Food Safety | Acidic foods cause cancer? Alkaline foods are healthier? Don’t be misled by the “acid-base theory”

Acidic foods cause cancer, alkaline foods are healthier, eating alkaline foods will give birth to a boy... When a diet is highly sought after and has ulterior commercial purposes, it will derive all kinds of magical "benefits". So, from a scientific point of view, what role does the acidity and alkalinity of food play in the human body?

Judging the acidity and alkalinity of food is not based on taste

Oranges are obviously sweet and sour, but they are not acidic foods. Vinegar is definitely acidic when tested with pH test paper, but it is an alkaline food. How to determine the acidity and alkalinity of a certain food? From a nutritional point of view, the acidity and alkalinity of food is not determined by the taste of the food, but by the acidity and alkalinity of its metabolites. After a certain food enters the human body for metabolism, the final product of acid anions such as phosphorus, sulfur, chlorine, nitrogen and other elements is dominated by sodium, which is called acidic food, such as pork, beef, chicken, duck, eggs, carp, oysters, shrimp, flour, rice, peanuts, barley, beer, etc.; after a certain food enters the human body for metabolism, the final product of metal cations such as calcium, magnesium, potassium, sodium and so on is dominated, which is called alkaline food, such as soybeans, tofu, spinach, lettuce, radish, potato, lotus root, onion, kelp, watermelon, banana, pear, apple, milk, etc.

The acidity and alkalinity of food does not affect the changes in the acidity and alkalinity of the body

Foods do have acidic and alkaline properties, and they do have some impact on health, but not enough to cause changes in body fluids, and have nothing to do with acidic or alkaline constitutions. The organs that regulate the acidity and alkalinity of human body fluids are mainly the lungs and kidneys, and have little to do with the gastrointestinal tract, which is responsible for digestion.

In fact, the human body is a powerful homeostatic system. For example, when people breathe and expel carbon dioxide, they are also reducing the acid load in the body. In addition, the kidneys, intestines, and stomach in the human body all have acid-base metabolism mechanisms. For example, gastric acid in the stomach can kill microorganisms and help digestion, and the alkalinity of the intestines can increase the absorption of nutrients. Therefore, the metabolic mechanisms of various organs, body fluids, and intracellular electrolyte balance make the human body run very stably. Therefore, the acidity and alkalinity of food are not enough as a theoretical basis for our choice of food. Although dietary guidelines recommend eating more fruits, vegetables, and milk, and less fish, meat, eggs, and refined grains, this has nothing to do with the acidity and alkalinity of food.

Reasonable diet and balanced nutrition are the dietary indicators

Although this statement about the acid-base properties of food does exist in nutrition, it is not necessary to be used as an indicator of diet. So, how should we choose food? The "Dietary Guidelines for Chinese Residents (2022)" gives a clear answer, that is, cereals are the main food, and the daily diet should include cereals and potatoes, vegetables and fruits, livestock, poultry, fish, eggs, milk and legumes. Eat more vegetables, fruits, milk, whole grains, and soybeans, and eat fish, poultry, eggs, lean meat in moderation. These are dietary measures proposed to improve the nutritional status of residents. If people eat according to the "acid-base properties of food", they will mislead themselves in their choice of food types.

Experts interviewed: Gu Zhongyi, Director of Beijing Nutritionist Association and Beijing Nutrition Society