Truth and myths about combining foods: the main mistakes that everyone makes

Oleg ShvetsSociety
Truth and myths about combining foods: the main mistakes that everyone makes

Together or apart? What is known about food compatibility?

Thousands of years of observation of the effects of food consumption have laid the foundation for nutritiology, the science of nutrition. In ancient India, Ayurvedic medicine studied and shaped the principles of food combinations. In Europe, this trend actively developed in the middle of the 19th century, when "trophology" or the "science of food combinations" emerged.

In the 20th century, the American surgeon William Hay revived this idea in his diet, in which he recommended not combining starch and protein. His example demonstrates the general features of newfangled diets, when the author's "insights" outweigh the reliability of available scientific evidence on their effectiveness.

Even in the twenty-first century, separate meals and a diet plan based on the principles of food combining remain at the top of the ratings among popular fad diets. Authors, gurus, and supporters of these approaches believe that the wrong combination of foods can negatively affect health and lead to diseases and digestive problems. On the contrary, the right food and drink combinations help to reduce weight and solve a number of other health problems.


Combined nutrition is based on the fact that the main groups of healthy foods have significant differences. They are usually divided into carbohydrates and starches, fruits and berries (including sweet and sour fruits and melons), vegetables, proteins, and fats. Sometimes foods are also classified as acidic, alkaline, or neutral.

The rules for combining foods may differ depending on the source. Some of the most common tips are: eat dairy products and fruits only on an empty stomach, avoid combining starch and protein, starch with acidic foods, do not mix different types of proteins and proteins with fats, eat vegetables and fruits separately, etc.

The principles of food combining are mostly based on two beliefs.

Since food is digested at different rates, consuming fast and slow digesting foods together causes a "blockage" in the digestive tract and prolonged stress on its organs, which negatively affects the digestion and absorption of nutrients.

Different foods require different enzymes to break down, which operate at certain pH (acidity) levels in the intestines. If two foods require different pH levels, the body will not be able to digest them properly at the same time.


A diet based on a combination of foods has been studied in only one study conducted in 2000. It looked at how it affects weight loss. Participants were divided into two groups: some were given a balanced diet, others were given a food combination diet. Both groups were allowed to eat only 1100 calories per day. After 6 weeks, all study participants lost an average of 6-8 kilograms. In other words, a diet based on food combining did not provide any benefits compared to a balanced diet.

In fact, there is no evidence to support most of the principles of food combining. Many of these diets were developed more than 100 years ago, when much less was known about nutrition and digestion. What we now know about basic biochemistry and nutritional science contradicts many of the rules of food combining.


The term "mixed meals" refers to meals that contain fats, carbohydrates, and proteins. The rules for combining foods are largely based on the idea that the body is unable to digest mixed meals. In fact, the human body has evolved to eat whole foods that almost always contain some combination of carbohydrates, proteins, and fats. For example, vegetables and grains are usually considered carbohydrate foods, but they also contain several grams of protein per serving. And meat, which is considered a protein food, has at least some fat.

The digestive tract is always ready to digest mixed food. When food enters the stomach, stomach acid is released along with the enzymes pepsin and lipase, which help to start digesting proteins and fats. Pepsin and lipase are released even if your food does not contain protein or fat. The food then enters the small intestine. There, stomach acid is neutralized, and the intestines are filled with pancreatic enzymes that break down proteins, fats, and carbohydrates. There is no need to worry that the body will have to choose between digesting protein and fat or starch and protein. It is prepared for this type of multitasking.


Another theory behind food combining is that eating the "wrong" foods together can interfere with digestion by creating the wrong pH for certain enzymes to function.

Indeed, enzymes need a certain pH range and not all enzymes in the digestive tract require the same pH. However, eating more alkaline or acidic foods does not significantly change the pH of your digestive tract. The body has several ways to keep the pH of each part of the digestive tract in the correct range. For example, the stomach is usually very acidic, with a low pH of 1.5-2.5. But when you eat, it can initially rise to 5. Then more stomach acid is released until the pH level returns to normal. A low pH helps to start digesting proteins and activates enzymes produced in the stomach. It also destroys any bacteria in the food.

The small intestine is not able to cope with such an acidic pH. As soon as stomach contents enter the small intestine, bicarbonate is released. It is very alkaline and neutralizes stomach acid, maintaining a pH of about 6-7. This is the level at which enzymes in the small intestine function best. Thus, the different levels of acidity in the digestive tract are well controlled by your body. If you eat very acidic or alkaline foods, the body adds more or less digestive juices to achieve the required pH level.


It is believed that the wrong combination of foods causes food to ferment or rot in the stomach. Namely, when food that digests quickly enters the stomach with food that digests more slowly, it starts to ferment. In fact, this is not true.

Fermentation and putrefaction occur when microorganisms begin to digest food. The stomach maintains such an acidic pH that bacteria cannot survive. There is only one place in the digestive tract where bacteria thrive and fermentation occurs. This is the large intestine, where trillions of beneficial bacteria live. They ferment any undigested carbohydrates, including fiber, and release gas and beneficial short-chain fatty acids. In this case, fermentation is good. The fatty acids produced by bacteria coordinate the immune system, reduce inflammation, control blood sugar, and reduce the risk of colon cancer.

To summarize. There is no convincing evidence that the rules for combining certain foods provide any benefits. In fact, most of the declared principles contradict the scientific principles of digestive physiology and metabolism.

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