Download Heart disease

Heart disease
http://www.nutrition.org.uk/nutritionscience/healthconditions/heart-disease.html
Key points
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Cardiovascular disease (CVD), which includes heart disease and stroke, remains one of the
main causes of death and ill-health in the UK.
Important risk factors for heart disease include obesity, high blood pressure, high blood
cholesterol and type 2 diabetes.
Eating a healthy diet, being physically active, not smoking and not drinking alcohol excessively
can all help to reduce the risk of CVD.
There are also a number of non-modifiable risk factors for CVD, such as age, gender, ethnicity
and family history of the disease.
Practical food-based advice to reduce the risk of CVD remains consistent with general ‘healthy
eating’ guidelines. These include to maintain a healthy body weight, eat 5 or more portions of
fruit and vegetables every day, reduce intake of saturates, reduce salt intake and eat at least
two portions of fish, one of which should be oily fish, each week.
Cardiovascular disease
Cardiovascular disease (CVD), which includes coronary heart disease (CHD) and stroke, is a
common cause of death and ill-health in the UK. It is, however, largely preventable. Death rates from
CVD are falling, but it is still a major cause of premature death (i.e. before the age of 65 years) in the
UK, and in 2002 accounted for 35% of premature deaths in men and 27% in women. CVD is also a
major cause of ill-health.
What is CVD?
There are two main events that lead to CVD:
Atherosclerosis is a process which causes narrowing of the blood vessels. It happens when a type of
fat in the blood called low density lipoprotein cholesterol (LDL cholesterol) accumulates and
oxidises in the vessel walls. This causes the vessel walls to ‘fur up’. The walls become thicker
because of an overgrowth of wall tissue and an accumulation of blood clot material which forms a
hardened plaque (atherosclerotic plaque). When this happens to the blood vessels that serve the heart
– the coronary arteries – this can result in a reduced flow of blood to the heart and may cause chest
pain, particularly during exercise. This is known as angina.
Thrombosis occurs when a large clot forms in the blood vessel, sometimes as a result of the rupture
of an atherosclerotic plaque. If this stops the blood supply from reaching the heart, it leads to a heart
attack. If it stops the blood from reaching the brain, this leads to a stroke. Blood clots form when
cells in the blood called platelets stick together.
What is cholesterol?
Cholesterol is a type of fat that is essential for the body in small amounts. It is produced in the liver
and some is also obtained from the diet. It is a constituent of cells, for example brain cells.
Cholesterol is carried around the body in the blood by particles called lipoproteins. Low density
lipoprotein (LDL) is often called ‘bad cholesterol’ because high levels of LDL in the blood promote
the accumulation of fat in the vessel walls. High density lipoprotein (HDL) is often called ‘good
cholesterol’ because it retrieves cholesterol from body tissues and helps to transfer it to the liver for
disposal. The level of cholesterol in the blood depends partly on genetic factors but diet is also
important.
Risk factors
There are a large number of risk factors associated with an increased risk of CVD. Some of these cannot be
altered, for example being male or older or having a family history of the disease. Other risk factors are
related to behaviour and lifestyle and these can be changed: for example, poor diet, lack of physical activity
and smoking. These lifestyle behaviours can lead to obesity, type 2 diabetes, high blood pressure and high
blood cholesterol levels, which increase the risk of CVD. Control of these risk factors is particularly
important for those people who have a non-modifiable risk, as these interact with each other and their effect
is cumulative.
Non-modifiable risk factors
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Men are more at risk of CVD than women; however a woman’s risk increases after she reaches the
menopause.
A family history of heart disease is associated with a greater risk of CVD.
Men aged over 45 years and women aged over 55 years are at a greater risk of developing CVD.
Individuals of a South Asian background have a greater risk of developing heart disease at a younger
age.
Modifiable risk factors
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Poor diet can lead to being overweight or obese and type 2 diabetes. Obese people tend to have
higher levels of blood cholesterol and high blood pressure, which increase the risk of CVD. A high
intake of saturated fatty acids can also increase the amount of cholesterol in the blood.
