Oh, but there are so very, very many reasons everyone already should be taking a magnesium supplement. Besides which, Mg prevents and treats heartburn as well as any proton pump inhibitor (PPI) as well. Really it is nothing less than the whole rationale behind PPIs that should be under question, as it is almost always low Mg intake that is responsible for heartburn in the first place!
The list of disease conditions that are caused or aggravated by low Mg is astoundingly long. Just the length of it and fact that you never hear of Mg in relation to these diseases is enough to make one suspect some sort of massive drug company conspiracy. Here is but a partial list: ADD, AGING, anger/aggression, all addiction (especially alcoholism), allergies, ALS, Alzheimer's, anxiety, arthritis, asthma, atherosclerosis, autism, bruxism, CANCER, carpel tunnel, chemical sensitivity, chronic fatigue, constipation, depression, diabetes, epilepsy, eclampsia, fibromyalgia, hearing loss, heart disease, hypertension, impatience, insomnia, kidney stones, metabolic syndrome (and perhaps all obesity), migraine headache, mitral valve prolapse, menopause, multiple sclerosis, nail biting, OCD, osteoporosis, peripheral vascular disease, PMS, many psychiatric disorders, PTSD, SIDS, sickle cell disorder, STRESS, stuttering, tinnitus, TMJ, and toxic shock. And this is by no means all disorder related to low Mg levels.
Perhaps the most common denominator of many of these disorders is poor nerve function. Mg improves nerve signalling among other things--particularly reducing excessive signalling (excess nerve function/nervousness is exacerbated by common dietary calcium excess). Another huge function is to decrease peroxynitrite nitrosation, this is a particularly important means of cellular damage throughout the body. Nitrosation is now thought to be likely the most damaging pathway of free radical oxidative damage.
Blood tests for Mg are notoriously inaccurate, failing to detect low Mg levels until they are quite dangerously low. This is because the body regulates blood levels very tightly drawing Mg from other tissues. A more accurate measure tests a sizable tissue sample, which is considerably more invasive.
And there is less and less Mg in the Western diet, but more and more competitive factors, which include everything we like to eat (from sugar, fats and phosphate to the most common vitamins). PPI induced Mg loss is but a tiny additional reason that everyone should be taking Mg for pretty much every health reason one can imagine.