• Consume a healthy, balanced diet.
• Aim for a healthy body weight and shape.
• Reduce saturated and trans fats and substitute with non-hydrogenated, unsaturated fats. Choose whole grains as the main form of carbohydrates, and consume a diet high in fruit and vegetables.
• Be physically active.
• Avoid use of (and exposure to) tobacco products.
Despite the major advances of clinical medicine, maintaining a healthy diet and lifestyle offers the greatest potential for reducing the risk of cardiovascular disease (CVD) in populations. Even for individuals, appropriate diet and lifestyle remain the foundation of clinical intervention for prevention.
Multiple diet and lifestyle factors influence the development of CVD and its risk factors and yet the vast majority of research studies have focused on individual dietary and lifestyle components and few studies examine the effect of a comprehensive approach. This chapter aims to review the components of a healthy diet and lifestyle, which contribute to cardiovascular health and identify some of the practical steps required for their implementation.
6.2 The components of a healthy lifestyle
6.2.1 Balance calorie intake and physical activity to maintain a healthy body weight and shape
To avoid weight gain, individuals must balance energy intake with energy expenditure.
Over the past 20yrs, the number of overweight and obese people has reached epidemic proportions in many countries. Both increased total adiposity [measured by body mass index (BMI)] and visceral adiposity (measured by waist hip ratio or waist circumference) increase the risk of CVD. Centrally obese individuals often show features of the metabolic syndrome including, small dense low-density lipoprotein (LDL) cholesterol, low high-density lipoprotein (HDL) cholesterol, raised triglycerides, elevated blood pressure and impaired glucose regulation. Weight reduction is appropriate for those who are overweight (BMI ≥25kg/m2) or for those with increased waist circumference (≥102cm in men, ≥88cm in women). Energy dense foods such as saturated fats and refined carbohydrates are targets for reduction but a balanced, healthy eating plan that is mildly hypocaloric, allows moderate fat and a variety of food choices has more chance of compliance than a typical low-fat diet. All adults should accumulate ≥30min of physical activity on most days of the week but more activity is associated with increased benefits and ≥60min is required when losing weight. Overweight people should aim to lose around 0.5kg per week. These changes are not easy and require sustained personal and family motivation and appropriate professional support.
6.2.2 Limit intake of saturated and trans fats and cholesterol
Geographic and migration studies have confirmed the link between intake of saturated fat, cholesterol levels, and CVD mortality. Prospective studies, such as the Nurses' Health Study show that higher intakes of both saturated and trans fats are associated with increased risk, whereas higher intakes of the unsaturated fats (polyunsaturates and monounsaturates) are associated with decreased risk. Mensink's meta-analysis of 27 feeding studies shows the relative effects on lipoproteins of different fatty acids, when substituted isocalorically for carbohydrates (Figure 6.1).
As a result of these studies, guidelines recommend limiting saturated fat intake to <7–10% and trans fats to <1% of the 25–35% dietary energy content which fat should contribute to a healthy diet. Health professionals and patients, however, find these numerical criteria difficult to interpret and recommendations to reduce saturated and trans fats should be practically based. Reducing saturated fats largely involves choosing lean meat and low-fat dairy products and reducing trans fats essentially means avoiding commercially fried and baked products. Responsible manufacturers are now producing virtually trans fat-free products but some trans fats are unavoidable as they occur naturally in dairy products.
The second major strategy to limit the intake of saturated and trans fats involves substituting them with unsaturated fats. A meta-analysis of trials of reducing saturated fat by using monounsaturated or polyunsaturated fats as a replacement has shown a risk reduction for CVD events of 24%.
Several prospective studies have shown an inverse association between nut consumption and CVD. Although high in fat, the predominant fats in nuts such as almonds and walnuts are unsaturated and therefore lower LDL cholesterol.
Dietary cholesterol also raises total and LDL cholesterol levels. There is a wide interindividual variation in the amount absorbed but as the amounts are usually small this means reducing saturated fat is a far more potent intervention to reduce serum cholesterol.
6.2.3 Consume fish, especially oily fish at least twice a week
The two major types of polyunsaturated fatty acids, delineated by the position of the double bond nearest to the methyl end of the fatty acid chain, are omega-3 fatty acids and omega-6 fatty acids. Linoleic acid (found in vegetable oils such as sunflower, soya bean, and corn) is the principal omega-6 fatty acid and, similar to all fatty acids, is a structural lipid and a source of energy. In addition, it is an essential fatty acid involved in the manufacture of prostaglandins and leukotrienes. Most people achieve adequate amounts. Intake of linoleic acid is usually recommended not to exceed 10% of dietary energy largely due to the lack of long-term safety assurance despite evidence for improved lipids with higher amounts.
