A controversial topic in nutrition is wether fruit, specifically the sugar in fruit, posses similar health consequences as table sugar. People in the media often say things like “sugar is sugar” and “sugar turns to fat.” Although I will admit that people need to focus less on refined sugar but eating a whole carbohydrate source like a banana is just not the same as eating a candy bar.
One of the biggest reasons why fruit has gotten a bad reputation in today’s society is because of its association with fructose, the major sugar found in fruit. Fructose, just like glucose, share the same amount of atoms per molecule, 6 carbons, 12 hydrogens, and 6 oxygens. Unlike glucose, fructose is primarily metabolized in the liver, where it is phosphorylated on the 1-position and bypasses the rate-limiting step of phosphofructokinase (Bray, 2007). This later leads to the formation of triglycerides and lipogenesis (Bray, 2007). Fructose has also been suggested to induce hepatic fibrosis (Kohli, et al., 2010). However, some evidence show that these harmful effects are due to the consumption of industrial fructose and not fructose from fruit (Petta, et al., 2013). So is fruit the problem or just refined sugar?
Another reason why there is a stigma regarding fruit sugar is that people believe it will cause blood sugar issues just as refined sugar might. However, this is not the case with eating whole fruit. One study looked at the effects of glucose and insulin concentrations during 0, 15, 30, 45, 60, 90, and 120 minutes after ingesting 35g of sucrose in 300mL of water, also known as table sugar, versus ingesting 35g of sucrose with 150g pureed berries or 300mL of nectar (Riitta, et al., 2012). The study concluded that the group that ingested the sugar with the berries had an improved glycemic profile (Riitta, et al., 2012). This was very interesting because the group that ingested the berries also ingested more carbohydrates in total. The authors stated that other studies found polyphenols and polyphenol-rich extracts to inhibit the digestion and the absorption of sugars and suppress postprandial glycemia (Riitta, et al., 2012).
In addition to the polyphenols found in fruit, fiber has also been shown to make a difference when it comes to the absorption of sugar. One study found dietary fiber, specifically soluble fiber, may reduce postprandial glucose by making the food in the GI tract thicker thus making it more difficult for the release and absorption of the sugar (Riitta, et al., 2012). This may also explain how another study found less insulin to be required for the maintenance of normal or improved postprandial glucose metabolism when white bread was consumed with berries (Riitta, et al., 2013).
So I suppose this means one should go for blueberry pancakes over regular ones, right? All I am suggesting is that whole foods most likely will have a different affect on the body than its refined counterparts. Although biochemistry may suggest a mechanism, we most likely will not see the same results as produced in a lab as people eat a combination of foods and within those foods contain a variety of nutrients. I believe the community that is affected the most by controversies like these are those who are suffering with weight and/or blood sugar issues. People may be avoiding healthy, whole fruits because they are scared that the sugar will make them gain weight and/or spike their blood glucose levels. This can be emotionally devastating for an individual who is determined to find success on their journey but are told to avoid fruits because they are high in sugar. Fruits, ideally whole fruits, are a perfect package of nutrients and simply looking at them as “sugars” or “carbohydrates” does not do them justice.
Bray, G. A. (2007). How bad is fructose? The American Journal of Clinical Nutrition, 86(4). Retrieved from http://ajcn.nutrition.org/content/86/4/895.full
Kohli, R., Kirby, M., Xanthakos, S. A., Softic, S., Feldstein, A. E., Saxena, V., Tang, P. H., Miles, L., Miles, M.V., Balistreri, W. F., Woods, S. C., Seeley, R. J. (2010). High-fructose, medium chain trans fat diet induces liver fibrosis and elevates plasma coenzyme Q9 in a novel murine model of obesity and nonalcoholic steatohepatitis. Hepatology, 52(3). Retrieved from http://onlinelibrary.wiley.com/doi/10.1002/hep.23797/abstract
Petta, S., Marchesini, G., Caracausi, L., Macaluso, F. S., Camma, C., Ciminnisi, S., Cabibi, D., Porcasi, R., Craxi, A., Marco, V. D. (2013). Industrial, not fruit fructose intake is associated with the severity of liver fibrosis in genotype 1 chronic hepatitis C patients. Journal of Hepatology, 59(6). Retrieved from http://www.journal-of-hepatology.eu/article/S0168-8278(13)00553-9/abstract
Riitta, T., Kolehmainen, M., Sarkkinen, E., Mykkanen, H., Niskanen, L. (2012). Postprandial glucose, insuline, and free fatty acid responses to sucrose consumed with blackcurrants and lingonberries in healthy women. The American Journal of Clinical Nutrition, 96(3). http://ajcn.nutrition.org/content/96/3/527.long
Riitta, T., Kolehmainen, M., Sarkkinen, E., Poutanen, K., Mykkanen, H., Niskanen, L. (2013). Berries reduce postprandial insulin responses to wheat and rye breads in healthy women. The Journal of Nutrition, 143(4). Retrieved from http://jn.nutrition.org/content/143/4/430.long