Is Food Combining Really Science-Based?
By Shayna Kay
Food combining is a method of eating popularized mainly by American social media influencers. They claim, that the diet has been successfully used in Europe for many years, and that it is rooted in ancient Ayurvedic medicine. Food combining involves consuming certain food groups in a specific order and combination in order to optimize digestive health. These main principles of food combining are based on the following claims:
Different foods digest at different rates.
Different foods require different environments to be digested optimally.
From these claims, there are a number of different guidelines for which combinations of foods should or should not be consumed in order to optimize digestion. Some examples include:
Do not combine proteins and starches.
Do not eat fruit after a meal, fruit should be eaten alone and on an empty stomach.
The majority of your diet should be comprised of vegetables.
Do not combine different types of protein.
Supporting Scientific Evidence
There is scientific evidence that supports specific food combinations. For example, foods rich in vitamin C should be consumed in combination with foods containing non-heme iron. This type of iron is usually found in food from plant sources and can be more difficult to absorb than heme iron, which is found in food from animal sources. Vitamin C has been shown to increase the absorption on non-heme iron (1,2). This is especially important for vegetarians and vegans who may be more prone to iron deficiency.
Conflicting Scientific Evidence
Most food combining claims are not supported by scientific evidence.
The rules of food combining attempt to categorize foods into broad groups based on their biochemical properties. These groups may not accurately represent how foods are digested. For examples, a study showed that different types of starches breakdown in the digestive tract at different rates (3). A popular food combining advocate claims that bananas are a “neutral” food, which can be combined with anything. This study showed a similar increase in stool weight (an indicator of digestive properties) for bananas and other starches including wheat (3). The food groupings commonly used in food combining do not accurately represent the digestive properties of foods.
Scientific evidence indicates that food combining principles are not the reason for weight loss experienced by individuals following food combining. A 2000 study found that when other factors are controlled, there is no difference in weight loss between individuals following a balanced diet and individuals following a dissociated diet, which is similar to the food combining diet (4).
Not combining proteins and starches may be the most restrictive food combining guideline. This is based on the claim that proteins and starches require different enzymes for breakdown in the digestive tract. It is true that specific enzymes break down proteins, starches and fats in the human digestive system. Pepsin is an enzyme involved in protein digestion and lipase is an enzyme involved in fat digestion. There is scientific evidence, however, that pepsin and lipase enzymes are released during digestion even if there is no protein or fat in the food being digested (5). The release of digestive enzymes is likely not sensitive to the food groups being digested or their combination.
Many food combining advocates also claim that one should not combine proteins and starches because proteins breakdown efficiently in an acidic environment, while starches breakdown efficiently in an alkaline environment. The digestive system drastically alters the acidity of all food during digestion, and it is not sensitive to the type of food being digested. When food and stomach acid enter the small intestine, they are neutralized with bicarbonate before the majority of enzymatic digestion occurs (6).
The human digestive system is adapted to extract nutrients from many different foods in different combinations. Studies have shown that the human intestine has a high tolerance for food combinations that are discouraged in food combining, and the human body can effectively remove gas that may cause bloating and discomfort (7). Although the food combining diet is not supported by scientific evidence, many people self-report that food combining has had a positive effect on their health. Becoming more mindful of the foods you are eating may help anyone begin to see positive results, without the harsh restrictions of food combining and other fad diets.
Bio: Shayna Kay
Shayna is in her third year of an Honors Bachelor of Science in Integrated Science specializing in Biology at Western University. She first became interested in health and wellness as a young dancer when she began to notice that other dancers struggled with their nutrition. She developed a passion for nutrition and health and began to apply her science education and research experience to find more reliable information. Shayna is passionate about science communication and finding creative ways to disseminate scientific findings to a larger audience.
Lopez, M.A., and Martos, F.C. (2004). Iron availability: an updated review. Int. J. Food Sci. Nutr. 55, 597-606. https://www.ncbi.nlm.nih.gov/pubmed/16019304
Teucher, B., Olivares, M., and Cori, H. (2004). Enhancers of iron absorption: ascorbic acid and other organic acids. Int. J. Vitam. Nutr. Res. 74, 403-19. https://www.ncbi.nlm.nih.gov/pubmed/15743017
Cummings, J., Beatty, E., Kingman, S., Bingham, S., & Englyst, H. (1996). Digestion and physiological properties of resistant starch in the human large bowel. British Journal of Nutrition, 75(5), 733-747. doi:10.1079/BJN19960177. https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/digestion-and-physiological-properties-of-resistant-starch-in-the-human-large-bowel/DDCB0F6BFE9D4A1F3046A674343AE6E4
Golay, A., Allaz, A.F., Ybarra, Y., Bianchi, P., Saraiva, S., Mensi, N., Gomis, R., and de Tonnac, N. Similar weight loss with low-energy food combining or balanced diets. (2000). International Journal of Obesity. https://www.nature.com/articles/0801185
Hooton, D., Lentle, R., Monro, J., Wickham, M., and Simpson, R. (2015). The secretion and action of brush border enzymes in the mammalian small intestine. Rev. Physiol. Biochem. Pharmacol.168, 59-118. https://www.ncbi.nlm.nih.gov/pubmed/26345415
Zhang, G., Hasek, L.Y., Lee, B.H., and Hamaker, B.R. (2015). Gut feedback mechanisms and food intake: a physiological approach to slow carbohydrate availability. Food Func. 6, 1072-89. https://www.ncbi.nlm.nih.gov/pubmed/25686469
Serra, J., Azpiroz, F., and Malagelada, J.R. (1998). Intestinal gas dynamics and tolerance in humans. Gastroenterology. https://www.sciencedirect.com/science/article/pii/S0016508598701337