DEFICIENCY

Zinc was demonstrated to be essential in animals in 1934 (experiments with rats)

1955 – Zn deficiency disease identified in pigs

Around 1960 – Zn deficiency in rural Iran shown to be responsible for endemic condition with:

• reduced growth
• anemia
• hypogonadism
• delayed sexual maturity and impotence
• enlarged liver and spleen
• dry, rough skin
• stupor
• geophagy (eating clay – up to 500 g per day)

1970s – studies in Denver, Colorado – double blind controlled trial of Zn supplementation (5 mg/day) in apparently healthy children (but low height for age):
Supplemented children (especially boys) showed higher growth rate than controls and increased height-for-age percentile.

(Experimentally induced) Zn deficiency

There is no Zn store in the body, so a serious reduction in Zn intake is followed very quickly – within a few hours – by the first signs of deficiency (unlike other nutrients).

• decrease in endogenous losses
• decrease in plasma concentration
• reduced cell division
• anorexia
• reduction in growth (if organism still growing)
• dermatitis
• compromised immune system
• general tissue dysfunction

A deficiency of Zn during early development can be teratogenic, -> animals with malformations including brain and eye defects, spina bifida, cleft lip and palate, etc.

Zinc, low birth weight and breastfeeding

Zinc deficiency in infancy leads to stunting, infectious disease morbidity and mortality, especially from diarrhea and pneumonia, in developing countries.

Zinc supplementation of low birth weight infants for first year improved growth and reduced morbidity/mortality.

Even in N. America, when infants are weaned, effects of zinc deficiency can be seen if complementary foods without zinc are not consumed.

(Hambidge KM and Krebs NF (2003) Pediatrics 112, 1419-1420)

Exposed/vulnerable groups

• Pregnant women (see introductory page)
• Small children (lower intake with junk foods; exposure to heavy metals)
• Older people (poor sense of smell and taste, poor appetite – vicious cycle)
• Poor (insufficient, low quality food)
• Vegans

In developing countries, iron and zinc deficiencies often occur together.

Diseases of the GI tract are complicated by Zn deficiency. Damage to the intestinal mucosa reduces normal absorption.

Zn supplementation reduced the incidence of persistent diarrhea in children and reduced the duration of acute diarrhea. Mechanism? Improved immune status? Correcting pathological changes in gut integrity?

Crohn’s disease patients may have low serum concentrations of Zn and show clinical features of Zn deficiency (from poor absorption). Similarly, short bowel syndrome is associated with Zn deficiency.