What are Natural Killer cells?

White blood cells act as part of the body’s immune defense, protecting us from a wide range of invading agents including viruses and tumours. Natural Killer cells are an important component of white blood cells. As Life Science explains, 'Natural Killer cells form the body's front line of defence....... Unlike our other immune cells, natural killer cells are always at the ready. They have an innate ability to recognize viruses and tumour cells, while other disease-fighting cells take precious time - two to three days - to build forces and learn what the enemy looks like'.

How do they work? - Natural Killer cells  work in three important ways. They:

  • Attack viruses and tumour cells
  • Signal the body to provide sufficient numbers of B and T cells (the immune system’s second line of defence)
  • Help to regulate our immune systems

While natural killer cells are an important part of our immune system they have two potential weaknesses. First, they need receptors to activate them and sometimes these receptors don’t work. Second, they can sometimes be deactivated by a type of T cell called regulatory T cells. That’s why some current researchers are exploring how best to activate our receptors or block the effect of regulatary T cells, to enable our natural killer cells to have maximum effect.

What other factors weaken our natural killer cells? Many of the factors that potentially make us unhealthy are believed to also weaken our natural killer cells, including:  

  • Obesity and smoking (Research reported on Plus One concluded, ‘Obese subjects have impaired NK cell activity that is more susceptible to the detrimental effects of cigarette smoke compared to lean subjects. This may play a role in the increase of cancer and infection seen in this population')
  • Processed foods and trans-fatty acids - As Udo Erasmus comments, in his book Fats that Heal and Fats that Kill, “Besides producing atherosclerosis in the arteries of animals, fried and deep fried (vegetable) oils can also impair cell respiration and other cell functions, inhibit immune functions, and lead to cancer.”
  • Alcohol and Stress
  • Modern chemicals (such as vehicle exhausts, disinfectants and pesticides).

In addition factors as varied as yo yo dieting and marijuana are now believed to weaken our natural killer cells.

What factors strengthen our natural killer cells? - The good news here, is that many of the factors we associate with a healthy lifestyle are believed to also strengthen our natural killer cells, and so help to protect us against viruses and cancers. These include:

  • A healthy diet, with a good range of vitamins and minerals (including vitamin D and selenium) – and with garlic, yoghurt, carrots, mushrooms and citrus foods all seen as likely to be beneficial.
  • Aerobic exercise
  • Omega 3 fatty acids (found in particular in oily fish) and monounsaturated fatty acids (for instance from extra virgin olive oil).

Other ways of strengthening our natural killer cells are believed to include electro-acupuncture, red ginseng, beta glucans supplements, neem and ginko biloba. 

So a healthy lifestyle, with a nutritious diet, aerobic exercise, not smoking and not drinking much alcohol is likely to strengthen the body’s natural killer cells, and increase the prospects of their successfully combating viruses and tumours.


Published 07/07/2011, Review date May 2015