The science of cardiovascular disease

NEW BNF Task Force report - Cardiovascular Disease: Diet, Nutrition and Emerging Risk Factors, 2nd Edition

Cardiovascular disease is a major cause of early death and disability across the world. The major markers of risk are well known, but such markers do not account for all cardiovascular risk. A new comprehensive Task Force report examines the evidence for emerging and novel risk factors, and their relationship with diet and nutrition. 

• Findings of the Task Force report and answers to common questions about cardiovascular disease are also available to download below.
• A useful resource 'Helping to protect yourself from heart disease and stroke' is also available below.
• Presentations from our speakers from the day of the Task Force Report Launch can be found attached below.

CARDIOVASCULAR DISEASE: Diet, Nutrition and Emerging Risk Factors, 2nd Edition.

Edited by: Sara Stanner and Sarah Coe
A report of the British Nutrition Foundation Task Force
Chaired by: Professor Keith Frayn

About the report

CARDIOVASCULAR DISEASE: Diet, Nutrition and Emerging Risk Factors covers everything from epidemiology to genetic factors, to inflammation and much more – offering invaluable advice on reducing risk factors and preventing CVD.

This new report:

• Authoritatively reports on the link between emerging aspects of diet, lifestyle and cardiovascular disease risk
• Focuses on novel risk factors of CVD, including the human gut microbiome and fetal and childhood origins, and how it can be prevented
• Features recommendations for interventions and future research
• Includes references, commonly asked questions that summarise the take-home messages, and an online glossary

Who will find it of interest?

CARDIOVASCULAR DISEASE: Diet, Nutrition and Emerging Risk Factors is an important information resource for those working in the field of cardiovascular health or involved in making decisions about health policy. It will be of interest to a broad range of health professionals, the food industry and those who disseminate about the effects of food and health.

How do I get a copy?

The report is available in paperback or as an e-book. Details of how to puchase the report are on Wiley's website here.

New consumer resource

Information from our Task Force report is summarised in our 'Helping to protect yourself from heart disease and stroke' chart, available to download below.

Key points:

• Cardiovascular disease (CVD) is a group of disorders of the heart and blood vessels. Approximately 26% of deaths in the UK are due to CVD.
• There are a number of factors which can have an effect on a person’s risk of developing CVD, including the composition of the diet.
• Consumption of long chain omega 3 polyunsaturated fatty acids, fish, fruit and vegetables, nuts, fibre and replacing saturated fats with polyunsaturated fatty acids are associated with beneficial effects on CVD risk (i.e. reduced risk), while consumption of saturated fatty acids, trans fatty acids and salt are associated with a negative effect on CVD risk (i.e. increased risk).
• The Mediterranean dietary pattern encompasses a range of these beneficial dietary factors and has been associated with a 10% reduction in CVD incidence or mortality.

Development of CVD

Cardiovascular disease (CVD) is a group of disorders of the heart and blood vessels, which includes coronary heart disease, heart attack and stroke. Approximately 26% of all deaths in the UK are due to CVD and 42,000 people die prematurely (under the age of 75) each year as a result of the disease. It is estimated 7 million people in the UK are living with CVD, which costs the NHS £6.8 billion a year. Coronary heart disease (CHD) is the leading cause of death in the UK, with around 1 person dying from CHD every 8 minutes. However, it is believed 80% of CHD and stroke could be prevented by changes to lifestyle factors, such as diet, physical activity and smoking.

Atherosclerosis is the narrowing of the arterial lumen (the space inside the artery), due to a build-up of plaque that consists of muscle cells, connective tissue, cholesterol (primarily low density lipoprotein (LDL) cholesterol) and calcium. The narrowing of the lumen restricts blood flow and if this occurs in the coronary arteries the supply of oxygen to the myocardium (muscular tissue of the heart) is deprived, causing an accumulation of lactic acid and resulting in angina (chest pain). The development of atherosclerosis starts in early life and gradually progresses throughout adolescence and early adulthood. However, the rate of development of atherosclerosis is influenced by CVD risk factors, such as high blood cholesterol and high blood pressure. If an atherosclerotic plaque ruptures or breaks down, a blood clot can form in the vessel (thrombosis) blocking the flow of blood. If this occurs in the coronary arteries it can lead to a heart attack and if the blockage occurs in a blood vessel that supplies the brain it can result in a stroke.

