The inner ear contains the highest concentration of zinc of any organ. Numerous clinical studies have shown a correlation between zinc deficiency, tinnitus and sensorineural hearing loss (SNHL) . SNHL is the most common type of hearing loss, occurring in 23 percent of the population older than 65 years of age. The term "sensorineural" is used to indicate some pathological change in structures within the inner ear or in the acoustic nerve.
One study showed that, "With zinc supplementation in patients who are marginally zinc deficient, there has been improvement in tinnitus and sensorineural hearing loss in about one-third of elderly adults."(1) Another clinical trial showed supplementation with 34-68 mg of zinc over a two week period produced". . . a significant decrease in the numeric scale (of the tinnitus)."(2) A French study using zinc to treat tinnitus found, ". . . positive results in about 52% of cases: in 15% there was a good amelioration and in 37% there was a smaller but significant amelioration of their symptoms. . . . (it is) more efficient in types of tinnitus of a continuous character than in other types."(3)
... Zinc plays a major role in keeping the thymus going. The thymus gland orchestrates the workings of the immune system. The thymus is big and robust when we are young but declines with age. When we are born, the thymus, tucked in the neck behind the top of our collarbone, is bigger than our heart. The shrinking starts at puberty and by the time we're sixty, it's a pale shadow of its former self. This parallels the rapid decline of our immune system. The shrinkage of the immune system is one of the most visible signs of aging.
Until recently, the experts considered this slow decline as an irreversible decline of advancing age. This is simply not true. French researchers recently found that immune systems of even the aged could be reversed. A group of institutionalized people, aged 73 to 106 years, was given a daily dose of 20 milligrams of zinc. All subjects were deficient in zinc. Their thymulin activity shot as much as 50 percent in just a couple of months. There were no side effects.
via Zinc, Tinnitus and Immune System Health - Tinnitus Information Center.
As they say, the dose is the poison. I don't think anyone should be taking more than 30 mg / day and what you should take really depends on what you are already getting in your diet. You can die from too much zinc. What a world this is: If you wear false teeth, you might have zinc poisoning from denture creme. Too much zinc can cause neurologic disease (panic attacks according to some, heart problems, etc.) and abnormally low copper levels in your blood (hypocupremia).