Physical activity helps to prevent risk factors for CVD such as high blood pressure, overweight and
obesity and the development of blood clots.
Smoking reduces the amount of oxygen that reaches the heart, raises heart rate and blood pressure
and makes the blood more likely to clot. It is therefore a major risk factor for CVD.
Excessive alcohol intake raises blood pressure, which can increase the risk of CVD.
Obesity and CVD
Obese people tend to have increased levels of blood cholesterol, high blood
pressure and an increased risk of type 2 diabetes.
Having fat deposited around the waist rather than on the hips and thighs
(often known as central obesity, or being apple-shaped) is a greater risk
factor for CVD. It is easier for fat around the waist to have access to the
blood supply of the liver. The fat then decreases the sensitivity of the liver
to insulin (which is associated with the development of type 2 diabetes)
and increases the production of very low density lipoprotein cholesterol
(VLDL cholesterol) (a risk factor for CVD). Waist circumference should
be less than 94 cm in men and less than 80 cm in women. A waist
circumference of over 102 cm in men and 88 cm in women confers a
substantially increased risk of CVD and other obesity-related conditions.
For people of South Asian origin, these figures are different: a waist
measurement of 80cm in women and 90cm in men puts health at risk.).
High blood pressure and CVD
Being obese, eating too much salt, drinking too much alcohol, doing too little physical activity and
smoking all tend to raise blood pressure. People with a high blood pressure (hypertension) have a
greater risk of getting CVD. High blood pressure puts a strain on the blood vessels which can make
them become weaker and narrower. This makes it more difficult for the heart to pump blood around
the body. To lower blood pressure it is important for adults to eat less than 6g of salt a day, eat plenty
of fruit and vegetables to provide potassium in the diet and to eat low fat dairy products to provide
calcium. Regular physical activity is also an effective way to lower blood pressure.
High blood cholesterol and CVD
Blood cholesterol level is affected more by the amount and type of fat in the diet than the amount of
cholesterol consumed in the diet. A high intake of saturated fatty acids can increase the amount of
cholesterol produced in the liver and so increase the amount of LDL-cholesterol in the blood. This
increases the risk of CVD. The main sources of saturated fatty acids in the UK diet include fatty
meats and meat products; butter, ghee and lard; cream, sour cream and ice cream; cheese; biscuits,
cakes and pastries; coconut oil, coconut cream and palm oil; many fried foods and confectionery.
Dietary cholesterol has a much weaker effect on blood cholesterol levels, and the main focus should
always be reduction of saturated fatty acids in the diet. The main sources of dietary cholesterol in the
UK diet include liver, egg yolk and shellfish.
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Fatty acids and CVD
All fats are a mixture of saturated and unsaturated fatty acids. Replacing dietary fats high in saturated
fatty acids with those high in either monounsaturated fatty acids or polyunsaturated fatty acids can
lower LDL-cholesterol levels. Monounsaturates can be found in many foods including olive oil,
rapeseed oil, meat and meat products and dairy products. Polyunsaturates are found in a wide range
of foods such as nuts, seeds, vegetable oils and oily fish. See – Sources of different types of fat in the
UK diet.
Omega 6 fatty acids are a type of polyunsaturated fatty acid found in seeds and vegetable oils, for
example sunflower oil, as well as products made from these oils such as spreads. Most of the
polyunsaturated fatty acids in the diet are omega 6. Click here for further information on types of fat.
Long chain omega 3 fatty acids are another type of polyunsaturated fatty acid that are found in oily
fish, in particular. The essential omega 3 fatty acid alpha-linolenic acid is found particularly in plant
derived foods, for example rapeseed oil. See ‘Essential Fatty Acids’. Omega 3 fatty acids do not
improve blood cholesterol levels but may protect against heart disease in other ways. Long chain
omega 3 fatty acids make the blood less viscous and less likely to clot and therefore reduce the risk
of a heart attack. These types of fatty acids also seem to protect against abnormal heart beats
(arrhythmias).
