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At the heart of general practice since 1960

Need to know: lifestyle

Public health expert Dr Matt Kearney answers questions on lifestyle issues from

GP Dr Des Spence

1. What are the benefits of exercise for health other than weight reduction?

Physical activity can halve the risk of CHD, diabetes and colorectal cancer. It substantially reduces the risk of hypertension, stroke, obesity, anxiety, osteoarthritis, osteoporosis and low back pain.

Regular moderate physical activity (five 30-minute sessions per week) can reduce both systolic and diastolic blood pressure in hypertensives by 6-7mmHg. It improves mental well-being and enhances cognitive function.

2. Does exercise referral work over the long-term and what type of exercise is best?

Exercise referral is a commonly used intervention to promote physical activity. A recent review by NICE found evidence of short-term impact (up to three months) but no evidence of long-term impact on physical activity levels in participants.

The NICE guidance on physical activity recommends that primary care professionals should use brief interventions to identify inactive adults and to recommend regular moderate activity – and there is clear evidence this is effective.

Examples of activity that can be incorporated into day-to-day lives include walking, cycling, gardening, household activities, dance and recreational activities.

3. Is there evidence that the Mediterranean diet is acceptable to the UK population and that it will impact on our lifespan?

The lower incidence of CHD in Mediterranean countries has been linked to a diet rich in vegetables, pulses, fruits and cereals, a moderate intake of fish and dairy products, a low intake of meat and modest consumption of wine.

The diet is high in unsaturated and low in saturated fats, and a rich source of essential fatty acids and antioxidants. The HALE

pan-European study found a Mediterranean diet plus healthy lifestyle to be associated with a substantial reduction in all-cause mortality.

The unsaturated fat content makes the

diet unpalatable to many outside the Mediterranean region, but the EPIC study has demonstrated significant reductions in all-cause mortality associated with a modified Mediterranean diet (substitution of polyunsaturated for monounsaturated fats).

4. The Government has suggested a 'traffic light' labelling system on foods – how will this work?

The Food Standards Agency has proposed a 'traffic light' system to simplify the nutritional information customers receive when buying food. Using this system, which has been adopted by a number of supermarkets, prominent labels list the amount of fat, saturated fat, salt and sugar contained in the product and each category is coloured red, amber or green.

Some foods will therefore have more than one colour on the label, for example green for sugar but red for salt.

For a healthy diet, customers are advised to aim for a balance of colours in their shopping basket with more greens and ambers and fewer reds overall.

5. Does restricting salt intake really impact on the risk of vascular events significantly?

Average salt consumption in the UK is 10g per day, far higher than the recommended maximum of 6g and the actual requirement of 3g. Excess dietary salt is the most important modifiable risk factor for hypertension.

A recent meta-analysis has shown a consistent dose-response between salt reduction and blood pressure – reducing salt by 3g per day can lower BP by around 5mmHg systolic and 3mmHg diastolic in hypertensives.

Lower but significant reductions are seen in normotensives. Conservative estimates suggest that a 3g/day reduction would reduce CHD by 10 per cent and strokes by 13 per cent. This effect would be doubled with a 6g/day reduction.

6. Does omega 3 really work?

Consumption of long-chain omega 3 fatty acids found in oily fish has been linked to the low incidence of heart disease in Greenland Eskimos. A protective effect has also been suggested against stroke, cancer and dementia. Potential mechanisms include a reduction in BP, triglycerides, arrhythmias, thrombotic tendency, inflammatory mediators and insulin resistance.

However, a recent high-quality systematic review has cast some doubt on the benefits, finding no clear evidence of effect on total mortality, cardiovascular events or cancer, and further research is required.

7. The advice around alcohol consumption

seems confusing. What is the amount that is beneficial for health and what is the amount deemed to be hazardous? Does it matter if it's wine or beer?

The Department of Health advises that alcohol consumption should not exceed three to four units a day in men and two to three units a day in women. Binge drinking, as well as regular consumption above these limits, is associated with increasing risk to physical and mental health.

Within these limits, there is no evidence of increased harm from particular types of beverage. Moderate consumption of red wine has been shown to reduce cardiovascular disease.

8. Patients often come in and ask about the 'five portions of fruit and veg a day' rule. How is one portion defined?

Daily intake of five portions of fruit and vegetables reduces mortality from cancer, CHD and stroke by around 20 per cent. For cancer, increasing fruit and vegetable consumption is the second most effective prevention strategy after smoking cessation.

