By Roberta H. Anding, MS, Baylor College of Medicine and Texas Children’s Hospital
Edited by Kate Findley and proofread by Angela Shoemaker, Wondrium Daily
Zinc is currently a popular supplement on the market. It plays many important roles in the human body, but Professor Anding explains why you should exercise caution when taking zinc supplementally.
Mineral Domino Effect
Before we explore the facts about zinc, understand that many of us think in terms of minerals by themselves—for example, vegetarians might take iron supplements because they feel they’re lacking in that particular mineral. In fact, though, minerals interact with one another, which we must consider when taking supplements. Zinc, iron, and selenium, in particular, can be thought of as dominoes.
“When you knock down one, there’s going to be a consequence to be paid down the way,” Professor Anding said.
Anding experienced this domino effect firsthand with a dilemma she faced in her clinical practice. She had a young person come in who was being evaluated for metabolic syndrome and diabetes.
In the discovery process, they saw that this individual’s HDL (high-density lipoproteins, also known as “good cholesterol”) was much lower than anticipated. Anding prescribed exercise to raise the HDL, but it kept going in the wrong direction.
“Little did we know that the mom was deciding that it was a really good idea, because it was cold and flu season, to take a whole lot of zinc,” Professor Anding said.
Going back to the domino analogy, it is possible to have too much of a good thing. Zinc is important in the maintenance of normal HDL cholesterol, but too much can actually drive down your HDL levels.
Zinc Facts and Functions
Over half of the body’s zinc supply is found in muscle tissue, and it’s also found in bone, eyes, prostate gland, testes, skin, and kidneys. Zinc is an essential mineral for supporting over 100 enzymes, strong cell membranes, and wound healing.
Thus, if you’ve had surgery, your zinc requirements will go up because you now have an increased need for wound healing. Zinc is also needed for tissue growth and repair, protein synthesis, DNA and RNA maintenance, blood clotting, and taste perception.
“Interestingly, in my clinical practice, oftentimes, one of the first signs that I see is when people tell me, ‘My food doesn’t taste like anything’ or ‘My food has a metallic taste to it,'” Professor Anding said. “That could actually be a zinc deficiency.”
Zinc is also needed in bone mineralization, healthy thyroid function, normal cognition, normal fetal development, and pubertal growth, and thus, deficiencies can present many health issues. You may be wondering, then, if you would benefit from taking zinc as a supplement.
As Professor Anding’s clinical example illustrates, taking zinc lozenges for colds can lead to unintended consequences, and research has shown conflicting results. Zinc gluconate may be the best form in lozenges, but a recent Cochrane database review showed no significant benefit from the use of lozenges.
Zinc supplementation may offer mild protective effects against age-related macular degeneration (AMD). Research from the 2001 Age-Related Eye Disease Study reported that 80 milligrams of zinc, which is a significant dose, plus antioxidants and copper, slowed the progression of AMD.
This is an example where the science is suggesting that more than what’s needed might be beneficial if you’re in that high-risk category. Supplemental zinc may also prove beneficial to the elderly, as zinc deficiency can be more common in this population. Keep in mind, though, that like iron, zinc can be toxic when taken in excess.
Bioavailability
The body absorbs anywhere between 15% and 40% of dietary zinc. Excess intake of iron or copper can interfere with zinc intake, showing how iron and zinc can compete with each other for absorption.
Two studies have shown that a high-calcium diet and calcium supplement decreased zinc absorption in postmenopausal women. Thus, if you’re postmenopausal and taking additional calcium to prevent bone disease, you can actually decrease your zinc absorption.
Medications can also have an impact on zinc status. Many of the high blood pressure medications—ACE inhibitors such as captopril—can interfere with your body’s ability to absorb and utilize zinc.
Oral contraceptives, aspirin, and thiazide diuretics are all medications that can interfere with zinc absorption. Professor Anding recommends reaching out to your pharmacist for advice in this area.
This can also work the other way, though, in that zinc can interfere with medications. We’ll explore this particular fact about zinc, along with dietary sources of zinc, in tomorrow’s article.
This article was edited by Kate Findley, Writer for Wondrium Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for Wondrium Daily.
Professor Roberta H. Anding is a registered dietitian and Director of Sports Nutrition and a clinical dietitian at Baylor College of Medicine and Texas Children’s Hospital. She also teaches and lectures in the Baylor College of Medicine’s Department of Pediatrics, Section of Adolescent Medicine and Sports Medicine, and in the Department of Kinesiology at Rice University.
