Nutrition and red meat An interactive PowerPoint presentation for A-level students
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Menu Click on the information section you wish to read. Click Questions, if you are ready to take the multiple choice quiz. Information 1. Macronutrients 2. Micronutrients 3. Satiety 4. Consumption guidelines Extension Questions End
1. Macronutrients The energy provided by meat is variable. Meat from all sources contributes to 17% of total energy intake and red meat contributes to 12% of total energy intake (NDNS 2009/10). Meat provides virtually no carbohydrate. Meat provides high biological value protein. Meat provides variable amounts of fat.
Protein in red meat Protein is needed primarily for growth, maintenance and repair of the body. Protein also provides energy, 17kJ per gram. Lean red meat contains a higher proportion of protein. Red meat provides on average: – 20-24g of protein per 100g (raw) – 27-35g of protein per 100g (cooked) When meat is cooked, the water content decreases due to heat. Therefore, the nutrients become more concentrated, including protein.
Amino acids Click to view the Digi Bite The building blocks of protein are long chains of amino acids. There are about 20 different amino acids commonly found in plant and animal proteins. For adults, 8 of these, have to be provided in the diet and are therefore defined as ‘essential’ or ‘indispensable’ amino acids. These are: • Leucine • Isoleucine • Valine • Threonine • Methionine • Phenylalanine • Tryptophan • Lysine.
Amino acids In children, arginine, histidine, cysteine, glycine, tyrosine, glutamine and proline are also considered to be essential (indispensable) amino acids, because children are unable to make enough to meet their needs. These are referred to as ‘conditionally’ essential. There may also be certain disease states during adult life when a particular amino acid becomes conditionally essential. Protein from animal meat contains the full range of essential amino acids which the body cannot make itself.
Protein requirements In most developed countries, the average protein intakes for all age groups are above the requirements. Reference Nutrient Intake (RNI) for adults: 56g/day (men) 45g/day (women) The average daily intake of protein in the UK is 87g for men and 65g for women which is more than sufficient (NDNS 2009/10).
Fat in red meat Fat supplies a rich source of energy and essential nutrients, e.g. fat-soluble vitamins and essential fatty acids. Fat is the key determinant in the amount of energy that meat provides. The greater amount of fat, the greater amount of energy provided by the meat. Energy, fat and protein content of lean and untrimmed cuts of red meat (per 100g) Source: Chan et a. 1995
Fat in red meat Fat provides the richest source of energy and should be consumed in moderation. Fat also provides fat soluble vitamins and essential fatty acids essential for good health. The three main types of fat found in meat: – Intermuscular fat (between the muscles) – Intramuscular fat (‘marbling’ within the muscles) – Subcutaneous fat (visible fat below the skin). The fat content of red meat varies widely depending on the cut and whether fat has been trimmed off. Lean meat generally has between 5 and 10% fat.
Fatty acid composition of red meat Fatty acid composition of red meat depends on whether or not the species is ruminant. Ruminant animals are cud-chewing, hoofed mammals with either three or four stomachs, e.g. cows and sheep. Different fatty acids have different effects on blood cholesterol and risk of heart disease.
Typical fatty acid composition (lean only, cooked) Meat from the ruminant species, such as cows and sheep, contain proportionately more saturated fatty acids (SFAs) compared with other types of red meat, e.g. meat from pigs. Non-ruminant meat (e.g. pork or bacon) usually has a higher unsaturated fatty acid content. Source: MAFF, 1995
Fatty acid composition of red meat Lean red meat contains similar proportions of monounsaturated fatty acids (MUFAs) and saturated fatty acids (SFAs). Lean meat is relatively higher in polyunsaturated fatty acids (PUFA) and lower in SFA compared with untrimmed meat. Cuts of meat with more visible fat will be higher in SFAs. Trimming fat off meat will help lower the proportion of SFA, as visible fat is higher in SFA than other types of fat in meat.
