Often touted as a great source of iodine, feijoas in fact have… none?

Joseph Stalin was feeling poorly. At age 70, he was suffering from lapses of memory and attacks of nausea. While orange juice “made his tongue smart” and caviar “tasted like putty”, his doctors had told him to eat as much fruit as possible—and there was one fruit in particular that made him feel better. 

“Stalin…took a peeled feijoa from the little round table and bit into it. As he sucked it his nausea went away, leaving a pleasant taste in his mouth with a faint tang of iodine…You didn’t have to tell a Georgian to eat fruit! Half closing his eyes, he took another bite.” 

As New Zealand’s biggest feijoa nerd, I was enchanted and intrigued when I discovered this (fictional) scene in the 1968 novel The First Circle, by the famous Russian writer and Soviet dissident Aleksandr Solzhenitsyn. Presumably, Solzhenitsyn has the dictator eat a feijoa because Stalin was originally Georgian, and feijoas are almost as beloved in that Eastern European nation as they are here in New Zealand. 

But the other thing that captured my attention was that “tang of iodine”. Really? 

The unique flavour of feijoas has been compared—unconvincingly, I think—to that of pineapples, strawberries, guavas and bananas. But I’d never heard of anyone else likening it to iodine.

 I have, however, frequently read claims online that feijoas are a superlative source of this essential nutrient, as well as high in lots of other healthy-sounding things. They’re often labelled a “superfruit” and people I met in Colombia while researching my feijoa book even called it “the fruit of eternal youth”. 

Our bodies can’t make iodine, but it’s crucial for hormone production and normal brain development, especially in babies and young children. As a child, I craved feijoas – and today, my own children will eat bucketloads of these green, fragrant treasures. Was there something to this, I wondered? Do our bodies know something our minds aren’t consciously aware of? Are super feijoas helping us to meet this need? 

Unfortunately, when I asked botanist, plant-collector and University of Auckland professor of nutrition Richard Mithen to review the scientific literature on feijoas’ nutritional content for me, he had bad news. “There does not seem to be anything particularly remarkable about feijoa on the basis of the analyses of known nutrients and phytochemicals,” he wrote. And he added: “its iodine content is insignificant.” Weird. 

Mithen encouraged me to contact Carolyn Lister at Plant and Food Research, who manages the New Zealand Food Composition Database.  According to old New Zealand data, feijoas had just 0.13 micrograms of iodine per 100 grams. (There are one million micrograms in a gram.) For context, the recommended daily iodine intake for adults is 150 micrograms, she said. To get that from feijoas you’d have to eat around 1,200 decent-sized ones every day of your life – and look, I’m as obsessed with feijoas as they come and even for me that feels… unachievable. 

That was old data, though, and analytical methods have improved since then. Feijoa varieties have changed, too. As it happened, Mithen had just completed a fresh study of New Zealand feijoas’ nutritional content. In 2022, she and her team bought a couple of kilos from a few different supermarkets, scooped out the flesh, and subjected it to an array of different lab tests.

This time, the iodine content came back “below the level of detection” – basically zilch. Nada. No iodine to speak of in feijoas. (The best ways to get it are by eating seaweed, fish, shellfish – or simply to use iodised table salt.)

So where did this story come from? 

The claim that feijoas are high in iodine wasn’t just cited in “why feijoas are good for you” listicles, but also a few scientific papers. When I traced the references back, they led to one Italian study from 2001 and a Russian paper from 1934. 

With the Italian paper, only the abstract was available, so neither the scientists nor I could scrutinise the methods. The Italian researchers claimed they’d found 3mg of iodine per 100 grams of fruit – three milligrams, or 3000 micrograms – making eating just two medium-sized feijoa comparable to chowing down on an 80g serve of karengo seaweed, the heaviest-hitter iodine-wise on New Zealand’s food composition database.  Mithen suspected the researchers might have gotten the units wrong by several orders of magnitude. “We find that sometimes in the scientific literature…things get lost in translation.”

Neither could I access the 90-year-old Russian study, but a recent paper by another Russian scientist, Oksana Belous, suggests an answer to the mystery. Oksana set out to test the chemical composition of feijoas grown around the Black Sea coast of Russia, near Georgia. She said the amount of iodine was “small”, finding “0.34 mkg%” of iodine in her feijoas – a unit Mithen didn’t recognise, but Belous told me in an email meant micrograms per 100g or 100ml.  

In her own paper, Belous wrote that the author of the 1934 study, L.V. Sergeyev, found three milligrams of iodine in a decilitre, or 100 mls of feijoa – a similarly superlative proportion as in the Italian study. But Sergeyev also noted that the feijoas he studied back in 1934 grew near the sea, and that the soil around them was covered with seaweed, presumably as a fertiliser. “Probably these factors led to an increase in the content of iodine in fruits,” wrote Belous. 