Risk factors for CVD

There are a number of factors which can increase or reduce the risk of CVD and the more risk factors a person has, the greater the chance of developing CVD.

Non-modifiable risk factors

• Family history
  A person is at greater risk of developing CVD if they have a family history of CVD, which is defined as:
  A person’s father or brother being diagnosed with CVD under the age of 55; or if a person’s mother or sister was diagnosed with CVD under the age of 65.
• Ethnicity
  Certain ethnic groups are at a greater risk of developing CVD; these are South Asian (Indian, Bangladeshi and Pakistani) and African Caribbean. People from a South Asian background are at a higher risk of developing CHD and, if also over the age of 65 years, are at a greater risk of having a stroke. People from an African Caribbean background are more likely to have hypertension.
• Age
  Prevalence of CVD increases with age, for example, data from 2011 suggest that about 35% of men over 75 years were affected by CVD compared with about 15% of 45-64 year olds.

Modifiable risk factors

• Socio-economic status
  Compared to people living in the more affluent areas of the UK, there are on average more premature deaths (under the age of 75) from CVD in the most deprived areas of the UK.
• Smoking
  Smoking is an independent risk factor for CVD and approximately 20,000 deaths from CVD each year are linked to smoking. After one year, smoking cessation reduces the risk of developing CHD by half compared to smokers and after 15 years the risk of CHD is equivalent to non-smokers.
• Blood pressure
  Approximately 30% of adults in the UK have hypertension (high blood pressure), which can damage and narrow arteries or can lead to an aneurysm. Reducing blood pressure can significantly reduce the risk of CVD events, e.g. coronary heart disease, stroke and heart failure.
• Blood cholesterol levels
  Elevated LDL cholesterol levels in the blood are associated with atherosclerosis and therefore this is a risk factor for CVD. A reduction of LDL cholesterol levels by 1 mmol/L can reduce deaths from CHD by 28% and CHD events by 27%. Elevated triglyceride levels and low high density lipoprotein (HDL) levels are also CHD risk factors. Modifying dietary fat intake can alter cholesterol concentrations, as discussed in the 'Fats and coronary heart disease' section below.
• Overweight/obesity
  Being overweight or obese is associated with hypertension, type 2 diabetes and high cholesterol levels which are all risk factors for CVD and a person is at a greater risk of developing CVD if their BMI is greater than 25. Abdominal fat is also associated with CVD and a person is at greater risk if their waist circumference is greater than 94cm (37 inches) for a man and 80cm (32 inches) for women. It has also been shown that weight reduction significantly reduces incidence of CVD (in those who are overweight to begin with).
• Physical activity
  A low level of physical activity is associated with overweight and obesity.  Meeting the current physical activity recommendations has been found to reduce the risk of CVD by 20-35%.

Dietary factors and risk of CVD

A number of dietary factors can modify the risk of developing CVD and each factor contributes to a person’s overall risk of developing disease. Diet can have both a negative and positive impact of CVD risk.

Nutrients

Fats and coronary heart disease

Saturated and unsaturated fatty acids
A high intake of saturated fatty acids can increase plasma LDL cholesterol. Current intakes in the UK exceed the recommendation of no more than 11% of food energy, for example intakes in adults aged 19-64 years are 12.7%. Studies have shown that replacing dietary saturated fatty acids with polyunsaturated fatty acids can lower the level of plasma LDL cholesterol and the total cholesterol to HDL cholesterol ratio. It has been estimated that replacing 5% of energy from saturated fatty acids with polyunsaturated fatty acids reduces the risk of developing CHD by 10%.

Evidence for the effect of replacing saturated fatty acids monounsaturated fatty acids on CHD risk has been inconclusive due to a smaller number of studies looking into this compared to those looking at polyunsaturated fatty acids but the data that is available also demonstrates a reduction in plasma cholesterol, though the effect size is smaller. National and international dietary guidelines recommend reducing saturated fatty acids in the diet and replacing with small amounts of unsaturated fatty acids.

