In the film The Martian, Matt Damon’s character, Mark Watney, is stranded on the red planet with nothing to eat but spuds. Now, a 36-year-old Australian is following the same diet, voluntarily.
In an attempt to lose weight and improve his relationship with food, Andrew Taylor has decided to eat nothing but potatoes for a year. But is this approach likely to work, or will he run out of nutrients? And could he have chosen a better single food to live on?
Just over a month into the diet, Taylor posted a photo on Facebook of some unfinished mash potato on his plate. This is a nice illustration of “sensory-specific satiety” – the theory that the pleasure we take in consuming a single food goes down as we eat more of it, so we stop eating so much.
He is probably feeling the benefits of his weight loss (10kg in the first month), with increased energy levels, and already will have reduced his chances of developing diabetes and other chronic conditions. But what will happen in the long term?
Enough protein and fat?
Eating around 3kg of potatoes a day will provide just over 2000kcal, a reasonable amount for a man of his size aiming to lose weight. But while potatoes are an excellent source of carbohydrates and fibre, he may struggle to get enough protein. A 120kg man may need up to 90g of protein, but this diet will provide only 60g.
Proteins are made up of a range of amino acids, including some that must be supplied in our diet, and potatoes contain a surprisingly good balance of these. But, despite spuds providing a good balance of amino-acids, there simply won’t be enough of them in Taylor’s diet.
Potatoes are also low in fat (only 9g per 3kg), so Taylor’s diet doesn’t supply enough of the two essential fatty acids (linolenic and linoleic acid), nor does it provide enough fat to aid the absorption of fat soluble vitamins: A, D, E and K.
We should also eat foods containing ready-made long-chain omega-3 polyunsaturated fatty acids, of which the only reasonable dietary source is oily fish. These fats have specific structural and functional roles in cell membranes, can act as hormones, and help to control blood pressure.
Vitamins and minerals
Taylor will get enough thiamine, niacin, vitamin B6, folate, vitamin C, potassium, magnesium, phosphorus and copper, even allowing for losses of these nutrients during cooking. Also, he has boosted his chance of getting enough vitamins A and E, iron and calcium by agreeing to include sweet potatoes in his diet. But his diet lacks vitamins D and B12.
Exposure to sunshine in Australia means that he should be making enough vitamin D, but unless he takes a supplement his stores of vitamin B12 may well run out before the end of the year. Prolonged deficiency will result in pernicious anaemia and possibly even irreversible nerve damage. Since he is allowing himself some seasonings, yeast extract would be a good choice, to top up levels of some of the other B vitamins, including biotin and riboflavin (vitamin B2). A lack of these will affect the way that he can use the energy from his food.
Also, his diet will provide only around 6mg of zinc and he will need up to 9.5mg a day. Zinc deficiency would become obvious in tissues with rapid turnover, such as the linings of our mouth, intestine and skin, resulting in reduced immunity and wound repair, and perhaps a loss of taste buds.
Other minerals that might be lacking in this diet include chloride, selenium and iodine, since levels of these depend on the soil in which the potatoes were grown. Using an iodine-enriched salt would be helpful in terms of chloride and iodine, but his diet would probably supply only 30μg of selenium, low enough to cause deficiency in most people. This could reduce immunity and lower reproductive capacity, as well as affecting thyroid function and antioxidant status.
Something better than potatoes?
Eating only one food probably won’t do any harm in the short term. However, there is no known food that supplies all the needs of human adults on a long-term basis. Since Taylor is determined to follow a one-food diet, then potatoes are probably as good as anything, as they contain a wider range of amino acids, vitamins and minerals than other starchy foods, such as pasta or rice. If he had chosen a single animal-derived food, he would have had no fibre in his diet and a poor intake of various vitamins, minerals and antioxidants. Fruits and non-starchy vegetables are very low in protein and fat, meaning he would have to plough through a huge amount to get enough sustenance.
Green is not always healthy
As a final caution, potatoes produce solanine, a glycoalkaloid poison. The amount in tubers of commercial varieties is generally low, but potato tubers that have been damaged in some way, or stored in the light, become green and produce more solanine. Eating even small quantities of green potatoes can cause nausea and vomiting, cramps, fever, dizziness, headaches, convulsions.