Alpha-linolenic acid (ALA—found in rapeseed [canola], flaxseed, soya bean oils and algae) is the plant precursor of the omega-3 group and the Lyon Diet Heart Study showed reductions in coronary and all-cause mortality in CHD patients who ate a diet enriched with ALA. Fish feeding on ALA-containing plankton produce other omega-3 fatty acids, chiefly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). EPA and DHA are technically not essential fatty acids as small amounts can be formed in the body from ALA. The amounts formed, however, are probably insufficient for a cardioprotective effect in most people. Both epidemiological studies of fish consumers and randomized clinical trials of fish or supplement consumption have shown reductions in coronary and total mortality, and particularly, sudden death. The mechanisms are unknown but omega-3 fatty acids may have anti-arrhythmic, anti-thrombotic, anti-inflammatory, and anti-atherosclerotic actions. High dose omega-3 fatty acids will reduce triglyceride levels. Eating fish (particularly oily fish, rich in EPA and DHA) is another way of displacing saturated fats from the diet and guidelines recommend two servings of fish (2 × 100g) a week.
The optimal balance between omega-6 and omega-3 fatty acids remains unresolved and some have proposed increasing the amount of omega-3 fatty acids at the expense of linoleic acid. As both have separate mechanisms for reducing CVD risk, it seems sensible to increase omega-3 intake without decreasing linoleic acid.
6.2.4 Consume a diet rich in fruits and vegetables
Observational studies have shown lower risk of CVD in people who consume a diet rich in fruits and vegetables, and short-term trials have shown improvement in CVD risk factors, such as blood pressure. Fruits and vegetables are low in energy density and are therefore very useful in weight-reducing diets. They are often high in fibre and contain multiple micronutrients. The mechanisms of benefit are obscure but include either positive benefits of macro- or micronutrients or just the displacement of other foods from the diet.
Although epidemiologic evidence suggests that a high intake of antioxidant vitamins (such as vitamin E, C, and B-carotene) is associated with lower CVD risk, trials of antioxidant supplements show no benefit and supplements are not recommended. CVD risk reduction with folic acid supplementation has also been disappointing. Naturally occurring polyphenols, especially flavonoids, found in grapes, olive oil, and tea, may be more effective but definitive recommendations are awaited. For the time being, a variety of fruits and vegetables are recommended, particularly those that are highly coloured (green leafy vegetables, berries, fruits) whose micronutrient content is higher. In addition, preparation techniques should preserve the micronutrient and fibre content without adding unnecessary calories, fats, sugar, or salt.
6.2.5 Choose whole-grain, high-fibre foods
The consumption of a diet high in the complex carbohydrates found in whole-grain products and fibre is associated with reduced CVD. Part of the effect comes from insoluble fibre, which promotes satiety by slowing gastric emptying and helps to control energy intake and therefore, weight. Soluble or viscous fibre, such as B-glucan or pectin, modestly reduces LDL cholesterol by about 2–3%.
Most cereal grains are highly processed before consumption, increasing their starch content but reducing their content of fibre, essential fatty acids, and other micronutrients. Starchy foods made from refined grains, such as white bread, are rapidly digested to glucose inducing rapid glycaemic and insulinaemic responses and are said to have a high glycaemic index (GI). Unrefined, whole-grain products (e.g., whole wheat, oats, barley, brown rice, and bulgar wheat) have a slower rate of digestion and lower GI values, which may also contribute to benefit.
6.2.6 Choose and prepare foods with little or no salt
There is a progressive dose–response relationship between sodium intake and blood pressure. Reduced intake reduces the risk of CVD, can prevent hypertension (particularly in older people), and lower blood pressure in treated patients. Diets rich in potassium (found in fruits and vegetables) offset the effect of high sodium.
Three-quarters of the salt we eat is already in the food we buy, so reducing sodium intake means making appropriate choices both in shops and food outlets as well as in the kitchen and on the table.
6.2.7 Consume alcohol in moderation
Many studies show that moderate alcohol drinking is associated with a reduced risk of CVD. The studies are difficult to interpret because of the influence of people who have stopped drinking for health reasons. Also, because of the many hazards of high alcohol consumption, drinking alcohol is not recommended for health reasons. High alcohol consumption is a common reason for hypertriglyceridaemia. If alcohol is to be consumed, levels associated with the epidemiology would suggest no more than two drinks a day.
