Natural killer (NK) cells and killer T-lymphocytes are special immune cells that destroy viruses and combat cancer. They release chemical bullets that perforate the protein coating of viruses and the membranes of cancer cells. Natural killer cells also damage the DNA of cancer cells and interfere with the replication of viruses.

To add further detail, NK cells release perforins into the membranes of their target cells. “Perforin” comes from the word perforate. So, perforins are a group of chemicals that shoot tiny holes into the membranes of their targets. Special enzymes from the NK cell granules then insert themselves into the target cells through these perforin channels. Enzymes, such as fragmentin, cause DNA fragmentation and the death of the target cells. Natural killer cells also exert an antibacterial action against the virus.

Lifestyle Factors that help or inhibit NK cells and T-lymphocytes

Dr. Morimoto and associates at the Osaka University Graduate School of Medicine investigated the association between lifestyle and mental health status and natural killer (NK) cells. The lifestyle habits they examined included cigarette smoking, alcohol consumption, sleeping hours, working hours, physical exercise, eating breakfast, balanced nutrition, and mental stress. Here is what they discovered: Participants with a good overall lifestyle showed significantly higher NK cell activities than those subjects with poor lifestyle habits. Subjects who complained of an unstable mental status had significantly lower NK cell activity than those who reported having a stable mental status. Consequently, when subjects were divided into four groups by lifestyle and mental health status, subjects who had poor or moderate lifestyle and reported unstable mental status showed the lowest NK cell activity and subjects who had good lifestyle practices and reported stable mental status showed the highest NK cell activity.

Other studies show that alcohol and insufficient sleep also decrease NK cell response. On the other hand, moderate aerobic exercise, a well-balanced vegetarian diet, and garlic improve their efficiency.

Mental attitudes significantly influence the efficiency of the NK cells, as well. Early in the last century health educator, Ellen White, observed: “The relation that exists between the mind and the body is very intimate. When one is affected, the other sympathizes”.Grief, anxiety, discontent, remorse, guilt, distrust, all tend to break down the life forces and to invite decay and death.”

Scientific studies confirm these observations. They show that major depression, for example, reduces NK cells’ effectiveness. A persistent negative outlook erodes both the ability of the NK cells and killer T-lymphocytes to destroy viruses and cancer cells. The emotions and reactive thinking common in depression, helplessness, loneliness, hopelessness, lack of social support, and unhealthy suppression of these feelings, not only depresses the mind but also the immune system.

Stress reduces the ability of NK cells to make interferon, a chemical that substantially decreases viral replication. However, problem-solving techniques and coping skills improve NK activity in stressed individuals. If the individual possesses high emotional stability and low anxiety, stress actually improves NK cell activity. On the other hand, the same stress can result in a significant decline in NK cells if the individual possesses high anxiety and low emotional stability.

Optimism improves NK cells’ ability to perform their job. Ellen White observed that “Courage, hope, faith, sympathy, [and] love, promote health and prolong life. A contented mind, a cheerful spirit, is health to the body and strength to the soul.” Could this also be true for the immune system? A modern medical journal confirmed this to be so, saying, “Self-confidence, openness, social support, effective coping skills, self-discipline, trust and faith, and a will to survive” improve NK cells’ efficiency.

Life Application

Perhaps the same principles that improve mental health and enable the immune system to overcome viruses and cancer can also help our community to overcome its moral and social ills. The negative attitudes of criticism and pessimism we entertain in the our homes can spread sin viruses like nosocomial infections1 in our community.

If we would engage in more genuine, systematic encouragement and promote more openness, faith, trust, coping skills, and social support among us, our world would become a much healthier place.



  1. Nosocomial infections are infections that are contracted within the hospital.