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Citrate to Sulfate: A Guide to Zinc

By Caitlin Beale, MS, RDN+

Zinc is an essential mineral that plays a part in more than 300 different enzymatic reactions in the body. From protein structure to DNA synthesis, zinc is necessary for many processes in the body to function normally. i It's involved in nutrient metabolism, cognitive function, fertility and reproduction, and bone health. ii iii iv  However, the role most people associate with zinc is its contribution to healthy immune system function.v 4 


Zinc is found in foods like shellfish, pumpkin seeds, meat, and seafood. Still, some studies suggest that certain groups of people may not get enough from their As a result, many turn to supplements to fill in the gaps, but choosing the right supplement can be overwhelming.  


How do you choose, and what form do you need when faced with so many options? This guide will take a closer look at the different forms of zinc so you can find the best choice for your needs. 


Choosing a Zinc Supplement: Start Here 


From pills to lozenges to nasal sprays, one of the first things to consider when choosing a zinc supplement is that certain forms may be better absorbed. You want to ensure that your body can absorb and use the zinc effectively with minimal side effects (some forms of zinc can cause GI upset). vii  


When you take a zinc supplement, you aren't taking zinc alone. Supplemental zinc isn't well absorbed on its own, so it's usually chelated (bonded) to another substance. This process increases the bioavailability of zinc in the supplement, making it more readily available for absorption. Think of it like a helping hand to get the zinc where it needs to go in your body. 


Zinc is often bound to inorganic or organic acids to create different forms, each with varying levels of absorbability and bioavailability. Organic acids tend to be better absorbed than other forms. viii   


Zinc absorption also depends on how much zinc you get in your diet and your zinc status (meaning the body takes what it needs). People with lower intakes may have better absorption rates than those who get more from their diet. 


Healthy proteins, veggies, oils and nuts.


Types of Zinc Supplements 


As mentioned above, zinc bound to organic acid tends to be better absorbed, so these forms are generally recommended over others.Examples of inorganic acids include sulfate and oxide. Examples of organic acids are gluconate, picolinate, acetate, and citrate.  


Let's dive into some of these forms in more detail. 


Zinc gluconate:  


Zinc gluconate, a compound formed by chelating zinc with gluconic acid (an oxidized form of glucose), is a widely used form of zinc. You'll find it incorporated into a variety of supplements, such as pills, capsules, lozenges, and sprays. Studies suggest that zinc gluconate can support healthy immune function. ix x  


Zinc citrate:  


Zinc chelated with citric acid is known as zinc citrate, another popular form of zinc found in dietary supplements. Research supports using supplemental zinc citrate to help maintain healthy zinc levels in the body. It's absorbed at similar rates as zinc gluconate and may be even more bioavailable than some forms of zinc. 7  


Zinc picolinate:  


A type of zinc chelated with an organic acid called picolinic acid (a derivative of the amino acid tryptophan), zinc picolinate is commonly used in supplements for its high absorption rate. Studies suggest that zinc picolinate is bioavailable and can improve zinc absorption in the body. A study comparing zinc gluconate and zinc picolinate found that both forms were well-absorbed, but zinc picolinate had a slight edge over gluconate. xi  


Zinc acetate:  


Zinc acetate is made by adding acetic acid with zinc (acetic acid is the main component of vinegar). Zinc acetate has been extensively studied for its role in supporting healthy immune function in scientific research. 3 10 Comparative studies examining zinc acetate and zinc gluconate in supporting normal immune function have revealed similar efficacy between the two forms. 10 


Zinc sulfate:  


You may have seen zinc sulfate in topical forms to support skin health, like in diaper rash creams, but it's also used in dietary supplements. Zinc sulfate is made by adding sulfuric acid with zinc and may have slightly lower bioavailability than other forms. Aside from being poorly absorbed, zinc sulfate may be more likely to cause stomach upset. 3 


Zinc oxide:  


That white nose and face paint used by lifeguards isn't only for show. Zinc oxide is used in sunscreen as a physical barrier to block UV radiation and protect the skin from harmful sun damage. It's often used as a coloring agent in products like cosmetics, so some consider it more of an additive than a nutritional form of zinc. Since it's also less bioavailable than other forms of zinc when used as a dietary supplement, it's not typically recommended as a primary form of zinc supplementation. 7 


Man taking his Pure Encapsulations supplements with water


Other Zinc Supplement Considerations 


Aside from choosing the right form of zinc, brand quality is an essential consideration when you purchase a supplement. Independent, ceritfied testing and quality ingredients are crucial when selecting zinc supplements to ensure your supplement is safe, free from harmful contaminants, and accurately labeled.  


Independent verification guarantees that the product contains the ingredients listed on the label, in the declared potency and amounts, without potentially harmful substances such as heavy metals, microbial contaminants, or other adulterants. 


The recommended daily adult intake of zinc is 15 mg and because there are many sources of zinc throughout the environment, exposure and toxicity are not uncommon.xii You should always consult your physician prior to starting any supplement regime as increased levels of certain trace minerals can become toxic. 


The quality of all the other ingredients in your supplement also matters. Fewer additives and fillers are less likely to cause adverse reactions or become a problem for people with allergies and sensitivities. 


Takeaway: Not All Zinc Supplements Are Created Equal 


Zinc supplements can support immune function and many other systems in the body, but not all zinc supplements are created equal. The form of zinc you choose can affect its bioavailability and absorption, so chelates like gluconate, acetate, picolinate, and citrate are optimal choices. 


Additionally, selecting a high-quality brand is crucial to ensure that the supplement contains the appropriate ingredients in the right amounts without harmful contaminants.  


Working with a healthcare provider to help you examine your diet and health history can help you determine if zinc supplementation is necessary and which form of zinc may be most beneficial for your needs.  


Caitlin Beale, MS, RDN is a registered dietitian and freelance health writer. She has a master's degree in nutrition and over ten years of experience as a registered dietitian.  


+The views expressed in this article are those of the authors. They do not reflect the opinions or views of Pure Encapsulations®.