The toxic dose doesn’t seem to have been definitively determined, and it’s not clear how well solanine is absorbed and metabolised, nor whether it builds up when eaten in small amounts over a long time. It’s clearly safe to eat “normal” quantities of potatoes (up to around 300g) on a daily basis, but the safety of eating ten times this, for a whole year, has not been established. But Taylor should be comforted by the fact that potatoes are a staple food throughout the world, albeit part of a slightly more varied diet.
Food trends in 2016
Food trends in 2016
1/11 Celeriac root
We had a kale obsession in 2015, but 2016’s vegetable sine qua non is predicted to be the knobbly celeriac root. Celeriac milk (Tom Hunt at Poco in Bristol serves it with winter mussels and wild water celery), celeriac cooked in Galician beef fat (from Adam Rawson of Pachamama, hot new chef in the capital) and salt-baked celeriac (to be found in Matthew and Iain Pennington’s kitchens at The Ethicurean in the West Country) are just a few examples.
2/11 Middle Eastern food
The Middle Eastern Vegetarian Cookbook (£24.95, Phaidon) by grand-dame Salma Hage, author of the bestseller The Lebanese Kitchen (whose halva is pictured here), is out in April
© Liz & Max Haarala Hamilton
3/11 Non-alcoholic cocktails
Grain Store mixologist Tony Conigliaro has created Roman Redhead, a riot of red grape juice, beetroot, pale ale and verjus, and Rose Iced Tea (black tea, rose petals, anise essence, pictured here)
The discerning will be slurping Hepple gin – from chef Valentine Warner and cocktail guru Nick Strangeway – which is punctuated with bog-myrtle nuances
5/11 Argyll and Bute
Restaurant followers are getting in a froth about Pam Brunton in Scotland, who opened the Inver restaurant in Argyll and Bute to acclaim last year
6/11 Andy Oliver’s Som Saa
One of the most eagerly awaited restaurants of 2016 will be the permanent incarnation of Andy Oliver’s remarkable pop-up Som Saa opening very soon in east London. Oliver, who worked at Thai god David Thompson’s Nahm in Bangkok, raised a whopping £700,000 through crowdfunding, and is renowned for his piquant Thai flavours and obsessive attention to detail, including in his home ferments and DIY coconut cream
© Adam Weatherley
Another ruminant in vogue is venison, with Sainsbury’s doubling its line for 2016. It provides a protein-packed punch, with B vitamins and iron, and it’s low in fat. Its entry into the mainstream is in part thanks to the Scottish restaurant Mac and Wild, just opened in London, whose Celtic head chef Andy Waugh (who also runs the Wild Game Co) has been touting it as street food for years (his venison burger pictured here)
From Brett Graham’s The Ledbury to Angela Hartnett’s kitchens at Lime Wood Hotel in the New Forest, Cabrito is the go-to goat supplier among the chef cognoscenti (roasted loin of kid pictured here) – but this year, domestic cooks can get in on the action, as Sushila Moles and James Whetlor of Cabrito offer their meat through Ocado
Mike Lusmore / mikelusmore.com
Coffee sage George Crawford is launching the much-anticipated Cupsmith with his partner, Emma. Crawford believes that 2016 is the year purist coffee will finally meet the masses; Cupsmith’s mission will be to make craft coffee as popular as craft beer on the high street. The company roasts Arabica beans in small batches, improving its quality – but sells it online, at cupsmith.com, in an approachable way: expect cheerful packaging and names such as Afternoon Reviver Coffee (designed for drinking with milk – no matter how uncouth, most of us want milk) and Glorious Espresso
10/11 120-day-old steak
Hanging meat for extremely long lengths of time has become an art. In Cumbria, Lake Road Kitchen’s James Cross is plating up 120-day-old steak (pictured here). The beef is from influential “ager” Dan Austin of Lake District Farmers, who is currently investigating the individual bacterial cultures that go into this maturing process
11/11 Lotus root
Diners can expect root-to-stem dining - cue the full lotus deployed by the Michelin-starred Indian Benares in its kamal kakdi aur paneer korma
Eat to live, or live to eat?
One food is not enough, but we don’t need an enormous range of foods. My great great grandfather, living in rural Aberdeenshire, had, like most of his contemporaries, a very limited diet of mainly potatoes, with oatmeal, kale and small amounts of fish and boiled beef. He lived into his nineties and claimed never to be bored with his diet, saying: “It’s just maet” (where the Scots word “maet” refers to food in general, not just meat). Food was fuel, rather than a form of comfort and entertainment. Perhaps that is the sort of relationship with food that Andrew Taylor is trying to achieve.