Seaweed Calcium

Calcium's one of the few supplements where taking more than you need carries a real cost, so here's the triage our naturopaths run before recommending one.

A good fit if

• You eat little or no dairy and haven't swapped in a fortified alternative
• You're postmenopausal or over 70, where the requirement rises
• You're buying it together with vitamin D, which is where the evidence is strongest
• Your doctor has recommended it as part of a bone plan

Check with us first if

• You've had kidney stones, where randomised evidence shows a raised risk.
• You take lithium, which can raise blood calcium on its own.
• You take dolutegravir or another HIV antiretroviral, where calcium can substantially reduce blood levels of the medicine.
• You take thyroid medicine, antibiotics or iron, all of which need separating from calcium by a few hours.
• You're already getting plenty from food and would be stacking a supplement on top.

• Calcium carbonate (item 1070). Best known for: The most calcium per tablet, and the cheapest. Absorption: 40% elemental calcium by weight; needs stomach acid, so take it with food. Typical use: Permitted listed with no conditions at all.
• Calcium citrate (items 1073, 1074). Best known for: Absorbed without needing stomach acid. Absorption: About 21% elemental calcium, so roughly double the tablet for the same dose. Typical use: The form to pick if you're on antacids or reflux medicine.
• Calcium amino acid chelate (item 1062). Best known for: The only calcium form with a legal composition cap in Australia. Absorption: Calcium is a mandatory component and its concentration is capped. Typical use: Check the elemental figure, which is usually low.
• Hydroxyapatite / MCHA (item 2643). Best known for: A whole-bone-derived calcium rather than a simple salt. Absorption: No cached head-to-head absorption trial. Typical use: Permitted listed, purpose codes A and E.
• Oyster shell calcium (items 3642, 3643). Best known for: A shell-derived carbonate. Absorption: Carbonate chemistry, so the same acid dependence. Typical use: Carries a mandatory mollusc allergen warning.

Reference values. The NHMRC Recommended Dietary Intake is 1,000 mg a day for men 19 to 70 and women 19 to 50, rising to 1,300 mg for girls and boys 12 to 18, and for older adults. Children 1 to 3 need 500 mg and 4 to 8 need 700 mg. Infants have an Adequate Intake of 210 mg to 6 months and 270 mg from 7 to 12 months.

Typical supplemental range. Australian labels usually carry 500 to 600 mg of elemental calcium per tablet, often with vitamin D. The number that matters is the elemental figure rather than the compound weight: carbonate is 40% calcium by weight and citrate about 21%, so a 1,250 mg carbonate tablet and a 2,400 mg citrate tablet deliver roughly the same 500 mg.

Upper level. The NHMRC Upper Level is 2,500 mg a day from all sources for everyone from age 1 upward. No Upper Level could be established for infants. Schedule 1 sets no dose cap on the common calcium salts.

Worth knowing. Add what's on the label to what you already eat, because the Upper Level counts food as well. Your needs depend on your age, diet and health circumstances. Talk to one of our naturopaths.

Food first, where the diet allows it.

• Dairy foods: the main Australian source of dietary calcium
• Bony fish such as tinned salmon and sardines: the bones are the calcium
• Legumes and some nuts: smaller contributions across the day
• Fortified soy drinks and cereals: fortification levels vary by brand; check the panel

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.

• History of kidney stones. Randomised evidence of harm: 1,000 mg calcium carbonate with 400 IU vitamin D3 increased renal calculi (HR 1.17).
• Lithium. Long-term use can cause hypercalcaemia, and combining it with calcium supplements could increase that risk.
• Dolutegravir and other HIV antiretrovirals. Calcium supplements can substantially reduce blood levels of the medicine.
• Postmenopausal women on 1,000 mg/day supplemental calcium. A meta-analysis of 13 double-blind placebo-controlled RCTs in 28,935 participants examined cardiovascular outcomes; discuss with your doctor.
• High doses generally. Calcium supplementation increased hypercalcaemia incidence in the colorectal adenoma trial set.
• Mollusc allergy. Oyster shell (item 3643) and oyster (item 3642) require the verbatim warning "Contains mollusc" or "Contains mollusc products".
• Upper Level. 2,500 mg a day from all sources for everyone aged 1 and over.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before starting.