Summary Introduction What are unsaturated fatty acids? Unsaturated fatty acids in the UK diet Unsaturated fatty acids in health and disease Unsaturated fatty acids and public health Conclusions Acknowledgements References Summary  Fat provides energy; indeed it is the most energy dense of all the macronutrients, with 1 g providing 37 kJ (9 kcal). However, the constituent parts of fat, fatty acids, are required by the body for many other functions than simply as an energy source, and there is an increasing awareness of the potential health benefits of specific types of fatty acids. Fatty acids are long hydrocarbon chains, with a methyl group at one end (the omega or n‐end) and an acid group at the other. Unsaturated fatty acids are hydrocarbon chains containing at least one carbon–carbon double bond; monounsaturated fatty acids contain one double bond, and polyunsaturated fatty acids (PUFAs) contain many double bonds. The position of the double bond relative to the omega end determines whether a PUFA is an n‐3 (omega 3) or an n‐6 (omega 6) fatty acid. Most fatty acids can be synthesised in the body, but humans lack the enzymes required to produce two fatty acids. These are called the essential fatty acids and must be acquired from the diet. In humans, the essential fatty acids are the n‐3 PUFA α‐linolenic acid and the n‐6 PUFA linoleic acid. Although humans can elongate dietary α‐linolenic acid to the long chain n‐3 PUFAs eicosapentaenoic acid and docosahexaenoic acid, the rate of synthesis may not be sufficient to meet requirements, and it is, therefore, recommended that good sources of these fatty acids, namely, oil‐rich fish, are also included in the diet. Fat is found in most food groups, and foods containing fat generally provide a range of different fatty acids, both saturated and unsaturated. In the UK, the major dietary sources of unsaturated fatty acids include meat & meat products, cereals & cereal products and potatoes & savoury snacks; primarily as a result of the vegetable oil used in processing. Recommended intakes of both total fat and the different types of fatty acids have been set for the UK population, and it is possible to monitor fat intake from the data collected in nationwide dietary surveys. As a population, we are not currently meeting these recommendations, so there is still scope for dietary change. In Western diets, n‐6 fatty acids are the predominant PUFAs, and this is in line with current dietary advice to consume a minimum of 1% energy as n‐6 PUFAs and 0.2% energy as n‐3 PUFAs. The balance of n‐3 and n‐6 PUFAs in Western diets has changed substantially over the last 100 years or so, and as the two families of PUFAs share a common metabolic pathway, concerns have been raised that this might be detrimental to health; what is becoming increasingly clear is that both n‐3 and n‐6 PUFAs have independent health effects in the body, and as intakes of the n‐6 PUFAs are within the guidelines for a healthy diet, concerns about the n‐6 to n‐3 ratio are driven by low intakes of n‐3 rather t...

Summary  The health benefits of including sufficient dietary fibre in the diet have been well described and have formed the basis of dietary recommendations around the world. However, dietary fibre is a complex dietary entity, consisting of many non‐digestible components of food. Debate surrounding the definition and measurement of dietary fibre has resulted in inconsistencies in labelling, description and recommendations set across the world. In the UK, dietary recommendations are made using the fraction of non‐digestible material described as non‐starch polysaccharide that is measured by the Englyst method. However, the Association of Official Analytical Chemists (AOAC) methods, used widely by the food industry, capture a much greater range of non‐digestible material, that some suggest should be included in any definition of dietary fibre. An attempt to resolve such discrepancies, possibly by taking an approach that considers the health effects of fractions not captured in the Englyst method, is probably overdue. Additionally, it is clear that the effects of these various non‐digestible components of dietary fibre are not interchangeable, and it is important that fibre comes from a range of sources to ensure maximum health benefits from the fibre in the diet. Traditional ‘insoluble’ fibres are required to add bulk as well as rapidly fermentable, viscous fibres to bring about cholesterol lowering. There is also a convincing argument for including slowly fermented components, such as resistant starches, that are well tolerated in the digestive system and can bring about improvements in gut function. Currently there is insufficient data from well designed human intervention trials to make specific recommendations on the amounts of these fibre components in the diet, but it may be useful for health professionals to talk in terms of the different food sources of these types of fibre, as well as total fibre amounts.

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Mycoprotein is a high protein, high fibre, low fat food ingredient derived from fermentation of the filamentous fungus Fusarium venenatum. Interest in the putative role of mycoprotein in lowering blood cholesterol concentrations, reducing energy intakes and controlling blood sugar levels has generated a small number of human studies investigating the effects of mycoprotein on cholesterol reduction, satiety and insulinaemia/glycaemia.In today's 'obesogenic' environment, in which there is an abundance of foods high in fat and/or sugar available to consumers, there is growing interest in foods that are both nutritious and satiating, but that are of low-energy density, and are low in saturates, salt and sugar. Mycoprotein has a favourable fatty acid profile (being relatively low in saturates), a fibre content that is comparable with other vegetarian protein sources, and a naturally low sodium content. Mycoprotein is a good source of zinc and selenium but the levels of iron and vitamin B12 in mycoprotein are low in comparison to red meat.A small number of studies investigating the cholesterol-lowering effects of mycoprotein have been carried out among normo-and hypercholesterolaemic adults. The published studies to date have a number of limitations (including small sample sizes and short study durations), but overall the studies report statistically significant reductions in total cholesterol amongst hypercholesterolaemic subjects (in the order of 4-14%). These results look promising in terms of the ability of mycoprotein to contribute modest but meaningful effects on blood cholesterol concentrations, as part of a varied and balanced diet. However, the exact amount of mycoprotein that would need to be consumed in free-living populations to have meaningful effects on cholesterol is a candidate for further confirmatory research.A number of studies have investigated the effects of mycoprotein in comparison with other protein sources on satiety. Several studies suggest that the effects of mycoprotein on satiety are greater than an equivalent amount of chicken but it is unclear what mechanism underlies this. The studies conducted so far are relatively small, and carried out under controlled conditions, so it is difficult to extrapolate the results to larger free-living populations.The promotion of mycoprotein could potentially be useful, alongside other strategies, in the management of obesity and type 2 diabetes, as it appears to show beneficial effects on glycaemia and insulinaemia in the small number of studies where this has been investigated. More research is needed to better understand the mechanism of action whereby mycoprotein influences glycaemia and insulinaemia, and whether there is any dose-dependent effect.This paper reviews the published evidence for mycoprotein and the topics above, draws interim conclusions about the role of mycoprotein in human health and identifies areas for future research.