History and nutritional composition of mycoprotein

Mycoprotein is a well-established and sustainably produced, protein-rich, high-fibre, whole food source, derived from the fermentation of fungus. Mycoprotein is derived from the Fusarium venenatum fungus and is the main component of Quorn™ foods which was launched in 1985^{(Reference Finnigan, Phillips and William4)} and is now sold in twenty different countries. F. venenatum A3/5 falls under the phylum of Ascomycota and is classed as a true fungus⁽⁵⁾. This filamentous micro fungus was first found in soil samples from a field located in Marlow, Buckinghamshire in the 1960s^{(Reference Finnigan, Phillips and Williams6)}. By the late 1960s, F. venenatum was used to develop mycoprotein and by 1984 was authorised for sale as a food by the UK Ministry of Agriculture, Fisheries and Food^{(Reference Wiebe7)}.

Today, mycoprotein is produced vertically in fermenters^{(Reference Trinci8)}. Harrison and Johnson^{(Reference Harrison and Johnson9)} have published a useful overview of mycoprotein production. Salts, pure glucose and ammonia are fed in through an airline and small amounts of biotin and choline added to facilitate growth. The fermenters operate continuously, running for approximately a month at a time. The fermentation broth is heat treated as they leave the fermenter to reduce the ribonucleic acid (RNA) content. Next, the product is pasteurised, and centrifuged to remove surplus liquid, leaving a paste resembling a dough. The paste is heated to set the dough into a solid billet, which is then cooled, cut into shapes, or minced and then frozen. The freezing processed enables ice crystals to form which forms hyphae into bundles that closely resemble the fibres seen in chicken. A new study^{(Reference Lonchamp, Stewart and Munialo10)} mapping the functionality of mycoprotein throughout the fermentation process concluded that there were previously unreported gelling, foaming and/or emulsifying properties for the different Quorn™ streams that could be further used to produce additional novel products.

From a nutritional perspective, mycoprotein has a low energy density, is low in total and saturated fat and contains negligible amounts of cholesterol^{(Reference Derbyshire and Ayoob11)}. It provides the nine main essential amino acids (AAs) and has a protein digestibility-corrected amino acid score of 0⋅996, indicating that it is a high-quality protein^{(Reference Edwards and Cummings12)}. It also meets the UK and European Commission^(13,14) nutrition claims requirements to be classed as ‘high in fibre’ due to it providing at least 6 g of fibre per 100 g. Mycoprotein is, therefore, a high-fibre food source and typically one-third of chitin (poly n-acetyl glucosamine) and two-thirds β-glucan (both 1,3 and 1,6)^{(Reference Denny15)}. Given the fibre profile of mycoprotein, as part of the Food and Drink Federations (FDF) new ‘Action on Fibre’ campaign⁽¹⁶⁾, Quorn™ have pledged to help narrow the gap between fibre intakes and dietary recommendations by: (1) making higher fibre diets more appealing, normal and easy for the population, (2) working with partners to raise awareness, resources and advocacy and (3) expanding their scientific research programme.

Mycoprotein further meets the UK and European Commission^(13,14) conditions of use for riboflavin, folate, source claims and high in folate, phosphorus, zinc and manganese claims, providing at least 30 % of the Nutrient Reference Value. Mycoprotein also provides useful amounts of choline (180 mg/100 g) but cannot be considered a source as no Nutrient Reference Value (NRV) has been set by Public Health England, UK or the European Food Safety Authority. Certain fungi such as mushrooms can contribute to 5-A-Day providing that this is an 80-gram portion – equivalent to 14 button or 3–4 heaped tablespoons of mushrooms, or 2 tablespoons of dried mushrooms⁽¹⁷⁾. However, mycoprotein derived from fungi is not currently recognised as contributing to the 5-A-Day.

Mycoprotein is not yet included pictorially within the Eatwell guide infographic though it is mentioned in the Eatwell guide booklet where it states under the closer look at protein section that ‘Other vegetable-based sources of protein include tofu, bean curd and mycoprotein; all of which are widely available in most retailers’. Given the growing evidence-based reflection is needed to consider its integration. The British Dietetic Association One Blue Dot Report⁽¹⁸⁾ which makes environmentally sustainable diet recommendations for the UK advises that daily intakes of plant-proteins should be raised, and we should ‘Prioritise beans and lentils, soya (beans, mince, nuts, tofu), mycoprotein (Quorn™), nuts and seeds’. A recent survey^{(Reference Roper, Lanza and Lewis19)} of 188 dietitians identified that 72 % agreed that UK EatWell guidance should be updated to integrate sustainable diets with 92 % reporting that meat-alternatives should be represented pictorially and 82 % confirming that mycoprotein should be represented within such an infographic.

