Calcium Ascorbate Powder

Choosing a vitamin C form is mostly about your stomach and what else you take. These are the questions our naturopaths ask in store, in short.

A good fit if

• Plain vitamin C tastes too sour for you, or feels sharp on an empty stomach
• You'd like an unflavoured powder you can split across the day
• You'd rather avoid the sodium in sodium ascorbate

Check with us first if

• You've had kidney stones or been told you make too much oxalate. Oxalate in urine went up at 1,000 mg of vitamin C a day.
• You're having chemotherapy or radiotherapy. The NIH advises talking to your oncologist before taking vitamin C or other antioxidant supplements.
• You take niacin with a statin. Vitamin C with other antioxidants may reduce the rise in HDL cholesterol you'd get from that combination.
• You take iron supplements or have your iron monitored. Vitamin C increases how much iron you absorb from plant foods and supplements (non-haem iron).
• You already take a calcium supplement, or you've been told to watch your calcium. Calcium ascorbate adds to your daily calcium, so check the label.
• It's for a child. Children need 35 to 40 mg a day, far less than a typical scoop.

• Calcium ascorbate. Best known for: Buffered, non-acidic vitamin C, usually as an unflavoured powder. Absorption: No difference from ascorbic acid at 250 mg. At 500 mg, some white blood cell and immune measures differed, in one early single-dose trial. Typical use: Powder stirred into water or juice, or tablets.
• Plain ascorbic acid (the comparison). Best known for: The form almost every vitamin C trial used, with no mineral added. Absorption: The benchmark: fully absorbed up to a single 200 mg dose, with absorption falling from 500 mg. Typical use: Tablets or powder, split across the day.
• Ester-C. Best known for: Calcium ascorbate plus vitamin C breakdown products, and the one buffered form with a published stomach trial. Absorption: Higher vitamin C in white blood cells at 24 hours than ascorbic acid in a small trial, with no difference in the blood. Typical use: Buffered tablets, often 1,000 mg once a day.
• Sodium ascorbate. Best known for: Buffered vitamin C with sodium instead of calcium. Absorption: No trial we hold compares it with ascorbic acid. Typical use: High-dose powders for people who want to avoid the acid.
• Liposomal vitamin C. Best known for: Vitamin C wrapped in phospholipid bubbles. Absorption: About 27% higher peak blood levels than standard vitamin C in one blinded 500 mg trial. Typical use: Liquids, softgels and capsules.

Reference values. Calcium ascorbate doesn't change how much vitamin C you need. The NHMRC recommended daily intake for adult men and women is 45 mg a day, rising to 60 mg in pregnancy and 85 mg while breastfeeding for ages 19 to 50. Children need 35 to 40 mg. Count the vitamin C, not the weight of the whole salt, because part of every gram is calcium.

Typical supplemental range. The trials that tested calcium ascorbate used single doses of 250 mg, 500 mg and 1,000 mg of vitamin C. Check your product's label for how much vitamin C a scoop actually gives you.

Upper level. Australia hasn't set an upper limit. In the NHMRC's own words: 'It is not possible to establish a UL for vitamin C, but 1,000 mg/day is a prudent limit.' That applies to calcium ascorbate just as it does to any other form.

Worth knowing. You absorb all of a single 200 mg dose, but absorption drops from 500 mg upwards, and the extra leaves in your urine. So a large daily amount goes further split into two or three smaller doses, and the calcium counts towards your daily total too. What you need depends on your age, diet and health, so talk to one of our naturopaths.

Food first, where the diet allows it.

• Red capsicum, raw, half a cup: 95 mg
• Orange, 1 medium: 70 mg, which already clears the adult RDI of 45 mg
• Kiwifruit, 1 medium: 64 mg
• Broccoli, cooked, half a cup: 51 mg

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• You have hereditary haemochromatosis or iron overload. NIH lists iron overload among the concerns with too much vitamin C.
• You have kidney stones or hyperoxaluria. Oxalate and urate in the urine rose at 1,000 mg of vitamin C a day.
• You're having chemotherapy or radiotherapy. NIH advises talking to your oncologist before taking antioxidant supplements.
• You take niacin with simvastatin. Vitamin C with other antioxidants may reduce the rise in HDL cholesterol.
• You take iron or have your iron monitored. Vitamin C increases absorption of non-haem iron.
• You take calcium supplements or need to limit calcium. Calcium ascorbate adds calcium to your daily total.
• You take high doses. NIH notes diarrhoea, nausea, stomach cramps and other stomach upsets.
• Children. The RDI is 35 to 40 mg a day.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before you start.