The Olive Leaf Extract products accounted for about 15 per cent of total group revenue and were growing all the time, with 27 per cent year-on-year growth, said Mr Hewlett.
The product is grown, harvested, extracted and bottled at the world's largest specialised olive leaf grove, with more than 1 million trees.
The research programme was exploring the effects of the extract's active phenolic components on supporting healthy cardiovascular function. The positive effect was associated with the absorption of active phenolic components from the extract. High levels of the pro-inflammatory marker measured in the study, and poor blood vessel function, are some of the key contributors to the development of cardiovascular disease.
"CVD [cardiovascular disease] continues to be the number one cause of death globally," said professor JPE Spencer, Hugh Sinclair Unit of Human Nutrition, University of Reading and corresponding author of the study. "It has been established that most CVDs are preventable via altering diets and lifestyle."
The study was important, but longer-term epidemiological studies were needed to establish definitive conclusions, he added.
Mr Hewlett said a longer and larger study of Olive Leaf Extract targeting cardiovascular health has been conducted, with publication expected this year.