Oyster Plus Zinc

Zinc is one of the few minerals where the right answer is usually an unglamorous dose taken with food, and this is the triage our naturopaths run before anyone gets as far as choosing a brand.

A good fit if

• You eat little or no meat, fish or shellfish, so your requirement sits at the higher end
• You want a modest everyday dose and you can reliably take it with a meal
• You would rather have a single-ingredient zinc than a combination bringing vitamin A or high-dose B6 you did not ask for
• Swallowing tablets is the obstacle. Chewables, liquids and powders exist at ordinary doses
• You are happy to review a high-strength dose after a few months rather than stay on it indefinitely

Check with us first if

• Taking a quinolone or tetracycline antibiotic. zinc binds them and reduces absorption of both; separate the doses by two to six hours.
• Taking penicillamine. Separate zinc from it by at least an hour.
• Taking a thiazide diuretic. Thiazides increase urinary zinc losses.
• You have been on 50 mg a day for months. Copper status is the thing to look at, because copper is what the Australian Upper Level was set to protect.
• Pregnancy or breastfeeding. The requirement rises, and many zinc products also contain vitamin A, which carries its own mandatory pregnancy warning here.
• A previous zinc dose made you feel sick. The form, the timing and the amount are all adjustable, so that is a conversation rather than a dead end.
• You are giving zinc to a child. The Upper Levels for children are a fraction of the adult doses on most shelves.
• You use a zinc-containing denture adhesive cream. Heavy chronic use has caused zinc toxicity, and it counts towards your daily total.
• You take prescription medicines. Check with your doctor, pharmacist or our naturopaths before starting.

• Zinc amino acid chelate / bisglycinate. Best known for: The Australian retail default. On a label it reads like 'zinc amino acid chelate 125 mg (equiv. zinc 25 mg)', which is where most of the confusion about dose starts. Absorption: Zinc bound to glycine. Schedule 1 caps the zinc content of zinc amino acid chelate at no more than 30 per cent of the chelate, and Australian labels commonly sit near 20 per cent. Typical use: Once-daily tablets and powders across the whole price range. Usually the easiest of the group on a sensitive stomach, though every label still says to take it with food.
• Zinc citrate. Best known for: A neutral taste, which is why it dominates chewables, liquids and children's formulas. Absorption: About 61 per cent bioavailable in young adults. Level with gluconate and better than oxide. Typical use: Chewable tablets, drops and practitioner-range single-ingredient products.
• Zinc gluconate. Best known for: The lozenge and cold-formula standard, and a low-yield salt: one Australian label declares 114.85 mg of zinc gluconate to deliver 15 mg of zinc. Absorption: About 61 per cent bioavailable, the same as citrate. Typical use: Lozenges and plain tablets. Gluconate forms bitter complexes with sweet carbohydrates, which is a genuine problem for lozenge palatability and therefore for finishing the pack.
• Zinc sulfate. Best known for: The research standard and the cheapest salt, used in a large share of the older clinical trials. Absorption: Well absorbed, but the most likely form in this table to cause nausea, particularly on an empty stomach. Typical use: Low-cost tablets and oral solutions rather than premium retail formulas. Schedule 1 also caps it at 5 per cent for topical use.
• Zinc picolinate. Best known for: A clinic favourite overseas, and the one oral form in this table with no item of its own in Schedule 1. Absorption: Chelated to picolinic acid. Head-to-head human absorption data against citrate or gluconate is scarce. Typical use: Mostly imported and practitioner-range products. Because no ZINC PICOLINATE item appears in Schedule 1, it cannot be an ingredient in an Australian listed medicine. Check what the label and AUST L number actually say.
• Zinc oxide. Best known for: The white mineral in sunscreens and barrier creams. Used on skin far more often than swallowed. Absorption: About 50 per cent bioavailable by mouth, the lowest of the common forms, even though it carries the most zinc per milligram of compound. Typical use: Primary sunscreens and nappy creams, where Schedule 1 requires sun-exposure warnings. Occasionally a cheap zinc source inside a multivitamin.
• Zinc acetate. Best known for: The salt used in the lozenge trials that reported the largest reductions in cold duration. Absorption: Designed to dissolve slowly in the mouth rather than be swallowed, releasing free zinc where the cold virus is. Typical use: Not available in an Australian listed medicine. No item named ZINC ACETATE appears in Schedule 1, so the best-studied lozenge salt is the one Australians cannot buy in a listed product.

