Yeah, here is some advice from a former exercise physiologist (cardiac and pulmonary rehabilitation) and personal trainer for over a decade.. eating healthy foods keeps you in tune.
Eating crap keeps you inflamed and... well.... shitty. All of the nutrition science that I was taught in the 90's at my college is now considered bullshit. "They" are even saying that Omega 3's might not be as great as once considered but that whole milk is better than the non fat......

WTF
If the goal is to increase running performance at 55 just because you want to increase running performance at 55 DO IT>>
But
if there is another objective or goal, starting to "run" at 55 MIGHT not be the best.
I hate running. I used to race 5 mile running races. 32.16 was my best time.......... 1995..... I also use to mountain bike race, a couple of 24 hour mountain bike races, blah blah.
I just did a stupid backpacking trip with a buddy who has been backpacking for 6 years and did the Tetons this summer along with all 46er's in the "dacks" within the last 3 years.
We did the Black forest trail in PA..I dusted off my backpacking gear that hasn't been used since 1994 and went along.
BIG MISTAKE: MY FEET were not conditioned for this and out of the 42 miles we were supposed to do, by the second night my feet were toast. . We did 26 miles and had to cut it short because of ME. Which I hated. NEVER AGAIN> Horrible pain. the Descents were excruciating. The blisters were folding back on themselves with every step. Did my best cutting them, moleskin, duct tape on the feet..... Nothing. Second most pain ever since I shattered my collarbone playing Rugby in 2006.
I have been riding my touring bike to school since we started 2 weeks ago. 4.25 miles out and 4.25 miles back. I have my panniers filled with my food for the week, along with clothes for the week (i have a shower in my office) on Mondays but the rest of the week my bags, for the most part, are empty. 8 years ago I used to ride 60 miles before work with my buddy. We would get up and out on the road by 4:30. Looking back, my question is why??? The answer: because we liked riding for performance for performance sake. Now at 48 I have no fucking interest in doing that ever again.
I use those 4+ miles as interval training. 100 pedal strokes hammering then some recovery. Blah blah blah.... However, in using my run keeper app., I increased my pace time for the week by 20 seconds from last week already and decreased my total time to work also, along with calories burned.
This week I will have to take one day off but will add one day of Mountain biking a week for two weeks and then two days a week (weekends)
I also lift weights (heavy) three times a week.
But I am still eating crap at least once a day..... which really pisses me off. Oh and red wine Fri. Sat. and Sun. a lot of red wine.... Not good for the waist line.
So yeah. great advice from me to you = not much.