Food Consumption

CHAPTER 3 Food Consumption




OBJECTIVES


By the end of this chapter you should be able to:



• list the major food groups


• identify the main sources of nutrients in Western diets


• understand the purpose of additives in food processing


• describe the main types of natural toxins, pollutants and pathogenic agents


• appreciate the similarities and variability in food and nutrient patterns in different population groups and countries


• describe the different types of vegetarian diets


• identify the nutrients most likely to be lacking from vegetarian diets


• understand how the health of vegetarians/vegans differs from those of omnivores


• understand the social, psychological, geographic and economic factors determining food choices and diet patterns


• be aware of changing trends over time including novel foods



3.1 INTRODUCTION TO FOOD CONSUMPTION


In this chapter the major food groups in the diet are presented in terms of their nutrient and non-nutrient content including food additives and food toxins and pollutants. The variability of dietary patterns between countries and between subgroups in the population is discussed, with special reference to vegetarians; the factors that account for dietary variations, and changing trends in food intake patterns (including novel foods) over time are also examined.



3.2 MAJOR FOOD GROUPS IN THE WESTERN DIET


Western diets are composed of several food groups that provide all the nutrients and non-nutrients for optimum health, including cereals and cereal products (eg bread); vegetables and fruit; roots and tubers; milk and other dairy products; meats, fish, eggs and other sources of protein; fats and oils. The food intake patterns for British adults are shown in Table 3.1. The non-nutrients discussed in this chapter include those for which there is evidence for a beneficial effect on human health, as well as other non-nutrients in foods such as contaminants, allergens and food additives that do not have specific health benefits.


Table 3.1 Food intakes among British adults



























































































Food group Foods g/day
Cereal White bread 64
  Wholemeal bread 28
  Other bread 13
  Pasta and rice 34
  High-fibre breakfast cereals 15
  Other cereals 5
  Potatoes (not fried) 68
  All starchy foods 227
Dairy Whole milk 162
  Reduced fat milk 62
  Cheese and dairy desserts 28
  All dairy products 253
Meat, fish, etc Meat and poultry 165
  Eggs 25
  Fish and shell fish 30
  Nuts and pulses 18
  All meats and alternatives 238
Vegetables and fruit Vegetables 143
  Fresh fruit 59
  Canned fruit and other fruit 77
  All vegetables and fruit 279

Data from Gregory et al 1990



Nutritional importance of major foods and food products in the Western diet



Cereals and cereal products


The major cereals in the human diet are wheat and rice followed by maize, barley, oats and rye. Cereals are the staple foods in almost all populations. Carbohydrates form the major part of the cereal grain and consequently these are often referred to as carbohydrate foods. Cereals represent the most important plant foods in the human diet for their contribution to energy and carbohydrate intake and their micronutrient content. In developed countries, such as the UK, cereals provide approximately 30% of the energy intake whilst in developing countries they contribute as much as 70% or more. In the UK, cereals also provide about 10% of dietary fat, 25% of protein and 50% of available carbohydrates. They also make a significant contribution to dietary fibre as non-starch polysaccharides (NSP). They contribute over 40% and 30% of iron and folate intakes respectively – especially breakfast cereals which contribute 20% and 15% respectively.



Vegetables and fruit


These include a wide range of plant families and consist of any edible portion of the plant including roots, leaves, stems, buds, flowers and fruits. Some fruits (tomatoes, cucumbers, marrows and pumpkins) are commonly classified as vegetables while the fruits that are sweet are classified as fruits. In the context of the human diets, root crops are usually classified separately. Fruits tend to be high in potassium and low in sodium and are the most important source of vitamin C. Although fruits and vegetables are quite low in B vitamins generally, green leafy vegetables are a good source of folates. Vegetables and fruits are important contributors to the intake of dietary fibre. Also, fruits and vegetables are important sources of such non-nutrients as the phytoprotectants, carotenoids and anthocyanins (flavonoids in berries).



Roots and tubers


Roots and tubers are the underground organs of many plants:



• Root crops (eg turnips, beetroots): Most roots have high water content and tend to be rich in carbohydrates as free sugars (with small amounts of starch in mature organs). They are generally low in dietary fibre, protein and micronutrients.


• Tubers (eg potato): Tubers are not true roots but rather underground stems that store large quantities of carbohydrate – usually starch. The potato is a stem tuber native to the Andes. All contain large amounts of starch and significant amounts of vitamin C and their high levels of consumption makes them an important source.



