The use of functional foods to meet dietary guidelines

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Many consumers struggle to meet dietary recommendations. The United States Department of Agriculture (USDA) reported in 1998 that the average intake of added fats and sugars was too high and the intake of fruits, vegetables, dairy products, lean meats and foods made from unrefined grains was too low compared with serving recommendations.9 Comparable findings in The Netherlands10 and the rest of Europe (supplement 2 to the British Journal of Nutrition 1999, vol. 81) have been reported.

Functional foods enriched with vitamins, dietary fibres or specific fatty acids, or foods that are designed to be low in sodium or saturated fat, can therefore make a valuable contribution to our diet, as will be discussed in the following paragraphs. The evidence-based strategies for a reduction in CVD risk have been used as a guide.

1.3.1 Substitute nonhydrogenated unsaturated fats for saturated and trans fats

Replacement of saturated or trans fat in the diet by carbohydrates or other types of fat reduces the risk of coronary heart disease.11'12 Margarines were rich sources of trans fat until about a decade ago, but food manufacturers have markedly reduced the trans fat content since reports on adverse health effects.

1.3.2 Increase consumption of omega-3 fatty acids from fish, fish oil supplements or plant sources

Fish oils are listed as functional food ingredients because of their remarkable effect on preventing sudden cardiac death.13 The recommended consumption of fish in Western countries is one or two portions per week. The average intake varies highly between countries, with a six- to sevenfold variation in total fish consumption in countries in Europe,14 but is lower than the recommendation. Instead of increasing the amount of fish in the diet, functional foods enriched with the n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) can be used. Several foods can be fortified with fish oil, for example margarines, dairy products, sausages, luncheon meat and french onion dip.15

Adding these products to an ad libitum diet significantly increased plasma and platelet EPA and DHA.15

Chicken eggs enriched with n-3 fatty acids may provide an alternative source of EPA and DHA. In populations where egg consumption is higher than fish consumption, in particular, this could be an effective strategy to increase n-3 intake.16 Chicken eggs can be enriched with n-3 fatty acids by feeding hens diets rich in flax seed or fish meal.17'18 It has been shown that consumption of two to four enriched eggs/day significantly increased polyunsaturated fatty acid (PUFA) concentrations in platelet phosplipids.19-21 Effects on blood lipids were variously shown to be absent to beneficial. Omega-3 enriched eggs can be a succesful source of n-3 fatty acids only if they are accepted by the consumer. In a sensory evaluation with 78 untrained volunteers no difference in taste was found, and storage life was no different for enriched and 'normal' eggs.21 Although three enriched eggs need to be consumed to provide approximately the same amount of n-3 fatty acids as one meal with fish, they can be a good source of n-3 fatty acids for consumers who do not like fish.

1.3.3 Consume a diet high in fruits, vegetables, nuts and whole grains and low in refined grain products

In the US, vegetable consumption is close to the recommended daily intake but fruit consumption is less than half of the recommended amount.9 In Europe, fruit and vegetable consumption is also below recommendations (supplement 2 to the British Journal of Nutrition 1999, vol. 81). As a consequence many consumers do not meet dietary recommendations for fibre, folate, vitamin C and other vitamins. For example, it has been estimated that approximately 50 per cent of Dutch consumers do not meet dietary recommendations for folate.22

Many consumers believe that a healthy meal takes more time to prepare.23 Ready-to-eat salads, fruits and ready-to-cook vegetables can increase consumption in consumers with limited time to prepare foods.

Foods enriched with fibres and vitamins can be an alternative to fruits and vegetables, but only to a certain point. For example, different dietary fibres have different effects on CVD risk: water-soluble dietary fibres such as pectin and guar gum appear to have stronger effects than insoluble fibres such as wheat bran.24,25 Thus, a mixture of various dietary fibres such as found naturally in fruits and vegetables appears to be necessary for a protective effect on CVD. Also, adding vitamins to foods to compensate for low fruit and vegetable intakes might not have the expected effects. For example, beta-carotene was widely believed to reduce cancer risk in smokers, because intake of carotene-rich foods was associated with less cancer, as were high levels of carotene in blood. However, it was found that carotene supplements increased risk of lung cancer in smokers.26 27 Large clinical trials of antioxidants have also had disappointing outcomes.28 Moreover, several other bioactive components from fruits and vegetables, rather than vitamins, may protect against CVD. Enrichment of foods with known vitamins and minerals might therefore not be enough.

Consumption of functional foods can make an important contribution to nutrient intakes. For example, consumption of micronutrient-enriched cereals was associated with significantly increased intakes of iron, B vitamins, vitamin D and fibre in an adult Irish population.29

1.3.4 Choose and prepare foods with less salt

Although not part of the strategies as proposed by Hu and Willett in their 2002 paper,2 reduced salt intake is another strategy to lower risk of CVD.30 Current average salt intake in Western populations is 9-12g/day31 and this should be reduced to 5-6 g/day according to most public health recommendations aimed at lowering blood pressure.31-33

Manufactured foods are the largest sources of salt in our diet, whereas cooking salt and table salt provide only 5-35 per cent.34-36 Thus, reductions in the amount of salt added by food manufacturers have a much larger impact in salt consumption than the advice to use less salt at home.35 Functional foods with reduced salt content such as soups and snacks - could therefore have a considerable impact on CVD risk.

Replacing sodium in the diet with potassium has been shown to reduce blood pressure.37 Mineral salts such as LoSalt, in which a third of the sodium has been replaced by potassium, could therefore be a good alternative to regular salt.

1.3.5 Foods with 'novel' ingredients

Most of the claims for benefits from novel ingredients have come from ecological or cohort studies.38 However, the effects of some ingredients on risk markers have been well investigated in clinical trials,39 and show promise of reducing disease risk.

Sterols and stanols

Margarines and yogurts have been enriched with plant stanols or sterols, which lower low-density lipoprotein (LDL) cholesterol by 10 per cent and could thus make an important contribution to prevention of coronary heart disease.40 Many well-controlled trials have documented the efficacy of sterols and stanols for lowering LDL, and no major adverse effects have been noted. However, long-term safety and clinical efficacy have not been evaluated in large-scale clinical trials of the size and duration customary for new drugs. The Health Council of The Netherlands therefore discourages the use of plant sterols by consumers who would not benefit from a cholesterol-lowering effect, e.g. children and pregnant women, and other regulatory agencies have suggested similar limitations.

Polyphenols

High intakes of tea rich in catechins and other flavonoid polyphenols have been associated with a reduced risk of coronary heart disease.41 A clinical trial to evaluate these effects would seem justified and feasible.

Isoflavones (phytoestrogens)

A high consumption of soy and soy protein has been associated with a low risk of CVD in ecological studies. Besides soy protein, phytoestrogens such as genistein might be responsible for the effects on CVD risk. Phytoestrogens comprise several groups of non-steroidal oestrogens including isoflavones and lignans. There is limited quantitative data on the absorption and metabolism of dietary phytoestrogens. Although it is now known that dietary phytoestrogens are metabolised by intestinal bacteria, absorbed, conjugated in the liver, circulated in plasma and excreted in urine, further clinical trials should determine the potential health effects of these compounds.42'43

Functional foods with isoflavones and other phytoestrogens include breakfast cereals, soft drinks, bakery and dairy products and snack bars.44

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