It may not be zinc overdose by itself but perhaps a disruption of the copper-zinc ratio?
www.westonaprice.org/modern-diseases/copper-zinc-imbalance-unrecognized-consequence-of-plant-based-diets-and-a-contributor-to-chronic-fatigue/Disruption of the copper-zinc ratio is an overlooked contributor to intractable fatigue that follows excessive reliance on a plant-based diet. The result is toxic accumulation of copper in tissues and critical depletion of zinc through excretion. This condition usually goes unrecognized because copper levels in the blood can remain normal. Also, most doctors are unprepared to meet with extreme zinc deficiency and its baffling effects on many systems of the body. Hair mineral analysis, competently used, is the tool which can unravel the complexities of this growing problem.