Why you should limit added sugar in your diet

Johanne Telnes Instanes
About the Author

Johanne Telnes Instanes, MD, PhD, is working 50% position at the University of Bergen, Norway. She is investigating the possible effect of mother´s diet during pregnancy on compulsive or impulsive behavioural traits in the child. The research is based on data from the Norwegian Mother, Father and Child Cohort Study (MoBa).

There are many sources of sugar in our diet.  So-called natural present sugar naturally occurs in food. One example is milk sugar (lactose) found in milk and yoghurt. Sugars in fruits are another example of natural sugar. In addition to sugar, these foods also contain important nutrients like vitamins and minerals.

There are also a lot of foods that contain additional, added sugar. Added sugar is usually understood as sugar added to food during food preparation or processing [1]. There are several reasons for adding sugars to food. Commonly they are used as sweeteners and to preserve food. They are also used to aid fermentation, when making beer for instance.

Examples of food often high in added sugar are sugar-sweetened beverages, baked goods, ketchup and breakfast cereals.  Added sugar is often used in making ultra-processed food, that is food based mostly or entirely on substances derived from food and additives (https://newbrainnutrition.com/ultra-processed-food-and-adhd/).

Why are we concerned about added sugar? Added sugar is a source of energy but with otherwise little or no nutritional value, and thus a source of so-called “empty calories”. Studies have shown associations between high intake of added sugar in early childhood and increased risk of type 2 diabetes, cardiovascular disease and obesity at a later age [2].

The amount of added sugar in food can be used as a proxy for overall diet quality (see previous blog about proxies: https://newbrainnutrition.com/fiber-a-proxy-for-diet-quality/). A high amount of added sugar indicates low diet quality, i.e. a diet not in adherence with national dietary guidelines  [3]. If you eat more than that, it is difficult to keep a healthy diet within the calory limit and at the same time get all the nutrients you need.    

According to American guidelines, added sugar should be limited to 10 percent of total calories per day [4]. As an example, if you´re eating 2,000 calories per day, you can eat about 50 grams of added sugar. That may sound a lot, but as an example, a 330 ml can of Coke contains about 35 grams of sugar (9  teaspoons). If you are drinking two cans in one day, you are already beyond the limit!

Is the amount of added sugar in the diet of pregnant women associated with behavioral traits in the offspring? As a part of the Eat2beNICE project we use data from The Norwegian Mother, Father and Child Cohort Study (MoBa). From this large observational study (we have data of about 40,000 mother-child pairs!), we have information on added sugar intake during pregnancy and behavioral features in the child up to 8 years of age. Thus, we can study the potential associations between the amount of added sugar in diet during pregnancy and possible symptoms of ADHD and autism in their children.


1.            Bowman SA. Added sugars: Definition and estimation in the USDA Food Patterns Equivalents Databases. Journal of Food Composition and Analysis. 2017;64:64-67. https://doi.org/10.1016/j.jfca.2017.07.013

2.            Neri D, Martinez-Steele E, Monteiro CA, Levy RB. Consumption of ultra-processed foods and its association with added sugar content in the diets of US children, NHANES 2009-2014. Pediatr Obes. 2019;14(12):e12563. https://pubmed.ncbi.nlm.nih.gov/31364315/

3.            Louie JCY, Tapsell LC. Association between intake of total vs added sugar on diet quality: a systematic review. Nutrition Reviews. 2015;73(12):837-857. https://pubmed.ncbi.nlm.nih.gov/26449366/

4.            U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. 9th Edition. December 2020. Available at DietaryGuidelines.gov. https://www.dietaryguidelines.gov/sites/default/files/2020-12/Dietary_Guidelines_for_Americans_2020-2025.pdf