Hi Tena,
I have been taking 15mg of zinc per day now for well over a year. However, my sense of smell has not returned. I don't take B12 though.
My taste is OK, even though as you say, it goes hand in hand with sense of smell. I can enjoy many different foods and appreciate the different tastes. I guess it is the usual explanation that we are all different.
Not sure what you mean about "moons on my fingernails".
Best wishes
Ron
PS Don't forget that zinc also protects against dysfunction of the BBB
http://lpi.oregonstate.edu/ss03/zinc.html

Although the antioxidant properties of zinc were first demonstrated in vitro, there is also clear evidence that zinc functions as an antioxidant in the body. One area of growing interest is the role of zinc as an antioxidant in the central nervous system (CNS), particularly the brain. Compared to other soft tissues, the human brain contains significant amounts of zinc. Among the essential trace elements, zinc is second only to iron in total concentration in the brain. Zinc deficiency has been proposed to lead to nervous system disorders, including mental disturbances, loss of sensory acuity, and impaired cognitive and psychological function. Notably, oxidative stress is associated with the development and progression of several different neuropathologies, including Alzheimer’s disease, ALS, and Parkinson’s disease.

We recently examined the role of zinc in maintaining the integrity of the blood brain barrier (BBB), which is the highly specialized blood vessel system of the CNS that serves to protect the brain by excluding toxic agents and other foreign compounds. Alterations or dysfunction of the BBB have been observed in many brain disorders. Free radicals may play an important role in damaging the BBB because it is especially sensitive to oxidative damage. This vulnerability may be due to the high polyunsaturated fatty acid content of the BBB membrane—fatty acids that are very susceptible to free radical attack—as well as the relatively low antioxidant capacity of the BBB. Oxidation of the membrane drastically compromises its barrier properties and may lead to subsequent brain tissue damage, resulting in a host of pathologies.

Our investigations have focused on the antioxidant function of zinc that may protect the BBB against oxidative damage. Using magnetic resonance imaging, or MRI, we have demonstrated that zinc deficiency in rats dramatically increases the permeability, or leakiness, of the BBB. Additionally, we have observed that when zinc deficiency is accompanied by oxidative stress, as might occur during a bacterial or viral infection, BBB permeability increases dramatically. These observations have led us to hypothesize that under normal conditions, zinc protects the BBB against oxidative stress through its antioxidant properties and in so doing, helps to maintain homeostasis within the brain and prevent the development of neurological disorders.

In our initial work we examined the consequences of the loss of BBB integrity during zinc deficiency. First, we noted significantly increased water content, or edema, of the brain as a result of zinc deficiency. Second, we observed increased protein oxidation within the brain. And third, we documented significant changes in brain energy metabolism. These observations led us to propose that these events may be pivotal in the development and pathogenesis of many brain disorders, and our laboratory will continue to define the important roles of zinc in disease prevention.