It may be last in the alphabetical list but Zinc is a crucial nutrient for health.
In fact it has a role in all human living cells.
What It Is
Our bodies contain approximately 2-3 g of zinc in total. 60% is stored in skeletal muscle, 30% in bone mass and 10% in remaining tissues.
An adequate dietary intake of Zinc does not ensure its absorption. It is estimated that the average dietary intake of Zinc by healthy adults is 6-15mg per day however less than half of this is absorbed.
The two factors that will influence zinc bioavailability in the diet are phytates and calcium. Phytates (wholegrains, seeds and nuts) can form strong and insoluble complexes making the zinc unobtainable. Calcium in the main antagonistic mineral to zinc and therefore calcium-rich diets can promote a zinc deficiency.
Zinc is available supplementally as Zinc sulfate or gluconate.
Dietary zinc is best absorbed from animal sources such as red meats, liver, eggs and seafood (especially oysters and shellfish). It can also be found in legumes such as lima beans and soybeans, miso, tofu, mushrooms, green beans and pumpkin seeds.
What It Does
Zinc is involved in many biochemical reactions. It is required for the building of all new tissues, for normal immune responses, nerve function, reproduction and as part of the army of protective antioxidants.
Deficiency Signs and Symptoms:
- Slow growth and development in children
- Neonatal death and low birth weight
- Hair loss or alopaecia
- Abnormal taste sensation
- Nail abnormalities
- Decreased immune function
Recent studies have shown the effectiveness of Zinc in reducing the frequency of infections in the elderly. It had protective effects against upper respiratory tract infections, the common cold and influenza. Furthermore, zinc is protective against age-related macular degeneration.
Zinc is especially indicated for men. A deficiency can decrease sperm production and is also implicated in the cases of impotence.
Recently, the role of zinc in behavioural disorders has been studied. A 2006 study identified that children with malnutrition (protein, zinc and iron deficiencies) at 3 years of age demonstrated higher behavioural problems at ages 8, 11 and 17 when compared to those children with sufficient nutrition.
Zinc is a fundamental co-factor in the production of neurotransmitters so its role in depression has been considered. A small study in 2003 published an improved response to antidepressant medication when taken with zinc supplements.
Zinc deficiency can be a sign of impaired taste (dysgeusia) with supplemental zinc showing an improved perception of taste. A zinc deficiency is intimately linked with Anorexia nervosa – it can be part of the initiating cause as well as a sustaining factor for abnormal eating behaviours.
- Encourages wound healing
- Reduces inflammatory acne lesions
- Reduces diarrhoea
- Improves intestinal permeability problems for those with Crohn’s Disease
- Lowers the recurrence of herpes simplex infections
- Improves recovery from Pneumonia
- Cognitive improvement in Alzheimer’s disease
How Much You Need
The RDI for zinc is 14mg per day for men and 8mg per day for women. Children between the ages of 1 – 8 require 3-4mg per day. Teenage boys require 13mg per day and teenage girls 7mg per day.
Higher doses are required for women during pregnancy and to prevent or treat specific diseases or conditions.
Acute adverse effects from high single doses of zinc include gastrointestinal irritation, nausea, vomiting and diarrhoea. Always take zinc with or after food.
Long term use of high dose Zinc (between 100 – 150mg per day) can interfere with copper metabolism as well as damage red blood cells and reduce white blood cell production.
The absorption of Zinc is affected by the following:
- Folate (B9)
Zinc interacts with the following medication and forms complexes:
- Tetracyclines and quinolones
It is recommended to separate the doses by 2 hours
The following drugs will increase zinc losses:
- Captopril and enalopril
- Thiazide and loop diuretics
Radiotherapy will also reduce plasma zinc levels
Did You Know?
During pregnancy, the mother’s zinc supplies are stored mainly in the placenta. During birth and the subsequent removal of the placenta, a dramatic loss of zinc can occur.
Post-natal depression if often linked with a deficiency in zinc.