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Unit 1 Part 1 Food Nutrition The goal of public health nutrition is to promote the nutrition-related health of the population. It is not surprising that people knew little about nutrition in the past when they were already on the brink of starvation. Nowadays£¬ with the development of the economy and society£¬ people not only need to consume an adequate amount of food£¬ but also should have a healthy and nutritious diet. Nutrition and its importance in human life take the center of stage£¬ and are highlighted in a tremendous amount of media coverage. As a result£¬ people receive a lot of information£¬ but maybe only some of the information is useful and helpful£¬ while the rest is inaccurate and even dangerous. Unhealthy diets are a key risk factor for the most prevalent noncommunicable diseases such as cardiovascular diseases£¬ diabetes mellitus and various types of cancer. According to the Global Burden of Disease Study 2017 (GBD 2017)£¬ unhealthy diets were responsible for 42% of deaths from cardiovascular diseases£¬ 32% from type 2 diabetes mellitus£¬ 7% from cancers£¬ and were responsible for 16% of all deaths among adults in Western Europe (GBD 2017 Diet Collaborators£¬ 2019). Therefore a significant health gain can be achieved through the prevention of noncommunicable diseases by policies aiming at improving the dietary intake of the population. Nutrition is an interesting topic to many people£¬ as eating is part of our life£¬ and delicious food is a temptation to people. In fact£¬ eating is one of the pleasures in our life£¬ especially in China which has a long history of diet culture. A healthy and reasonable diet is very important to people£¬ because it can provide the nutrition that people need. Since the last decade£¬ new views on the conceptual role of diets have been proposed in the science of nutrition. It is generally considered that the primary role of nutrition is to provide enough nutrients to fulfill the basic nutritional requirements of normal human body functions. Recent advances in food and nutrition science now support the concept that diets may have a significant role in the modulation of various functions in the human body. This implies that diets or food could contribute to an improved state of human well-being£¬ a reduction of risks related to certain diseases£¬ and even an improvement in the quality of life. Usually£¬ we consume different kinds of foods£¬ such as milk£¬ egg£¬ meat£¬ fruit and vegetable products. Although we have a large variety of foods available£¬ they contain only a limited number of constituents£¬ such as proteins£¬ fats£¬ carbohydrates£¬ vitamins£¬ minerals and water. These substances allow our organisms to grow£¬ maintain themselves and work well. Relationships between diets and health have been shown at various levels of dietary patterns£¬ food groups£¬ foods and nutrients. Many foods contain essential nutrients. Other substances are of little importance as parts of nutrients may even be harmful to human health. Examples include the allergenic proteins in egg white£¬ fish£¬ legumes and some natural plant substances£¬ such as antitoxins£¬ which could affect the thyroid£¬ oxalic acid and gossypol. Modern studies in nutritional physiology have made it clear that human diets may consist of a great variety of foods£¬ but the nutrients contained in foods must be calorie-wise in the right form. Today£¬ about 50 substances should be supplied on a regular basis to ensure human health£¬ including essential amino acids£¬ essential fatty acids£¬ minerals£¬ vitamins and water. Apart from breast milk in infancy£¬ there is no food specially designed by nature for human beings£¬ so it is not surprising that no single food on its own can bring sufficient nutrients and satisfy the human body¡¯s needs. A high intake of nutrients is required for any human body to function well. We only need nutrients supplied in foods£¬ rather than all the substances in foods£¬ and thus we should get a wide range of foods with full nutritive values. 1. Protein Requirement As stated previously£¬ proteins have the highest nutritive value to contribute to human health if they contain an adequate amount of essential amino acids in the right relationship. In general£¬ this is more often the case that proteins in animals are more abundant than those in vegetables. This is the reason why animal proteins have a higher biological value. Therefore£¬ animal proteins should be adequate in diets. Fish£¬ meat£¬ milk and eggs are ideal sources of animal proteins. Soyabeans are an especially valuable source of vegetable proteins. The concept of minimum physiological protein or minimum protein balance means the minimum amount of protein food with which the human body can reach a nitrogen equilibrium between intake of nitrogen in foods containing proteins and elimination of nitrogen in decomposition products (such as urea in urine). It is well known from the experience of mass feeding in times of crisis and from an