Not all zinc forms are created equal, especially when it comes to immunity! The primary goals of zinc supplementation are to absorb it as efficiently as possible and of course, to make sure it actually boosts immunity and gut health.
The secondary goal (for most people) is to avoid digestive disturbances, which are common with cheaper forms of zinc.
The two are related: higher absorption means less excess zinc passing through the body and causing uncomfortable side effects.
We'll break down what the research says on each of the most commonly-used forms of zinc. We've listed them from the very best form of zinc (so even if you don't choose our recommended zinc, here, you can still make sure you're not wasting your money or choosing an irritating zinc!):
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Zinc Picolinate
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Zinc Bisglycinate
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Zinc Acetate
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Zinc Gluconate
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Zinc Citrate
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Zinc Sulfate
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Zinc Oxide
Zinc Picolinate: Best for Improving Levels & Least Irritating
Zinc picolinate is zinc bound with picolinic acid, an acid naturally found in the body. In a double-blind, four-period trial comparing zinc picolinate, citrate, and gluconate, it was found that hair, urine, and red blood cells levels rose only with the use of zinc picolinate meaning that picolinate is the only of the three that was measurably absorbed.
Zinc Picolinate is the best form of zinc for absorption overall. The four charts below show the results of the study, "Comparative absorption of zinc picolinate, zinc citrate and zinc gluconate in humans".
Zinc Hair Levels (ppm) After 4 Weeks: Comparison of Picolinate, Citrate, and Gluconate
Zinc Urine Levels (ppm) After 4 Weeks: Comparison of Picolinate, Citrate, and Gluconate
Zinc Red Blood Cell Levels (ppm) After 4 Weeks: Comparison of Picolinate, Citrate, and Gluconate
Zinc Blood Serum Levels (ppm) After 4 Weeks: Comparison of Picolinate, Citrate, and Gluconate
Zinc Bisglycinate: Best Absorbed by Blood
This form of zinc is a chelate, meaning it is bound to another (typically organic) molecule. In this case, the zinc is bound to glycine, an amino acid. The benefit of chelating is that it doesn't compete with other minerals in the absorption so it is more readily absorbed by the digestive tract.
One study showed 43% higher absorption of zinc bisglycinate compared with zinc gluconate. Another study compared the absorption of zinc picolinate, zinc gluconate, zinc bisglycinate, and zinc oxide.
After four hours, both blood plasma levels and red blood cell levels of zinc were highest from participants taking zinc bisglycinate, followed by picolinate, gluconate, and the lowest from oxide.
This doesn't necessarily mean that zinc bisglycinate is better, but rather that it elevates blood zinc levels more in the short term. The study mentioned in the section above is a better reference as it's over four weeks vs. four hours in this study.
Longer-term studies between bisglycinate and picolinate will make the best form of zinc for absorption clear, but the two studies done so far look very promising for zinc bisglycinate.
Zinc Acetate: Best Lozenge Zinc
Where zinc gluconate (below) is good, the citric acid-based zinc acetate is even better. A meta-analysis comparing acetate and gluconate lozenges at various dosages found that zinc acetate reduced common cold duration by 40% and zincgluconate reduced it by 28%, meaning acetate was far more effective.
For cold lozenges specifically, zinc acetate is the best form of zinc.
Zinc Gluconate: Shortens Colds
Zinc gluconate (made with gluconic acid) is most commonly found in lozenges (in fact, you'll almost only find zinclozenges with gluconate or acetate). It's most effective when in syrup or lozenge form as this allows longer direct contactwith the virus in the throat.
One review of 496 schoolchildren found that on average, their common cold duration was shortened from 9.0 to 7.5 days by taking zinc gluconate lozenges. Another study found it ineffective at shortening the duration.
If you're taking zinc to treat or sooth an existing illness rather than to prevent one, this can be a good option (although asmentioned in the zinc picolinate and bisglycinate sections above, it isn't the best form of zinc for absorption so we don'trecommend it for long-term supplementation, especially since poorly-absorbed zinc can cause serious irritation and sideeffects!).
Zinc Citrate: Moderately Well Absorbed
A comparison between zinc citrate (also from citric acid), gluconate, and oxide showed that zinc citrate was absorbedabout as well as zinc gluconate, and better than zinc oxide.
Zinc Sulfate: Reduces Severity (But Not Duration) of Colds
Zinc sulfate is nearly the only form you'll find in liquid zinc (with a few notable exceptions!) and it's the cheapest form of zinc. Unfortunately, we don't have a lot of good things to say about this one as it's not chelated like some of the others so the body doesn't absorb it well. It's a zinc salt that can cause stomach irritation as it competes with (and significantly decreases) intestinal calcium absorption.
There isn't a lot of research available that directly compares zinc sulfate to other forms of zinc (especially when it's specific to immunity) but we do know that compared to zinc oxide, zinc sulfate decreases iron absorption. It's been shown to reduce severity but not duration of cold symptoms (but was not compared to any other form of zinc in the study).
One of the few comparison studies between sulfate and a chelated zinc was done on broiler chicks and showed that chelated zinc was more bioavailable and effective. Overall, it seems that zinc sulfate isn't the best form of zinc.
Zinc Oxide: Effective Topically
When compared to other forms of zinc, zinc oxide just doesn't measure up. However, it can be used topically for a varietyof skin ailments (like eczema) and of course, makes a great mineral sunscreen.
Zinc Dosage
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Age
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Male
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Female
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0-6 Months
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2 mg
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2 mg
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7-12 Months
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3 mg
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3 mg
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1-3 Years
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3 mg
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3 mg
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4-8 Years
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5 mg
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5 mg
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9-13 Years
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8 mg
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8 mg
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14-18 Years
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11 mg
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9 mg (12 mg if pregnant, 13 mg if lactating)
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19+ Years
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11 mg
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8 mg (11 mg if pregnant, 12 mg if lactating)
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Bottom Line
There are a lot of zinc supplements out there and they all claim to do the same thing, but there's a huge variation in the effectiveness and absorption of different zinc forms. Many people experience digestive discomfort after consuming zinc supplements, and this is usually a sign that they're either taking too much or they're taking a poorly-absorbed form of zinc.
It's important to supplement with a moderate amount (too much can do more harm than good) but it's also important to pay attention to what type of zinc is listed on the label to find the best form of zinc for your needs.
If you're consuming a liquid or softgel form of zinc, you'll benefit the most from zinc picolinate or zinc bisglycinate (or a combination of the two, like Why Not Natural's found here). The best form of zinc (picolinate) is harder to come by in a lozenge form, but zinc acetate is the most helpful when it comes to shortening a cold.
Follow the zinc supplementation recommended dosage carefully- this means if you're taking lozenges, you don't want to consume multiple servings of a highly concentrated dose. Zinc can be toxic in high amounts, but it does also need to be consumed daily.
There are other forms of zinc available besides those listed in this article, but they may not be as thoroughly studied so use with caution.
No matter which form you choose, always consult with your doctor your personal best form of zinc and take a part of a complete diet.
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Reference (others linked directly)
*Comparative absorption of zinc picolinate, zinc citrate
and zinc gluconate in humans
S. A. Barrie, J. V. Wright, J. E. Pizzorno, E. Kutter and P. C. Barron