Optimal walking speed

How fast you should move in order to improve your health?
In many studies, the more intense runners are healthier than those who walk or run more moderately. However, this is not the entire picture, there are studies that say moderation is wiser. Confusingly, and perhaps unfortunately there is literature that will support whatever makes you happy.
From the linked blog:
“This risk of death is lower even with a very minimal energy expenditure. The lowest-energy-expenditure group in each study is walking at about 3 mph for 20 to 40 minutes per day. In other words, a mile or two of walking. In exchange, their risk of death goes down by 10 percent.
"Walking a bit farther — say, 2 to 3 miles at 3 mph — gets you an additional death reduction of about 30 percent. But walking more than that, or more than an hour a day at this speed, is no better.”
“If we take this research at face value, we learn a few things. First, some exercise reduces your risk of death. Second, the optimal walking/jogging exercise is light to moderate jogging. The optimal speed is between 5 and 7 mph, and if you do 25 minutes about three times a week, you’re all set. Nothing in the data suggests that running more — farther, or faster — will do more to lower your risk of death.”

What do you think ? Agree /Disagree?