Fatty acid composition of red meat The main fatty acids provided by red meat are: Palmitic acid C16:0 Shown to increase cholesterol Stearic acid C18:0 No affect on cholesterol Within red meat, there are also minor amounts of these: Myristic acid C14:0 These are both shown to increase cholesterol more potently than Palmitic acid. Lauric acid C12:0
Polyunsaturated fatty acids in red meat The main polyunsaturated fatty acids (PUFAs) in red meat are the essential fatty acids linoleic (n-6) and alpha-linolenic acid (n-3). Dietary intakes of n-6 are within recommended ranges, but intakes of n-3 could be improved. When ingested, n-3 is transformed into long chain PUFAs (docosahexaenoic acid and eicosapentaenoic acid). Intakes of long chain PUFAs have been associated with decreased risk of atherosclerosis, heart attack and cancer. Meat makes an important contribution to long chain n-3 for those whoeat little or no oily fish. Meat and meat products (including poultry) provide 18% of n-6 PUFAs and 17% of total n-3 PUFAs (NDNS 2000/01).
Further changes in the composition of meat Advances in food processing technologies, breeding programmes, changes in animal feeds and modern butchery techniques have led to a decrease in fat content of carcase meat. There is on-going research on reducing total fat and improving the fatty acid composition of red meat. Oil seeds (linseed/rapeseed) in animal feed can increase the proportion of PUFAs (long chain n-3 fatty acids). Grass-fed ruminants have higher levels of PUFAs. Click to view the Digi Bite
Processed meats and meat products In general, processed meats and meat products are more likely to contain a higher content of sodium than lean meat. Sodium enhances and modifies the flavour and physical properties of the meat product. This also helps preserve the food product. However, processed meats and meat products can provide extra nutrients not typically found in meat for example, carbohydrate and fibre.
2. Micronutrients Meat and meat products can make an important contribution to nutrient intakes in the diet. Meat contains a range of micronutrients (vitamins and minerals). According to EU legislation Regulation (EC) No.1924/2006: When a serving (100g/100ml) provides 15% of the EU Recommended Daily Allowance (RDA) it can be considered “a source of”. Foods contributing 30% of the EU RDA, can be classed as “a rich source of”. According to EU labelling legislation beef, lamb and pork can be classified as a “Source” or a “Rich source” of several nutrients. (Regulation (EC) No 1924/2006)
Micronutrient composition of meat ≥15% of the RDA per 100g = Source; ≥30% of the RDA per 100g = Rich source
Iron Iron provided by meat has a high bioavailability. This means the body absorbs a greater amount of the nutrient when compared to other foods. Iron is important as an oxygen carrier in blood (haemoglobin) and in muscle (myoglobin). It is also required for many metabolic processes. Red meat provides 12% iron for men and 9% for women. (SACN (2010) Iron and Health)
Zinc Zinc is essential for cell division, growth and repair. It is also necessary for normal reproductive development, healthy immune system and healing wounds. Red meat provides 32% zinc for men and 27% women. (SACN (2010) Iron and Health)
Iron and Zinc A number of factors affect the bioavailability and absorption of dietary iron and zinc, including the composition of the diet. Eating red meat provides highly available iron and zinc. Meat also enhances the absorption of iron from the whole diet (both meat and non-meat sources) and may also enhance the absorption of zinc from the diet. People who choose not to consume red meat can be at a much greater risk of iron and zinc deficiency than people who regularly eat meat.
Vitamin B12 Meat and animal products are the only foods that naturally provide vitamin B12. Vitamin B12 is needed for building proteins in the body, red blood cells, and normal function of nervous tissue. A lack of vitamin B12 has been associated with higher levels of homocystene. This has been linked to an increased risk of cardiovascular disease. Vitamin B12 is also found in milk, cheese, eggs, fish, yeast extract and fortified breakfast cereals.
Vitamin D Low vitamin D status is becoming increasingly common in the UK population. The best source of vitamin D is from the skin coming into contact with the sunlight. Oily fish is the main dietary source of vitamin D, however, only 27% population eat oily fish. Meat, therefore, does have a role to play in providing vitamin D. (SACN (2004) Advice on fish consumption: benefits and risks)
3. What is satiety? Hunger is a compelling need or desire for food. Satiation is the sensation which prompts the termination of eating. Satiety is the feeling of fullness which persists after eating. Lunch Energy intake Satiation Snack Satiety Time Hunger
What affects satiety? Satiation will determine the amount consumed in one sitting. While, satiety will determine the length of time until the next meal. Anything food or drink consumed can affect satiety. For example: Protein Energy from protein, in a sufficient dose, generally has a greater effect on satiety than an equivalent amount of energy from carbohydrate or fat (Benelam, 2009).
