An overview of zinc
Zinc is an essential nutrient that the body gets from the food we eat. It can be found in certain foods while it is added to others during processing. The amount of zinc needed in the body is very small and hence it is considered a micronutrient. The total amount in the body is thought to be only 2gms (300mmol). This however, doesn’t mean that its importance is minor. Contrary to that view zinc is vital in more than 100 enzymatic processes. In addition to these, it plays a role in the following functions.
- Protein synthesis
- Immune system
- Fetal growth
- Normal cell division
- Normal growth and development
- DNA synthesis
- Wound healing
Zinc distribution in the body
The body has no specific way of storing this trace element. For this reason, intake must be consistent to maintain its functions in the body. Most of the zinc in the body is in the muscles and bones. This accounts for about 85% of the total amount. The skin and liver has about 11% while the rest is found in the remaining tissues.
Zinc is absorbed from the gut. The presence and type of proteins available determine the rate of absorption. It is excreted in the urine and the loss is determined by the available amounts in the body.
Signs and symptoms of zinc deficiency
Zinc deficiency may not be identified immediately when it starts. The body can reabsorb the mineral if necessary by reducing the amount lost in urine. This absorption-resorption process can keep the body fairly well supplied for some time. Prolonged nutritional deficiency or underlying cause that leads to excessive loss will eventually lead to signs and symptoms of ill-health. The symptoms are more pronounced in severe deficiency while they are milder in marginal forms. However, even in cases of marginal deficiency, health problems can arise. The general signs and symptoms include:
- Loss of appetite
- Weight loss
- Poor immunity with an increased for infections such as malaria, pneumonia and others.
- Corneal clouding
- Deteriorating vision
- Eye disorders
- Skin disorders
- Loss of taste
- Hair loss
- Poor sexual maturation
- Poor wound healing
- Mental fogginess
- Poor growth and development
Since these signs and symptoms can be due to other causes, a detailed history, examination, and relevant laboratory investigations should be carried out to confirm or rule out zinc deficiency.
Laboratory tests are not very reliable for assessing the state of zinc in the body. The history and the risk factors for zinc deficiency are considered together to decide whether supplementation is needed or not.
Groups at risk of zinc deficiency
These are people who have inadequate nutritional zinc availability (either due to poor intake and or poor absorption), those with increased loss, and those with increased demand for zinc. These include:
- Those with persistent diarrhea
- Those who have had certain gut surgeries
- Those with malabsorption syndrome
- Chronic diseases such as kidney, liver, and blood disorders such as sickle cell
- Pregnant mothers
- Nursing mothers
- Exclusively breastfed older children
- Those aged over 65 years
- Those using medications that inhibit or accelerate the loss of zinc
- This is due to the avoidance of animal sourced zinc which is usually more biologically available. The consumption of larger amounts of leguminous foods also affects the availability of zinc. Legumes contain phytic acid which is known to bind and inhibit zinc availability.
Good meal planning can help vegetarians to avoid deficiency issues. Nutritional supplements (discussed below) are also a good way of closing this potential nutritional gap.
Sources of zinc
Zinc is available in many foods. Some foods however, have higher amounts which make them good sources. Plant foods rich in zinc include:
- Baked beans
- Cashew nuts
- Pumpkin seeds
- Peanut butter
- Sunflower seeds
- Chia seeds
This is another source of zinc. In most cases the zinc is one of the ingredients in a multivitamin and multi-mineral supplement. Compare the product here. There are various preparations that include:
- Zinc gluconate
- Zinc citrate
- Zinc oxide
- Zinc picolinate
These preparations vary in how zinc is absorbed. Studies suggest that picolinic acid enhances zinc absorption. It is important to check the type of zinc in a supplement. Zinc oxide is the least absorbable among the common nutritional zinc compounds.
Health benefits of zinc
Extensive research has established the many health benefits of nutritional zinc. These include:
- Supports the immune functions. One of the areas that this has been shown to be the case is in the production of white blood cells. These are part of the body’s disease fighting mechanisms.
- Supports better wound healing
- Reduces the risk or severity of diarrhea in susceptible or afflicted persons.
- May reduce the duration of the common cold
- Reduces risk of age-related macular degeneration
- Supports healthy pregnancy and delivery of healthy babies
- Supports normal growth and development
- Supports good neurological development and mental functions
The dosage of zinc varies when used for the treatment of specific health conditions. For normal health maintenance, the recommended daily allowance (RDA) is as follows:
Recommended dose per day
Infants 7-12 months
Children 1-3 years
Children 4-8 years
Children 9-13 years
Adolescents 14-18 years
Adults 19 years and above
11mg (Males) 9mg (Females
11mg (Males) 8mg
18 years and below 12mg
19 years and above 11mg
18 years and younger 13mg
19 years and above 12mg
Interaction and safety
Zinc toxicity can occur if high doses are taken. It is advisable to stick to the recommended doses as per the supplement manufacturer’s guidance. When used for the treatment of a disease condition, the dose prescribed by the doctor should not be exceeded. Basic is a nutritional product that offers only 50% of zinc’s RDA. At this level even where you get zinc from food sources, the likelihood of side effects due to excess intake is unlikely.
Zinc interacts with some vitamins and minerals. There are also medications that can affect the availability of this nutrient.
- Prolonged large doses of zinc prevent copper availability to the body
- Prolonged use of iron supplements can impair zinc availability to the body
- High calcium doses in laboratory studies impair zinc availability in study animals
- Folate bioavailability is increased by zinc
- Vitamin A functions are enhanced by zinc availability
If you are on any medications, talk to your doctor and confirm how the medications could interact with the zinc supplements you are taking.
Nutritional supplements are not made equal. Always insist on quality of the supplement and the reputation of the manufacturer. For example, start here and see what qualities of a good product are.
For detailed information on other nutrients that works together with zinc for overall health, go here.
“Front Matter." Institute of Medicine. 2001. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: The National Academies Press. doi: 10.17226/10026.
World Health Organization and United Nations Children Fund. Clinical management of acute diarrhea. WHO/UNICEF Joint Statement, August, 2004
Oregon State University. (2009, September 17). Zinc Deficiencies A Global Concern. ScienceDaily. Retrieved October 17, 2017 from www.sciencedaily.com/releases/2009/09/090917115700.htm
Hambidge M. Human zinc deficiency. J Nutr. 2000;130(5S Suppl):1344S-1349S