High-sugar diets raise heart disease risk in healthy people

A groundbreaking study has found that just 3 months on a high-sugar diet alters fat metabolism in such a way that it may cause even healthy people to raise their risk of heart disease.

The study suggests that the liver deals with fat differently on a high-sugar diet than it does on a low-sugar diet.

The researchers, led by a team from the University of Surrey in the United Kingdom, describe their findings in the journal Clinical Science.

They report how otherwise healthy men had higher levels of fat in their blood and liver after consuming a high-sugar diet for 12 weeks.

They also found that the men's fat metabolism bore similarities to that of people who have non-alcoholic fatty liver disease (NAFLD), a condition that develops when fat builds up in the liver.

"Our findings provide new evidence that consuming high amounts of sugar can alter your fat metabolism in ways that could increase your risk of cardiovascular disease," comments Bruce Griffin, a professor of nutritional metabolism at the University of Surrey.

NAFLD raises heart risk

Estimates suggest that NAFLD affects 30 to 40 percent of adults in the United States. It is more common in people who have obesity and type 2 diabetes.

Although NAFLD most often develops in adults, there is evidence to suggest that it affects nearly 10 percent of children in the U.S. aged between 2 and 19.

There is also evidence to suggest that NAFLD can increase people's risk of cardiovascular disease, which is also known as heart and blood vessel disease or simply heart disease.

Cardiovascular disease is mainly associated with atherosclerosis, a condition that develops when a fatty deposit called plaque builds up in the linings of blood vessels and restricts blood flow. This can lead to a blood clot that blocks the vessel, resulting in a heart attack or stroke.

Around 92.1 million adults in the U.S. have "some form of cardiovascular disease" or are living with the after-effects of stroke.

Changes to fat metabolism

In the new study, 11 men with NAFLD and 14 healthy men were fed one of two diets, a high-sugar diet or a low-sugar diet, for 12 weeks.

Both had the same amount of daily calories, except that in the high-sugar diet, sugar accounted for 26 percent of total calories, whereas in the low-sugar diet it accounted for 6 percent.

The study was designed as a "randomized cross-over," which means that each participant followed first one diet and then the other, and that the order in which they followed them was randomly assigned.

The team wanted to find out whether the amount of fat in the liver affects how sugar consumption influences cardiovascular health. The liver plays an important role in fat metabolism, or the process through which fats are transported and broken down for use in cells throughout the body.

The researchers compared changes in various biomarkers of fat metabolism, including lipids and cholesterol in the blood, in the two groups as they followed the two diets.

They found that, after 12 weeks on the high-sugar diet, the men with NAFLD showed changes in fat metabolism that have been linked to a raised risk of heart disease.

It was also found that, after the high-sugar diet, the healthy men - whose livers had previously shown a low level of fat - had higher levels of fat in the liver, and their fat metabolism also resembled that of the men with NAFLD.

The researchers note that while most adults are unlikely to consume the amount of sugar in the study's high-sugar diet, some children and teenagers may actually consume this amount due to their high intake of sugar-sweetened drinks and candy.

"This raises concern for the future health of the younger population, especially in view of the alarmingly high prevalence of NAFLD in children and teenagers, and exponential rise of fatal liver disease in adults."

Prof. Bruce Griffin