Peru put black octagons on sugary, salty packaged food in 2019. Two years later, 1,032 Lima children were getting a third less sugar from those products, but more from instant soup and chocolate

Since June 2019, packaged foods and drinks in Peru that go over set limits for sugar, sodium or saturated fat carry a black octagon on the front saying 'ALTO EN' (high in), plus the line 'avoid excessive consumption'. Products with trans fats get one that says 'avoid consuming it'. The law behind them, Law 30021, was written to protect children. A study published on 25 October in the journal Nutrients is one of the first to follow the same Peruvian children over time to see what happened to what they ate.

Researchers from Universidad Peruana Cayetano Heredia in Lima and the University of North Carolina at Chapel Hill visited homes in four districts of Lima, two in the north and two in the south, chosen to cover middle-high and middle-low income neighbourhoods. Between April and June 2019, around the time the first labels came in, trained dietitians interviewed 1,283 mothers of children aged 3 to 5 about what the child had eaten and drunk over the previous 30 days, using a questionnaire with photos of portion sizes. In May to September 2021 the same team asked the same questions by phone, because of COVID-19 rules; 1,032 mothers (80.4%) took part again, by then with children aged about 5 to 8. Sugar, sodium, saturated fat and calories were worked out from the labels of products photographed in Lima supermarkets in each period, so reformulated recipes counted.

Fewer children were eating some of the products by 2021. Breakfast cereals and bars dropped from 78.4% to 62.9% of children, packaged desserts such as gelatin from 49.7% to 31.8%, and salty crackers, sweets and gummies, flavoured dairy drinks and formulas also fell a little. Others went up: chocolate from 58.7% to 65.1%, instant soups from 15.2% to 19.2%, processed meats such as hot dogs and nuggets from 76.9% to 80.7%, and plain milk from 55.5% to 61.1%. Children also drank more water, a median of 900 mL a day against 718 mL.

Among children who ate the products at both visits, the median calories from all the packaged foods and drinks studied fell from 487 to 373 kcal a day. Median sugar from them fell from 45.1 to 31.4 g a day, about 14 g or three and a half teaspoons less, sodium from 469 to 399 mg, and saturated fat from 8.4 to 7.0 g; all four changes were statistically firm. Flavoured dairy drinks and dairy desserts gave the biggest drops in calories. Sweet bakery products, instant soups, processed meats and chocolate gave more calories than before, and instant soups and processed meats added sodium.

The authors are careful about what this shows. With no comparison group, the study can't separate the labels from everything else that changed between 2019 and 2021: the children were two years older, the second survey ran in a different season, schools were shut and many Peruvian families had less money for food during the pandemic. Part of the drop could also come from companies reformulating products to avoid an octagon, including using more low-calorie sweeteners. The first survey started just before the labels became compulsory, so some labelled products may already have been on shelves. Intake was reported by mothers, the questionnaire agreed only low to moderately with detailed food diaries, and mothers with only primary schooling were much less likely to stay in the study (44% against 84% of those with higher education), which could make the changes look better than they were. The study covered selected packaged products, not the whole diet or home cooking.

What the authors take from it is that the overall direction was down, but not evenly, and that the products whose use held steady or grew, such as chocolate, instant soups and processed meats, are the ones to watch. A second, stricter set of limits came into force in September 2021, after the follow-up interviews had started, so its effect is not captured here.