Canary Wharf in London on a Thursday lunchtime, and platoons of well-groomed office workers descend into a warren of underground malls in search of lunch: something healthy, natural and delicious – a little edible holiday from urban desk life. All the big chains are here to tempt the 100,000 ravenous workers, who needn’t step outside all day: from Eat, Leon and Pret a Manger to Wagamama, Waitrose and Marks & Spencer. The longest queue is in the vast Waitrose, snaking past fridge after fridge of hermetically sealed, ready-to-eat food.

Step a little closer and look at that food, and a trend quickly emerges: at Pret a Manger, you can wash your avocado wrap down with “naturally rehydrating” coconut water, then grab a pot of dairy-free coconut yoghurt with mango for afters. You might have already had the coconut porridge for breakfast, and if that wasn’t coconutty enough for you, the top four items on the “Barista Specials” board are – drum roll – coconut-milk coffees. At Eat, it’s a mango-and-coconut-milk chia pot; at the Virgin Active cafe, a coconut granola with “pina colada” topping. Waitrose has more than 145 coconut-containing products (although, yes, that does include some toiletries), Morrisons sells 213 and Tesco no fewer than 394.

In the UK, coconut water – an acquired taste – was predicted as a “bizarre” trend back in 2010. Yet, seven years later, the market for all things coconut is still expanding. April saw Pret a Manger report record profits – and cite coconut as its most popular new ingredient. Coconut has, of course, been a much-loved staple of cuisines around the world since time immemorial, but, according to the UN’s Food and Agriculture Organisation (FAO), global demand is growing at 10% a year. The global market for coconut water hit $2.2bn in 2016.

Coconut’s myriad uses scratch a number of gastronomic itches, being acceptable to vegans, the lactose-intolerant and those who “avoid dairy” as a lifestyle choice. It provides a rich milk substitute, and its sweet-smelling oil is big with dairy-free baking fans; coconut flesh can be dried and ground down to a gluten-free flour (the Nourished Kitchen food blog extols its high fibre and protein counts but doesn’t mention the 14% fat and 18% sugar); coconut water is sold in gyms as electrolyte-rich, post-workout hydration – a natural sports drink. All these products offer the tempting transparency of being free from perceived nasties (AKA synthetic chemicals). Chopped from palm trees in tropical paradises and shipped directly to the expensive aisles of health-food shops, coconuts are catnip to lifestyle bloggers.

The coconut’s reputation as a health food, however, is controversial, and riddled with false advertising, lawsuits and the misappropriation of scientific research. Things recently came to a head in the US, when, last month, the American Heart Association issued a report that warned consumers off coconut oil because of its absurdly high saturated fat content – higher, at 82%, it pointed out, than the amount in beef dripping (50%) or butter (63%). This has whipped the wellness industry into a defensive lather, and the ensuing tussle between science and believers has, inevitably, been referred to by some media outlets as “coconutgate”.

Researching the nutritional benefits of coconut reveals a vocal subculture of health-panacea enthusiasts. There are books produced by reputable publishing houses with titles such as The Coconut Miracle and The Goodness of Coconuts, along with numerous websites that will tell you coconuts can stimulate fat-burning, repair damage from degenerative brain disease, shrink tumours, make your hair bigger, hydrate you better than water, boost your immune system, combat ageing and ward off bacterial, viral and yeast infections.

The humble coconut has acquired the aspirational sheen of celebrity endorsement. We can’t entirely blame Gwyneth Paltrow and her lifestyle empire, Goop, for popularising coconut as a superfood, but, unsurprisingly, she can take some credit. In a 2013 interview, she announced that she uses coconut oil “a lot” in cooking and on her face (“it’s supposed to clear up your skin”, she had read on the internet). She detoxifies her mouth with it, too, swilling it around in an “ancient” process called oil pulling. A kit, which includes a tiny bamboo spoon and peppermint lip balm, can be purchased via the Goop shop for $36. However, Paltrow is not the only celebrity to profit from coconuts. Launched in the US in 2004, and the UK in 2010, Vita Coco is the big kahuna of coconut water. Not only is Rihanna a front-woman for the brand, but Madonna, Matthew McConaughey, Demi Moore and Anthony Kiedis of the Red Hot Chili Peppers all shrewdly invested in the company. A $1bn sale to PepsiCo is rumoured to be on the cards.

With its claims of being “super-hydrating” and “nutrient-packed” (later dropped, after consumers sued them for being misleading), and its sexy “Born in Brazil” tagline (also later dropped), the brand steamrollered into retail refrigerators the world over. It is even selling coconuts back to the Philippines, the world’s biggest exporter, on the basis that cartons are hygienic (except when a squid-like foreign body gets inside) and way more convenient than climbing trees while holding a machete.