Mithen thought that was possible, too. Imagine a ripe feijoa falling onto a carpet of iodine-rich, decomposing algae. It wouldn’t take much seaweed residue left on the skin to skew the results. Alternatively, it’s possible that the feijoa trees Sergeyev studied absorbed some iodine from the seaweed and soil and expressed it in their fruit, but new studies would be needed to prove it, Mithen said. 

“Different plants take up different minerals to different degrees, which is why some fruits and vegetables are better sources of certain nutrients than others. It’s not as simple as if the mineral’s here in the soil, it will be taken up.” 

Solzhenitsyn died in 2008, so we can only guess at his motives for including iodine-tasting feijoas in his political novel. My hunch is that he read that old Russian paper while researching a suitably “Georgian” fruit for Stalin to snack on. (Although, of course, feijoas originally hail from South America.) 

There are myriad reasons to enjoy feijoas – their delicious flavour, nostalgic fragrance, intense seasonality, and the way their ridiculous abundance encourages you to share them with neighbours, colleagues, and complete strangers (they’re not called New Zealand’s most socialist fruit for nothing!) They’re also a decent, if not spectacular, source of fibre, folate and Vitamin C, Mithen’s study found. 

Just don’t rely on them for your daily dose of iodine. 

 Kate Evans is a journalist and the author of a new book about feijoas, FEIJOA: A Story of Obsession and Belonging (Moa Press). 

CCTV cameras, self-checkout machines, data-gathering loyalty cards, facial recognition: supermarkets gather an obscene amount of information about customers. Can they be trusted with it? 

Every day for the last few weeks, J Frank*, an Auckland software developer, has checked the letterbox. He’s been waiting for mail from Woolworths containing their new Everyday Rewards cards, the supermarket chain’s loyalty programme.

Concerned about how much information the supermarket has about him, Frank has devised a way to get the bonuses of loyalty discounts without the big data tradeoff: have four or five different cards under fake names, which he takes turns switching out with his other flatmates, so no one person has the same buyer activity associated with them. Living near two Woolworths supermarkets, he goes to the supermarket chain a lot – but while they might know his address, he’s determined that he won’t have his individual data monetised by the chain. 

“My main concern is where this data is going, and who else is using it,” Frank says. It might seem that his shopping information is innocuous – a bunch of bananas here, a bottle of milk there – but he doesn’t like the idea that this information might linger for years on unseen databases, potentially being shared without oversight, beyond his control. Even if the information is secure, it’s the principle of the thing: he wonders what the supermarket chain gains from having individual information about their customers. 

But his qualms aren’t quite enough to stop him from wanting the discounts the Everyday Rewards card offers, so the fake names, and the somewhat reluctantly recruited flatmates, are his compromise. 

Frank’s card shuffling might seem paranoid: most people probably have at least a few loyalty cards loitering in their wallets, filled with bookshop stamps or outdoor store discounts or fuel savings codes. By sheer virtue of frequency of visit and variety of products available, the supermarket card will probably have more information about you than a coffee shop or fuel station – but is it really anything to worry about? 

The discounts on a loyalty card are just a sweetener, says Gehan Gunasekara, co-founder of independent group the Privacy Foundation and a law professor who has worked with students researching loyalty schemes. What makes that scuffed bit of plastic really valuable, fake name or no, is your data. “They know everything you buy, every item, which store it’s bought from, how often you go to the supermarket, which brands you like,” Gunasekara says. “That’s really fine-grained data – it can tell the story of your diet, your preferences, your whole life.” 

Getting people to care about privacy can be an uphill battle, which Gunasekara is very familiar with: after several decades of business being increasingly digital, surrendering your personal information, voluntarily or thoughtlessly, has become so prevalent that the event itself is quotidian. When you click “accept all cookies” or tick a terms and conditions box without reading said terms and conditions, when you tag your location on an Instagram post or look up your local public transport timetable, you are placing another coin into the dragon’s hoard of digital information. 

No-one is immune: Vladimir Putin’s location has been deduced from the ads served to the phones of his immediate retainers; secret American military bases have shown up as hot spots of digital exercise data on Strava. 

At the supermarket, though, the exchange of personal information for food is more tangible. At the entrance, you might be greeted by a sign with small text alerting you to new cameras or a facial recognition trial. Look up from the bewilderingly expensive limes, and you’ll spot dozens of CCTV cameras on the ceiling, like little black blisters. Increasingly, cameras hover above the self checkout too. And if you want those member prices – which can be significantly cheaper than the normal ones – don’t forget you’re giving away some information when you swipe your phone or card against the scanner. 

