Why 20 Minutes Is the Magic Number for a Healthier Immune System

More isn't always better—and that's even true when it comes to your workouts. According to science, squeezing in 20 minutes of vigorous exercise can not only give you cardio benefits but boost your immunity, too.

Building a case for the 20-minute exercise

A 20-minute exercise may sound more like a warm-up than a workout, but a 2017 study published in Brain, Behaviour, and Immunity suggests otherwise. Researchers found that as little as 20 minutes of exercise can have anti-inflammatory effects that boost your immune system. They specifically monitored the effects of one 20-minute session of moderate treadmill exercise, but senior author Suzi Hong, PhD, in the department of psychiatry and the department of family medicine and public health at UC San Diego School of Medicine, says, that fast walking appears to have similar effects.

In the study, 47 participants first gave a blood sample before exercising. Then, they walked on a treadmill for about 20 minutes—with the intensity adjusted for each person’s fitness level—then provided another blood sample immediately after. The blood samples showed that the exercise caused a five per cent decrease in the number of immune cells producing a cytokine, or protein, called tumour necrosis factor—TNF. (More on TNF later.)

Here’s why that’s important: Exercise activates the sympathetic nervous system, a pathway that increases heart rate, blood pressure, and breathing rate. When this happens, the hormones epinephrine and norepinephrine are released into the bloodstream and activate a cellular reaction that suppresses cytokines, including TNF.

TNF has some admirable qualities, like boosting immune responses and killing cancer cells, but it also has pro-inflammatory properties. Though inflammation is a necessary part of our immune systems, too much of it can lead to autoimmune diseases, including rheumatoid arthritis and multiple sclerosis, as well as fibromyalgia.

Why and how exercise can reduce inflammation

Previous research has already demonstrated that exercise can reduce inflammation, but the significance of this study is in the physiological explanations about why and how this happens, says Carmen Terzic, MD, PhD, chair of the physical medicine and rehabilitation department at the Mayo Clinic in Rochester, Minnesota.

Moderate exercise also has an abundance of other health benefits, like controlling hypertension and diabetes, preventing Alzheimer’s, reducing anxiety and stress, and slowing the aging process. Dr. Terzic says that people who engage in moderate exercise regularly can increase their lifespan by up to 10 years. “Exercise is our best medicine for almost every single disease you can think of,” she says.

The best part? Light to moderate exercise is as simple as taking the stairs instead of the elevator. Or, it can even be spending a few more minutes walking your dog. That’s right—no gym membership required.

Next, check out these simple habits to naturally boost your immune system.