Unit 2　Food Nutrition

Food and food products have become commodities produced and traded in a market that has expanded from an essentially local base to an increasingly global one.Changes in the world food economy are reflected in shifting dietary patterns，for example，increased consumption of energy-dense diets high in fat，particularly saturated fat，and low in unrefined carbohydrates.These patterns are combined with a decline in energy expenditure that is associated with a sedentary lifestyle—motorized transport，labour-saving devices in the home，the phasing out of physically demanding manual tasks in the workplace，and leisure time that is preponderantly devoted to physically undemanding pastimes.

Furthermore，rapid changes in diets and lifestyles that have occurred with industrialization，urbanization，economic development and market globalization have accelerated over the past decade.This is having a significant impact on the health and nutritional status of populations，particularly in developing countries and in countries in transition.Nutrition is coming to the fore as a major modifiable determinant of chronic disease，with scientific evidence increasingly supporting the view that alterations in diet have strong effects，both positive and negative，on health throughout life.

2.1　Food and Nutrition

Food refers to what humans eat for the consumption of more than one nutrient，which is composed of carbohydrates，fats，proteins and water.Almost all foods are of plant or animal origin expect some other sources such as fungi.Fungi is used in the preparation of fermented and pickled foods.When food is abundant，it is wasted or treated as a commodity. However，when food is scarce，it is regarded as the staff of life and its distribution becomes a highly emotional issue.Food production worldwide is increasing faster than population，but distribution is uneven，reserves are limited，and bad weather conditions could lead to widespread famines.

Nutrition refers to both the absorption and usage of food，including all the elements that are intaked，digested，absorbed in the human body.An extremely important aspect of food is nutrition，which is especially true for vulnerable groups such as infants and young children.Therefore，we use accurate diet assessment which is important for assessing the relationship of diet to health outcomes；identifying factors（e.g.biological，environmental，psychosocial）influencing dietary intake which could be targeted for change；assessing chan ges over time in diet（surveillance）and evaluating the outcome of dietary interventions.Yet accurate dietary assessment remains a challenge；perhaps especially when children are the subjects.

2.1.1　The Nutrients

Nutrients refers to substances which have trophic function，including proteins，lipids，carbohydrates，vitamins，minerals and water.All of the nutrients except for mineral elements and water are calssified as organic chemicals because they contain carbon.

About 60％ of the human body is water by weight，which is constantly lost from the body and must constantly be replaced.Carbohydrates and fats or lipids are especially important energy-yielding nutrients.Proteins play a big role in functionality such as texture，water binding，emulsification，gel formation，and foam formation.

Vitamins are organic chemicals，other than essential amino acids and fatty acids that must be supplied to an animal in small amounts to maintain health.The vitamins are divided into two general categories based on their solubility in either water or fat.The fat-soluble vitamins are vitamins A，D，E，K；the water-soluble vitamins include vitamin C（ascorbic acid），niacin，thiamin，riboflavin，folacin（folic acid），pantothenic acid，pyridoxine，vitamin B₁₂and biotin.

Depending on whether or not they are required for human nutrition and have metabolic roles in the body，the mineral elements are classified as either essential or non-essential. Some examples of essential ones are sodium，potassium，calcium，and phosphorus.Some examples of non-essential ones are iron，iodine，manganese，zinc，and fluorine.

2.1.2　Nutrients and Food Processing

Food processing is the methods and techniques used to transform raw ingredients into food for human consumption.The effects on the losses of vitamins and minerals of cereals cooked by different methods are different.The losses of minerals are mainly water-soluble losses.The losses of B vitamins in cooking include water-soluble loss，heating loss，oxidation loss and alkali treatment loss.Vitamin B₁often reaches the highest loss rate of vitamins.

In the processing of tofu products，the mineral content is often increased.Soybean itself is rich in calcium，Tofu is an important source of dietary calcium and magnesium elements because calcium or magnesium salt is used as tofu coagulant.The micronutrients in soybean are basically preserved in soybean products.However，there are still some B vitamins lost in water-soluble loss.Most of them are lost in precipitation and some loss is caused by heating degradation.

Fresh vegetables is the main consumption form in daily diet.There will be significantly changes in vitamins and minerals contents in vegetables because of the processing of curing，

drying，quick freezing and canning.In particular，the water-soluble loss and decomposition loss of vitamin C，vitamin B₁and folic acid will caused by heating.

In the processing of meat，poultry and fish，the loss of water-soluble vitamins is more obviously than the losses of proteins and minerals.The fat content will be changed according to different processing methods.

Dairy products are a kind of food that is rich in nutritions.There will be little effects on the milk proteins but different levels of losses of vitamins and minerals in the proper processing methods.

2.2　Nutrition Education

The increase in obesity and chronic diseases such as diabetes and heart disease worldwide reflects the complex interactions of biology，personal behaviour and environment.Consequently，there has been a greater recognition of the importance of nutrition education.Nutrition education needs to address food preferences and sensory-affective factors；person-related factors such as perceptions，beliefs，attitudes，meanings，and social norms；and environmental factors.

Nutrition education has been defined as“any combination of educational strategies，accompanied by environmental supports，designed to facilitate voluntary adoption of food choices and other food and nutrition-related behaviors conducive to health and well-being；nutrition education is delivered through multiple venues and involves activities at the individual，community，and policy levels.”

Technical Terms

scarce［skes］adj.　缺乏的，不足的；稀有的

commodity［］n.　商品，货物；日用品