Transcript Nutrition and red meat.

Nutrition and red meat
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for A-level students
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Information
1. Macronutrients
2. Micronutrients
3. Satiety
4. Consumption guidelines
Questions
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Extension
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.
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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.
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Amino acids
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.
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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.
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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).
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Fat in red meat
Fat supplies a rich source of energy and essential nutrients, e.g. fatsoluble 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)
Meat (barbecued or grilled)
Rump steak – lean
Rump steak – lean and fat
Leg joint of lamb – lean
Leg joint of lamb – lean and fat
Loin chops of pork – lean
Loin chops of pork – lean and fat
Energy
(kcal)
176
203
210
236
186
255
Fat
(g)
5.7
9.4
9.6
13.0
6.8
15.8
Protein
(g)
31.2
29.5
30.8
29.7
31.1
28.3
Source: Chan et a. 1995
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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.
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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.
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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.
Type of red meat
Bacon (grilled)
Pork
Total SFA
Total MUFA
n-6 PUFA
n-3 PUFA
Lamb
Beef
0%
20%
40%
60%
% of fatty acid g/100g
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80%
100%
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.
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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
Lauric acid C12:0
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These are both shown to increase
cholesterol more potently than
Palmitic acid.
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 who
eat 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).
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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.
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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.
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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)
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Micronutrient composition of meat
Nutrient per
100g
Beef
Lamb
Pork
Vitamin A
Calf liver
Rich source
Vitamin B1
Rich source
Rich source
Source
Rich source
Vitamins B2
Source
Vitamin B3
Rich source
Rich source
Rich source
Rich source
Vitamin B6
Rich source
Source
Rich source
Rich source
Vitamin B12
Rich source
Rich source
Rich source
Rich source
Rich source
Source
Rich source
Source
Rich source
Iron
Source
Zinc
Rich source
Selenium
Potassium
Source
Source
Source
Source
Phosphorus
Source
Source
Source
Rich source
≥15% of the RDA per 100g = Source; ≥30% of the RDA per 100g = Rich source
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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)
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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)
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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.
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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.
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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)
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3. What is satiety?
Hunger is a compelling need or desire for food.
Satiety is the feeling of fullness which persists
after eating.
Snack
Energy intake
Lunch
Satiation is the sensation which prompts the
termination of eating.
Satiation
Satiety
Time
Hunger
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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).
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What affects satiety?
Dietary fibre
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.
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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.
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What affects satiety?
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.
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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.
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4. How much red meat should we eat?
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.
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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 Bulletin 36, 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).
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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.
Male
Age, years
Female
4-10
11-18
19-64
65+
4-10
11-18
19-64
65+
Vitamin A
5
12
8
3
4
14
5
1
Riboflavin
1
8
4
5
1
20
11
2
Folate
0
2
2
0
0
6
3
3
Iron
1
6
1
2
1
45
21
0
Calcium
0
7
4
2
2
18
8
2
Magnesium
0
27
16
18
3
50
11
9
Potassium
0
17
11
14
0
31
23
18
Zinc
5
11
9
9
8
19
3
0
Selenium
0
22
25
31
1
44
50
52
Iodine
2
8
5
0
3
20
9
1
Source: National Diet and Nutrition Survey, Rolling Programme Years 1, 2 and 3, 2008-2011
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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.
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Red meat and cardiovascular disease
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.
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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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Question 6
Fill in the gaps.
Iron provided by meat has a ____ bioavailability. This means the body
absorbs a ________amount of the nutrient when compared to other
foods.
1. high, lower
2. low, lower
3. low, greater
4. high, greater
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Question 7
Which of the following functions does not require the
mineral zinc?
1. Improve eyesight in dim light.
2. Normal reproductive development.
3. Healthy immune system, healing wounds.
4. Cell division, growth and repair.
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Question 8
Which of the following is not a source of vitamin D for
the UK population.
1. Oily fish
2. Red meat
3. Sunlight on the skin
4. Filtered water
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Question 9
Which of the following does not provide Vitamin B12?
1. Vegetables
2. Red meat
3. Milk
4. Eggs
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Question 10
Fill in the gaps.
The government recommends people who are consuming ______g or
more of red meat a day, should consider reducing their intake to ____g
a day.
1. 50, 20
2. 90, 70
3. 100, 200
4. 200, 100
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Extension
Q1. Explain the functions of the nutrients provided
by red meat.
Q2. Define the meanings of the terms:
•
saturated fatty acids (SFAs)
•
unsaturated fatty acids (USFAs)
•
polyunsaturated fatty acids (PUFAs).
Q3. Describe the factors which can influence
satiety.
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