Beware of "Hidden Hunger" under satiety

China's total grain output has achieved an "eleventh consecutive increase", and it is basically not a problem for people to have enough to eat, but satiety does not mean eating well. The deficiency of trace elements and vitamins that people take through food is called "hidden hunger". The latest survey report of "Nutrition and Health status of Chinese residents" shows that nutritional imbalance, malnutrition and micronutrient deficiency are quite common in Chinese population. About 45% of the total population in our country lacks vitamin A, 49% have insufficient zinc intake, 22% of children under five years of age have iron deficiency anemia, and 11% of adults have iron deficiency anemia.

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The nutritional content of fruits and vegetables has indeed decreased.

Countries such as the United Kingdom, the United States, Germany and Japan have found that the decline in nutrients such as fruits and vegetables does exist through the analysis of food nutrients for decades. For example, Japanese food nutrition analysis from 1950 to 2000 showed that vitamin A per 100g spinach decreased from 8000IU units to 700IU units, microbiotinC from 150mg to 35mg, iron from 13mg to 2mg, carrots from 13500IU units to 1500IU units, vitamin C from 10mg to 4mg, iron from 2mg to 0.2mg.

Donald Davis, an American scholar, analyzed 13 nutrients and yields of 43 horticultural crops recorded by the United States Department of Agriculture from 1950 to 1999. It was found that the contents of protein, calcium, phosphorus, iron, riboflavin (vitamin B2) and vitamin C in these fruits and vegetables "did decline" in the past half century: the iron content of carrots decreased by 24%. The vitamin C content of eggplant decreased by 44%. The calcium content of the western blue flower has been reduced by 37%, and the riboflavin content of the wax gourd has dropped sharply by 52%. "the minerals in vegetables in grocery stores today are an average of 5% to 40% lower than they were 50 years ago," Davis said. " According to the estimation of the United Nations, the number of people with hidden hunger in the world is as high as 20 to 3 billion.

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How recessive hunger comes into being

The human body needs 13 vitamins and 16 trace elements. Most vitamins and minerals do not synthesize themselves in the human body, but can only come from food. For human beings, except for some aquatic products, these nutrients are mainly "dependent" on the soil.

The uneven distribution of elements on the earth's surface can lead to hidden hunger and even disease. For example, there is very little selenium in the soil of Keshan County, Heilongjiang Province. In the 1990s, although people were full, their selenium intake was only 6-8 micrograms per day, which led to the occurrence of Keshan disease. Compared with the former, intensive modern farming brings about the lack of vitamins and minerals in agricultural products, resulting in a wider range of hidden hunger, mainly due to the following two reasons.

Genetic dilution effect Modern agriculture is committed to cultivating new varieties and improving crop yield, resistance to diseases and insect pests and the ability to adapt to the climate. Low-yield varieties are constantly eliminated and new varieties with high yields are continued. When farmers switch to a higher-yielding crop variety, they mainly use nitrogen fertilizer to stimulate its faster growth, and theoretically, the absorption of trace elements by roots needs to be carried out at a faster rate. But for the same soil, the soil supply of trace elements or the absorption of plant roots can not keep up, which leads to crops absorbing more water and synthesizing more carbohydrates, while the concentration of trace elements is reduced.

Environmental dilution effect under the modern intensive agricultural production mode, serious soil erosion will take away the minerals of the topsoil, and after years of cultivation, the soil will become hardened, and the roots and water will not easily extend downward. The large-scale production of modern agriculture pays more attention to the application of chemical fertilizer and little or no organic fertilizer, and removes the aboveground harvest from the field, and there is no exogenous supplement for trace elements. At the same time, the excessive application of pesticides reduced the transformation ability of microorganisms to soil minerals. In addition, soil pollution is also easy to cause the antagonism of some trace elements and lead to the decrease of some trace elements in agricultural products. A simulation study shows that with the intensification of Greenhouse Effect, the concentration of trace elements in agricultural products may be further diluted.

Dr. Corell, a Nobel laureate in medicine, pointed out: "the poor soil and chemical pollution have caused plants to lose their original nutrients. If animals eat these plants, their meat, milk and eggs can not have the original nutrients." Even if the dietitian knows how to mix nutrition, he can't eat healthily. "

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How to eliminate hidden hunger

Food fortification is a direct means to eliminate hidden hunger. Add clearly scarce elements to the body's food, such as salt iodization, wheat flour with zinc or vitamin A, etc. Dietary diversification is an effective way to alleviate recessive hunger, and eating whole grains can help reduce the possibility of recessive hunger compared with deeply processed foods. Because of deeply processed rice and flour, mineral elements and vitamins will be greatly reduced. For example, after rice finishing, iron, calcium and phosphorus will lose 63%, 40% and 48% respectively, and vitamin B1, B2 and B6 will lose 77%, 63% and 61% respectively.

There are two main ways to eliminate hidden hunger from the source:

Soil fortified application to soil or direct spraying to crop leaves is the main means to improve the level of crop mineral elements. Denmark, Norway and other countries have obvious selenium deficiency in the soil. Since 1984, these countries have implemented the action plan of applying selenium to farmland. The selenium content of wheat in Norway has increased from 0.01 mg / kg to a stable 0.25 mg / kg. As a result, the national selenium intake has been improved. Soil testing and formula fertilization has been implemented in China for many years, which is mainly aimed at the supplement of nitrogen, phosphorus and potassium in order to increase production. In the future, with the in-depth development of soil testing and formula fertilization, it is expected that its field will be expanded to mineral elements, which will not only improve grain yield but also improve its "quality".

Biofortification increases the content of micronutrient elements in existing crops that can be absorbed and utilized by the human body by means of breeding, reduce and prevent the global problems of human malnutrition and micronutrient deficiency, especially in developing countries (poor people). The zinc content in the iron-fortified wheat varieties cultivated by the International Tropical Agricultural Research Institute is 60 mg / kg, 2.4 times that before cultivation; the excellent wheat lines cultivated by the International Wheat and Maize Center have iron content of 47 mg / kg and zinc content of 55 mg / kg, which is nearly double that of the varieties planted in large areas at present. The biofortification project in China began in 2004 to cultivate new varieties or lines of rice, wheat, corn and other crops rich in micronutrient elements (iron, zinc, carotenoids). Iron and zinc are as high as 749 mg / kg and 135 mg / kg respectively, which is 420 times higher than that of common wheat and common wheat.