What you need to know about zinc

What is zinc? 

Zinc is a trace mineral that is essential for immune function, protein synthesis, wound healing, DNA synthesis, and the production of new cells. Because zinc is not naturally stored in the body, consistent daily intake is important through a healthy and varied diet. 

What are the benefits? 

Zinc plays a role in growth and development and is essential for the normal functioning of the cells and antibodies that make up your immune system. Mild to moderate degrees of zinc deficiency can impair the normal functioning of your immune system, and can increase the susceptibility to a variety of viruses, bacteria and bugs.

It also plays a key role in wound healing and skin integrity. This is, thanks to the way it helps to maintain and strengthen the epithelial layers of skin and the mucosal membranes within the skin. 

Zinc is a crucial trace mineral involved in male reproductive health including hormone metabolism, sperm formation and sperm motility. Even short-term dietary zinc depletion may result in a reduction in serum testosterone levels and sperm counts. concentrations, seminal volume, and total seminal zinc loss per ejaculate. 

Zinc foods include seafood, meat, dairy and cereals, legumes, nuts, and seeds.

Food sources

When it comes to dietary intake, the main sources of zinc are oysters, seafood, meat, dairy and cereals, legumes, nuts, and seeds.

Like iron, the body is able to absorb zinc better from animal sources than plant-based proteins, and as a result, those following a vegan or vegetarian diet may need to consume up to 50 per cent more than the recommended amount of zinc daily in order to maintain healthy levels.

This is because a compound known as phytic acid present in whole grains, legumes, nuts, seeds, and other plant-based foods, binds to zinc and blocks it from being absorbed, meaning less is available for the body from such sources. That being said, just because absorption is lower, they are still great sources of zinc. 

How much do you need? 

The amount of zinc you need each day varies by age and gender. 

Children aged 1 - 3 have a recommended daily intake (RDI) of 1 - 3 mg which increases to 4 mg from 4 to 8 years of age and to 6 mg from 9 to 13 years. Once boys reach 14 years their RDI increases to 13 mg per day and for girls it increases to 7 mg.

Adult men require 14 mg per day and for women the RDI is 8 mg. During pregnancy this increases to 11mg per day and during lactation the RDI for zinc is 12 mg.

Signs of zinc deficiency

Because zinc is not naturally stored in the body, not consuming enough zinc increases the risk of deficiency. 

Symptoms of zinc deficiency include:

• a slow functioning immune system, which may show as common cold symptoms
• slow wound healing
• and you might even notice you don't taste and smell flavours as well as you normally would

Considering zinc supplementation? 

Those following a vegan or vegetarian diet may be at a greater risk of zinc deficiency because of the reduced absorption rate of zinc in plant-based foods.

Some people with certain gastrointestinal conditions may benefit from a zinc dietary supplement to prevent deficiency. This is usually related to changes in the way the body absorbs zinc with these conditions. 

Pregnant women usually require larger amounts of zinc due to high fetal requirements, while lactation may also deplete maternal zinc stores. For these reasons, the RDI is higher for pregnant and lactating women.

Iron and zinc can interfere with each other's absorption, so women taking high levels of iron supplements during pregnancy should monitor their zinc levels due to possible impaired absorption. 

If you need more advice or are unsure about your zinc status, please see your health professional before starting supplements. 

Can you take too much? 

The upper level of zinc intake is set to 40mg/day for adults which would be very unlikely to reach with food alone, but may be exceeded with high doses and the incorrect use of supplementation.

Side effects may include nausea if taken on an empty stomach.

This is why mineral supplementation should not replace a balanced diet. They can only be of assistance if the dietary intake is inadequate. If you believe you may be deficient in zinc, always consult your health professional first.

Reviewed by the healthylife Advisory Board December 2021