How much zinc do I need?

Wednesday, September 12, 2018. Author Dr Haran Sivapalan

Foods rich in zinc

Shellfish, a hearing aid battery and a US penny manufactured after 1982. What do these three items have in common? They all contain zinc – a trace metal that is essential for all living organisms.

Despite the ubiquity of this mineral in living organisms, zinc’s importance in the human body was only relatively recently uncovered. It wasn’t until 1961 that the first clinical case of zinc deficiency was diagnosed: a syndrome characterized by delayed growth, intellectual disability and an impaired sense of taste and smell.

While such severe zinc deficiency is extremely rare, mild or ‘marginal’ zinc deficiency is relatively common particularly in the developing world, where it affects around 2 billion people. Failing to get enough zinc in your diet is linked to poorer immune function, worse blood sugar control, and low testosterone levels.

Currently, the Recommended Daily Intake of zinc is 8mg for females, 10-12mg for pregnant or lactating females, and 14-15mg for males.

Let’s take a more in-depth look at why it’s important to hit these target intakes and how can you can achieve them.

Why is zinc important?

On a molecular level, zinc is key to the function of over 300 enzymes; the biological molecules that sustain life by speeding up various chemical reactions in the body. Zinc also plays a vital role in gene expression, the process by which genes are activated to produce the proteins they encode. Finally, zinc is fundamental to cell signaling, the complex system of chemical communication between cells.

As a result of all these vital molecular functions, zinc supports several broader biological processes, including cell division, cell growth, maintenance of healthy nerves, strengthening of the immune system and regulating the release of hormones, including the sex hormones, estrogen, progesterone, testosterone, and insulin.

Zinc and insulin

Zinc is crucial to the production, storage, release and action of insulin – the hormone that allows sugar (glucose) in our bloodstream to be taken up and used by cells for energy.

As you may remember from high-school biology lessons, insulin is secreted by an organ called the pancreas. More specifically, insulin is made by cells in the pancreas termed ‘beta cells.’  Within these beta cells, insulin is stored in small reservoirs, called vesicles, which is where zinc plays an important role. Zinc gets transported into these vesicles, using an aptly-named zinc-transporter protein, (encoded by your SLC30A8 gene, which we test at FitnessGenes), where it helps to bind to insulin. 

Interestingly, the G allele of the SLC30A8 gene is associated with poorer blood sugar control and risk of diabetes, an effect that may be due to changes in the secretion and function of insulin.

After insulin is secreted by the pancreas, zinc also enhances insulin’s effects, by facilitating the uptake of glucose into muscle and other tissue. By contrast, a deficiency of zinc is linked to less sensitivity (or more resistance) to the effects of insulin making it more difficult for tissues to absorb glucose, leading to higher levels of glucose in the blood and, ultimately, an increased risk of diabetes and obesity.

Keeping in mind the importance of zinc to insulin function and glucose metabolism, studies demonstrate that zinc supplements can improve control of blood sugar levels in people with diabetes, obesity and other metabolic diseases.

Zinc and the immune system

Your white blood cells that fight infection, either producing antibodies or engulfing foreign cells, are also heavily reliant on zinc. Consequently, when you are ill with a bacterial or viral infection, you may temporarily require more zinc. Conversely, people who are zinc deficient may be more susceptible to certain infections. 

From a therapeutic perspective, some studies suggest that zinc supplements can help reduce the duration of common colds, but the evidence is mixed. Even when you’re not ill, however, you’ll need to ensure you get enough zinc through your diet to support a healthy immune system.

Zinc and testosterone

There is some evidence to suggest that zinc supplements can help to boost testosterone levels, but here’s the kicker: you must already be zinc deficient to reap this benefit. If your zinc levels are healthy, increasing your zinc intake alone will not elevate your testosterone levels. 

Am I at risk of zinc deficiency?

Several genes influence whether or not you are at risk of zinc deficiency, and whether you should up your zinc intake. As mentioned before, certain people with the G allele of the SLC30A8 gene are at risk of higher blood sugar levels and may benefit from upping their zinc intake for better glycemic control. If you’re a FitnessGenes member, you’ll find your zinc requirement under your Personal Insights.

If you’re vegetarian, you may also need more zinc, particularly if your diet is mainly focused around whole grains and beans because these foods contain high amounts of phytic acid (or phytate), which binds and lowers your absorption of zinc.

Alcoholics are at a higher risk of zinc deficiency, as excessive, long-term alcohol intake is linked to increased excretion of zinc in the urine and lower stores of zinc in the liver.

What foods are good sources of zinc?

Shellfish, lean red meats, poultry, eggs, legumes, nuts, and seeds are excellent sources of zinc. Below is the zinc content of various foods:

Oysters (cooked): 27-50mg per 6 oysters
Beef: 3.7-5.8 mg per 3 oz.
Turkey 1.0 mg per oz.
Baked Beans: 1.8-5.8 mg per cup.
Chicken (dark meat): 1.6-2.7 mg per 3 oz.
Cashews: 1.6mg per oz.
Chickpeas: 1-2.6mg per cup
Milk: 1.0mg per cup (8fl oz).

Zinc supplements

If you’re struggling to get enough zinc through your diet alone, it’s worth taking a supplement. A low dose of 5-10mg per day is ideal for topping up any shortfall from your whole-food consumption. For those with a higher risk of zinc deficiency, a higher dose of 25-45mg per day is recommended. Generally, it’s best to take these supplements in the morning.

I hope you enjoyed this blog.  Please read my other articles and let me know if you have any questions.

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