6 February 2018

Too much sugar decreases the function of blood vessels


A new study reports that excess sugar intake decreases blood vessel function and lessens blood flow in only 14 days. One of the reasons for this effect is that high sugar intake "caramelizes" elastic fibers in blood vessels, causing them to lose elasticity and not be able to dilate properly. These changes in the blood vessels are risk factors for cardiovascular disease. The study was published in the renowned 'Journal of Physiology '.

The ability of blood vessels to regulate blood flow is vital for our physical health. As such, any reduction in the ability of a vessel to dilate can reduce the delivery of blood to parts of the body, but will also increase blood pressure. This can ultimately strain and stress the heart and can with time lead to the development of cardiovascular disease.

Sugar reduces blood flow

In a study designed to examine the physiological mechanisms affected as blood flow decreases, 12 healthy young male participants consumed sugar water containing 225 grams of sugar, in addition to their regular diet, every day for 14 days. On day 14, blood flow to the legs had been reduced by 17%.

Researchers measured the participants' blood flow while they were sitting down and performing a dynamic kicking movement.

”We measured the participants' blood flow while they were sitting down and performing a dynamic kicking movement against resistance with one leg. We used this test because we know that the body’s ability to increase blood flow to the active muscle during exercise is superb," says article author and assistant professor Lasse Gliemann, of the Department of Nutrition, Exercise and Sports. Gliemann emphasizes that under normal conditions, something would definitely be wrong with the vascular system if blood flow to the leg was reduced: "When we can demonstrate that sugar has had just a slight effect on blood flow during movement, the influence of sugar is highly significant. That the impact was an entire 17% came as a surprise to us all."

Extended, excessive sugar consumption may be a one way street

225 grams per day is a sizeable helping of sugar. Researchers intentionally chose to administer subjects this large dose of sugar because the primary research aim was to investigate which molecular mechanisms in blood vessels would be affected by chronically elevated blood sugar. While 225 g is a lot, it is close to the actual amount consumed by heavy soda drinkers, for example. Thus, the study underscores the importance of being aware of what we consume.

A can of sugar containing soda every now and then does no harm if one’s normal diet is healthy and varied. But if you subject your body to sustained and massive sugar intake, as we did with our subjects, the result is that - in only 14 days - blood flow will resemble that of some men who are over the age of 65", according to co-author and Professor Ylva Hellsten of the Department of Nutrition, Exercise and Sports. She adds that the 12 young male participants stopped drinking the sugar water after the 2-week trial and that when they did, their ability to regulate blood flow returned to normal.

Research from The Department of Nutrition, Exercise and Sports has previously shown that one liter of Coca-Cola per day, corresponding to an intake of 106 grams of sugar per day, for 6 months has negative consequences for blood pressure as well as fat storage in both liver and muscle tissue.

"What is interesting about our study is that we now begin to understand the specific effects of long-term intake of a diet high in sugar, an intake most probably leading to the development of cardiovascular disease. But, to fully comprehend the effects will require a major interventional study in which subjects are exposed to increased sugar loads for extended periods of time", concludes Professor Hellsten.

About the study

The study is published in the article, ’Endothelial mechanotransduction proteins and vascular function are altered by dietary sucrose supplementation in healthy young male subjects’ and funded by Independent Research Fund Denmark and The Danish Toyota Foundation.

The other abovementioned study, in which the subjects received 1 liter of Coca-Cola per day is ’Sucrose-sweetened beverages increase fat storage in the liver, muscle and visceral fat depot: a 6-mo randomized intervention study’, which was published in American Journal of Clinical Nutrition in 2011.