As well as reducing mortality, increased consumption has been associated with

improved control in asthma, COPD and

diabetes.

Examples of a fruit portion are half a large grapefruit, a slice of melon, two satsumas, one tablespoon of raisins or a glass of 100 per cent juice. Vegetable portions include three tablespoonfuls of cooked carrots, peas or sweetcorn, or one cereal bowl of mixed salad. Portion sizes for children are proportionately smaller.

9. What is the effect of fibre in the diet and does it make a difference what the source is?

By providing bulk, dietary fibre is an effective laxative and can improve weight control by reducing unhealthy snacking. Large retrospective studies have suggested an association between high-fibre diets and reduced risk of colonic carcinoma, although conflicting evidence has emerged from recent prospective studies.

There are two types of fibre – insoluble, found in wheatbran, and soluble, found in oats, brown rice, pulses, fruit, potatoes and some green vegetables. Soluble fibre reduces cholesterol absorption from the gut and may therefore protect against cardiovascular disease. By delaying gastric emptying, it also slows glucose absorption and can improve glycaemic control in diabetes.

10. How much improvement in lipid profile can be achieved by diet alone?

There is strong evidence that replacing saturated with unsaturated fats and increasing fish, fibre and nuts in the diet is effective at lowering cholesterol.

A number of foods – margarine, yogurt, orange juice – are now fortified with plant sterols which reduce gut absorption of cholesterol. Benecol contains stanol esters derived from wood pulp. Evidence suggests that an average intake of 2g per day can lower total cholesterol levels by 10 per cent and LDL by 14 per cent. There is no effect on triglyceride or HDL levels.

Recent studies suggest that a greater impact may be seen in individuals consuming an average diet than in those already following a low-fat diet.

The main disadvantage of these products is their cost, which puts them beyond the reach of many people in lower socioeconomic groups.

11. Is there much evidence for the benefits of vitamin and mineral supplements, rather than getting the nutrients from food itself? What is the evidence for increasing folic acid and homocysteine levels?

Although there is good evidence that the combination of vitamins and minerals in a healthy diet does help to prevent cardiovascular disease and cancer, there is no consistent evidence that supplementing individual vitamins or minerals has the same effect.

Observational studies have suggested a positive association between high homocysteine levels and risk of cardiovascular and thrombo-embolic disease.

As folic acid is effective at lowering serum homocysteine, folate supplements have been suggested for CHD prevention and are included in the proposed 'polypill' along with aspirin, a statin and three antihypertensives.

However, a recent meta-analysis has challenged the causal relationship between homocysteine and CHD and therefore the benefit of folic acid in preventing CHD. Further trials are under way and the results will be awaited with interest.

12. What are the proven effects of stress and should GPs give advice on stress? Should they target specific groups, for example, people with type A personality?

The Whitehall II study has shown that people suffering high levels of work-related stress have higher rates of mental illness, heart disease and low back pain. Work-

related stress is determined not just by the psychological demands of the job, but by

the combination of high demand and low control.

The type A personality – characterised as ambitious, aggressive and competitive – has been associated with increased cardiac morbidity and mortality. Recently, a 'distressed' personality type has been proposed. This type D personality tends to be gloomy, anxious and socially withdrawn and is also associated with a higher risk of CHD.

Presentation with stress-related symptoms is very common in primary care, and as a supplement to counselling it is often helpful to advise on methods of stress management such as physical exercise, caffeine reduction and relaxation techniques. However, there is no evidence that targeting particular personality types is of value.

What I will do now

Dr Des Spence comments on the answers to his questions

• The current fad for omega 3 in everything needs to be reviewed, as clearly the studies do not support

some of the wild claims that have

been made

• Vitamin supplements seem to have

no beneficial effects but patients continue to buy them by the barrow load – this will reinforce my current negative advice

• As I suspected, it really isn't possible

to pigeonhole people and there

seems little point in targeting stress interventions at perceived personality types

• The simplicity and accessibility of 'five

a day' does make this appealing as a short intervention in primary care

• Changing social infrastructure might be of more benefit than exercise referral as it has no proven long-term effect

Des Spence is a GP in Glasgow

Matt Kearney is a GP in Runcorn, Cheshire,

and a public health practitioner

in Knowsley PCT – he is also a member of

the NICE public health interventions advisory committee

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