Replacing saturated fats with wholegrain carbohydrates also appears to reduces the risk of CHD, however no effect on CHD risk is seen when saturated fat is replaced with refined carbohydrates.

Long chain n-3 fatty acids 
The long chain n-3 fatty acids (also known as omega 3 fatty acids), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) may reduce the risk of CVD via effects on the development of atherosclerosis and thrombosis, by reducing inflammation and coagulation (blood clotting). DHA and EPA may also stabilise atherosclerotic plaques, reducing the risk of plaque rupture which can lead to thrombosis. A small amount of DHA and EPA can be made in the body from alpha linolenic acid (ALA), a short chain n-3 fatty acid found in oils, nuts and seeds. However, the best source of DHA and EPA is oily fish and they are also present in smaller quantities in shellfish, red meat and eggs.

Trans fatty acids
There is a strong association between trans fatty acids and an increased risk of developing CHD. This is because consumption of these fatty acids can raise LDL cholesterol and decrease HDL cholesterol. Trans fatty acids are found naturally in foods produced from ruminant animals and are also produced during the process of partial hydrogenation of edible oils. In the UK use of partially hydrogenated vegetable oils has been largely eliminated and so levels of trans fatty acids in the food supply are low. Current intake of trans fatty acids in the UK is between 0.5-0.6% of total energy intake, which is in line with the recommendation that trans fatty acid intake should not exceed 2% of total energy.

Fibre
Diets high in fibre are associated with reduced risk of CVD. It is believed one potential mechanism for the benefit on CVD risk is the effect of fermentable fibres from foods like oats and fruit on cholesterol levels. Consumption of these types of fibre can reduce the level of total and LDL cholesterol in the blood because the amount of cholesterol absorbed in the small intestine is reduced. Additionally, as a result of the fermentation of fibre in the colon, specific short chain fatty acids are produced which have been found to inhibit cholesterol synthesis in the liver. In SACN’s 2015 report, Carbohydrates and Health, a 9% reduced risk of CVD was estimated with every 7g of additional fibre intake and an intake of 30g/day for adults was recommended. However, current intakes are well below this recommendation at around 18-19g for adults aged 19-64 years.

Salt
A high intake of salt can increase the risk of hypertension which is a risk factor for CVD. Reducing salt intake can help to lower blood pressure and therefore reduce the risk of developing CVD. It is recommended that consumption of salt should be limited to a maximum of 6g/day, however despite intakes reducing over recent years, the average intake for adults in the UK is 8g/day.

Foods

Fish
Oily fish is one of the richest dietary sources of n-3 fatty acids and it is believed its cardioprotective effects are due to the high content of the long chain polyunsaturated fatty acids DHA and EPA. Additionally, consuming fish may displace other foods such as red meat, which is typically higher in saturated fat, from the diet. Current UK recommendations are to consume 2  x 140g portions of fish per week, one of which should be oily, which would provide approximately 450mg long chain n-3 fatty acids/day, depending on which fish are chosen. Fish intakes tend to increase with age, with older adults consuming the highest amount in the UK. However, average intakes in all age groups are below recommendations. Older adults consume the most oily fish, with average intakes of 12-13g/day while children between the ages of 1.5 and 10 years consume the least. Overall, average population intakes in adults in the UK are 8g/day.

Fruit and vegetables
Meeting the current recommendation for fruit and vegetables (at least 5 x 80 g portions per day) can lower the risk of developing CVD. More recent research has started to look at fruit and vegetable subtypes to understand which specific fruit and vegetables may be most beneficial in reducing the risk of CVD. Citrus fruits and cruciferous vegetables have been found to have a positive impact on the function of the cardiovascular system but overall there isn’t enough evidence to make specific recommendations about the types for fruit and vegetables to consume. Therefore consuming plenty of a variety of fruit and veg is key. 

Nuts
Consumption of nuts is associated with reduced mortality from CVD and randomised controlled trials have reported reduced levels of LDL cholesterol, something which is thought to occur due to the fatty acid composition of nuts as they are low in saturated fatty acids and high in monounsaturated fatty acids. Nuts also contain important nutrients including n-3 polyunsaturated fatty acids (especially walnuts), fibre, magnesium, potassium, vitamin E and phytochemicals. 

