What Is Zinc?
Zinc is a trace mineral involved in immune function, wound healing, DNA synthesis, and the activity of over 300 enzymes in the body. It’s not stored in any meaningful reserve, so a steady daily intake — from diet or supplements — is needed to maintain normal levels.
Why Your Body Needs It
EFSA-authorised health claims for zinc are among the broadest of any mineral:
- Contributes to the normal function of the immune system
- Contributes to the maintenance of normal skin, hair, and nails
- Contributes to normal DNA synthesis and normal protein synthesis
- Contributes to the protection of cells from oxidative stress
- Contributes to normal cognitive function
- Contributes to normal fertility and reproduction
- Contributes to the maintenance of normal testosterone levels in the blood
- Contributes to normal acid-base metabolism
- Has a role in the process of cell division
Signs of Zinc Deficiency
Overt zinc deficiency is uncommon in the UK/EU, but mild insufficiency is more common than assumed, especially in specific groups. Reported signs include:
- Frequent colds or slow recovery from infections
- Slow wound healing
- Hair thinning or shedding
- Loss of taste or smell
- Dry or rough skin
- Reduced appetite
Who’s Most at Risk
- Vegetarians and vegans — plant sources of zinc are less bioavailable due to phytates that inhibit absorption
- People with gastrointestinal conditions affecting absorption (Crohn’s, coeliac disease)
- Heavy alcohol consumers — alcohol increases zinc excretion
- Older adults, whose dietary intake and absorption often decline
- Athletes with high training volumes, who lose zinc through sweat
How Much Do You Need?
UK Reference Nutrient Intakes are 9.5mg/day for adult men and 7mg/day for adult women. EFSA’s Population Reference Intake is similar, ranging roughly 9.4–16.3mg for men and 7.5–12.7mg for women depending on dietary phytate levels. The EFSA-set upper tolerable intake for total zinc (diet plus supplements) is 25mg/day — going meaningfully above this for extended periods can interfere with copper absorption.
Food Sources
- Red meat and shellfish (oysters are exceptionally high)
- Poultry
- Dairy products
- Legumes, nuts, and seeds (particularly pumpkin seeds) — though less bioavailable than animal sources
- Wholegrains
Zinc Picolinate vs Citrate: Which Form Is Best?
Both picolinate and citrate are well absorbed, and either is a sound choice — the difference between them is smaller than the difference between either one and cheap zinc oxide.
Zinc picolinate is zinc bound to picolinic acid, a compound the body produces naturally to help transport minerals across the intestinal wall. It has a long-standing reputation as the best-absorbed form, based largely on an older comparative study, and it remains the most common choice in premium supplements.
Zinc citrate is bound to citric acid. Absorption is comparable to picolinate in most direct comparisons, and it has a milder taste — which matters if you’re taking a powder or a chewable rather than a capsule.
Zinc bisglycinate is a third well-absorbed option, bound to the amino acid glycine, and tends to be the gentlest on an empty stomach.
Zinc oxide is the form to avoid where you can. It’s cheap, it’s common in budget multivitamins, and it’s considerably less bioavailable than any of the above. If a product doesn’t state the form on the label, it’s usually oxide.
The practical takeaway: pick whichever of picolinate, citrate or bisglycinate is available at a sensible dose from a manufacturer you trust. Don’t pay a premium for one over another on absorption grounds — the evidence doesn’t support a meaningful gap between them.
- Zinc picolinate, citrate, or bisglycinate are generally well absorbed
- Zinc oxide is cheaper but less bioavailable
- Take with food if it causes stomach upset, though this can slightly reduce absorption
- Avoid stacking multiple zinc-containing products (multivitamin + standalone supplement) without checking your total daily intake against the 25mg upper limit
Best Time to Take a Zinc Supplement
Take zinc with or just after a meal, and keep it away from iron. Those two rules cover almost everything that matters.
With food, not on an empty stomach. Zinc on an empty stomach causes nausea in a significant number of people — it’s the most common complaint about zinc supplementation. Taking it with food reduces absorption slightly, but a dose you actually keep down beats a theoretically better-absorbed one you stop taking.
Evening is often the practical choice. Not because absorption is better at night, but because it keeps zinc separated from iron and calcium, which are more commonly taken at breakfast. Zinc and iron compete for the same absorption pathway, and taking them together reduces uptake of both.
What to keep apart from your zinc dose:
| Take separately (2+ hours) | Fine together |
|---|---|
| Iron supplements | Vitamin C |
| Calcium supplements | Vitamin D |
| High-dose magnesium | B vitamins |
Watch your total, not just the dose on the bottle. EFSA’s tolerable upper intake is 25mg per day from all sources combined. Many multivitamins already contain 10–15mg, so adding a 25mg standalone supplement puts you over. Sustained intake above the limit can interfere with copper absorption, which causes problems of its own.
A separate case: lozenges during a cold. The evidence for zinc shortening a cold involves lozenges specifically, at doses well above daily maintenance, started within about 24 hours of symptoms appearing. That’s a short-term therapeutic use over a few days — not an ongoing routine, and not a reason to take 75mg daily through the winter.
Our pick: Solgar Zinc Picolinate 22mg — a well-absorbed form suited to supporting immunity during higher-demand periods.
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This page is for general educational purposes only and is not medical advice.
Frequently Asked Questions
Can you take zinc and iron together?
Better not to — take them at least two hours apart. Zinc and iron compete for the same absorption pathway in the gut, so taking them simultaneously reduces how much of each you take up. The usual arrangement is iron with breakfast (alongside vitamin C, which improves iron absorption) and zinc with your evening meal. If you’re taking both because you’re deficient in both, this spacing matters more, not less. See our iron guide for why iron should only be supplemented after a blood test confirms a deficiency.
Can you take zinc and vitamin C together?
Yes, freely — there’s no interaction, and they’re often combined in the same product. Just keep an eye on your total zinc intake across all supplements against the 25mg daily upper limit. Our vitamin C guide covers how the two compare for immune support.
Should zinc be taken with or without food?
With food, in most cases. Absorption is marginally better on an empty stomach, but zinc is a common cause of nausea taken that way. Taking it with a meal is the more practical choice for anyone planning to take it consistently.
How much zinc is too much?
EFSA sets the tolerable upper intake at 25mg daily from all sources. Short-term higher doses (as in cold lozenges) are used deliberately for a few days, but sustained intake above 25mg can interfere with copper absorption and, at much higher levels, affect immune function — the opposite of the intended effect.
How long does zinc take to work?
It depends what you’re taking it for. If you’re correcting a shortfall, changes in things like taste perception or skin can take several weeks. For the specific case of shortening a cold, zinc lozenges need to be started within roughly 24 hours of symptoms appearing to show the effect seen in trials.
Does zinc really boost testosterone?
Zinc has an EFSA-authorised claim for contributing to the maintenance of normal testosterone levels in the blood — note the wording. It supports normal levels where zinc status is adequate; it doesn’t raise testosterone above normal in men who aren’t deficient. Supplementing beyond your requirement won’t produce an additional effect.
Sources & Further Reading
- NHS — Vitamins and minerals: Others
- NIH Office of Dietary Supplements — Zinc Fact Sheet
- EFSA — Health claims on zinc
- Linus Pauling Institute — Zinc Micronutrient Information
- Examine.com — Zinc
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