Mycoprotein bioavailability and resistance-training muscle adaptations

Mycoprotein has been shown to be a bioavailable protein source^{(Reference Dunlop, Kilroe and Bowtell20)}. Dietary proteins comprise AAs linked by peptide bonds that are hydrolysed in the lumen of the gastrointestinal tract to form dipeptides, and tripeptides which are then utilised by bacteria in the small intestine or absorbed into enterocytes^{(Reference Wu21)}. The AAs that are not degraded in the small intestine move into the portal vein and peripheral circulation for protein synthesis in skeletal muscle and other tissues^{(Reference Wu21)}. Several anabolic stimuli can stimulate MPS which includes nutrition (protein ingestion), daily physical activity and resistance exercise (RE)^{(Reference Damas, Phillips and Vechin22)}.

There are different speeds of protein turnover across pools in the body and AA availability is an important regulator of muscle protein metabolism. Rates of muscle protein turnover in humans are around 300–400 g/d – amounts that largely exceed levels of protein intake (≈50–80 g/d)^{(Reference Schutz23)}. After undertaking RE the response of MPS lasts for approximately 24–48 h^{(Reference Tipton and Wolfe24)}. Therefore, interactions between any meals ingested and protein anabolism will occur during this time and impact on levels of muscle hypertrophy and reconditioning^{(Reference Tipton and Wolfe24)}. Leucine is a particularly important branched-chain AA, responsible for switching on intracellular machinery^{(Reference Duan, Li and Li25)}. It enhances protein synthesis via the activation of the mammalian target of rapamycin (mTOR) signalling pathway in skeletal muscle^{(Reference Duan, Li and Li25)}. Around 80 % of leucine is typically used for MPS and rest is converted to metabolites (α-ketoisocaproate and β-hydroxy-β-methylbutyrate) in skeletal muscle^{(Reference Duan, Li and Li25)}. Subsequently, it is thought that some of the main functions of leucine, i.e. protein synthesis may be modulated by these metabolites. AAs act as a signal to muscle tissue depending on the size and type of meal. The foods that we ingest, and corresponding levels of AAs oscillate throughout the day.

Dietary protein is a central macronutrient but the concept of what constitutes ‘protein quality’ is complex. This can encompass: (1) the quantity of AAs (protein density), (2) digestibility and (3) bioavailability. Recent research has studied whether bolus ingestion of mycoprotein (as part of its wholefood matrix) would stimulate MPS rates more than a leucine-matched bolus of protein concentrated from mycoprotein. It has been shown that protein consumption significantly raised plasma essential amino acid and leucine concentrations (P < 0⋅0001), but more rapidly and to greater magnitudes when derived from the milk protein concentrate^{(Reference West, Monteyne and Whelehan26)}. MPS synthesis, however, increased in rested and exercised muscle in both conditions indicating that the ‘form’ of delivery was irrespective.

Taken together, there has been growing interest in how much protein we need^{(Reference Carbone and Pasiakos27,Reference Richter, Baerlocher and Bauer28)} , the daily distribution of protein^{(Reference Reis, Loureiro and Roschel29,Reference Deldicque30)} and now the ‘type’ of protein is gaining attention from a health and environmental perspective^{(Reference Mariotti and Gardner31)}. To draw to an end, a recent randomised-controlled trial^{(Reference Monteyne, Dunlop and Machin32)} determined whether a mycoprotein-based diet could support daily myofibrillar protein synthesis rates that were comparable with an omnivorous diet. The study recruited older adults (n 19; mean age 66 years) who ingested a 3-day isocaloric high-protein diet where protein was derived from animal or mycoprotein sources. They also undertook a daily unilateral leg extension RE. The research team found that both dietary protein sources resulted in equivalent rested and exercised daily myofibrillar protein synthesis rates. Overall, this implies that mycoprotein can robustly increase MPS rates, sustaining protein synthesis rates to levels comparable to omnivorous diets over several days.

Mycoprotein and cardiometabolic health

Several studies in the past have shown beneficial effects on glycaemia and insulinaemia when mycoprotein has been ingested acutely^{(Reference Turnbull and Ward33–Reference Turnbull, Leeds and Edwards35)}. Turnbull and Ward^{(Reference Turnbull and Ward33)} was one of the first publications to demonstrate that mycoprotein (ingested in milkshake) could significantly improve postprandial glycaemic response 60 min after ingestion (13 % reduction) and insulinaemic response 30 min after consumption (19 % reduction) in healthy young males and females.