Meat and meat products


Meat has comprised an important part of the human diet for a large part of our history and still is the centrepiece of most meals in developed countries, providing about 15% of total energy intakes. In many developing countries, non-animal-based sources of protein such as legumes are still dominant. In the US and the UK the most important meat sources are pigs, sheep and cattle. In the UK poultry (chicken) has now become the most popular meat source. Meat products such as sausages, salami and pork pies account for almost half of total meat consumption. In developed countries, meats are an important source of protein (contributing about 50% of the UK protein intake), total fat (about 20% of total fat in the UK diet) and saturated fat in the diet.



Fish


While fish catches worldwide are on the increase according to FAO (Food & Agriculture Organization of the UN), fish stocks are being depleted due to over-fishing. The main sea-food consumed is white fish, oily fish and sea-food invertebrates. Fish are an important source of good quality protein and are low in fat (except for the oily fish which provide a very good source of long-chain polyunsaturated fatty acids – PUFA). Fish are also a major source of iodine which has been accumulated from their environment. Also, they may be an important source of calcium (in fish with fine bones) and vitamin D.



Eggs


The most widely consumed eggs in the UK are hens’ eggs. Lipids found in eggs are rich in phospholipids and cholesterol. The fatty acid profile shows a high proportion of polyunsaturated fatty acids to saturated fatty acids (high P:S ratio).



Milk (and other dairy products)


Cows provide the bulk of all milk consumed in the UK. Milk is an excellent source of many nutrients. The major protein in milk is casein, while lactalbumin and immunoglobulins are responsible for the transfer of maternal immunity to the young animal for a short period following birth. Milk from ruminant animals, such as the cow, contains a large proportion of short chain fatty acids produced from the fermentation of carbohydrates in the rumen. Milk and its products provide 10% of total energy intake in the UK, about a quarter of the saturated fat intake, and are excellent sources of many inorganic nutrients especially calcium and certain vitamins (both fat-soluble and water-soluble). Other dairy products include cheese, which contains, in a concentrated form, many of milk’s nutrients, and yoghurt which is produced from the culturing of a mixture of milk and cream products with the lactic acid-producing bacteria, Lactobacillus bulgaricus and Streptococcus thermophilus and other bacterial cultures (eg Lactobacillus acidophilus, Bifidobacteria). The contribution of dairy products to the UK diet (and to that of many other Northern European countries) is very important. They can be an important source of calcium and riboflavin, especially in children and adolescents.



Fats and oils


Fats are solid at room temperature (due to a high relative concentration of saturated fatty acids) while oils are liquid and usually of plant origin, either from the flesh of the fruit (olive oil) or from the seed (sunflower and linseed). They have a higher concentration of unsaturated fatty acids. Lipids that are isolated from animal products tend to be solid fats such butter, lard and suet. Margarine is made from highly unsaturated fats such as sunflower, which have beneficial effects on serum cholesterol. In many countries, including the UK, margarines are required by legislation to be fortified with vitamins A and D so that they are nutritionally equivalent to butter.



Food sources of nutrients and health related non-nutrients


The importance of specific foods to the nutrient intake of a group in the population depends both on the nutrient composition and the frequency and level of consumption. In the UK population cereals and cereal products, including cakes and biscuits, are the important sources of carbohydrate. Meat, fish, eggs and dairy products are the main sources of protein and fat, whilst fruits and vegetables supply dietary fibre and various vitamins and minerals. Table 3.2 summarizes the macronutrient content of selected foods.



Table 3.2 Typical values for macronutrient content of selected foods (% of wet weight)

image

Fruits, vegetables, grains, legumes, nuts and teas are rich sources of phytonutrients (see chapter 5). Phytonutrients (also called phytoprotectants), while not regarded strictly as nutrients, may have certain health benefits. They are extremely varied in their chemical composition, the plants in which they are found and their putative beneficial effects. There are tens of thousands of phytonutrients in plants that have not yet been tested for health benefits. A diet rich in a variety of plant foods (of different colours) ensures a good intake of phytonutrients. Polyphenols are a group of phytonutrients present in onion, apple, tea, red wine, red grapes, grape juice, strawberries, raspberries, blueberries, cranberries, and certain nuts; they are also known as secondary plant metabolites. Much of the total antioxidant activity of fruits and vegetables is related to their phenolic content.



Contribution of macronutrients to energy needs


The energy needs of the body are provided by the three macronutrients: carbohydrate, fat and protein. Alcohol is the other energy source. Carbohydrate and fat are the primary fuel sources and for this purpose they can largely be used interchangeably.


