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Reducing cholesterol and improving diet to prevent CHD

Carol Clapham
RGN MSc BSc
Nurse Practitioner
Eaton Socon Health Centre
Nurse Practitioner
The Health Station
Hitchin, Herts
E:carolclapham@onetel.com

Diet is fundamental in the fight against coronary heart disease (CHD) as it affects so many aspects of health. If a patient is asked "Do you eat a healthy diet?" then they nearly always answer "yes" or "most of the time". But what is a healthy diet and what is the evidence regarding diets and lifestyle? The Mediterranean diet (see Box below) has been shown to provide a protective effect for up to 4 years after a myocardial infarction (MI); nursing advice on CHD prevention should therefore include advising patients on eating a cardioprotective diet.(3)

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Mediterranean diets and low-fat diets have also been shown to improve endothelial function in hypercholesterolaemic men.(4) There is insufficient evidence to demonstrate that antioxidant vitamins (b carotene and vitamin E) reduce the risk of CHD but eating more fruit and vegetables does reduce the risk of heart attack and stroke.(5)
Exercise can also help to reduce mortality. People who undertake moderate levels of daily exercise experience 30-50% reduction in relative risk of CHD compared with people who are sedentary. The risk of sudden death after strenuous activity is rare, more common in sedentary people, and does not outweigh observed benefits.(5)

Cholesterol
"Systematic reviews and large subsequent randomised controlled trials have found that ­lowering cholesterol in people with previous ­cardiovascular events substantially reduces the risk of overall mortality, cardiovascular mortality and non-fatal cardiovascular events." (6)
Cholesterol is a lipid mainly produced in the liver which is utilised in building cell membranes and forming hormones. A small proportion of cholesterol is obtained from the diet and transported to the liver. Lipids are not water soluble and must bind to apoproteins before being transported around the body. These are classified as very low-density (VLDL), low-density (LDL) and high-density (HDL) lipoproteins.
Excess cholesterol can become deposited in the small blood vessels leading to atherosclerosis, increasing the risk of stroke, heart attack and peripheral vascular disease. High HDL and low LDL cholesterol levels increases the risk.
Low levels of HDL cholesterol are a major risk factor for the development of coronary artery disease (CAD) and atherosclerosis. Statins will usually lower the harmful LDL and also raise the beneficial HDL cholesterol. Simvastatin has demonstrated the most consistent ability to raise HDL cholesterol level.(7) Atorvastatin has also demonstrated a favourable cost-effectiveness profile, for achieving National Service Framework (NSF) LDL cholesterol and total cholesterol targets.(8) Simvastatin and pravastatin have been shown to reduce mortality in clinical trials.(9)

The evidence
Systematic reviews have found that combined use of cholesterol-lowering therapy and diet is more effective than lifestyle measures alone.(5) Evidence supports the safety and benefits of aggressive cholesterol-lowering therapy, with no lower threshold for LDL levels.(10) All patients discharged from hospital post-MI who are not already taking a statin should be assessed and have treatment initiated at 12 weeks after the MI.(11) An initial serum cholesterol level should be taken to exclude familial lipid disorders and to identify those patients that do not require treatment. The National Service Framework for CHD recommends annual testing.
It is one thing knowing the evidence but how can this help in a consultation, and how can the nurse influence behaviour change? Keith Tone's "Health Action Model"  highlights the important influence that self-esteem has on behaviour.(12) Patients with a high self-esteem are more likely to be motivated into finding ways of healthier living and by using this model a health professional can help to boost an individual's self-esteem, helping patients to resist outside pressures and influences. It is also important to assess the patient's motivation for change and the Prochaska and DiClemente's model of change can assist.(13)

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Motivational interviewing helps patients to internalise and reflect on their own behaviour. It also helps the nurse to assess the patient's readiness for change. Questions could include:

  • After taking a health history it appears you have several risks and I am concerned about the ­following …
  • I would like to talk to you about your diet and how this may be affecting your health.
  • How do you feel about your diet?
  • What concerns you about your diet, lifestyle and risk factors?
  • Are you considering making any changes now?
  • Do the pros of changing outweigh the cons?

