Is tracking your food purchases good for your health?

With a packet of biscuits in one hand and her smartphone in the other in the biscuits sucrées aisle of her local Hyper U supermarket west of Paris, Nathalie sees red. Literally.

"Look at that!" she says showing me her phone. 0/100 is marked in red lettering.

"This is one of Malo's [her 12-year-old son's] favourites but it's not only full of sugar and saturated fats, there are four additives as well including one health risk," she says.

Nathalie clicks on the additive in question: E450. "A mineral which, taken in excess, can lead to bone marrow and kidney problems," she reads.

"Honestly, that they can put this sort of thing in food aimed at children drives me nuts!" she says.

We scan an Italian alternative whose packaging gives you the impression those biscuits have been hand-made by peasant women wearing black shawls.

The score is not much better: "Malo hates shopping with me now," says Nathalie. "You spend ages scanning and he can never have what he wants."

The app, having activated the red alert, suggests a healthier alternative. It's organic, containing wholewheat, fruit and fibre.

"You end up buying a lot more organic stuff so it's more expensive," she says.

Nathalie is one of a growing number of people using Yuka, an app developed in France, to shop more healthily. Not just for food but cosmetics and toiletries too.

Download it and you can use your phone to scan the barcodes of any one of the six million products on the Yuka database (about 1,200 new ones a day) and it'll tell you immediately – green for good, red for bad, yellow for could be better. If you want to know more, you can delve further. Pages and pages if you want.

Started in 2015, Yuka now has 85 million users in 12 countries: numerous European ones plus the US, Canada and Australia.

The third-biggest user is the UK with around five million, second is France with six million, but the biggest by a very long way is the US with 28 million.

Yuka has some high-profile fans in the US. For example, Donald Trump's Secretary of Health and Human Services, Robert F Kennedy Jr, says it's his favourite app.

Yuka was founded in France where it still has its headquarters, but three years ago co-founder and CEO Julie Chapon moved to the States because the app was doing so well there.

She says the app is more successful in the US because the need is greater. "I'm thrilled to be in a country where there is still so much progress to be made," she says, diplomatically.

In France, Yuka is one facet of a wider food-tracking phenomenon.

In 2012, a French programmer called Stéphane Gigandet launched a free, online and crowdsourced food product database called Open Food Facts during the Food Revolution Day organised by English chef Jamie Oliver.

A community-driven non-profit rather than a private company, it now makes available information on over four million food products around the world.

Also, two months after Yuka's launch, the French government started its Nutri-Score labeling. It's creator was the food researcher Serge Hercberg from Paris' Sorbonne University.

"I was inspired in particular by the UK's Traffic Light system which gives green, amber or red lights for sugar, fat, salt, calories... but I wanted something simpler. The Nutri-Score gives a global score. You can tell at a glance whether a product is going to be good or bad for your health," he says.

Introduced after a bit of an arm-wrestle with the food industry, Nutri-Score is a voluntary front-of-pack label for pre-packaged food. Many big food manufacturers such as Danone and Nestlé have adopted it widely, but some brands – especially where they'd score poorly - simply opt out.

"Applications like Yuka and Open Food Facts fill that gap," says Hercberg.

They also go further than Nutri-Score, giving info, for example, about additives (chemicals added to preserve or colour food for example which are coded as e-numbers) whose presence is a strong indicator that food is ultra-processed.

The Yuka drawback? Christian Reynolds, Reader in Food Policy at City St George's University, London says tech is one of a basket of solutions but research shows the limits.

"I supported a [British government] review on how people interact with labels and information, and the take home from that was that few people have the time, capacity or inclination to engage with shopping and food choices beyond routine."

Hercberg see the limitations to food tracking systems as well: "Unfortunately, they essentially only touch the more privileged section of the population, who are not those most at risk of health problems linked to the way they eat."

He considers the Nutri-Score labeling system he created and apps like Yuka and Open Food Facts to be allies.

They are all about sharing information, which they already do among themselves. Yuka has its own food scientists but replies essentially on academic publications and publicly-available data. It incorporates Nutri-Score data in its product assessments.

Unlike Nutri-Score and Open Food Facts, Yuka is a private company and profitable says CEO Julie Chapon.

However, she stresses that revenue does not come from advertising, sponsored rankings or product placement.

"We have never accepted money from brands to influence our ratings or recommendations. Our revenue comes from users, through the premium version of the app," she says.

The percentage of Yuka users who pay for premium is tiny but that suffices because the total number of users is so enormous, she adds.

Chapon says there is evidence that Yuka has an impact on shopping habits. In 2024 a company survey of 20,000 users indicated that 94% of them put products back on the shelf when the app showed a red rating.

As for evidence of how this app is changing the food produced and sold, the most striking example is probably the French super and hyper-market chain Intermarché, France's third largest with over 2,100 stores.

It says it has changed a lot of its own brand product formulations because of their Yuka scores.

"Since 2017, we have reformulated over 3,000 recipes and taken out 160 additives… Last year alone, we re-worked the formulations of around 300 products," the company said in a statement.

In April this year it even started putting products' Yuka scores on its online shopping site.