High dietary intakes of trans fatty acids can increase the risk of heart disease. Trans double bonds are
found naturally in small amounts in foods produced from ruminant animals, e.g. milk, beef and lamb.
In the past, most of the trans fatty acids in the UK diet were the result of partial hydrogenation
(hardening) of vegetable oils to make semi-solid fats but this process is no longer in use in Britain. In
the UK, most retailers and manufacturers have now removed trans fats from their product ranges and
as a result intakes have fallen in recent years and are now well below the maximum intake
recommended. So, in the UK, trans fatty acid intake is no longer regarded as a problem but high
intakes still exist in other parts of the world.
Dietary factors and CVD risk
In addition to the type of fat in the diet, there are a number of other diet related factors that may affect the
risk of CVD.
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Soluble fibre is a type of fibre found in foods such as oats,
fruits, vegetables and pulses. It has been shown to reduce
blood cholesterol levels by reducing the amount of cholesterol
absorbed from the intestine. It may therefore reduce the risk of
CVD.
Resistant starch is fermented by gut bacteria in the large
intestine producing short chain fatty acids. These short chain
fatty acids may help reduce blood cholesterol levels. Resistant
starch is found in whole or partly-milled grains and seeds,
pulses and some breakfast cereals.
Eating more than 25g/day of soya protein (a glass of soya milk typically contains 7g, a portion of
tofu 4g), included in a diet low in saturates, has been shown to reduce blood cholesterol
concentrations.
‘Cholesterol-lowering spreads,’ that contain plant stanols/ sterols can help to reduce the level of
blood cholesterol if eaten as part of a healthy varied diet.
Research has shown that people consuming a diet rich in wholegrain cereals have significantly lower
rates of heart disease. Wholegrain cereals contain a number of components that may contribute to a
reduced risk, such as vitamin E and dietary fibre. They also contain resistant starch and
oligosaccharides (a type of carbohydrate) that are fermented by intestinal bacteria to short chain fatty
acids, as well as plant sterols, and all of these can help reduce blood cholesterol.
Sodium is one of the dietary and lifestyle factors that has been linked to high blood pressure
(hypertension) but others include an excess alcohol consumption, excess energy intake (leading to
overweight/obesity) and physical inactivity. Hypertension is often symptomless, but it increases the
risk of heart disease and stroke. A diet that is not high in sodium and contains plenty of fruit and
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vegetables (sources of potassium) and moderate amounts of low fat dairy products (the ‘DASH’ diet)
has been shown to lower blood pressure.
It has been suggested that antioxidant vitamins such as
vitamin C, beta carotene and vitamin E may offer some
protection against CVD by preventing free radicals from
damaging arteries and the cells that repair such damage. More
research is needed before dietary recommendations can be
made. However, there is good evidence that eating plenty of
fruit and vegetables is protective.
Several studies indicate that middle-aged and older people
who regularly drink small amounts of alcohol (1-2 units/day)
are at lower risk of heart disease than non-drinkers. Much of
this effect has been attributed to an increase in HDL
cholesterol. Heavy drinking, however, increases the risk of heart disease and stroke.
Some studies have shown consumption of mycoprotein to lead to modest but meaningful reductions
in blood cholesterol, when consumed as part of a healthy varied diet.
The regular consumption of nuts has been associated with favourable effects on blood cholesterol
and reduced risk of CVD. Nuts are, however, high in energy so should be consumed in small
amounts.
Physical activity
Physical inactivity and low fitness are major independent risk factors for coronary heart disease; those who
are inactive and unfit have almost double the risk of dying from coronary heart disease. Physical activity
also has a beneficial effect on preventing stroke and modifying cardiovascular risk factors such as high
blood pressure and blood lipids (e.g. improving HDL cholesterol levels). Regular aerobic physical activity
(activities in which you demand more oxygen because you become breathless) can also improve overall
cardiovascular fitness. 30 minutes of moderate intensity physical activity at least 5 times a week is
recommended to reduce CVD risk.