Both processed and prepared foods often contain high levels of sugar. It's thought that the average American eats almost half a cup of added sugar every day, which is two or three times higher than the recommended level for men and women, respectively. Added sugars are lurking in many foods and drinks. Excessive sugar intake has been linked to obesity, increased blood pressure and risk of heart disease, and type 2 diabetes.
Researchers have now found evidence that excessive sugar consumption may be detrimental to mitochondria, organelles that are known as cellular powerhouses. High sugar levels may reduce their efficiency and energy output. The findings have been published in Cell Reports.
Although we need glucose, or sugar, to survive, it's important to enjoy it in moderation, noted corresponding study author Ning Wu, Ph.D., an assistant professor at Van Andel Institute. "We found that too much glucose in cells, which is directly linked to the amount of sugar consumed in one's diet, affects lipid composition throughout the body, which in turn affects the integrity of mitochondria. The overall effect is a loss of optimal function," explained Wu.
To model excess glucose uptake by cells in a live organism, which the study noted "is not a trivial task," the researchers deleted a gene called TXNIP (thioredoxin-interacting protein), that would normally prevent glucose uptake. In this work, researchers used that knockout model to show that excess glucose makes mitochondria less efficient by lowering the level of polyunsaturated fatty acids (PUFAs) in the mitochondrial membrane. PUFAs have roles in a variety of mitochondrial and cellular functions.
In this mouse model, glucose was being used to form other fatty acids that don't work as well as PUFAs. They are not as flexible, and that causes problems in the mitochondrial membrane, increasing stress in the organelle, causing damage, and impairing their efficiency.
The researchers were able to rescue the problems in the mice by giving them a ketogenic diet that was low in sugar. That suggested that in mice, a reduction in glucose consumption and the repair of mitochondrial membranes could restore normal function in the organelle. PUFA supplementation became beneficial after the excess sugar intake was halted as well.
"Although we may not always notice the difference in mitochondrial performance right away, our bodies do," said Wu. "If the lipid balance is thrown off for long enough, we may begin to feel subtle changes, such as tiring more quickly. While our study does not offer medical recommendations, it does illuminate the early stages of metabolic disease and provides insights that may shape future prevention and therapeutic efforts."
More work will be needed to confirm that this data holds true for humans.