The largest studies on the subject show strong, dose-dependent benefits from endurance training, including running.
There are two points here. 1) There is a lot of evidence that marathon type running is BAD for you. Not running period, just heavy long distance running. 2) Strength training and sprints have better health benefits, with the added bonus they take a small fraction of the time of distance running.
Here's a report on a study that monitored over 100,000 people:
Paul Williams, Ph.D., author of the study, found that men who ran two or more marathons per year were 41 percent less likely to suffer from high blood pressure, 32 percent less likely to have high cholesterol, and 87 percent less likely to be diabetic than non-marathoners. Those who ran only one marathon every two to five years also had significantly lower risk for these conditions than non-marathoners.
The benefits of running marathons were largely independent of total number of miles run per year by participants, indicating that isolated distance running bouts in preparation for marathons may have been effective in decreasing risk of disease. Even runners who didn't run marathons - those who included longer runs as part of their usual exercise routines - were less likely to have high blood pressure, diabetes, or high cholesterol.
http://www.medicalnewstoday.com/articles/140104.php
Here's a different piece on how regular hour-long runs stimulate neurogenesis and memory improvements in middle aged humans:
http://www.dana.org/news/brainwork/detail.aspx?id=7374
Distance running is one of the most beneficial things you can do for yourself. Racing marathons is also fine, with sufficient training.
Comparing non-exercisers to marathon runners is irrelevant. I repeat: marathons inflict measurable physiological damage. A fit person who got fit by means other than long distance running would not have this damage.
There is a much greater volume of clinical research oriented around treadmills and distance running in general because it is very easy to quantify and study. This does not by consequence recommend distance running.
The 32,000 person study in the American Journal of Clinical Nutrition (1999) I mentioned above found that there are.
Can you refer me to any peer-reviewed research linking sprint training or weight training with equal or greater benefit in any of the health indicators that Paul Williams's found distance running improved? Or any research demonstrating that strength training induces neurogenesis?
If not, then please stop sharing what you personally "doubt" or "suspect" is the case. It's just not constructive.
I can't see that.
> equal or greater benefit in any of the health indicators
Insulin resistance, for sure.
> strength training induces neurogenesis
What google informs me about neurogenesis is that it's tied to VOmax training, which long distance running is not especially good for. Interval training, a la tabata intervals, is best for that.
I very much suspect the mental benefits from actual sports exceed running. The stimulation from tennis or basketball would surely do your mind more good than pounding pavement.