Human growth, development, and life maintenance depend on diets providing various nutrients, which are metabolized into heat energy (calories) for consumption in growth, physical and mental labor. An average male worker aged 18-60 needs about 2800-3000 calories per day, while a female worker of the same age needs 2500-2700 calories. After 60, a male light worker needs about 2200 calories daily, and a female needs 1900 calories. Pregnant and breastfeeding women require more calories. Children need fewer calories. Insufficient nutrient intake leads to malnutrition and related diseases, while excessive nutrition can also cause many diseases.
In the United States, approximately 35% of cancer-related deaths are related to diet and nutrition. The incidence of digestive tract cancer is higher in China, thus cancers related to diet and nutrition account for over 50% of the total. With the significant improvement of living standards, the dietary structure of Chinese residents has rapidly changed. The proportion of grains and vegetables has decreased, while the proportion of high-fat, high-protein, and high-sugar diets has significantly increased. The heat energy provided by the diet far exceeds the actual needs, and the diet is unbalanced. Consequently, the incidence of lifestyle diseases such as diabetes, cardiovascular diseases, and cancers has skyrocketed, severely threatening the health of the population.
The six essential elements in diet are necessary for humans: protein, fat, carbohydrates, vitamins, minerals, and dietary fiber. The first five are nutrients, and although dietary fiber is not a nutrient, it is closely related to metabolism, disease, especially cancer and cardiovascular diseases, so we list it as one of the essential elements.
In a reasonable dietary structure, protein accounts for 10%-15% of total calories. Adults need about 0.8-1.2 grams of protein per kilogram of body weight daily, with each gram providing 4 calories. For example, a 60-kilogram average adult needs 70 grams of protein daily. Rice or flour weighing 500 grams can provide 50 grams of protein, one egg provides 6 grams, vegetables contain a small amount of protein, beans contain 20%-40%, milk contains 3%, and lean meats and fish contain more than 60%-80% protein. Calculated like this, our daily diet can easily exceed 70 grams of protein.
Fat intake should not exceed 25%-30% of total calories. Each gram of fat provides 9 calories. Main sources of fat include fatty meat, animal oil, plant oil, butter, meat, peanuts, beans, and nuts. Adults generally need about 72 grams of fat per day (mainly from plant oil). It has been reported that in some large cities in China, fat intake accounts for more than 30% of total calories in residents’ diets, which should be cause for concern.
Carbohydrate intake should account for about 60% of total calories. Each gram of carbohydrate provides 4 calories. Sources mainly come from starchy foods, such as grains, potatoes, vegetables, and fruits. Diversity in diet, with grains as the main staple, and more consumption of mixed grains, fresh vegetables, and fruits ensure adequate intake of various vitamins, minerals, and dietary fiber, promoting health.
Three-high diet refers to a diet high in sugar, fat, and protein. Long-term overconsumption of calories can cause obesity, and may also lead to diabetes, cardiovascular diseases, and cancer. The dietary structure in Western countries consists of 40%-45% fat, resulting in a high incidence of breast cancer, colon cancer, and prostate cancer compared to countries with a low-fat diet, which is 5-10 times higher. Over the past 30 years, living standards in China have improved significantly, and the proportion of fat in some residents’ diets has increased from 10%-15% during the early days of liberation to over 30%. Studies have found that the incidence of breast cancer, colon cancer, prostate cancer, endometrial cancer, and ovarian cancer in large cities in China has significantly increased in the past decade. Animal experiments have shown that a high-fat diet, whether from vegetable oil or animal fat, can promote the occurrence of cancers such as breast and colon cancer. Further research has demonstrated a clear relationship between the incidence of prostate cancer, endometrial cancer, ovarian cancer, and leukemia and excessive fat in the diet.
Many teenagers, adults, and some elderly people have ceased to be accustomed to drinking plain water and often consume sugary beverages. As water is consumed every day, excessive sugar enters the body, along with the intake of other carbohydrates, exceeding the actual needs of the body. Many people have little daily exercise and consume fewer calories, allowing the sugar in the body to be converted to fat and stored in the body, which is one of the causes of obesity. Alcoholic beverages can also provide higher calories, with 1 milliliter of spirits providing about 7 calories.
Long-term uncontrolled high-protein diets can also lead to obesity. At a recent American nutrition conference, American fast food was accused of being “the industry that makes fat people,” with the total calorie content of a fast food meal already exceeding the daily calorie needs of the body 3 to 5 times, and was accused of “killing as many Americans as tobacco.” The American Cancer Society found that the greater the degree of obesity, the higher the risk of various cancers, and the higher the cancer mortality rate. To prevent cancer, we should avoid high-calorie diets and avoid the “Three High” diet.