6.2.8 Avoid use of and exposure to tobacco products
There is overwhelming evidence for the adverse effects of tobacco and secondary exposure to tobacco smoke. The effects relate to the amount and duration of exposure. All smokers should be professionally encouraged to permanently stop smoking (Ask, Assess, Advise, Assist, and Arrange).
6.3 Other dietary factors
6.3.1 Soy protein
In people with high cholesterol, a large amount of soy protein (25g/day) may lower LDL cholesterol by up to 6%. How much of this relates to substitution of animal fats and how much to a direct effect is unclear.
6.3.2 Plant sterols
Plant sterols are analogues of cholesterol, providing structural integrity to cell membranes as well as being a starting material for hormones. Small amounts exist naturally in the diet but larger amounts (around 2g/day) can lower LDL cholesterol by 10%. Both unsaturated plant sterols and saturated plant stanols are incorporated into a variety of foods such as spreads, yoghurts, mini-drinks, milk, and orange juice and their effects are almost identical. When recommended, the energy content of each food should be taken into account and long-term compliance is required. At present, plant sterols have no CVD outcome data.
A number of studies have combined the cholesterol-lowering properties of a number of foods in a (portfolio) approach. A low fat diet enriched with plant sterols, soy protein, soluble fibre, and almonds lowered LDL cholesterol by 29%, equivalent to a low dose statin.
6.4 Putting it all together
Diet and lifestyle modifications can effectively alter CVD risk factors and lower CVD risk. Combining dietary and lifestyle changes is more effective than modifying any single factor alone. Analyses from the Nurses' Health Study showed that 74% of CHD events could be prevented by not smoking, eating a healthy diet, maintaining a healthy body weight, exercising regularly, and being prudent with alcohol. Changes in sodium and saturated fat intake, smoking, and vegetable consumption in North Karelia, Finland, have more than halved CVD. Change to low-fat vegetarian diet, moderate aerobic exercise, smoking cessation, and psychological support could reduce LDL cholesterol by 37.2% and angiographically reduce the progression of disease. A caveat here is that low-fat regimens are hard to follow and have been replaced by changes in the types of fats consumed as described earlier. The Lyon Diet Heart Study impressively reduced CHD death by more than 70% using a Mediterranean diet enriched by alpha linolenic acid.
Changing diet and lifestyle patterns would fail if information was not clearly understood and expressed in a meaningful way to patients. Approaches such as the (Eatwell) plate have proved successful in demonstrating the relative proportions of the major dietary components. A number of practical tips to implement diet and lifestyle recommendations are shown in Table 6.1.
Table 6.1Practical tips
Food choices and preparation
How do I know if saturated fat is high
How do I know if salt is high
>;1.5g/100g (or 0.6g sodium) ≤0.3g/100g (or 0.1g sodium)
A variety of options now exist for designing attractive and CVD-friendly diets. The diet should include healthy types of fat and carbohydrate and balance energy intake and expenditure. Together with regular physical activity, avoidance of tobacco and maintaining a healthy weight, such interventions may prevent the majority of CVD in western populations.
JBS2 (2005). Joint British Societies' guidelines on prevention of cardiovascular disease in clinical practice. Heart, 91(Suppl V), v1–v52.Find this resource:
Fourth Joint Task Force of the European Society of Cardiology and Other Societies on Cardiovascular Disease Prevention in Clinical Practice (2007). European guidelines on cardiovascular disease prevention in clinical practice: executive summary. European Heart Journal, 28, 2375–414.Find this resource:
Lichtenstein AH, Appel LJ, Brands M et al. (2006). Diet and Lifestyle Recommendations Revision (2006). A Scientific Statement from the American Heart Association Nutrition Committee. Circulation, 114, 82–96.Find this resource:
Diets consistent with the recommendations exemplified in this chapter are DASH (Dietary Approaches to Stop Hypertension) http://www.nhlbi.nih.gov/health/public/heart/hbp/dash and TLC (Therapeutic Lifestyle Changes) http://www.nhlbi.nih.gov/cgi-bin/chd/step2intro.cgi
Mensink RB, Katan MB (1992). Effect of dietary fatty accids on serum lipids and lipoproteins. A meta-analysis of 27 trials. Arteriosclerosis and Thrombosis, 12, 911–9.Find this resource: