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Dietary interventions to help lower cholesterol levels

Sue Baic
MSc RD
Senior Lecturer in Nutrition and Public Health
Department of Exercise, Nutrition and Health Sciences
University Of Bristol

Despite gradually falling rates, cardiovascular disease (CVD) remains the leading cause of mortality in the UK, accounting for more than one in three of all adult deaths.1 The majority of cases of CVD are preventable and primary prevention, in particular, has enormous scope to reduce overall mortality rates.

A variety of factors, such as family history, age, smoking, obesity, hypertension, hypercholesterolaemia and type 2 diabetes, are all-important in determining CVD risk. The overall risk of CVD is much increased when several of these factors occur together. All major heart health guidelines recommend those at high risk of CVD should receive guidance on relevant
dietary advice.

Two out of three adults in the UK have a raised cholesterol level, making it an important target for lifestyle advice for nurses in primary care.2 Fortunately, several dietary strategies are effective for reducing total (T-C) and low density lipoprotein cholesterol (LDL-C) levels and CVD risk, whether or not patients are treated with lipid-lowering drugs.

Reducing saturated fat
The vast majority of research has suggested that the amount of saturated fat in the diet is a major influence on both total and LDL-C.3 Recently-eaten saturated fat is converted into blood cholesterol by the liver and also reduces the rate of removal of cholesterol from the body. Cutting down on saturated fat in the diet and partially replacing some of it with unsaturated fats is the most effective way of reducing blood cholesterol.

The main types and sources of dietary fats are shown in Box 1. A list of suggested replacements is shown in Table 1 to help achieve a change in fat profile of the diet, which would help to reduce cholesterol by around 5-10%. The recommended daily amounts for saturated fat intake are no more than 20 g per day for women and no more than 30 g per day for men.
Although not having specific effects on total or LDL-C there is good evidence to suggest that omega-3, the unsaturated fat found in oily fish, offers cardio protective benefits.4

[[Box 1 chol]]

[[Tab 1 chol]]

Recommendations are to include a minimum of two portions of fish per week, at least one of which should be oily. Fresh, frozen, canned or smoked varieties can be used to replace some red meat and cheese dishes as a source of protein in the diet. Cheaper types, such as mackerel, herring, sardines or pilchards, are just as good as salmon, trout and fresh tuna. An alternative is to take fish body oil capsules offering around 1 g of omega-3 fatty acids per day.

Dietary cholesterol is found in shellfish, eggs and offal. However, cholesterol from our food has much less of an effect on blood cholesterol than the cholesterol made in the liver in response to saturated fat in the diet. Indeed, major heart health organisations, including the UK Food Standards Agency and the British Heart Foundation, advise that patients need only cut down on eggs or other cholesterol-containing foods if they have been specifically advised to by a GP or registered dietitian. This can occur as part of specialist dietary advice given to people with familial hypercholesterolaemia - a genetically inherited cholesterol raising disorders (1 in 500 in the UK).

Increasing the intake of soluble fibre
Soluble fibre is a type of dietary fibre that dissolves in water in the gut to form a gel. This, in turn, soaks up cholesterol like a sponge and carries it out of the body. Good sources of soluble fibre include oats and oat bran, nuts, beans and pulses. Foods such as peas, lentils and chickpeas can be incorporated into salads, casseroles or soups. Soy products such as tofu, soy mince, soya milk or soya yoghurt are also rich sources of soluble fibre.

Fruit and vegetables containing soluble fibre are also valuable, and you can advise patients to aim for at least five different portions each day. Fresh, frozen, pure juice, canned and dried all count towards this total. A portion is roughly the size of the palm or one glass for juice or smoothies.

Wholegrains
The Joint Health Claims Initiative in the UK has recently acknowledged the importance of wholegrains in approving the claim, "People with a healthy heart tend to eat more wholegrain foods as part of a healthy lifestyle". Regular consumption of wholegrains at around two to three servings per day is associated with improvements in risk factors such as total and LDL cholesterol.5 Table 2 shows some examples of wholegrains and suggestions for use.

[[Tab 2 chol]]

Functional foods for cholesterol lowering
Patients may want to consider including foods enriched with plant stanol and/or sterol products in the diet. Stanols and sterols are found naturally but only in very small amounts in many plant foods. They inhibit both the absorption of dietary cholesterol and the re-absorption from bile, thus increasing the amount lost in the faeces. Their site of action is in the gut and very little is actually absorbed systemically. A dose of around 2 g of plant stanols or sterols per day lowers LDL by about 10%.6 This level is most easily obtained from fortified foods such as mini drinks, spreads, juices, milks and yogurts including some supermarket own branded products. To obtain optimal cholesterol lowering follow the manufacturer's instructions on recommended daily amounts.

Several researchers have demonstrated cholesterol-lowering effects of combining several plant-based dietary strategies with a low-fat diet. A diet with plenty of wholegrains and soluble fibre, vegetable protein (nuts, soya), stanols or sterols can reduce blood cholesterol by up to 25%.7

Weight loss
In an overweight patient, a weight loss of as little as 10% from the initial starting weight can result in clinically beneficial changes of around 10-15% to both total and LDL-C levels.8 Patients can be supported in setting a realistic weight loss target and rate of steady weight loss of 1-2 lbs (0.5-1 kg) per week. This can be achieved on a low-fat diet combined with regular physical activity. Advice may be useful on reducing portion sizes of foods and eating plenty of low energy but filing fruit and vegetables. Many patients find that a reputable commercial weight loss group which offers monitoring and support in addition to sound dietary advice may be effective.9   

Helping to modify diet
Individualised lifestyle counselling is time-intensive but can be very effective in helping patients change. Discussing a "typical" day with a patient can help assess initial motivation or confidence, and explore ambivalence about changing lifestyle. In addition, counselling can help patients identify personal barriers to change and generate possible solutions to overcome them. It can also enable patients to negotiate meaningful and realistic goals, especially when supported by appropriate written resources. Encouraging the use of a food diary is a useful method for both identifying potential changes and for monitoring progress.

Conclusion
Cardiovascular disease is a major public health problem in the UK. There is enormous scope to impact on risk factors such as raised cholesterol levels with interventions on diet. Health professionals in primary care are identified as a reliable source of trustworthy lipid-lowering information. As a result they are ideally placed to offer practical evidence-based advice, support and monitoring to patients to prevention of CVD events and to reduce overall risk.

References
1. British Heart Foundation (BHF). Coronary Heart Disease Statistics 2008. London: BHF; 2008.
2. Department of Health (DH). Health Survey for England 2003. London: DH; 2004.
3. Stanner S (ed). Cardiovascular Disease: Diet, Nutrition and Emerging Risk Factors. London: Blackwell Publishing/British Nutrition
Foundation; 2005.
4. Hu FB, Bronner L, Willett WC et al. Fish and omega-3 fatty acid intake and risk of coronary heart disease in women. JAMA 2002;287:15-21.
5. Steffen LM, Jacobs DR Jr, Stevens J, Shahar E, Carithers T, Folsom AR. Associations of whole-grain, refined-grain and fruit and vegetable consumption with risks of all-cause mortality and incident coronary artery disease and ischaemic stroke: the Atherosclerosis Risk in Communities (ARIC) Study. Am J Clin Nutr 78(3):383-90.
6. Katan, MB, Grundy, SM, Jones P et al. Efficacy and safety of plant stanols and sterols in the management of blood cholesterol levels. Mayo Clin Proc 2003;78(8):965-78.
7. Jenkins DJ, Kendall CW, Faulkner DA et al. Assessment of the longer-term effects of a dietary portfolio of cholesterol-lowering foods in hypercholesterolemia. Am J Clin Nutr 2006;83:582-91.
8. Scottish Intercollegiate Guidelines Network (SIGN). Obesity in Scotland: Integrating Prevention with Weight Management. Edinburgh: Royal College of Physicians; 1996.
9. Truby H, Baic SM, de Looy A et al. Randomised controlled trial of four commercial weight loss programmes in the UK: initial findings from the BBC "diet trials". BMJ 2006;332(7553):1309-14.

Resources
The British Dietetic Association (BDA) "Food Fact Sheets" written by registered dietitians on key areas of a cardio-protective diet
W: www.bda.uk.com/latest-food-facts.php

Downloadable food diary and evidence-based advice on weight loss
W: www.bdaweightwise.com

British Heart Foundation
W: www.bhf.org.uk/publications/search.asp

Food Standards Agency (FSA)
W: www.eatwell.gov.uk/healthydiet

HEART UK
W: www.heartuk.org.uk