Concerning leg cramps, what has worked well for me over the years is flax seed oil.  When I first started doing seven to 10 day “juice fasts”, I would always get horrible leg cramps, typically in my hamstrings and occasionally my quads.  I commented about that to someone at a local vitamin store and was recommended to try taking flax seed oil.  I purchased a large bottle of 1,000 mg gel caps and started taking 4 each twice a day when doing the juice fast(s) and the leg cramps disappeared. 

After that, I started taking flax seed oil on a regular basis, mostly three to four 1,000 mg gel caps per day.  When the idea of doing a self-contained bicycle trip came along, I continued taking flax seed oil.   On my first few short trips of about 400 miles, I carried a large “bottle” of gel caps and took four or five in the morning before starting out and took five or six at the end of the day.  Not  only did I not have leg cramps, but my skin seemed to recover almost overnight from “sunburn”, even when using limited amounts of sunscreen.  Flax seed oil gel caps are somewhat heat tolerant, so, I made sure to pack the bottle deep inside my panniers to keep it cooler during the day.  If the bottle got warm, I would have to reach inside and break the gel caps apart, but that was typically after an eight or 10 hours on-the-road day.   On my most recent tour in 2019, I took five to six gel caps morning and evening and had no problems with leg cramps, either while training or doing actual loaded miles on the tour.

At the same time, I was taking a healthy dose of a calcium/magnesium blend. 

Additionally, as an aside, several years ago I read on a German language website that flax seed oil helps prevent the build-up of plaque inside the blood vessels and allegedly dissolves built up plaque if taken in sufficient quantity on a regular basis and helps maintain healthy cholesterol levels.  While undergoing cataract surgery, I was at the eye doctor’s office for a follow-up visit after the first surgery and one of the technicians was commenting to me that a couple of days previously, her doctor had done a blood screen to check her cholesterol levels, which were “out” according to the doctor, who then wanted to put her on medication.  She was not keen on that and told the doctor she was going to get a second opinion. 

I told her about what I had read on that German language website and suggested she purchase some 1,000 mg gel caps and start taking three or four twice a day for at least a couple of weeks before getting the second opinion, but not to say anything to the second doctor about taking the flax seed oil, lest he poo-poo such a thing.  At the same time, I suggested nothing-ventured-nothing-gained and at worst, she would be out the cost of the bottle of gel caps.  It was five or six weeks later that I saw her again when I had gone to the office for a check-up after the second cataract surgery.  I asked her if she had purchased some flax seed gel caps (yes) and asked her the result:  The second doctor asked her why she requested a cholesterol check, as everything was normal.

That is my two cents worth.  

Rich one thing to be cautious of with some magnesium supplements is B6 toxicity. 

It’s a well documented phenomenon. Too much vitamin B6, can cause really disabling nerve damage. Peripheral neuropathy, and that's a very miserable condition. There’s a very  long recovery time from this condition , if it's reversible at all. 

Some  preparations of magnesium are not pure magnesium, and they have vitamin B6. 

It’s not necessarily obvious, so you've got to look at the back of the packet or container. Pure magnesium is preferable.

this sounds weird, but pickle juice works. I asked a surgeon at Tacoma general hospital, who’s a cyclist too, about it. His answer? I use it regularly when I’m on a long trip. 

Another non drug thing I do is stretch my calves out fully before sleeping. Lie on the bed and grab your toes with your hand, slowly stretch out. You’ll feel it. I hold the stretch for 30 seconds.