Zinc is an essential trace mineral and is one of the most abundant to be found in the body. It is naturally found in some foods, added to others and also available as a dietary supplement. You have approximately 2-3g with around 60% is in the muscles that support your skeleton and 30% is in the bones. So if nothing else zinc plays an important part in keeping you upright. The remaining 10% is found in the teeth, hair, nails, skin, liver, leukocytes (white blood cells), prostate, sperm and testes.
So what are some functions of Zinc in the body?
Zinc makes things happen
Zinc is used in by over 100 different enzymes in body, that are involved in the chemical processes of building things that the body needs or breaking down stuff that it doesn’t want. Here are a couple of examples.
- Thyroid function – Zinc is used to make the hormone (TRH) that signals the thyroid to make thyroid hormones. It converts the protein we eat into amino acids, including tyrosine which powers the thyroid hormone production. Finally it is involved in the making of T3 the active form that is used in the muscles
- Formation of bone – Zinc is used by enzymes in the production of collagen and alkaline phosphatase (ALP), which are important for bone formation. It is also used to make calcitonin, a hormone that inhibits the breakdown of bone.
- 30% of the zinc found in a cell is found in the nucleus. This makes sense as it is very involved with DNA and the replication of cells and proteins needed by the body.
Zinc is important for immunity
Zinc is very important in the first line of defence in our bodies. This first line is represented by physical barriers, such as the skin and mucous membrane linings inside the body. Zinc is found in the mucous secretions of the respiratory system and on the surfaces of lungs and throat. It has an antimicrobial effect, so helps to kill inhaled bacteria and viruses before they get chance to take hold. Zinc is also secreted in the saliva and the mucous membranes of the digestive system to kill any ingested invaders.
However, it is not just supporting the barriers that makes zinc important for immunity. Zinc also supports white blood cell production and the activating of the B and T cells required by the immune system to fight viruses and bacteria.
Zinc is a great antioxidant
It appears that zinc protects our cell membranes against the oxidative damage that can be caused by other metals in the body, such as iron or copper. It also forms part of an important antioxidant in the body called superoxide dismutase. This is used by the liver to bind toxins that are the removed from the body.
What are some common zinc deficiency signs?
- Poor sense of taste or smell
- Stretch marks
- White spots on the nails
- Poor growth – mostly in children
- Hair loss
- Poor wound healing
- Chronic and severe diarrhoea
- Poor immunity
- Poor night vision
- Dry skin
What can cause deficiency?
- Phytates that can be found in wholegrain, rice, corn and legumes can reduce absorption. This means that strict vegetarians and vegans are at risk of low zinc as these foods often contribute highly to their diet.
- Zinc absorption is impaired by iron, copper and calcium
- Oral contraceptive
- High perspiration – so athletes can lose a lot in sweat
- Diarrhoea – people with persistent diarrhoea can become deficient. This can include people with inflammatory bowel disease and other digestive conditions with impaired absorption.
- Diabetes, liver or kidney disease
- Caffeine and high alcohol intake
- Antacids and antibiotics
- Stress – zinc decreases and copper increases in stress
Testing for Zinc deficiency
- Serum zinc – Measures zinc in the blood stream
- Hair Testing – Zinc is one of the minerals that can be tested through hair analysis
- Zinc oral taste test –This test is often done in pharmacies. It works by taking a mild zinc solution into the mouth and assessing by what you can taste. Results are assessed as follows:
Grade 1 (Poor zinc status) - No specific taste or sensation. Just like water
Grade 2 ((Mild deficiency) – No initial taste, but gradually starts to taste dry, mineral like, furry or sweet
Grade 3 (Good zinc status) – A definite taste straight away that intensifies over time
Grade 4 (Optimal zinc status) – Strong unpleasant metallic taste immediately that does not go away for ages
Be aware that too much zinc is also a bad thing. Zinc toxicity symptoms include nausea, vomiting, loss of appetite, abdominal cramps, diarrhea and headaches. Ensure you get yourself tested at your local pharamcy - use the pahramcy locator on the right hand side to find the local store near you!
What foods are high in Zinc?
- Animal proteins such as chicken, lamb, beef, eggs
- Fish and seafood especially oysters
- Vegetarian sources include nuts, legumes, wholegrains, miso, tofu, brewer’s yeast, mushrooms, green beans, seeds (like pumpkin, sesame), green leafy vegetables, avocado
- Sea vegetables like kelp and spirulina
Practical applications of zinc
As one of the deficiency signs of zinc is poor night vision, you can see it is important for eye health. Locally its antioxidant actions help to protect the eye from age related macular degeneration caused by oxidative damage. Zinc is also needed by the liver to synthesise vitamin A, which is very important for good eyesight. It is also part of the mechanism to transport it in the blood to the eye area.
Zinc found in the skin has antioxidant properties that provide UV protection. Due to its importance in the production of collagen it is important for wound healing and makes it important for dry and allergic skin conditions. It is very beneficial in the treatment of acne. This is due to its role in the regulate oil glands and also because of its anti-inflammatory actions in the skin. If you think of teenage boys, needing lots of zinc for growth and sexual development, with acne, zinc is perfect.
Traditionally oysters are known as an aphrodisiac and this may be due to their high zinc content. Since zinc is shown to be stored in the prostate, sperm and testes, you can imagine it must be beneficial to men’s health. Research has shown that supplementation of zinc can increase sperm count, motility and morphology.
With regards to prostate health zinc can help to reduce the chances of prostate enlargement. This is important for men over 50, as they are at increased risk of BHP (Benign prostatic hyperplasia).
Mood and Brain health
Amounts of zinc can be found in the brain and it has been shown to reduce oxidative damage. Oxidative damage of the brain is linked to the progression of some diseases, such Alzheimer’s and Parkinson’s disease.
Regarding mood zinc has a calming effect on the brain and deficiencies can lead to agitation and mood swings. Zinc can be depleted by stress and copper is increased. The balance of these two minerals is important for balanced mood. Low levels of zinc have been found in those with major depression and there is a hypothesized link between zinc and serotonin uptake in the brain. There have also been studies showing benefits for children with autism and ADHD. There are also links between low zinc and post natal depression.
Zinc is one nutrient you can look at to improve your immune system to try and prevent those ills and chills. There is also data to suggest that if you catch something zinc supplementation can help to move it on much quicker.