What affects satiety? Dietaryfibre Fibre can affect satiety but this depends on the type of fibre and the quantity consumed. The more viscous the fibres (such as pectin and guar gum) are the most effective at increasing satiety.
What affects satiety? Liquid vs solid Liquids are often thought of as less satiating than solid foods but liquid foods such as soup, can actually be more satiating than solids containing the same amount of energy. It may be that people are less aware of the energy content of drinks that they consume in response to thirst and so they don’t compensate by subsequently eating less. If the fluid is embedded as part of the food (e.g. yogurt) it has a greater influence on satiety. In addition, if the fluid - containing food is perceived as part of a meal (e.g. soup) it appears to enhance satiety.
What affects satiety? Click to view the Digi Bite Energy density This is the amount of energy in a given weight of food or drink (kJ/g). The energy density of foods (drinks generally have very low Energy Density values due to the high water content) has a major impact on satiety. Foods and diets with a low energy density appear to be more satiating for a given energy content.
Increasing satiety Research has shown that consuming a diet higher in protein, for example a diet containing lean red meat, may help increase satiety (Benelam, 2009). An increase in satiety, or the feeling of fullness, can help to support weight loss and promote maintenance of a healthy weight.
4. How much red meat should we eat? Click to view the Digi Bite The report “Iron and Health” (SACN 2010) led to new guidance on eating red and processed meat from the Department of Health (Feb 2011). This recommended that adults who eat more than 90g of red and processed meat a day should reduce their intake to 70g a day on average. Approximately, 42% men and 12% women consume more than 90g of red or processed meat a day (NDNS 2000/01). Most people in the UK are already consuming less than the recommendation.
How much red meat should we eat? A recent review of red meat found that within the context of a healthy, varied diet lean red meat contributes protein, long chain n-3 fatty acids, and micronutrients such as iron, zinc, selenium and vitamin D and vitamins B3 and vitamin B12. (Wyness et al. (2011) Red meat in the diet: an update. Nutrition Bulletin36, 34-77). Some of these nutrients are more bio-available in meat than alternative food sources, and some have been identified by SACN as being in short supply in the diets of some sections of the population (SACN 2008).
Vitamin & mineral intakes: percentage below LRNI This table shows the proportion of the UK population who have intakes below the Lower Reference Nutrient Intakes (LRNI) as highlighted below. Source: National Diet and Nutrition Survey, Rolling Programme Years 1, 2 and 3, 2008-2011
Additional findings The Department of Health recommendations are a result of studies investigating red meat consumption and cancer. The most studied cancer in relation to red and processed meat intake is colorectal cancer. Other cancer sites that have been investigated in relation to meat include stomach, lung, pancreas, oesophagus, endometrium and breast. SACN suggested that red and processed meat intake was probably associated with increase risk of colorectal cancer. Research results relating to other cancer sites are inconclusive.
Red meat and cardiovascular disease Click to view the Digi Bite Red meat contains saturated fatty acids, a high intake of which can increase risk of cardiovascular disease (CVD). Red meat also contains other fatty acids (PUFAs and MUFAs) and important micronutrients that may decrease risk of CVD. Lean red meat can be promoted as part of a healthy diet for CVD prevention.
Question 1 What are the building blocks of protein? 1. Carbohydrate 2. Amino acids 3. Polyphenols 4. Fatty acids
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Question 2 Which macronutrient is the key determinant in the amount of energy that meat provides? 1. Carbohydrate 2. Fat 3. Folate 4. Protein
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Question 3 True or false? Meat from the ruminant species, such as cows and sheep, contain proportionately more saturated fatty acids (SFAs) compared with other types of red meat, e.g. pork or bacon. 1. True 2. False
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Question 4 Which of the following statements is false? 1. It is now recognised that it is the type of fat that is particularly important for cardiovascular disease. 2. Red meat provides fat, saturated fatty acids and the essential omega-6 (n-6) and omega-3 (n-3) polyunsaturated fatty acids. 3. The amount of fat is constant in red meat regardless of the animal and the cut. 4. Foods which contain fat can provide essential fatty acids and fat soluble vitamins, which the body needs for good health.
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Question 5 What is satiety? 1. The compelling need or desire for food. 2. The amount of food consumed in one sitting. 3. Nuclear fuel use and deforestation 4. The feeling of fullness which persists after eating.
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