Who would have thought it? Maybe 13 is a lucky number after all, at least for some. A new JAMA study showed that exercise substantially reduces the risk of 13 cancers. We have discussed the benefits of exercise in reducing breast and colon cancer in Exercise and Cancer, but this new study showed reduced risk not only in those two cancers, but also lung, liver, esophagus, kidney, stomach, endometrium, blood, bone marrow, head and neck, bladder and rectal cancers in physically more active individuals. Most of these associations held true regardless of body size or smoking history. So virtually everybody can lower their cancer risk with exercise.
All of us know someone affected by cancer so these results should prompt us to share this knowledge with as many people as possible and we hope that you will do that.
This was a large study that pooled data from 12 large prospective studies performed in the United States and Europe between 1987 and 2004 involving 1.44 million study participants. The study assessed the relationship between leisure-time physical activity and the incidence of 26 cancers. One common cancer that exercise did not affect one way or the other was prostate cancer.
Here’s an important point. The reduced risk of those 13 types of cancer was associated with moderate to vigorous activity. The other key point is that there was greater reduction in cancer the more exercise participants performed. So there was a dose-dependent response. So a little exercise is good, but more is better.
What is Moderate to Vigorous Exercise?
How much exercise is necessary to reduce cancer risk? The good news is the answer is not much. When you hear moderate exercise you probably envision performing exercise at a level that makes you sweat and vigorous exercise as something that leads you to huff and puff. But, moderate to vigorous activity is actually something more “sedentary” or more tame. So you don’t have to be training for a triathlon to meet the criteria of moderate to vigorous activity.
When we talk about exercise we talk about frequency, intensity, and time (or FIT). Let’s start with intensity. Activity intensity is sometimes measured in METs or metabolic equivalents. One MET equals resting metabolic rate while sitting. METs can range from 0.9 METs during sleep to 23 METs as in running a mile at 4:17 pace. Moderate activity falls in the 3 to 6 MET range and vigorous activity is anything above 6 METs. See examples below.
- Walking at 3 mph pace = 3 METs
- Walking at 4 mph pace = 5 METs
- Cleaning, washing windows, sweeping garage = 3 METs
- Sweeping floors or vacuuming carpet = 3 to 3.5 METs
- Mowing the lawn with power mower = 5 METs
- Playing badminton – 4.5 METs
- Ballroom dancing (slow to fast) = 3 to 4.5 METs
- Golf (pulling clubs) 4.5 METs
- Doubles tennis =5 METs
- Bicycling on flat surface at 10-12 mph pace = 6 MET
- Walking at 4.3 mph pace = 6.3 METs
- Jogging at 5 mph = 8 METs
- Jogging at 6 mph = 10 METs
- Running at 7 mph = 11.5 METs
- Bailing hay = 8 METs
- Digging ditches = 8.5 METs
- Singles tennis = 8 METs
- Bicycling flat surface at 12-14 mph = 8 METs
- Bicycling flat surface at 14 to 16 mph = 10 METs
As you can see moderate activity can be obtained doing most household chores. Now the next questions. We discussed intensity of activity, but how much activity and how often? The best evidence suggests 30 to 60 minutes of moderate to vigorous activity daily which is 21 MET-hours per week or more (walking 3 mph an hour a day 7 days a week). Really not that much. There is little reason why all of us cannot get this much activity.
How Does Exercise Lower Cancer Risk?
Inflammation contributes to cancer risk and so does insulin resistance (elevated blood sugar or diabetes). Exercise improves insulin sensitivity improving blood sugar control. In the long run exercise reduces inflammation though acute bouts of strenuous exercise can cause inflammation, but the net effect of regular exercise is that it reduces inflammation. Exercise also improves hormonal balance and imbalance of hormones raises the risk of certain female cancers like breast and endometrial.
Exercise and NEAT
This post ties into our previous articles, How Much Do You Do It? and Staying Active is NEAT which discuss non exercise activity thermogenesis or NEAT. NEAT is all the calories you burn exclusive of those that you burn during volitional exercise. The best way to improve NEAT is to simply not sit. If you have little time for exercise just find ways to be more physically active throughout the day especially at the work place. And, do some of those household chores yourself. Become a busy beaver.