Zinc is an all-important mineral that your body needs. While it is found in a variety of foods, this nutrient is also often taken as a supplement to ward off illness and keep the body functioning optimally. Yet taking too much could expose you to the risk of side effects that range from the uncomfortable to the potentially life-threatening.
Your Body Needs Zinc For Normal Growth, Reproduction, And Immune System Health
Zinc is an essential trace mineral second only to iron in concentration in the body. Your immune system, growth, reproduction, blood clotting, thyroid function, insulin function, and even smell, taste and sight depend on the availability of adequate zinc in the body.1 Not getting enough zinc could expose you to the risk of skin problems, appetite loss, slowed wound healing, immune disorders, and mental lethargy. In growing children, it can cause growth failure and impact gonadal development in boys.2
You can increase dietary intake of zinc by consuming some of the foods that are rich in the nutrient.3 Oysters, red meat, poultry, some seafood like crab and lobster, whole grains, beans, nuts, and dairy are all good sources. People who don’t get enough through diet may turn to supplements. With supplements, however, you will need to be extra cautious about how much you consume. Because, as you will see, too much zinc can create a host of problems of its own.
Side Effects Range From Fever And Fatigue To Vomiting And Dizziness
Here’s a quick reference list of the side effects people typically experience. While some of these may occur as an adverse reaction to zinc supplements, they are mostly linked to excessive use. When you take a lot of zinc at doses higher than recommended, it is potentially dangerous and can cause some problems that may manifest soon after consuming them. These may become ongoing issues if intake is sustained at high levels.4 In the next sections, you will also find out more about the more problematic as well as long-lasting effects.
- Fever
- Fatigue
- Stomach pain
- Vomiting
- Nausea
- Diarrhea/stomach upset
- Metallic taste in the mouth
- Drowsiness
- Dizziness
- Headache
- Loss of muscle coordination
- Alcohol intolerance
- Hallucinations
- Anemia
- Coughing5
Can Alter Taste Perception And Cause Nausea
A rather unpleasant side effect of having a lot of zinc is that it can cause your taste perception to be altered. For instance, in one study, researchers found that zinc lozenges used to treat the common cold can bring on nausea and a change in your taste sensations.6 Nausea and vomiting are not uncommon for high levels of zinc intake as well. People also describe a metallic taste in the mouth after taking zinc supplements.7 Severe nausea has even been reported in one instance, within just 30 minutes of taking the equivalent of 570 mg of elemental zinc.8
May Inhibit Immune System Function
Zinc in recommended amounts can support immune function. Unfortunately, in excess it has been known to cause the secretion of proinflammatory cytokines, signaling proteins that increase inflammation. It may also inhibit the function of your immune system by limiting the activity of T cells, white blood cells/lymphocytes that have a central role in your body’s immune system.9
Can Raise Prostate Cancer Risk
High levels of zinc intake as supplements could even influence prostate carcinogenesis and may as much as double your risk of prostate cancer, according to some researchers.10 The study looked at responses from nearly 47,000 men studied over a 14–15 year period. No tangible link was found between prostate cancer and dietary zinc; modest supplement usage in the short term also did not seem to affect risk levels. However, high dose supplement intake and use over a prolonged period significantly raised risk.11
- Zinc supplements (of any amount) for 10 or more years increased risk of advanced prostate cancer by 2.4 times.
- Taking supplements of over 100 mg a day increased risk 2.3 times.
Can Cause Loss Of Smell
If you inhale zinc through your nose via nose gels, you could face a permanent loss of smell. In one report, the initial result of deeply inhaling an intranasal gel with zinc was a burning sensation that lingered for several hours. After this, a loss of sense of smell (anosmia) was reported in patients with this condition.12 And that’s why the US Food and Drug Administration urges consumers to avoid nose sprays containing zinc.
May Lead To Decreased Copper Absorption And Anemia
A copper deficiency has been widely reported among patients taking treatments involving large doses of zinc supplements. Copper and zinc have what is called a competitive absorption relationship – in other words, they’re fighting it out to bind to the same protein. When you take in a lot of zinc, copper’s ability to bind becomes weaker and causes a drop in its absorption in the body.13
Studies have shown this effect kicking in at just 60 mg of zinc a day, 50 mg of which came from a supplement and the balance from the diet.14 With less copper absorption, you open yourself up to the risk of anemia due to lower hemoglobin. Copper is vital for its production, after all. This problem seems to potentially occur at doses greater than 40 mg.15
Having too much zinc might even cause the levels of the bad low-density lipoprotein (LDL) cholesterol in the body to rise.16 According to some reports, taking 150–450 mg of zinc may reduce levels of the good high-density lipoprotein (HDL) cholesterol in your body.17 In one study, it reduced HDL by as much as 25 percent below baseline values (the minimum levels you should have), leading researchers to suggest it could even be atherogenic, causing fatty deposits in your arteries.18
Limit Zinc Intake To Recommended Levels
The recommended daily intake of zinc is 11 mg for adult males and 8 mg for adults women. During pregnancy and lactation, women may need to take up to 11 to 12 mg a day. The upper limit you should avoid crossing – and one where side effects start to appear – is around 40 mg or higher.19
Zinc’s topical use and oral doses of under 40 mg are believed to be likely safe for most people. But you will need to see how your body responds to smaller doses to check for any reactions or adverse side effects first. Always consult a doctor before you start taking zinc supplements because, as you now know, the downside of having too much can be just as bad or worse than a zinc deficiency.20 Symptoms like gastrointestinal distress have been known to happen at doses just slightly higher than supplemental zinc – 50 mg to 150 mg, underlining the need to stay within the tolerable upper limit.21
Excessive Intake Is Bad, But Supplements Pose Greater Risk
The tolerable upper limit of zinc – around 40 mg/day – refers to the maximum you should consume regardless of whether it is from food, fortified foods, supplements, or even water. Consuming zinc from food itself poses no major problem or side effects because you won’t usually have more than this upper limit in a normal diet. But when you end up having too much overall from supplements as well as food or a combination of both, it could suppress the immune response, adversely impact cholesterol levels, lower copper in the body, or lead to other side effects just described.22
Pregnant Women, Lactating Mothers, People With HIV/AIDS Or Menke’s Disease: Strictly Avoid Excessive Zinc Intake
While having too much zinc is potentially problematic for anyone, there are some who need to especially vigilant:
- Pregnant women and breastfeeding mothers should stick with the recommended range because not enough is known about the impact during pregnancy. It is considered possibly unsafe in breastfeeding moms and likely unsafe for pregnant women when taken in high doses.23 There have been reports of premature deliveries and one stillborn baby linked to excessive zinc intake but the evidence is sketchy at best.24
- Those with Menke’s disease are especially vulnerable due to their already compromised copper absorption and should avoid heightening the problem through zinc intake.25
- Anyone with HIV/AIDS should take zinc with caution because there have been suggestions that it may reduce survival time.26
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