i really think magnesium is a big part of your puzzle, e.
the article below is mostly on track. however, AFAIK bottling has nothing to do with magnesium content of beverages.
the distinction should be city water vs ground water.
both sea water and fresh ground water contain magnesium.
city water has magnesium removed so that pipes don't get clogged.
that said, read on:
The Ignored Nutrient Magnesium and High Blood Pressure
...Paul Mason, a member of Life Extension, is concerned about getting the message across. Not only about magnesium and high blood pressure but the drinking habits of Americans which can cause heart disease and cardiovascular problems...
Paul Mason ... produces evidence based on extensive scientific data that magnesium is a, if not the missing link to heart disease, and high blood pressure control.
Examples of low Magnesium and High Blood Pressure with other complications
"Nature’s Calcium Channel Blocker" is the name they give to magnesium because it does what Calcium channel antagonists do, block calcium. It also modulates vascular tone.
Magnesium stimulates the production of nitric oxide, a mechanism at work when we exercise, helping to relax and dilate blood vessels. Not enough however causes a rise in calcium which restricts them...
...[adequate] levels of calcium but low levels of magnesium can cause persons to become obese especially concentrating most of the weight gain around the stomach. These people are highly likely to develop high blood pressure, diabetes and insulin intolerance, known factors contributing to heart attack.
Magnesium and High Blood Pressure - Foods and Supplements
Drinking bottled water for health is a well established and growing trend with many drawbacks. At most you will only find about 30% of magnesium RDA in bottled water, making it a less than adequate source. Finding sources to make up the remaining 70% could be a challenge.
Choosing foods containing magnesium not only can be frustrating but tiring work, trying to find and match up magnesium food sources as well as potassium food sources, and so on. ... farming methods and over-production have depleted the soils of vital minerals.
A wise and easier choice would be to supplement the diet with a balanced mineral, trace mineral and vitamin solution, eliminating the headache when planning daily menus.
You can buy a mineral supplement that contains all your minerals, trace minerals and vitamins in ionic form, so they can be absorbed through the intestines and into the cells.
Keep in mind, although there is an abundance of good quality potassium, calcium, vitamin d, and magnesium supplements on the market, they need to be in correct measurement in relation to each other, so exercise caution when choosing which supplement to take...