The Solution to Sustainable Eating Is Not a One-Way Street

By 2050 the Earth has to feed a population approaching 10 billion.The recent report from the EAT-Lancet Commission on Healthy Diets from Sustainable Food Systems (Willett et al., 2019) documents that the conditions for a sustainable, healthy, and nutritious diet for a growing global population can only be established via an acute and major change in the global food systems.This change involves a diet with much more plant-based food than now, including 500 g vegetables and fruit every day and little or no red meat.It is well-known that most people have difficulties eating that much green.The barriers to eating enough vegetables and fruit may be of both psychological, physiological, social, and cultural nature.In addition, plant-based food is lacking in the basic tastes sweet and umami that humans over evolutionary time scales have been primed to crave (Wrangham, 2009).Without confronting these fundamental facts, we may fail in providing for a more green and sustainable future for the planet.In the present Opinion we propose a solution to meet these challenges by the adoption of a holistic flexitarian approach shaped by fundamental insight into taste, and in particular, how to sustain sweetness and umami in a green diet, using only minimal sources from the animal kingdom.A sustainable diet may be defined as "a diet comprised of foods brought to the market with production processes that have little environmental impact, is protective and respectful of biodiversity and of ecosystems, and is nutritionally adequate, safe, healthy, culturally acceptable, and economically affordable" (Pimentel and Pimentel, 2003;Aleksandrowicz et al., 2016;Chai et al., 2019).This is often exemplified as plant-based diets.The literature typically divides plant-based diets into three major groups being flexitarian, vegetarian, and vegan.Common for these diets is that animalbased food, seen in an omnivore diet, is substituted to a smaller (flexitarian), larger (vegetarian), and absolute (vegan) extent.In recent years, an increasing interest in eating more sustainable has been observed and more people are eating a vegetarian and flexitarian diet (Horseman, 2019;Yougov.com, 2019) and sustainability is even described as a megatrend (Mittelstaedt et al., 2014;Hale, 2018).Thus, it may appear that academia (Reijnders and Soret, 2003;Scarborough et al., 2014;Van Kernebeek et al., 2014) as well as some first-mover consumers, are agreeing that meat is not sustainable.However, it must not be forgotten that meat comes in various degrees of sustainability.In addition, meat may often be strongly linked to social and cultural traditions, and it has a high nutritional content and umami taste.Cutting it out of the diet completely may, therefore, pose some significant challenges for some consumers.The EAT-Lancet report (Willett et al., 2019) points out that the global food systems in the Anthropocene are the main reason for the changes in the Earth's ecosystems, including climate changes.Agriculture is responsible for using 40% of the land (Foley et al., 2005), 30% of greenhouse emissions (Vermeulen et al., 2012), and 70% of freshwater use (Steffen et al., 2015).Fisheries have fully exploited 60% of the wild stock, overfished another 30%, and the global catch has declined in recent decades.The cost of this type of food production has been a great loss in biodiversity, damage to whole ecosystems, as well as the emission of excess nutrients and greenhouse gasses.In addition, crucial global cycles of carbon, phosphorus, and nitrogen have been disturbed.At the same time, food waste from production to consumption is skyrocketing.