Reducing intake of added sugars, especially those higher in fructose, can quickly result in significant health benefits.
Keep in mind we are not talking about naturally occurring sugars in whole foods like fruit, but sugars and sweeteners added to foods and drinks, and sugars naturally present in honey, syrups, fruit juices and fruit juice concentrates.1
In a recently released review, a group of researchers discuss the relationship between high added fructose consumption, the liver’s conversion of sugar to fat, and increased risk for metabolic syndrome, type 2 diabetes, heart disease and nonalcoholic fatty liver disease (NAFLD).
Fructose and fatty liver
The review, published in the Journal of the American Osteopathic Association, addressed the link between high consumption of products with added sugar and increased fat synthesis in the liver.2
Sugar is a type of carbohydrate. This is important to understand, as the quality of the carbohydrate source matters when it comes to the conversion of sugar into fat, according to the authors.
Sources of complex carbohydrates – those found in whole foods bundled with fibre such as green veg, sweet potato, and legumes – appear to have no affect; sources of added sugar, particularly those high in fructose, do.
Fructose, you see, is metabolised exclusively in the liver. When there is excess, it is turned to fat.
When the liver is fatty, it struggles to do its multitude of jobs to keep us alive and well and can result in shifts in metabolic markers such as increased blood lipids and insulin resistance.
Sub out the sweet stuff for super quick health benefits
A recently published study was included in the review to support the relationship between dietary fructose consumption its impact on metabolic markers and the liver.
Published in the journal Gastroenterology,3 a cohort of obese children aged between 9 and 18 years were prescribed identical diets to their own based on energy and macronutrient ratios, except added sugar was replaced by sources of complex carbohydrates. This resulted in the fructose content being no more than 4% of total kilocalories.
It is handy to remember at this point that the World Health Organization recommends we all limit intake of free (added) sugars to 5% of total intake.
Researchers found by day 10, participants already had reductions in metabolic measurements including blood cholesterol, blood pressure, and insulin resistance. Significantly, liver fat reduced by over 50%, and there were reductions in (the dangerous) visceral fat and conversion of dietary sugars to fat.
The conversion of sugars (fructose in particular) to fat is a process known as de novo lipogenesis (DNL), and contributes to non-alcoholic fatty liver disease, disrupting metabolic health.4
“This study provides further evidence that carbohydrate quality, specifically fructose, plays an important role in liver fat accumulation and hypertriglyceridemia and that DNL is an important factor in these processes.“
For one shift in dietary practice, these are quite remarkable results. Long-term, it indicates reduced risk for health complications such as liver disease, type 2 diabetes, and cardiovascular disease.
“Our study clearly shows that sugar is turned into fat, which may explain the epidemic of fatty liver in children consuming soda and food with added sugar,” says Schwarz. “And we find that fatty liver is reversed by removing added fructose from our diet.”
Natural vs added sugars
Remember, as mentioned above, fruit which naturally contains fructose is not what we are concerned with here – it is the added sugar in packaged food and drinks like soft drink and juice we want to limit.
And added sugar intake needn’t be cut out entirely (unless that works for you!). The recommendation is to limit to no more than 6 teaspoons (25g) per day, for health benefits, and none whatsoever for children under the age of 2.
By Angela Johnson (BHSc Nut. Med)
- World Health Organization 2015, Information note about intake of sugars recommended in the WHO guideline for adults and children, viewed 4 July 2017, <http://who.int/nutrition/publications/guidelines/sugar_intake_information_note_en.pdf>
- Schwarz, J Clearfield, M & Mulligan, K 2017, ‘Conversion of Sugar to Fat: Is Hepatic de Novo Lipogenesis Leading to Metabolic Syndrome and Associated Chronic Diseases?’, The Journal of the American Osteopathic Association, vol. 117, 520-527, viewed 28 August 2017, <http://jaoa.org/article.aspx?articleid=2646761>
- Schwarz, J, Noworolski, SM, Erkin-Cakmak, A, Korn, NJ, Wen, MJ, Tai, VW, Jones, GM, Palii, SP, Velasco-Alin, M, Pan, K, Patterson, BW, Gugliucci, A, Lustig, RH, & Mulligan, K 2017, ‘Effects of Dietary Fructose Restriction on Liver Fat, De Novo Lipogenesis, and Insulin Kinetics in Children With Obesity’, Gastroenterology.
- Softic, S, Cohen, DE, & Kahn, CR 2016, ‘Role of Dietary Fructose and Hepatic De Novo Lipogenesis in Fatty Liver Disease’, Digestive Diseases And Sciences, vol. 61, no. 5, pp. 1282-1293.