On one hand, maybe this is fine. After all, most data is not used to identify and target individuals; revealing to some faceless goon in an office that you, in particular, have a weakness for Monday kombucha. Instead, it’s embedded in automatic processes, used in aggregate. Some serve a direct benefit to consumers: if the data shows that more people are buying a brand of chocolate biscuits at one supermarket, then that store can order more to keep everyone in stock. Your buying patterns could also be used to recommend particular products to you if you’re logged into the website or the app. And while discounts might simply be a sweetener to encourage people to sign up to membership cards, they do offer genuine savings when many people are struggling to afford food. 

“We use non-identifiable and aggregated data gathered through the Clubcard programme to better understand our customers so we can place them at the centre of our decision making,” a Foodstuffs spokesperson says (Clubcard is New World’s customer card; Paknsave doesn’t have one). Data collected through the Clubcard programme isn’t sold to third parties, although it is shared with partner organisations like Flybuys. 

Woolworths say that their card data is well protected, too, despite Everyday Rewards being dogged by privacy concerns, including concerns about the way the card can link your car’s licence plate to your shopping. (Update: Woolworths has clarified that license plate data is not linked to Everyday Rewards cards.) According to the Everyday Rewards privacy policy, customer data can be used “to understand shopping habits and likely preferences”, enabling direct marketing to the customer. It can also be shared with Google and Facebook for advertising and data matching, as well as analytics companies and market research providers (details aren’t provided on what providers these are, and what their privacy polices are). 

Of course, you’re only going to know this if you read the terms and conditions in full, instead of just ticking the box to say you’ve read them. 

In person, customers have to opt-in to using the card. This can feel galling given non-member prices can be as much as 1.6x more than member prices for items like canned tomatoes. For people who shop online, there’s no choice at all: Woolworths’ online ordering systems are now completely integrated with Everyday Rewards, so that you can’t order online without being signed up. New World online shopping is also integrated with Clubcard. 

“We have to ask if consumers are getting value for the data they’re generating,” says Gunasekara of the Privacy Foundation. 

Gunasekara says that companies should be trying to minimise the data they gather from customers, and that the data that is collected should be reasonable. You can’t get online shopping delivered without giving the company your address, for instance – but do they really need to know your gender identity? 

Once data has been gathered, it needs to be securely stored, which can be a liability for companies, because if the data is valuable to them, it’s valuable to others. Recent data breaches in New Zealand and overseas have targeted DNA data, vaccination information and personal loan accounts, and those are just the ones that are high-profile enough to be reported on. (Both supermarket chains say data security is important to them. “We have cybersecurity measures, encryption, access controls as well as administrative measures such as robust policies and procedures for security, data and privacy,” a Woolworths spokesperson says.)

While data generated during your weekly grocery shop might seem less important than information about your health or finances – surely your personal craving for balsamic vinegar chips doesn’t mean much? – it’s powerful in aggregate. Dubbed “surveillance capitalism”, the ability to collect, store and use data at big volumes has been enabled by digital technology, and Facebook and Google are some of the world’s most profitable businesses because of how much information they have about what people are into. Supermarkets are only doing what all these other businesses did first.

Loyalty cards are only one piece of the bigger puzzle of surveillance. Neither supermarket chain confirmed how many CCTV cameras they have on average, but in Australia, that number is 62. The future of supermarkets likely has more cameras, not less: Foodstuffs is currently trialling a technology that allows facial recognition in stores for trespassed customers, and Woolworths is adding extra cameras to self checkouts to ensure items are scanned correctly.

Supermarkets aren’t the only companies that use CCTV: there are at least 10,000 publicly owned CCTV cameras in New Zealand and as many as 400,000 privately owned ones. But supermarkets are different because they provide daily, essential nourishment – something much harder to avoid than a targeted ad for a fancy face cream chasing you across the internet. “The kind of leverage these companies have to collect information is very one-sided,” Gunasekara says. You need food, and in many places one supermarket or the other is the only place to get it, so privacy concerns come second to necessary sustenance. 

Given how widespread surveillance is, Frank’s persistence in using fake names for his Everyday Rewards card seems almost quaint, one small effort at resisting a system that takes a torrent of customer information as a given. Even as someone exceptionally aware of privacy violations, he can’t resist the discounts from an Everyday Rewards card. Think of all the people who are truly struggling to afford groceries. Is a choice to give up some privacy in exchange for slightly cheaper food a choice at all? 

In the digital world, the data harvesting and surveillance we have been putting up with for decades is silent and seamless. At the supermarket, it’s much more in-your-face. There it is, in the black eyes of the CCTV cameras. There it is, in the weekly email of recommended products from New World, your face briefly blinking on a screen before being deleted if it’s not a match. There it is, when you’re swiping your rewards card at the self-checkout machine, handing over your personal data before you can take your food home. 

Could the increasingly surveilled supermarket be the catalyst that finally makes us care about our privacy?

*Name has been changed to protect – you guessed it – privacy. 

This article has been updated to clarify that Woolworths does not link license plate data to Everyday Rewards cards.