Earlier work by the Imperial College research^{(Reference Bottin, Swann and Cropp36)} group undertook randomised controlled trials showing that mycoprotein test meals (low 44 g; medium 88 g or high 132 g) reduced insulin release at all levels of intake in overweight young adults compared with a chicken meal control. Mechanisms were investigated and not thought to involve changes in the satiety hormones, peptide tyrosine-tyrosine or glucagon-like peptide-1.

Researchers at the University of Exeter (2021)^{(Reference Coelho, Monteyne and Dirks37)} have further studied the effects of integrating mycoprotein within diets and impacts on insulin sensitivity, glycaemic control and plasma lipoprotein profile. Earlier studies have shown links with mycoprotein ingestion and 0⋅1–0⋅2 mmol reductions in cholesterol across a period of a week^{(Reference Turnbull, Leeds and Edwards34,Reference Turnbull, Leeds and Edwards35)} . In a randomised, parallel-group trial^{(Reference Coelho, Monteyne and Dirks37)} normolcholesterolaemic young adults (mean age 24 years) ate a fully controlled diet for 1 week providing 180 g mycoprotein per day or meat/fish. In the mycoprotein group, glycaemic control did not change but free cholesterol, total plasma cholesterol (0⋅4 mmol/l reduction over 1 week), LDL-cholesterol, HDL2-cholesterol and the smaller lipoprotein particles significantly reduced (by 14–19 %) compared with 3–11 % reductions in the control. The mycoprotein diet provided 6 g/d more dietary fibre^{(Reference Coelho, Monteyne and Dirks37)} proposed to induce cholesterol-lowering effects; a theory that is in line with epidemiological and other intervention studies^{(Reference Soliman38,Reference Nie and Luo39)} . The type of fibre present in mycoprotein – two-thirds branched β-glucan and one-third chitin which creates a fibrous 88 % insoluble matrix may also be attributed to these cholesterol-lowering mechanisms^{(Reference Turnbull, Leeds and Edwards34,Reference Turnbull, Leeds and Edwards35)} .

When considering such mechanisms relating to dietary fibre intake and cardiometabolic health, it is important to consider which fibre components possess the physical characteristics required to induce favourable health effects^{(Reference McRorie JW and McKeown40)}. It is well recognised that mycoprotein is a high-fibre food source. The fibre form is typically one-third of chitin (poly n-acetyl glucosamine) and two-thirds β-glucan (both 1,3 and 1,6)^{(Reference Denny15)}. It is known that fibre fermentation yields short-chain fatty acids (SCFAs), induced by colonic bacteria which can modulate glucose and lipid parameters^{(Reference Cronin, Joyce and O'Toole41)}. This, in turn, has been associated with satiety and reduced energy intake^{(Reference Chambers, Morrison and Frost42)}. Research at the University of Glasgow^{(Reference Harris, Edwards and Morrison43)} has studied the SCFA-generating capacity of mycoprotein. An analysis of in vitro batch fermentations demonstrated that both mycoprotein and mycoprotein fibre were both fermentable and produced a total SCFA production of 24⋅9 (1⋅7) and 61⋅2 (15⋅7) mmol/l, respectively. An in vitro gut model at the Quadram Institute, Norwich Research Park^{(Reference Colosimo, Mulet-Cabero and Warren44)} has further studied the mechanisms behind mycoproteins’ ability to modulate blood lipid levels. The study showed that mycoprotein can inhibit gut lipases and sequester bile salts, which could be plausible underpinning mechanisms. Further studies are warranted to add to these findings.

Taken together, these findings show that mycoprotein appears to lower glycaemic and insulinaemic response to a meal. Short-term research^{(Reference Coelho, Monteyne and Dirks37)} indicates that replacing meat with mycoprotein for one week does not affect insulin sensitivity or glycaemic control. However, longer-term research^{(Reference Turnbull, Leeds and Edwards34)} shows that >80 g/d mycoprotein (5 g/d fibre) over 1–8 weeks reduces total and LDL-cholesterol under eucaloric conditions, which may be beneficial for glycaemic control if maintained. Effects appear to be attributed to fibre composition and modified lipid absorption within the gut^{(Reference Turnbull, Leeds and Edwards34)}. An array of mechanisms have been purported and largely attributed to the fibre component of mycoprotein. These include the modulation of SCFAs, inhibition of gut lipases and impaired cholesterol/bile absorption. Ongoing research is needed but mycoprotein appears to show great promise as a dietary component for metabolic health.

