carbohydrates to determine their effects on heart disease risk factors like blood pressure, cholesterol, and body weight.
Free sugars consist of glucose, fructose, and sucrose and also include sugars naturally found in honey, syrups, and fruit juice. Examples of complex carbohydrates are starchy foods like rice or pasta.
The study, published in the American Journal of Clinical Nutrition, performed a systematic review and meta-analysis of the past studies; the researchers collected and summarized empirical evidence from past studies and used statistics to summarize the results.
Analysis of Past Research
The investigators analyzed a total of 28 studies involving 510 volunteers.
After comparing the data, they found that when free sugars were substituted for complex carbohydrates, there were no significant increases in blood pressure. However, they did find significant increases in HDL (good) cholesterol, LDL (bad) cholesterol, and triacylglycerols – the main components of body fat.
It’s important to note, though, that the results for LDL cholesterol and triacylglycerol were inconsistent and the researchers found evidence for publication bias. After they adjusted for missing studies and bias, they found that the increase in cholesterol and triacylglycerols lost significance.
Overall, they found that substituting free sugars for complex carbohydrates does not have an effect on blood pressure or body weight. Their effects on cholesterol remain unclear.
Although this study could not distinguish whether the harmful effects of sugar are caused by sugar itself or an excess of calories, it did highlight the limitations of individual studies. The authors noted that their wide variability and the inconsistency of treatments made it difficult for them to draw firm conclusions. They suggest future independent trials assess whether reducing free sugar intake would improve risk factors for heart disease.
Written By: Jessica Gelar, HBSc