Exploited? A Filipino coconut farmer. Photograph: Ted Aljibe/AFP/Getty Images

The drink, consumers have been told, is rich in potassium, an electrolyte our bodies need in order to recover from dehydration. This happens to be meaningless, though, without a decent whack of sodium, says Linia Patel, a dietitian and British Dietetic Association spokeswoman. “Without the key electrolyte, sodium, the drink doesn’t optimally hydrate,” she says. “Sure, it’s a type of fluid to take on board, but if you’re doing high-end performance sport, a sports drink, which may have more sugar but more sodium and less potassium, would probably rehydrate you better.” Besides, she points out, most mortals don’t exercise enough to need special drinks. Even if you’ve been for a really intense half-hour run? “No,” she laughs. “Sadly not. Drink water.”

This is not to say that unadulterated coconut water isn’t a mildly nutritious sweet drink to enjoy as an occasional treat – but the smallest carton (330ml) of Vita Coco will set you back 59 calories – and watch out for other brands adding sugar.

Jack Fitzgerald, a consumer-protection lawyer in San Diego, sees health claims for coconut water as small-fry in the public-health stakes. “We do have a lawsuit against Viva Labs right now,” he says, about their coconut oil, which, as well as being touted as extra-virgin, 100% raw, organic and cold-pressed, has been marketed as a healthy alternative to butter. But they’re not the only targets. Other companies currently the subject of lawsuits include Nutiva, the largest manufacturer of coconut oil in the US, as well as purveyors such as Nature’s Way, Costco and Better Body. They all sell “coconut oils where the labels have health and wellness claims”.

In general, when his team has sent letters to manufacturers, they have changed their labels pretty quickly, “although some continue to litigate over it”, he says. Out of the hundreds of coconut oil producers, “most of them don’t make health claims. The ones who make health claims happen to be some of the bestselling coconut oils. That’s not a coincidence.”

No one is denying that coconut oil contains more saturated fat than butter and lard. Where the coconut contingent has gained leverage is in the murky, emerging landscape of good fats and bad fats. “The thing in coconut that makes it different,” says Patel, “are medium chain triglycerides (MCTs), which are a type of fatty acids. They get absorbed differently, so the body can use them immediately.”

There is a popular theory that the MCTs in coconut oil promote fat-burning – the same pseudoscience behind the soundly rubbished Bulletproof Coffee fad, in which butter and coconut oil are added to coffee, promising clearheadedness and weight loss. The evidence cited is a small human study from 2003 in which people fed a diet rich in MCTs shed some body fat. One of these MCTs is lauric acid, which coconut fetishists are keen to point out is abundant in breast milk. Because what could be more naturally nourishing than breast milk (which evolved to fuel the extremely rapid growth that is unique to babies)?

Even the study’s author, Marie-Pierre St-Onge, of Columbia University, has distanced her work from the coconut claims. “I think the data that we’ve shown with medium chain fatty acids have been extrapolated very liberally,” she has said. She wasn’t even studying coconut oil, which is only partly made up of MCTs, whereas she fed people solely MCTs. “You can’t compare a study that uses just MCTs with coconut oil,” says Patel.

“All the [health] claims are marketing hype based on fairy stories,” says Laurence Eyres, of the New Zealand Institute of Chemistry, who reviewed the literature on the effects of coconut oil on humans last year. “Their advice is scientifically incorrect and unethical.” In his paper, he wrote: “The evidence of an association between coconut consumption and risk factors for heart disease is mostly of very poor quality.” Nevertheless, he suggests that when compared with other plant oils, coconut “raises total cholesterol … although not as much as butter does”.

Better than butter? Maybe … a young girl drinking fresh coconut milk. Photograph: Getty Images/EyeEm

So manufacturers aren’t fibbing about it being better than butter? According to Jim Mann, a professor in Human Nutrition and Medicine at the University of Otago, who authored the leading study on this, “Coconut oil is indeed as high in saturated fat as butter, but there are four major saturated fatty acids which contribute to total saturated fat. Coconut oil is relatively high in lauric acid. Butter is relatively low in this fatty acid and high in both myristic and palmitic acids. Lauric acid is associated with a better lipid profile than myristic and palmitic, so butter has an overall worse profile than coconut oil on this important predictor of coronary heart disease.” Crucially, though, he still does not encourage the use of coconut oil. “Although it may be preferable to butter, there is evidence that total saturated fat (regardless of which saturated fatty acid is involved) is associated with adverse health outcomes – heart disease being the main culprit, but there’s also some evidence in relation to diabetes.”

