nutrients Review Starchy Carbohydrates in a Healthy Diet: The Role of the Humble Potato Tracey M. Robertson, Abdulrahman Z. Alzaabi , M. Denise Robertson and Barbara A. Fielding * Department of Nutritional Sciences, University of Surrey, Guildford, GU2 7WG, UK; [email protected] (T.M.R.); [email protected] (A.Z.A.); [email protected] (M.D.R.) * Correspondence: b.fi[email protected]; Tel.: +44-(0)-1483-688649 Received: 4 October 2018; Accepted: 6 November 2018; Published: 14 November 2018 Abstract: Potatoes have been an affordable, staple part of the diet for many hundreds of years. Recently however, there has been a decline in consumption, perhaps influenced by erroneous reports of being an unhealthy food. This review provides an overview of the nutritional value of potatoes and examines the evidence for associations between potato consumption and non-communicable diseases. Potatoes are an important source of micronutrients, such as vitamin C, vitamin B6, potassium, folate, and iron and contribute a significant amount of fibre to the diet. However, nutrient content is affected by cooking method; boiling causes leaching of water-soluble nutrients, whereas frying can increase the resistant starch content of the cooked potato. Epidemiological studies have reported associations between potato intake and obesity, type 2 diabetes and cardiovascular disease. However, results are contradictory and confounded by lack of detail on cooking methods. Indeed, potatoes have been reported to be more satiating than other starchy carbohydrates, such as pasta and rice, which may aid weight maintenance. Future research should consider cooking methods in the study design in order to reduce confounding factors and further explore the health impact of this food. Keywords: potato; obesity; satiety; T2DM; CVD; nutrition; resistant starch; fibre 1. Introduction According to current UK government guidelines, carbohydrate (CHO) intake should be maintained at a population average of approximately 50% of total energy intake [1] and this is strongly supported by a recent meta-analysis indicating that a carbohydrate intake of 50–55% is optimal [2]. The intake of free sugars within the recommendation should not exceed 5% [1]. This is broadly in line with the WHO Scientific Update on carbohydrates in human nutrition (2007) which recommends a minimum of 50% of total energy intake from CHO, with free sugars restricted to <10% [3]. It is further recommended that carbohydrates consist mainly of starchy foods, such as potatoes, pasta, rice and bread, at about one-third of our total food intake [4]. The potato is historically a starch-rich staple food, originating over 7000 years ago in Peru as reviewed [5]. Potatoes have been an important, affordable food in our diet for hundreds of years and the economic and health consequences of the Irish potato famine between 1845 and 1849 are widely known. As a staple food, the potato still plays an important role in global food security, providing a sustainable food supply and lessening poverty and malnutrition in many parts of the world as highlighted in the Food and Agriculture Organization of the United Nations (FAO) review ‘International Year of the Potato’ [6]. Sustainability of a crop is partly determined by the area of land required, and the water and energy requirements. A ton of potato produced requires only 0.06 ha of land, while rice and wheat require 0.24 and 0.35 ha of land, respectively [7]. Moreover, potato and wheat need less water compared to rice [7] and despite the potato having the highest Nutrients 2018, 10, 1764; doi:10.3390/nu10111764 www.mdpi.com/journal/nutrients Nutrients 2018, 10, x FOR PEER REVIEW 2 of 28 Nutrients 2018, 10, 1764 2 of 28 Nutrients(80%), 2018the ,energy 10, x FOR produced PEER REVIEW per litre of water is greatest for the potato. In addition, the potato 2has of the28 lowest carbon footprint of the three [7]. As a crop, potatoes require cool, but frost-free conditions, (80%), the energy produced per litre of water is greatest for the potato. In addition, the potato has the watersuiting content many geographical (80%), the energy areas. produced However, perduring litre storage, of water potatoes, is greatest require for the chilling potato. and In ventilation, addition, lowest carbon footprint of the three [7]. As a crop, potatoes require cool, but frost-free conditions, thewhich potato increases has the lowestthe demand carbon for footprint energy of [ the5]. threeMost [7cultivated]. As a crop, varieties potatoes are require of the cool, species but frost-free Solanum suiting many geographical areas. However, during storage, potatoes, require chilling and ventilation, conditions,tuberosum [ suiting8], and manyover the geographical last 60 years, areas. plant