Inadequate magnesium is highly common in the West, largely due to modern-day farming methods, but it's also exacerbated by stress and many medications. A magnesium deficiency, which often goes hand-in-hand with a calcium deficiency, is common in depressed patients (JAMA, 1973; 224: 1749-51). Interestingly, the levels of magnesium in the spinal fluid is especially low in patients who are suicidal (Ann N Y Acad Science, 1986; 487: 221-30).
Another potential culprit is low levels of blood potassium, which is particularly common if you take diuretics (Psychosomatics, 1981: 22 (3): 199-203). It's also common for patients to have a raised level of sodium in their cells (Gerontology Clin, 1971; 13: 232-45).
Underpinning all these deficiencies may be faulty digestion. Besides food sensitivities, it's important to rule out a deficiency in hydrochloric acid. An insufficient amount of stomach acid may reduce the ability of your gut to absorb many nutrients, and you may develop many deficiencies, even if you are eating an adequate diet. In one case, a patient who'd suffered from depression for 17 years had a dramatic reversal as soon as he was given hydrochloric acid and a B vitamin supplement (Nutr Abstr Rev, 1959; 29: 273).
Dr Melvyn Werbach
Adapted from Dr Werbach's books Nutritional Influences on Mental Illness (Third Line Press) and Healing Through Nutrition (Thorsons).