Nitric oxide scavenging by food: implications for in vivo effects of diet

Recent advice to the general public is to increase intake of fresh fruit and vegetables, a message based on the assumed benefits of the antioxidant content of plant substances. Although there have been numerous studies on the reactive oxide species scavenging of fresh food products, few studies have focused on whether or not compounds in the diet can modulate the levels of nitric oxide (NO). Nitric oxide is a key signalling molecule that controls vasodilation and blood pressure, along with a range of other physiological events. Here, it is shown that commonly used food substances, such as cabbage, broccoli, kidney bean and oranges, all have the capacity to scavenge NO from solution, and therefore can potentially alter the level of NO in humans, with ramifications for the physiological systems that NO regulates. Using spinach, at least one element of the NO scavenging ability was shown to be heat-unstable, although heat-treating of other leaf materials had little effect, showing that NO scavenging will still occur after cooking. It is proposed that the NO scavenging of dietary components needs to be investigated more thoroughly before the full effects of increasing antioxidants through increased intake of fresh fruit and vegetables can truly be understood.