Researchers found almond skins improved the ability of the white blood cells to detect viruses while also increasing the body’s ability to prevent viruses from replicating and so spreading inside the body.
They discovered that even after the almonds had been digested in the gut, there was still an increase in the immune system’s defence against viruses.
The scientists, who are based at the Institute of Food Research in Norwich and the Policlinico Universitario in Messina, Italy, said their findings suggest that the nuts can increase the immune system’s ability to fight off a wide range of viruses, including those that cause flu and the common cold.
They said although they have still to carry out research on how many almonds must be eaten to obtain a beneficial effect, it was likely that eating almonds regularly could help protect people from becoming infected with viruses in the first place, while it could also help those already infected to fight off their illness.
Dr Giuseppina Mandalari, from the Institute of Food Research, said: “Almond skins are able to stimulate the immune response and thus contribute to an antiviral immune defence.”
The researchers, whose work is published in the scientific journal Immunology Letters and was funded by the Almond Board of California, found that even after digestion in a laboratory simulation of a human gut, the almonds skins were still able to increase the immune response.
They tested the immune response to infection by the Herpes Simplex Virus 2, which can cause cold sores and is a notoriously difficult virus to treat due to its ability to evade the immune system by dampening down the body’s inflammatory response.
They found that almond skin extracts were effective against even this virus.
But they found that almond skins that had been removed through blanching in boiling water, which is common process to remove skins from almonds, had little effect on the immune system.
The researchers say they are still to identify exactly what it is in almond skins that cause the antiviral activity, but they believe it could be due to compounds known as polyphenols.
It is thought they increase the sensitivity of white blood cells known as helper T cells, which are involved in fighting off viruses. They said it was likely that other nuts may also have this sort of activity.
Dr Martin Wickham, who was also involved in the study at the Institute of Food Research, said: “It is an area of huge interest to find natural alternatives that will have an antiviral activity.
“Nutritional guidelines recommend eating around three ounces a day to benefit from the fibre and other nutritional components in almonds, but we have still to do the work to see whether this would be enough to have an antiviral affect.
“This was just an initial study to find out if almond skins have this antiviral activity.
“The herpes simplex virus is a very good model of viral infection because it is known to evade the immune system, so because the almonds had an impact on this virus, it is fair to assume that it will have an impact on other viruses.”