How bad is fructose compared to regular sugar?
Fructose places a greater burden on the liver than glucose and raises triglycerides, belly fat and uric acid more. But regular sugar is already half fructose, so the practical difference is smaller than you might think. The greatest health benefit comes from cutting back on sugar-sweetened drinks, regardless of the type of sugar.
Regular table sugar (sucrose) is already half fructose. The difference lies in how your body processes those two halves. Glucose is absorbed by virtually all cells. Fructose goes almost entirely to the liver, which converts it into fat, triglycerides and uric acid. Several randomised studies show that fructose leads to more belly fat, more liver fat and higher triglycerides than glucose1. Glucose does not do this to the same extent.
At chronically high doses, fructose is clearly harmful in mouse studies: it causes insulin resistance, obesity and high blood pressure. In humans the picture is less clear-cut. At high intake, disturbed blood lipids and poorer liver function have been demonstrated, but at moderate doses there is no convincing evidence of direct harm2. Whether findings from mouse studies on liver fat accumulation translate one-to-one to humans remains uncertain3.
A separate risk of fructose is that it raises uric acid levels in your blood. The liver uses a great deal of energy when processing fructose, and uric acid is a by-product of that process. A higher fructose intake is associated in men with a greater risk of gout1,4. With regular glucose this risk is much smaller.
The form in which you consume sugar matters at least as much as the type. In mouse studies, liquid sugar led to greater calorie intake and more liver fat than the same amount of solid sugar5. Soft drinks therefore combine two risks: a large amount of sugar and the liquid form. Whether you look at high-fructose corn syrup (a widely used sweetener in soft drinks) or at regular sugar makes little difference. Both contain comparable ratios of fructose and glucose, and the same epidemiological association with overweight and cardiovascular disease applies to both2,1.
There is one small exception: in people with type 2 diabetes, fructose produces a smaller blood sugar spike immediately after a meal than regular sugar. However, measured over three hours the difference is not statistically significant, so this advantage is of little practical value6.
All claims are based on one review article (PMID 20086073), supplemented by experimental and clinical studies (PMID 23493538, 3891268, 25010715, 34359974, 7443098). Most of the evidence in humans is of moderate strength; strong evidence comes almost exclusively from mouse studies.