Reference values. NHMRC Nutrient Reference Values, Recommended Dietary Intake unless noted: infants 0 to 6 months 2.0 mg/day (Adequate Intake); 1 to 3 years 3 mg; 4 to 8 years 4 mg; 9 to 13 years 6 mg; boys 14 to 18 years 13 mg; girls 14 to 18 years 7 mg; men 19 years and over 14 mg; women 19 years and over 8 mg. Pregnancy 10 mg at 14 to 18 years and 11 mg at 19 to 50 years; breastfeeding 11 mg at 14 to 18 years and 12 mg at 19 to 50 years. The 7 to 12 month band is not reproduced here because it was not captured from the source, and estimating it would be worse than omitting it.

Typical supplemental range. Australian labels run from about 15 mg to 50 mg of elemental zinc in a single daily dose. Plain single-ingredient tablets commonly sit at 15 to 25 mg; combination and high-strength products run 30, 40 and 50 mg, and the 50 mg products are at the ceiling Schedule 1 allows for a listed medicine. Anything above 25 mg must carry the zinc warning statement quoted below, so the warning on the box is a useful shortcut for reading the dose.

Upper level. NHMRC Upper Level of Intake, which the source states applies to total zinc intake from food, water and supplements including fortified food: 4 mg/day at 0 to 6 months; 5 mg at 7 to 12 months; 7 mg at 1 to 3 years; 12 mg at 4 to 8 years; 25 mg at 9 to 13 years; 35 mg at 14 to 18 years; 40 mg for adults 19 years and over. Pregnancy and breastfeeding 35 mg at 14 to 18 years and 40 mg at 19 to 50 years. Two instruments to hold in mind at once: the 50 mg ceiling in Schedule 1 governs how much zinc a listed medicine may recommend, while the 40 mg adult Upper Level is a nutrition reference for everything you swallow in a day from every source. The regulatory ceiling sits above the nutrition ceiling, and both statements are correct.

Worth knowing. Read the elemental zinc figure, not the weight of the compound. The same trap as iron. Two Australian labels make it concrete: 114.85 mg of zinc gluconate provides 15 mg of zinc, and 125 mg of zinc amino acid chelate provides 25 mg. The big number on the ingredient line is roughly five times the zinc you get, and the line that matters begins 'equiv. zinc'. Take zinc with food unless a practitioner says otherwise. Your needs depend on your age, diet and health circumstances. Talk to one of our naturopaths.

Food first, where the diet allows it.

• Oysters, farmed, raw: about 32 mg per 85 g
• Pacific oysters, cooked: about 28.2 mg per 85 g
• Beef, bottom sirloin, roasted: about 3.8 mg per 85 g
• Blue crab, cooked: about 3.2 mg per 85 g
• Rolled oats, cooked: about 2.3 mg per cup
• Pumpkin seeds, roasted: about 2.2 mg per 28 g

This list is the part of the page we will not shorten. If any of it applies to you, talk to one of our naturopaths or your doctor before starting.

• Quinolone and tetracycline antibiotics. zinc binds them; separate the doses by two to six hours.
• Penicillamine. Separate zinc from it by at least one hour.
• Thiazide diuretics. They increase urinary zinc excretion.
• Long-term doses of 50 mg or more. Interfere with copper absorption; copper deficiency can cause anaemia and neurological disease.
• Total intake above the NHMRC Upper Level. 40 mg/day for adults, counting food, water, fortified food and supplements together.
• Infants and children. Upper Levels are far lower: 4 mg (0 to 6 months), 5 mg (7 to 12 months), 7 mg (1 to 3 years), 12 mg (4 to 8 years), 25 mg (9 to 13 years), 35 mg (14 to 18 years).
• Empty stomach, or a dose above 25 mg. Nausea, vomiting, gastric distress, headache, dizziness and loss of appetite are the recognised effects of excess or badly timed zinc.
• Pregnancy and breastfeeding. Requirements rise, and many zinc products also contain vitamin A, which carries a mandatory pregnancy warning on Australian labels.
• Zinc-containing denture adhesive creams. Chronic excessive use has caused zinc toxicity and copper deficiency; some creams contain 17 to 34 mg of zinc per gram.
• Combination zinc formulas. Commonly contain vitamin A and vitamin B6, each with its own mandatory Australian label warning. Read the whole label, not only the zinc line.
• Products marketed as zinc picolinate. No ZINC PICOLINATE item appears in Schedule 1, so check whether what you are buying is an Australian listed medicine.
• Zinc lozenges. Schedule 1 does not include zinc acetate, the salt used in the trials that showed the largest effect, so an Australian lozenge is not the same product that was studied.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before starting.