Stanols and Sterols
If eaten as part of a healthy balanced diet, plant sterols and stanols have been found to lower plasma LDL cholesterol levels by 7 – 12 % and in turn reduce the risk of CHD. The European Food Safety Authority (EFSA) have deemed the evidence for this reduction in cholesterol robust enough to approve a health claim. The structure of plant sterols and stanols is similar to that of cholesterol and so these compete with cholesterol for absorption in the intestine. This results in less LDL cholesterol being absorbed and instead more is taken up by the liver. This beneficial effect on plasma lipid levels is seen with a daily consumption between 1.5 and 3.0g. Plant sterols and stanols can be found naturally in foods such as fruits, vegetables, nuts and vegetable oil however, an average healthy diet will not contain enough to elicit the positive effect on cholesterol levels. Instead, ‘cholesterol-lowering’ foods, such as yogurt drinks and spreads, are available which have been enriched with sterols and stanols to contain the recommended level. Sterols and stanols are only targeted at people who have high LDL cholesterol level, as no great effect is seen with other populations.

Alcohol
Previously, moderate alcohol consumption was thought to be associated with a reduction in CVD mortality, however a large body of evidence suggests the potential positive effects of moderate consumption were overestimated. Current advice that both men and women should not drink more than 14 units of alcohol per week is based on keeping health risks at a low level and a safe limit has not been set.

Dietary patterns and risk of CVD

Mediterranean diet
Observational studies have found following a Mediterranean dietary pattern to be beneficial in reducing mortality and morbidity from CVD (as well as other nutrition-related diseases e.g. cancer) and adherence to this dietary pattern has been associated with a 10% reduction in CVD incidence or mortality. A Mediterranean diet consists of:

• a high intake of plant foods comprising mainly fruits and vegetables, cereals and whole-grain breads, pulses, nuts and seeds;
• locally grown, fresh and seasonal, unprocessed foods;
• large quantities of fresh fruit consumed daily whereas concentrated sugars or honey are only consumed a few times per week in smaller quantities;
• olive oil as a main cooking ingredient and source of fat;
• low to moderate amounts of cheese and yogurt;
• low quantities of red meat and higher quantities of fish;
• low to moderate amounts of red wine often accompanying main meals.

In general a Mediterranean style diet contains moderate amounts of fat which is mostly unsaturated and is high in fibre and phytochemicals. It is believed potential mechanisms for the beneficial effect this dietary pattern has on CVD include anti-inflammatory effects and improvements in endothelial function. Additionally, the Mediterranean diet has been found to have beneficial effects on risk factors for CVD, such as obesity, waist circumference, diabetes and hypertension.

Emerging research

Milk and dairy products and risk of CVD
In more recent years, research has started to explore associations between dairy consumption and risk of developing CVD. As discussed on page 4, intake of saturated fatty acids increases the levels of LDL cholesterol in the blood, which is a risk factor for CVD. Dietary advice for the prevention of CVD has therefore focused on reducing intakes of saturated fatty acids. Among UK adults, milk and dairy products are one of the main dietary sources of saturated fatty acids in the diet, along with cereals and cereal products and meat and meat products. However, evidence from prospective cohort studies and meta-analyses have suggested milk and dairy products (excluding butter and cream) may not have a negative effect on the development of CVD and in some cases may reduce the risk of CVD. Although the mechanism is not clear, other components within the food matrices of milk and dairy products (such as minerals [e.g. calcium, potassium and magnesium] and bioactive peptides) may potentially have beneficial effects on risk factors for CVD including reducing blood pressure, arterial stiffness (a risk factor for atherosclerosis) and reducing lipid absorption.

Further reading:
O. Markey, D. Vasilopoulou, D. I. Givens and J. A. Lovegrove (2014). Dairy cardiovascular health: Friend or foe? Nutrition Bulletin. 39 (2), 161-171.

Guo, J., Astrup, A., Lovegrove, J.A. et al. (2017). Milk and dairy consumption and risk of cardiovascular diseases and all-cause mortality: dose–response meta-analysis of prospective cohort studies. European Journal of Epidemiology. 32 (4), 269–287.

Information reviewed August 2017.