How to calculate fructose and glucose contents in food

How to calculate fructose and glucose contents in foods?

Pawel Malczewski
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Short summary

Sucrose consists of half glucose and half fructose. Consuming sucrose has the same effect in our body as consuming equivalent amounts of fructose and glucose separately.

Since in nutrient databases free fructose and free glucose are shown separately and combined fructose and glucose are shown as sucrose, the calculation of the total amount of fructose or glucose needs to also include their hidden amounts in sucrose contents. For a quick answer click here.

Explanation

Many nutritional online sources fail to treat sucrose as a combination of fructose and glucose. When discussing the effects of simple sugars on the body, statements such as “product X has 60% of sucrose and only 1% of fructose” are completely misleading.

This confusion usually comes by misinterpreting how the nutrients are listed in the nutrient databases and the scientific research publications. Basically, it fails to understand that:

  • Sucrose = 50% fructose + 50% glucose;
  • Fructose = Free fructose + 50% of sucrose;
  • The effects on the body of fructose and glucose combined into sucrose is the same as fructose and glucose separately. (1)Caspary WF. Physiology and pathophysiology of intestinal absorption. Am J Clin Nutr January 1992. Vol. 55 no. 1 299S-308S. Available here.

Nutrient Databases

The amounts of nutrients are usually taken from official government run databases such as USDA’s.

These databases correctly show sucrose, fructose and glucose amounts separately, as they appear in food. Fructose and glucose can be found in foods on their own or/and as part of sucrose.

Here are two examples:

  • Table sugar has 99.8% sucrose, 0% fructose and 0% glucose. This means that there are no fructose or glucose on they own but paired together in glucose. (2)USDA. Nutritional composition of table sugar. Available here.
  • Honey fructose contents are 40.94%, glucose 35.75% and sucrose only 0.89%. What it means is that only 0.89% of fructose and glucose is combined in sucrose pairs and the rest is separated. (3)USDA. Nutritional information for honey. Available here.

Scientific papers
Some nutrient lab studies show sucrose, glucose and fructose contents of some foods as separate amounts. This is correct, depending on the purpose of the studies.

For instance, the purpose of this study (4)Rao SS, Attaluri A, Anderson L, Stumbo P. The Ability of the Normal Human Small Intestine to Absorb Fructose: Evaluation by Breath Testing. Clin Gastroenterol Hepatol. 2007 Aug; 5(8): 959–963. Available here. on maple syrup sugar composition is, as stated in the beginning of the paper, to learn more about the chemical composition of maple syrup for non-nutritional purposes, such as determining the levels of artificial de-colorization. Hence, it shows the amount of sucrose (65.1%), of fructose (0.7%) and of glucose (0.6%).

Using the results of this study for nutritional purposes, without re-calculating fructose and glucose contents, is incorrect and misleading.

This study was referred to in some online discussions on the topic of toxic effects of high fructose consumption. (read more on this topic here..) It was incorrectly concluded by some that maple syrup is mainly sucrose so there is no reason to worry about fructose.

Conclusion

Back to top

For nutritional purposes, sucrose should be treated as half fructose and half glucose. If using nutrient databases or scientific papers, it is necessary to re-calculate the components in order to obtain the actual glucose/fructose amount.

References   [ + ]

1. Caspary WF. Physiology and pathophysiology of intestinal absorption. Am J Clin Nutr January 1992. Vol. 55 no. 1 299S-308S. Available here.
2. USDA. Nutritional composition of table sugar. Available here.
3. USDA. Nutritional information for honey. Available here.
4. Rao SS, Attaluri A, Anderson L, Stumbo P. The Ability of the Normal Human Small Intestine to Absorb Fructose: Evaluation by Breath Testing. Clin Gastroenterol Hepatol. 2007 Aug; 5(8): 959–963. Available here.

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