Mine was always low until pregnancy, when I developed very severe pre-eclampsia at only 28 weeks. I had no risk factors & was very fit, normal weight, with a healthy diet.
I'm now in my early 50's & I guess the inevitable has happened, where I asked for a check at the GP surgery, it was found to be very high (ended up at A&E).
So I've started in medication, lost some weight.
I already run 5K a couple of times a week, average 8K steps daily, no added salt, oily fish 1-2 x a week, aim for 5 a day etc.
But I've been getting headaches, especially at work, and my home monitor is showing me mostly above 90 in the morning (diastolic/lower number).
So I phoned the GP surgery & got a bit of a lecture about stress, diet & exercise.
I'm a single parent working full-time in a stressful role (NHS). I can't change these things.
Just feeling a bit dispirited 
What had worked for other people?