However, biotechnology during has storage, complemented potatoes, requireconventional chilling potato and which increases the demand for energy [5]. Most cultivated varieties are of the species Solanum ventilation,breeding resulting which increasesin specific the genotypes demand or for cultivars energy [ 95]].. The Most potato cultivated is a globally varieties important are of the crop, species with tuberosum [8], and over the last 60 years, plant biotechnology has complemented conventional potato Solanuman estimated tuberosum 377 million[8], and tonnes over the harvested last 60 years, in 2016, plant only biotechnology falling short of has the complemented other starch staples, conventional maize, breeding resulting in specific genotypes or cultivars [9]. The potato is a globally important crop, with potatowheat breeding, and rice resulting(Figure 1). in specific genotypes or cultivars [9]. The potato is a globally important crop, an estimated 377 million tonnes harvested in 2016, only falling short of the other starch staples, maize, with an estimated 377 million tonnes harvested in 2016, only falling short of the other starch staples, wheat, and rice (Figure 1). maize, wheat, and1200 rice (Figure1). s) 1200 1000 s) 1000 800 800 600 600 400 400 200 Annual production tonne Annualproduction (million 200 0 Annual production tonne Annualproduction (million Potatoes Rice Wheat Maize 0 Potatoes Rice Wheat Maize Figure 1. Global production of major starchy carbohydrate crops in 2016 [10]. Figure 1. Global production of major starchy carbohydrate crops in 2016 [10]. China is estimatedFigure 1. Global to produce production the most of major potatoes starchy in carbohydrate the world with crops many in 2016 European [10]. countries in the topChina twelve is estimated (Figure 2). to produce the most potatoes in the world with many European countries in the topChina twelve is estimated (Figure2 ).to produce the most potatoes in the world with many European countries in the top twelve (Figure 2). 100 90 100 80 90 70 80 60 70 50 60 40 50 30 40 20 30 10 20 Annual production Annual tonnes) production (million 0 10 Annual production Annual tonnes) production (million 0 Figure 2. Top twelve producers of potato by country in 2016 [10]. Figure 2. Top twelve producers of potato by country in 2016 [10]. Many European countries are also in the top ten worldwide potato consumers, when potato Figure 2. Top twelve producers of potato by country in 2016 [10]. supplyMany per capitaEuropean is used countries as an estimate are also of in consumption the top ten (Figureworldwide3). potato consumers, when potato supply per capita is used as an estimate of consumption (Figure 3). Many European countries are also in the top ten worldwide potato consumers, when potato supply per capita is used as an estimate of consumption (Figure 3). Nutrients 2018, 10, 1764 3 of 28 Nutrients 2018, 10, x FOR PEER REVIEW 3 of 28 200 ) 180 capita 160 per 140 120 100 80 Annualsupply (kg 60 Figure 3. Annual per capita supply of potatoes, available for food, in 2013, as a marker of potential Figureconsumption 3. Annual [10 per]. Figurescapita supply estimated of potatoes, based on available the amounts for food, produced, in 2013, as exported a marker and of imported,potential consumptionwith deductions [10]made. Figures for lossesestimated during based storage on the and amounts transport produced, and amounts exported used forand seed, imported, animal with feed, deductionsand non-food made uses. for losses during storage and transport and amounts used for seed, animal feed, and non-food uses. Annual per capita data from 2013 also shows that potatoes and potato products are the third mostAnnual consumed per capita in the data diet, from behind 2013 wheat also andshows rice that [10 ].potatoes Although and maizepotato rates products higher are in the terms third of mostworld consumed production, in the it diet, is used behind in large wheat quantities and rice [ as10] a. Although raw material maize for rates the higher manufacture in terms of of glucose, world production,fructose, and it is high used glucose in large corn quantities syrup, asas animala raw material feed, and for is the also manufacture increasingly of used glucose, for industrialfructose, andapplications high glucose [11]. corn syrup, as animal feed, and is also increasingly used for industrial applications [11]. Despite the current recommendations for starch in the diet, the nutritional value of the potato couldDespite easily bethe overlooked, current recomm partlyendations because it for is not starch counted in the towards diet, the the nutritional ‘five-a-day’ value fruit andof the vegetable potato couldintake easily recommendation be overlooked, [4] and partly because because it