Vegetarian and vegan dog foods just need a few tweaks to make them nutritionally complete diets.

Analyses reveal that meat-free dry kibbles meet dogs’ protein and fat requirements, lacking only sufficient iodine and B vitamins. With supplements or – better yet – improved commercial preparation, plant-based dog food could keep the animals healthy while reducing the environmental impact of the pet food industry, says at the University of Nottingham, UK.

“As long as they’re getting all of the essential nutrients from those ingredients, then the dogs are going to thrive,” she says.

Many vegans and vegetarians who own dogs struggle with the ethics of feeding meat to their omnivore pets, says , also at the University of Nottingham. Responding to that concern, pet food manufacturers have started offering plant-based foods to consumers.

Government organisations like the European Pet Food Industry Federation and the Association of American Feed Control Officials require standardised testing of commercial pet foods and additives to ensure they meet nutritional standards. Even so, most pet foods worldwide do not go through robust nutritional testing by independent research teams, says Gardner.

Brociek, Gardner and their colleagues analysed 25 commercial dry foods for healthy adult dogs – 19 containing meat and six based exclusively on plants. Among the latter, two were labelled as vegetarian and four were vegan.

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None of the foods met all the official nutritional guidelines for dogs, despite being packaged as nutritionally complete, the researchers say. Even so, all the foods had acceptable concentrations of protein, fatty acids and essential amino acids.

Most – including five of the six plant-based foods – didn’t have enough iodine, but seaweed could easily make up for that deficiency.

Vitamins in general were sufficient across the board, except for vitamin B, which came up particularly short in plant-based foods. Dogs low in vitamin B can have issues with their skin, nerves and digestive systems, so manufacturers should supplement those foods, the researchers say.

The findings point to oversights in all kinds of dog food manufacturing, not just those based on plants, says at Murdoch University in Australia. “Consumers are expecting that if products are labelled as being nutritionally sound, and that will be true, but clearly it’s not true,” he says.

“I believe a vegetarian diet can be adequate if carefully supplemented with nutrients lacking in plants – as is the case for humans who choose a vegetarian diet,” says at the University of Pisa in Italy. Owners should avoid making their own plant-based foods for their pets, she adds.

Pet dogs have evolved to be able to eat a wide variety of foods, so feeding them well-balanced, plant-based meals can satisfy their nutritional needs while avoiding the , like greenhouse gas emissions, says Gardner.

“They’re true omnivores,” he says. “As most Labrador owners – myself included – will tell you, they’ll eat anything.”

The amino acid taurine was once thought to decline with age, and animal research suggested that taurine supplements could delay ageing. But a new study shows that the decline doesn’t happen consistently. In fact, taurine levels tend to increase in people over time, suggesting that low levels of the nutrient aren’t a driver of ageing.

Previous research has shown that taurine concentrations decline in men as they age and that people with higher taurine levels at 60 years old tend to have better health outcomes. This, along with evidence that taurine supplements extend lifespan in mice and monkeys, suggested that low taurine contributes to ageing.

The trouble is that taurine fluctuates in response to other factors too, such as illness, stress and diet – therefore, declines in this key amino acid may not be due to ageing. at the National Institute on Aging in Maryland and her colleagues analysed taurine levels in 742 people between 26 and 100 years old. The participants, about half of whom were women, didn’t have underlying health conditions and provided three to five blood samples between January 2006 and October 2018.

On average, taurine levels were almost 27 per cent higher in women at 100 years old than at 26 years old and rose about 6 per cent in men between the ages of 30 and 97. Similar results were seen in 32 monkeys that underwent three to seven blood draws between 3 and 32 years of age. Between 5 and 30 years of age, taurine levels rose 72 per cent in female monkeys and 27 per cent in male monkeys, on average.

Together, these findings indicate that taurine levels are not a reliable indication of ageing. What’s more, taurine levels also varied widely between people and even within individuals over time, suggesting that other environmental factors influence them, says Fernandez.

However, some people may still benefit from taurine supplementation, says Fernandez, pointing to studies that show it helps regulate blood sugar in people with type 2 diabetes or obesity. But whether it can delay ageing in otherwise healthy people is an open question.

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at Rutgers University in New Jersey says he and his colleagues are currently conducting a clinical trial of taurine supplementation in middle-aged adults. “We hope to finish the trial by the end of 2025,” he says. “Hopefully it will generate sufficiently rigorous data to show whether or not taurine supplementation delays the pace of ageing in humans or increases health and fitness.”