Ask the Dietitian: What to Think About Zinc

In the last of our seven-part series on minerals, we speak with Sheah Rarback about zinc. Sheah is a registered dietitian nutritionist with the University of Miami Health System.

UMiami Health News: Why do we need zinc?

Sheah Rarback: Zinc is involved in so many different processes in the body, including DNA. It helps cells function, processes protein, heals wounds and helps us grow and develop. It’s also essential to healthy vision, which is why it’s found in AREDS supplements recommended for people with macular degeneration. Zinc also affects our ability to taste and smell.

Probably best known for boosting immunity, this mineral is a common ingredient in many over-the-counter (OTC) cold remedies.

UMHN: Speaking of cold remedies, does zinc ward off colds or just shorten the duration if you already have a bug?

SR: Zinc doesn’t prevent colds, but may shorten the duration. If you take a cold remedy containing this mineral, follow the directions. Typically, people consume several lozenges in a row to soothe a cough or scratchy throat. Doing that with a lozenge containing zinc could cause nausea and vomiting. And, by the way, there’s no evidence that nasal sprays with zinc stop a cold. Back in 2009, the FDA warned that certain zinc-containing nasal sprays and gels caused loss of smell. Those products were recalled, but just because something is sold over-the-counter doesn’t mean you can use it indiscriminately.

UMHN: Generally, do we get enough of this nutrient in food? Are there situations when you recommend supplements?

SR: Zinc-rich foods are common, so deficiencies aren’t an issue in the U.S. However, some health conditions do reduce your ability to absorb or cause you to excrete too much of this mineral:

  • Gastrointestinal surgery and digestive disorders
  • Kidney disease
  • Liver disease
  • Sickle cell disease
  • Diabetes
  • Cancer
  • Chronic diarrhea
  • Alcoholism
  • Taking certain antibiotics, arthritis medications and diuretics
  • Pregnancy and nursing
  • Age: adults age 60+ are more likely to have zinc intakes below the average daily requirement

Also, vegetarians and vegans could lack zinc because they typically eat more legumes and whole grains. These foods contain antioxidant compounds which interfere with zinc absorption.To solve this, simply soak beans, grains and seeds for several hours before cooking and eat leavened versus unleavened grain products. Also, people who follow a plant-based diet also miss out on the most easily absorbed form of this mineral, which is found in meat.

If you take medications that interfere with zinc absorption (Cipro, tetracycline or Rheumatoid Arthritis (RA) drugs), eat two hours before taking your medication or wait four to six hours after a meal to take medication.

UMHN: What does a zinc deficiency look like?

SR: Signs include stunted growth, compromised immunity, appetite loss, slow-healing wounds, hair loss, diarrhea, weight loss, lethargy, impotence and delayed sexual maturity. It’s difficult to detect these deficiencies in a blood test. When I work with at-risk patients, I review their eating habits to see how much dietary zinc they’re getting. I then recommend foods that fit their lifestyle and preferences. I may also recommend a multivitamin with zinc. The truth is, if your diet is low in this mineral, it will be low in other nutrients. That’s why I always consider the diet first.

UMHN: Is it possible to overdose on this nutrient?

SR: Yes, if you consume too many lozenges containing zinc. Besides nausea and vomiting, you could experience appetite loss, headaches, cramps or diarrhea. Don’t use more than what’s recommended. If you take an AREDS formula plus a multivitamin, read the labels. Both supplements may contain zinc, putting you at risk of overload.

UHMN: Which foods help maintain healthy levels of this mineral?

SR: These foods contain the highest amounts of zinc:

  • Shellfish including: cooked oysters (avoid the health risks of raw oysters), lobster, crab
  • Poultry (dark meat contains more zinc than white meat)
  • Beef
  • Pork
  • Fortified breakfast cereal
  • Oatmeal
  • Baked beans
  • Chickpeas
  • Kidney beans
  • Dairy products
  • Cashews
  • Almonds
  • Green peas
  • Flounder or sole

The Takeaway: Zinc is a multifaceted mineral that boosts immunity, improves eyesight in people with macular degeneration and helps us grow and develop normally. Deficiencies are rare, but if you have a chronic disease, are pregnant or nursing, over age 60, take antibiotics, diuretics or RA medicine, have a registered dietitian evaluate your diet. Vegetarians are more prone to deficiencies — solve this by soaking beans, nuts and seeds a few hours before cooking or eating. You might lack sufficient levels of this and other nutrients if you’re lethargic, have no appetite, hair loss, slow-healing wounds or get sick frequently. On the opposite end of the scale, you may overload on zinc if you take AREDS eye vitamins and zinc supplements or if you eat too many zinc-infused lozenges. As always, your best bet to maintain sufficient levels of vitamins and minerals is eating a healthy, balanced diet.

Q&A compiled by Nancy Moreland, a contributing writer for UMiami Health News.