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Sugar and high protein diets - does sugar affect protein absorption?

Protein - it’s one of the essential building blocks for developing your hair, eyes, organs and even your body’s muscles. It helps repair and maintain the tissues in your body. Many of the hormones and enzymes in our body are also primarily made up of proteins.  

Many people looking at protein-rich diets do so for various reasons, including helping to manage body weight, improving feeling of fullness and helping the body recover after moderate to high-level exercise. Does sugar have any particular role to play in the absorption of protein in the body? Does sugar affect, help, stop or hinder the absorption of this critical nutrient? To answer this, we need to look at how proteins are absorbed by the body.

What are the benefits of protein?

Proteins are found in both animal and plant foods. The major sources in our diets are meat, poultry, fish, cereal-based foods and dairy. They are also found in eggs, nuts and soy products. Protein helps the body in many ways, including but not limited to:

  • Stimulates new muscle growth 
  • Helps with bone, tendon and ligament growth and repair
  • Provides a source of dietary energy
  • Increases satiety (feelings of fullness)
  • It is the building block for hormones and neurotransmitters
  • Supports energy metabolism

How is protein digested and absorbed by the body?

Digestion of protein begins in the stomach. Food is mixed with an enzyme called pepsin which helps proteins break down into chains of amino acids called peptides. Gastric acid also helps to partially break up proteins to allow pepsin better access.

Once this food moves into the small intestine, a range of other enzymes (trypsin, elastase, and chymotrypsin) are released from the pancreas and start to reduce peptides into amino acids and di- and tri-peptides (small chains of amino acids). These are then absorbed into the bloodstream via transporters located in the wall of the small intestine.

Does sugar affect protein absorption in the body?

Many people may be concerned about the effect of consuming sugar with a protein rich meal. When it comes to protein absorption the evidence doesn’t suggest that sugar has any negative or positive effect. The protein digestion and absorption process does not seem to be affected by sugar.

Does eating sugar and protein together affect the body in other ways?

An intervention study of 27 adults in the US found having a sugar-sweetened drink with a high protein meal reduced fat breakdown, compared to when having a drink sweetened with sucralose (a non-nutritive sweetener). It is important to note this is only one study, in a specific population and under specific conditions. 

Protein can help lower the Glycemic Index (GI) of a meal. Combining carbohydrates and protein can promote a more gradual release of glucose into the blood. 

Protein can also slow down stomach emptying and the rate at which carbohydrates are digested and absorbed. It can stimulate insulin secretion, which helps to lower blood glucose levels.  Controlling blood glucose levels is important for diabetes management and prevention, and following a low GI diet can help. Low GI diets can also provide benefits to non-diabetics, like helping with weight maintenance and satiety. 

Read more about Glycemic Index

Read more about the digestion and absorption of sugar



  • NHMRC & Ministry of Health. Nutrient Reference Values for Australia and New Zealand: Protein. Accessed 9 March 2021 at:
  • Mann J and Truswell AS. (2017). Essentials of Human Nutrition, 5th Edition. Oxford:Oxford University Press.
  • Goodman BE. (2010). Insights into digestion and absorption of major nutrients in humans. Adv Physiol Educ, 34:44-53.
  • Casperson AL, Hall C & Roemmich JN. (2017). Postprandial energy metabolism and substrate oxidation in response to the inclusion of a sugar- or non-nutritive sweetened beverage with meals differing in protein content. BMC Nutrition, 3:49.
  • Glycemic Index Foundation. Low GI Explained. Accesses 14 April 2021 at: 
  • Meng H. et al. (2017). Effect of macronutrients and fiber on postprandial glycemic responses and meal glycemic index and glycemic load value determinations. The American Journal of Clinical Nutrition, 105(4): 842–853.


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