Mycoprotein, food sustainability challenges and representation within FBDG

The global food system makes a significant contribution to greenhouse gas emissions (GHGEs), from production through to processing. The message to strive towards the consumption of healthy and balanced diets needs to be sustained, yet the concept of what these constitute is changing as the environmental ramifications of food production methods gains attention. The United Nations Food and Agricultural Organisation⁽⁴⁵⁾ defines a sustainable food system as: ‘a food system that delivers food security and nutrition for all in such a way that the economic, social and environmental bases to generate food security and nutrition for future generations are not compromised’. An in-depth publication by Bené et al. ^{(Reference Bene, Fanzo and Prager46)} has further identified twenty-seven key indicators as proxies for the sustainability of food systems and within these the role of diet diversification is recognised.

The global population is expanding and anticipated to exceed 10 billion by 2050⁽⁴⁷⁾. There are several driving forces behind this which include more females surviving to reproductive age, improved fertility rates and ageing populations⁽⁴⁸⁾. In the United Kingdom (UK), the Office for National Statistics⁽⁴⁹⁾ project that population is expected to rise by 3⋅2 % from mid-2020 to mid-2030. By the year 2040, this is projected to reach 70 million and the number of people aged 85 years is predicted to double to 3⋅1 million by 2045 (from 1⋅7 million in 2020), forming 4⋅3 % of the UK population⁽⁴⁹⁾.

Given these prominent shifts in population growth several food sustainability challenges exist. For example, 2 billion individuals globally are overweight and at the other end of the spectrum around 2 billion have ‘hidden hunger’⁽⁵⁰⁾. Animal diseases have disrupted regional and international trade of animal products, competition of land, energy and water is rising and climate change (drought, storms and increasing extreme weather events) have been impacting on food production⁽⁵⁰⁾.

A recent publication in Nature journal^{(Reference Humpenoder, Bodirsky and Weindl51)} calculated the projected environmental benefits associated with replacing ruminant meat with mycoprotein. It modelled the outcomes of 20, 50 and 80 % replacement of the per-capita protein consumption from ruminant meat with mycoprotein^{(Reference Humpenoder, Bodirsky and Weindl51)}. Results showed that 20 % replacement of ruminant meat with mycoprotein globally offsets projected increases in pasture area and lowered annual deforestation and related CO₂ emissions by half, while also reducing methane emissions^{(Reference Humpenoder, Bodirsky and Weindl51)}. It was further concluded that such substitutions would help ruminant meat demand from 2025 to remain static, offsetting projected increases in global pasture demands for feed^{(Reference Humpenoder, Bodirsky and Weindl51)}.

While dietary movements have a valuable role to play in facilitating the ease of future food supplies and counteracting environmental ramifications, these changes will not come about unless populations are educated and well-informed about food systems and dietary guidelines. A modelling study^{(Reference Springmann, Spajic and Clark52)} using data from FBDG from eighty-five countries demonstrated that most (up to 87 % of countries) were incompatible with the Paris Climate Agreement and other environmental targets. Another review of forty-three national FBDG^{(Reference Martini, Tucci and Bradfield53)} further revealed that environmental impacts of the diet were considered infrequently, particularly in older sets of FBDG which overlooked and aligned less well with environmental and sociocultural aspects of food and diet. Focusing in on protein messages, a global review of FBDG from ninety countries^{(Reference Herforth, Arimond and Alvarez-Sanchez54)} showed that not all protein messages were universally echoed. Within these, the embedment of alternative fungal-derived proteins, including mycoprotein, are barely mentioned. While sizeable discrepancies between FBDG (and protein guidance within these) exists globally, the potential benefits for the planet from an environmental perspective remains comparatively small.^{(Reference Derbyshire55)}

A recent review^{(Reference Katz, Doughty and Geagan56)} further argues that current definitions of what constitute ‘protein quality’ are antiquated and should move to include health and environmental outcomes corresponding to specific food protein sources. Indeed, the concept of ‘protein diversification’ is gaining attention and fungal proteins such as mycoprotein have a viable role to play within this^{(Reference Derbyshire55,Reference Derbyshire57,Reference Coelho, Monteyne and Dunlop58)} . As we have seen in this symposium, research of the past and present shows that mycoprotein has both health and sustainability credentials. At least sixteen controlled trials have now investigated inter-relationships between mycoprotein and health^{(Reference Derbyshire and Ayoob11)}. Further work^{(Reference Derbyshire59)} shows that given growing multimorbidity's, expanding and ageing populations, the integration of fungal mycoprotein within daily diets could benefit health across the lifespan, including the narrowing of the present fibre gap.