A rare artery disease that threatens eyesight was less common in French women who ate their plants the healthy way, and the sweets-and-white-bread version did nothing

Giant cell arteritis is the kind of illness most people only hear about when it happens to a parent. It almost always starts after 50: a new, stubborn headache, a tender scalp, an aching jaw when chewing, sometimes blurred or double vision. The arteries at the temples are inflamed, and without quick treatment with steroids it can lead to blindness or stroke. Its cousin, polymyalgia rheumatica, brings pain and morning stiffness in the shoulders, neck and hips, and the two sometimes turn up in the same person. Age and being a woman raise the risk of both, but what else sets them off is still largely a mystery. A team at Université Paris-Saclay, Inserm and the Paris public hospitals asked whether diet plays a part. Their study was published in the European Journal of Nutrition on 7 October 2026.

They used E3N, a French study that has followed 98,995 women since 1990, all insured through a national health plan that mainly covers teachers. In 1993 the women filled in a detailed food questionnaire. From it the researchers scored three versions of a plant-based diet, using a method developed at Harvard. The overall score rewards eating plants and marks down animal foods. The 'healthful' score rewards only the better plant foods, such as whole grains, fruit, vegetables, nuts, legumes, vegetable oils, tea and coffee, and marks down refined grains, potatoes, juices, sweets and sugary drinks along with animal foods. The 'unhealthful' score turns that around. Cases were picked up from repeated questionnaires and confirmed against the medicines the women were reimbursed for.

Of 60,187 women who could be included, 602 developed one of the two conditions over a median of 17.6 years after filling in the food questionnaire: 142 giant cell arteritis, 373 polymyalgia rheumatica and 87 where the doctors couldn't say which. For the two together, and for polymyalgia on its own, none of the three diet scores made any difference. Giant cell arteritis was the exception. Women in the top third of the healthful score had a 38% lower risk than those in the bottom third, after allowing for age, energy intake and other factors, and the risk fell step by step across the thirds. The overall plant score gave an odd pattern: the middle third, not the top, had the lowest risk. The unhealthful score showed nothing.

This needs reading carefully. The result rests on 142 cases split three ways, so the confidence interval runs from a 61% lower risk to only 3% lower, close to no effect at all. Diet was measured once, in 1993, years before most of the illnesses began, and people's eating changes. It's an observational study, so women who ate the healthy plant foods may have differed in other ways the adjustment didn't capture, and the findings come from French women, many of them teachers, not from men or other countries. We could read only the paper's summary, so the exact list of factors the authors allowed for comes from it alone. The authors call it the first evidence from a long-running study that diet quality is tied to giant cell arteritis, and a reason to look harder at food and inflammatory rheumatic disease, not a prevention plan. Still, it's one more case where the kind of plant food mattered more than simply eating less meat.