Skin, nails and hair<unk>  may manifest as acne, eczema, xerosis (dry, scaling skin), seborrheic dermatitis, or alopecia (thin and sparse hair). It may also impair or possibly prevent wound healing. Mouth<unk>  can manifest as non-specific oral ulceration, stomatitis, or white tongue coating. Rarely it can cause angular cheilitis (sores at the corners of the mouth). Vision, smell and taste Severe<unk>  may disturb the sense of smell and taste. Night blindness may be a feature of severe<unk> , although most reports of night blindness and abnormal dark adaptation in humans with<unk>  have occurred in combination with other nutritional deficiencies (e.g. vitamin A). Immune system Impaired immune function in people with<unk>  can lead to the development of respiratory, gastrointestinal, or other infections, e.g., pneumonia. The levels of inflammatory cytokines (e.g., IL-1β, IL-2, IL-6, and TNF-α) in blood plasma are affected by<unk>  and<unk>  supplementation produces a dose-dependent response in the level of these cytokines. During inflammation, there is an increased cellular demand for<unk>  and impaired<unk>  homeostasis from<unk>  is associated with chronic inflammation. Diarrhea<unk>  contributes to an increased incidence and severity of diarrhea. Appetite<unk>  may lead to loss of appetite. The use of<unk>  in the treatment of anorexia has been advocated since 1979 by Bakan. At least 15 clinical trials have shown that<unk>  improved weight gain in anorexia. A 1994 trial showed that<unk>  doubled the rate of body mass increase in the treatment of anorexia nervosa. Deficiency of other nutrients such as tyrosine, tryptophan and thiamine could contribute to this phenomenon of "malnutrition-induced malnutrition". Cognitive function and hedonic tone Cognitive functions, such as learning and hedonic tone, are impaired with<unk> . Moderate and more severe<unk> es are associated with behavioral abnormalities, such as irritability, lethargy, and depression (e.g., involving anhedonia).<unk>  supplementation produces a rapid and dramatic improvement in hedonic tone (i.e., general level of happiness or pleasure) under these circumstances.<unk>  supplementation has been reported to improve symptoms of ADHD and depression. Psychological disorders Low plasma<unk>  levels have been alleged to be associated with many psychological disorders. Schizophrenia has been linked to decreased brain<unk>  levels. Evidence suggests that<unk>  could play a role in depression.<unk>  supplementation may be an effective treatment in major depression. Growth<unk>  in children can cause delayed growth and has been claimed to be the cause of stunted growth in one third of the world's population. During pregnancy<unk>  during pregnancy can negatively affect both the mother and fetus. Animal studies indicate that maternal<unk>  can upset both the sequencing and efficiency of the birth process. An increased incidence of difficult and prolonged labor, hemorrhage, uterine dystocia and placental abruption has been documented in<unk>  deficient animals. These effects may be mediated by the defective functioning of estrogen via the estrogen receptor, which contains a<unk>  finger protein. A review of pregnancy outcomes in women with acrodermatitis enteropathica, reported that out of every seven pregnancies, there was one abortion and two malfunctions, suggesting the human fetus is also susceptible to the teratogenic effects of severe<unk> . However, a review on<unk>  supplementation trials during pregnancy did not report a significant effect of<unk>  supplementation on neonatal survival.<unk>  can interfere with many metabolic processes when it occurs during infancy and childhood, a time of rapid growth and development when nutritional needs are high. Low maternal<unk>  status has been associated with less attention during the neonatal period and worse motor functioning. In some studies, supplementation has been associated with motor development in very low birth weight infants and more vigorous and functional activity in infants and toddlers. Testosterone production<unk>  is required to produce testosterone. Thus,<unk>  can lead to reduced circulating testosterone, which could lead to sexual immaturity (Ananda Parsad, et al.) hypogonadism, and delayed puberty.
Zinc deficiency
Zinc toxicity
Manganese deficiency 
Boron deficiency 
Lead poisoning
Iron deficiency
Selenium deficiency
Copper deficiency