A new research review, published in Frontiers in Immunology^[1], has found that a simple glass of citrus juice – for example orange or grapefruit – contains key nutrients and bioactive substances that help our immune system to work efficiently.

Scientists examined evidence from nearly 200 different studies and reports, and concluded that vitamin C, folate and polyphenol compounds in citrus juices have the capacity to impact on immune health, fight inflammation and improve our defence against bacteria and viruses.

Co-author, Philip Calder, Professor of Nutritional Immunology at Southampton University, said: “A weak immune system increases susceptibility to infections and allows these to become more severe. One component of the immune response is inflammation. Where inflammation is excessive or uncontrolled it can damage body tissues, sometimes irreparably, and affect our ability to fight infections. Having a diet rich in antioxidant foods and drinks is one way to control inflammation and ensure the body can mount an effective immune response. Trials in humans confirm that orange juice consumption reduces inflammation.

“Citrus fruit juices are particularly good sources of vitamin C and folate, which have roles in strengthening the gut and skin barriers which are our first line of defence against viruses and bacteria. In addition, these nutrients – which are absorbed well from fruit juices –support the function of many types of immune cells including phagocytes, natural killer cells, T-cells and B-cells.

“Another area of research is the bioactive polyphenols found in citrus fruit juices which include hesperidin, narirutin and naringin. These not only have anti-inflammatory effects but could also have direct anti-viral effects according to emerging data from modelling studies”.

Dr Carrie Ruxton, from the Fruit Juice Science Centre, comments: “The evidence about the positive role that fruit juices play in the diet continues to build. We know from several large studies that a daily glass of pure fruit juice provides vitamin C, folate and potassium, can help to lower blood pressure, and reduces the risk of stroke. Now it’s clear that citrus juices can also contribute to immune health which is crucial as we all get back to our normal lives”.