If you have concerns about heart health, you should pay attention to added and free sugar intake. Excess consumption isn’t good for heart health, in part due to the impact on the liver.
The liver and the heart
Development of non-alcoholic fatty-liver disease (NAFLD) has been linked with high intake of added sugars, particularly sugar-sweetened beverages, even in kids.
When fatty, the liver’s function is compromised. It can result in increased levels of unhelpful very low-density lipoprotein (VLDL) particles, due to their overproduction in the liver and/or decreased clearance of from the blood.1
VLDL transport fats in the blood. The more VLDL particles, the higher the blood levels of fats, known as triglycerides. While a little is normal, high levels of triglycerides can contribute to a hardening of blood vessel arteries that can lead to a heart attack.1
Knowing all this, a group of researchers from the University of Surrey in the U.K. set up a trial to ascertain if the amount of liver fat could influence the handling and metabolism of fat in the blood in response to the amount of dietary sugar consumed, and therefore it’s flow-on impact on cardiovascular health.1
Two groups of men participated in the trial – a group with NAFLD and a ‘healthy control’ group with low levels of liver fat.
For 12 weeks, the two groups were placed on high or low sugar diets.
Those on the high-sugar diet consumed 650 calories (26% of total energy) of sugar per day. The low-sugar group participants consumed no more than 140 calories (6% of total energy) of sugar per day.
The sugar content was from added sugars, not those naturally occurring in whole foods such as fruit or dairy.
After only 12 weeks, those with NAFLD and on high-sugar diet showed changes in their fat metabolism – the biochemical process through which fats are transported in the blood and broken down for use by cells throughout the body – associated with heart disease.
Those with low liver fat to begin with (a.k.a the ‘healthy control’ group) consuming a high-sugar diet experienced an increase in liver fat. They also began to metabolise fat in similar ways to those with NAFLD.
Overall, this resulted in higher levels of fat in the blood, indicating an increased risk of heart disease, attacks and strokes. Not good.
“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,” said study author Bruce Griffin.
“While most adults don’t consume the high levels of sugar we used in this study, some children and teenagers may reach these levels of sugar intake by over-consuming fizzy drinks and sweets. 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.”
High versus low sugar intake
The high-sugar diet had participants consume 650 calories from the sweet stuff daily. That is 40 teaspoons (just over 160g), compared to 8.5 teaspoons consumed by the low-sugar group.
You will find approximately 40 teaspoons in 4x 375ml cans of Coke; around 5x 53g Mars Bars; or nearly 1.5x 190g packets of Allen’s Jelly Beans. And if you’ve seen That Sugar Film, you’ll know this is the amount Damon was consuming.
While few people will have 5x Mars Bars in a day, added sugar intake can add up if frequently consuming seemingly ‘healthy’ foods that are high in added sugar, such as flavoured yoghurt, pre-made sauces, tinned soups, cereal and muesli bars in addition to the obviously sweet stuff, such as a handful of jelly beans, a can of soft drink, a chocolate bar.
Eating less added sugar
A little added and free sugar is okay for most people. For health benefits, the World Health Organization recommends limiting free and added sugar intake to 5% of total energy intake, equating on average to 6 teaspoons (25g) per day. For kids, it should be less, and for those under two years, none at all.
The best ways to avoid over consuming added sugar is to keep reading labels for added sugars, and whenever possible, choose real whole food. By enjoying whole foods, including plenty of plant foods, you naturally leave little room for ultra-processed foods and the added sugar (and other unhealthful ingredients) they contain. And you’ll be helping your liver and heart at the same time.
By Angela Johnson (BHSc Nut. Med)
- Umpleby, AM, Shojaee-Moradie, F, Fielding, B, Li, X, Marino, A, Alsini, N, Isherwood, C, Jackson, N, Ahmad, A, Stolinski, M, Lovegrove, JA, Johnsen, S, Mendis, J, Wright, J, Wilinska, ME, Hovorka, R, Bell, J, Thomas, LE, Frost, G, & Griffin, BA 2017, ‘Impact of liver fat on the differential partitioning of hepatic triacylglycerol into VLDL subclasses on high and low sugar diets’, Clinical Science, [ePub ahead of print]