And what of coconut oil’s myriad other medicinal claims? Insufficient evidence. “We can’t say it’s going to be preventing or curing Alzheimer’s,” says Patel. It does have its uses – frying at very high temperatures being one of them. It remains stable when very hot, so, unlike olive oil, it won’t start smoking and breaking down into toxic substances if you’re doing a stir-fry (sauteeing with olive oil is fine though – anything below 242C, or 210C for extra virgin). Having said that, if you’re not vegetarian, you can also fry with lard at high temperatures, which is a mere 32% saturated fat. Vegetable oils, such as sunflower, should be avoided, she cautions: “They are omega-6 polyunsaturated oils, which we should be consuming less of, as they promote inflammation.”

A little coconut oil for occasional high-temperature frying and added flavour is the way to go. “In a curry or stir-fry it tastes amazing,” says Patel. All fats contain about the same calorific content, she adds, “but remember to keep saturated fat to 10% of your overall energy intake, which accounts for 20-30g a day, depending on gender. In 2tbsp of coconut oil, you have 24g of saturated fat.”

Dairy-free is increasingly viewed as a healthy option, too, but Patel doesn’t recommend substituting coconut milk for cow’s milk. She points out that a Pret a Manger mango and coconut yoghurt pot contains slightly more saturated fat than a Mars bar (although with less sugar). “Very similarly to coconut oil,” says Patel, coconut milk “has a higher amount of saturated fat than milk. It is low in protein and low-calcium and it contains a high amount of calories. Portion control, I would say.” If you can’t have dairy but you are not allergic to nuts, Patel recommends alternating almond or rice milks instead, “from a calorie point of view”.

Meanwhile, the coconut craze ploughs on, regardless of what boring old scientists have to say, and there’s more to the market than food and drink. The beauty industry is doing a roaring trade in coconut products, and the husk around the outside is used for making rope, mattresses and car seats, while a cruder form of oil is processed as a base for eco detergents. Coconut sap is sold as a sweetener and you can make buildings out of coconut wood.

Coconut farming, however, is a different story. Contrary to the marketing images of coconuts being plucked from Brazilian paradise, “95% of coconuts are harvested by small-scale farmers, rather than in industrial plantations, and 90% of those small-scale farmers are in Asia Pacific,” says Angie Crone, who manages Fair Trade USA’s coconut programme. It has been working with growers in the Philippines since 2013, and more recently in Thailand and Sri Lanka. Unsurprisingly, the financial spoils from the coconut craze do not tend to reach growers. “Around 40-60% of the 3.5 million coconut farmers in the Philippines are living in poverty, on less than a dollar a day,” says Crone. Many farmers only have one processor they can sell to, so it’s take or leave the fluctuating prices offered. Meanwhile, there’s talk of illegal, lucrative exports of precious coconut saplings to China.

So should mass coconut consumption join quinoa and avocados as a source of guilt for western consumers, who find themselves yet again fuelling rainforest-slashing cartels? Peter Thoenes, a trade analyst for oil crops and oil crop products at the FAO, thinks not. “After many years of trying to promote value in coconut, these markets are now starting to grow, and this is a very welcome trend,” he says.

Meanwhile, the nearly 7,000 farmers working with Fair Trade USA and cooperatives formed with government support, are starting to invest in seedlings to replace unproductive senile trees. They are also learning about diversification, which ensures there are cash crops, such as cacao, coffee and chilli peppers, to sell locally while waiting for young trees to mature. Freedom from monocropping (growing the same thing year after year) comes with an added environmental bonus. Because Fair Trade USA is spearheading work with coconut farmers, most Fair Trade-accredited brands come from the US, but among those available in the UK are coconut oils from Tiana, Nutiva and Spectrum; coconut water from Naked Juices; Hope Foods’ organic spreads; and skincare from Eco Lips and Cocokind.

“Typically, small-scale farmers are using fewer pesticides and there’s more biodiversity because they’re able to plant other things,” says Crone. Farmers are starting to build up calamity funds, too, in preparation for natural disasters, and building demo farms to learn about best practices. “All of this will then bolster the supply-chain challenges.” Wait, did she just say “supply chain challenges”? “Demand is growing at 10% but production in Asia Pacific, where the majority of coconuts are grown, is only growing at about 2%.” Let the stockpiling begin.

• This article was amended on 13 July 2017. An earlier version said that a 330ml carton of Vita Coco coconut water “will set you back 254 calories”. The correct figure is 59 calories. The earlier figure was based on erroneous nutritional information on Vita Coco’s UK website at the time of writing. A further amendment was made on 14 July 2017 to clarify that the lawyer Jack Fitzgerald has a current lawsuit against Viva Labs, not Vita Coco. Mr Fitzgerald was previously involved in a lawsuit against Vita Coco. The article was also amended on 25 July 2017 to give the correct the figure for farmers working with Fair Trade USA as nearly 7,000, not 9,000.

