Natural salicylates: foods, functions and disease prevention

Salicylic acid and related compounds are produced by plants as part of their defence systems against pathogen attack and environmental stress. First identified in myrtle and willow, the medical use of salicylate-rich preparations as anti-inflammatory and antipyretic treatments may date back to the third millennium BC. It is now known that salicylates are widely distributed throughout the plant kingdom, and they are therefore present in plant products of dietary relevance. In the UK, major food sources are tomato-based sauces, fruit and fruit juice, tea, wine, and herbs and spices. In mammalian cells, salicylic acid demonstrates several bioactivities that are potentially disease-preventative, including the inhibition of production of potentially neoplastic prostaglandins, which arise from the COX-2 mediated catalysis of arachidonic acid. Moreover, it appears to be readily absorbed from the food matrix. This has led some to suggestions that the recognised effects of consuming fruit and vegetables on lowering the risk of several diseases may be due, in part, to salicylates in plant-based foods. However, published estimates of daily salicylic acid intake vary markedly, ranging from 0.4 to 200 mg day(-1), so it is unclear whether the Western diet can provide sufficient salicylates to exert a disease-preventative activity. Some ethnic cuisines that are associated with lowered disease risk may contain considerably more salicylic acid than is obtainable from a Western diet. However known protective effects of acetylsalicylic acid (Aspirin™) may have lead to an over-emphasis on the importance of dietary salicylates compared with other bioactive plant phenolics in the diet.