I remember reading about this many, many years ago, so I tried to see if it was archived somewhere on this newfangled internet thingy.
After the the close of WWII and Indian independence, many Hindus opted to settle in Great Britain. They ate their traditional foods, imported from abroad. This population of Hindus began to show signs of malnutrition.
Analysis of their imported foodstuffs did not provide an answer. It was only when the same foodstuffs were analyzed back in their homeland was the riddle solved. There was so much bug contamination, it was supplementing their vegetarian diet. This contamination was absent in the British versions, due to strict import controls.