Elior UK has worked with Barts Health NHS Trust to achieve the Gold Catering Mark at the trust's Mile End, the Royal London, St. Bartholomew's and Whipps Cross sites.
The Soil Association's Food for Life Catering Mark provides an independent endorsement for caterers that are taking steps to improve the food they serve.
The gold award recognises the highest standards of provenance and traceability and shows that meals are freshly prepared using environmentally sustainable and seasonal ingredients.
Robin Givens, sales director at Elior UK, said: "Elior is committed to providing healthy, tasty meals that have been sourced responsibly, ethically and, where possible, locally. We've undertaken a number of measures to promote these aims at Barts, including reducing the level of salt in our recipes, removing table salt and making fruit cheaper than main desserts.
"We also put out table talkers and posters to let customers know what local produce we use and we leave out customer comment cards to help us improve. Being a responsible company is something Elior take very seriously and we're absolutely thrilled to have achieved the Food for Life Gold Catering Mark with Barts Health NHS Trust."
Kenny Hanlon, associate director of estates and facilities for the Royal London Hospital, added: "The health and wellbeing of our patients, visitors and employees is always our first priority. It's important we set a good example of healthy eating and environmental responsibility too. Achieving the Bronze Catering Mark was a big step for us and we're thrilled to have now achieved Gold, with the help of our partner Elior UK."
Elior operates catering contracts across business & industry, health & care homes, defence, education, stadia and heritage sectors.
The Catering Mark now serves more than 1.6 million meals to schools, nurseries, hospitals, universities, workplaces and other venues.