Patterns of consumption of the macronutrients have changed radically from our ancient ancestors where the relative contribution to energy of these macronutrients has been estimated as 34% protein, 45% carbohydrate and 21% fat, contrasting to that of a typical current Western diet of 15% protein, 46% carbohydrate and 39% fat. In the developing countries such as in Asia and Africa protein levels are lower (10%), carbohydrates higher (60–70%) and fats considerably lower (20%) (Table 3.3). The currently acceptable (ie healthy) macronutrient distribution ranges (AMDR) are 10–15% of energy from protein, 25–30% of energy from fat and 45–65% of energy from carbohydrate.



Table 3.3 Mean energy intake and macronutrient energy intakes in 14 EU member states

image


KEY POINTS




• Food groups that provide nutrients in the diet are cereals and cereal products; vegetables and fruit; roots and tubers; milk and other dairy products; meats, fish, eggs and other sources of protein; fats and oils


• Non-nutrients in food include those considered to have a potentially beneficial effect on human health such as natural phytoprotectants, as well as food additives that do not have specific health benefits, and toxins and pollutants that are detrimental to health


• In a typical Western diet the percentage of total energy provided by protein is about 15%, carbohydrate 46% and fat 39%


• In developing countries these percentages are typically protein 10%, carbohydrate 60–70% and fat 20%


• Current guidelines for the contribution to energy intake are 10–15% for protein, 45–46% for carbohydrate and 25–30% for fat



3.3 EFFECTS OF FOOD PROCESSING AND STORAGE



Types of food processing


Foods are processed either to improve their palatability and digestibility or to extend their lifetime before deterioration reduces sensory or microbial quality to a level where they can no longer be consumed. The methods vary in the temperatures used and in the contact with water or oil as heat transfer media. Other variables that affect the rate of destruction of nutrients are the presence of oxygen, light and the pH of the aqueous phase.


Cooking processes such as roasting, boiling, baking, frying and fermentation have been used for thousands of years. Preservation processes such as salting or drying in air have also been applied for hundreds of years. Many of these methods result in losses of nutrients through leaching of water soluble vitamins or oxidation, especially of vitamin C. Modern industrial processes have been developed to maintain or improve flavour, texture, and nutritional or other quality aspects. Preservation techniques have been improved so as to increase the shelf life of products, whilst maintaining optimal quality. These include pasteurization, canning, refrigeration and freezing, freeze drying, irradiation and high pressure processing. The modern methods result in less loss of nutrients. Industrial processing techniques are focusing more on producing healthy foods without loss of palatability, such as foods with lower fat or salt content.



Food additives


The use of additives in food in the UK is strictly controlled by legislation to protect the health of the consumer and to prevent fraud. Additives are allowed for specific functions (antioxidant, colour etc) and are restricted to those listed in the regulations.


Preservatives are substances added to foods to inhibit microbial spoilage. Common foods including meats, cheeses, baked goods, fruit juices and soft drinks are likely to include preservatives. Even if sterile foods are produced initially by thermal processing, infection with bacteria, fungi and yeasts can occur in these foods, which are often not consumed at one sitting, and preservatives are required to extend the shelf life of the products. Sorbic acid, benzoic acid, sulfites, thiabendazole, nitrites and biphenyl are amongst the substances approved for use as food preservatives.


Flavours added to food may be natural components derived from raw materials such as spices by physical processes such as extraction or distillation. A range of essential oils, including clove oil and orange oil, are widely used for flavouring foods. Synthetic flavours are also used.


Colours. The classes of natural or nature-identical colourings used for food include carotenoids, chlorophyll, anthocyanins and betalaines. Besides these, some synthetic compounds are allowed for addition to food. Most concern has been expressed about tartrazine.


Sweeteners. Since the sugars present are significant contributors to the calorific content of many foods, the food industry has developed a range of zero-calorie or low-calorie, high-potency sweeteners, including aspartame, saccharin, acesulfame K and cyclamates. Sucralose was developed as a non-nutritive sweetener in the 1970s as a derivative of sucrose with excellent flavour and stability. Sugar alcohols including sorbitol, mannitol and xylitol have comparable sweetness and about the same calorific content as sucrose but they are absorbed more slowly from the digestive tract and do not raise postprandial blood sugar and insulin levels and are therefore suitable for sweetening diabetic foods.


Processing aids

Related posts:

Diet and the Lifecycle Nutrition and the Hard Tissues Diet and the Gastrointestinal Tract Body Composition and Energy Balance Nutritional Epidemiology and Nutritional Assessment Diet and Disease

Stay updated, free articles. Join our Telegram channel
Tags:
Jun 13, 2016 | Posted by in ENDOCRINOLOGY | Comments Off on Food Consumption

Full access? Get Clinical Tree
Get Clinical Tree app for offline access