If the patient is unaware of any problems then the role of the nurse is to educate them, providing information and offering support for when they are ready to change.
"Self-monitoring" is an essential skill for increasing self-awareness. For patients at risk of CHD a good starting point is to ask them to keep a food and lifestyle diary. Finding out what the patient actually eats and drinks on a regular basis is more useful than just telling a patient what to eat. The diary could also include details of activity to give a bigger picture of overall lifestyle. Keeping a diary not only helps the professional to assess the patient's lifestyle, but also helps the individual to realise their own risks. The nurse can use the lifestyle diary to highlight areas of risk, offer education and explore areas for change. The British Heart Foundation provides excellent leaflets and recipe booklets that the nurse can give to the patient. If necessary a referral to a dietitian may be required.
At each visit discuss with the patient, simple realistic goals with a timescale. Start with small, achievable goals and don't rush, eg, lose 2-4lb over the next 2-4 weeks or eat three portions of fruit a day.
End each consultation with an assessment of their motivation level, eg, on a scale of 1-10 how likely do you feel you will be able to make these changes? A full health history should be taken and individual risks assessed and therapy initiated if required.
Guidelines are abundant and each practice should be able to develop CHD guidelines, agreeing the role of the nurse in CHD management, clinic protocols with treatment and referral criteria.
Remember, even small changes could have significant outcomes and help to reduce the risk of CHD.

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References

  1. De Lorgeril M, Renaud S. Mediterranean alpha-linoleic acid rich diet in secondary prevention of ­coronary heart disease. Lancet 1994;343:1454-9.
  2. Singh R, Dubnov G, Niaz M, et al. Effect of Indo-Mediterranean diet on progression of coronary artery disease in high risk patients. Lancet 2002; 360:9344.
  3. De Lorgeril M, Salen P Martin JL, et al. Mediterranean diet, traditional risk factors and the rate of cardiovascular complications after MI: final report of the Lyon Diet Heart Study. Circulation 1999;99:779-85.
  4. Fuentes F, Lopez-Miranda J, Sanchez F, et al. Mediterranean diets and low fat diets improve endothelial function in hypercholesterolemic men. Ann Int Med 2001;134:1115-9.
  5. NICE. Clinical evidence - the ­international source of the best available evidence for effective health care. Issue 6. London:NICE; 2001.
  6. Clinical evidence concise -the ­international source of the best available evidence for effective health care. Issue 7. London: BMJ Publishing Group; 2002.
  7. Chong PH, Kezeke R, Franklin C. High density lipoprotein cholesterol and the role of statins. Circulation 2002;66:1037-44.
  8. Wilson K, Marriott J, Fuller S, et al. A model to assess the cost effectiveness of statins in achieving the UK NSF target cholesterol levels. Pharmacoeconomics 2003;21(Suppl 1):1-11.
  9. National Prescribing Centre for the NHS. Secondary prevention of myocardial infarction. MeReC Bull 1999;10(2).
  10. Evans M, Roberts A, Rees A. The future direction of cholesterol lowering therapy. Curr Opin Lipidol 2002;13:663-9.
  11. NICE. Clinical evidence concise - the international source of the best available evidence for effective health care summary of guidance issued to the NHS in England & Wales. Volume 2. London:?NICE; 2001.
  12. Tones BK. Making a change for the better: the health action model. Healthlines 1995;27:17-9.
  13. Prochaska JO, DiClemente CC. The transtheoretical approach: crossing ­traditional boundaries of therapy. Illinois: Dow-Jones/Irwin; 1984.

Resources
National Service Framework for CHD
W:www.doh.gov.uk/heart/index.htm

British Heart Foundation
14 Fitzhardinge Street
London W1H 6DH 
T:020 7935 0185
Heart Information Line
T:08450 708070
W:www.bhf.org.uk