Iron absorption from ferric orthophosphate in a malted cocoa drink
What it found
In 11 healthy adults, iron from ferric orthophosphate was absorbed about as well as iron from ferrous sulphate when the drink was taken on an empty stomach.
In rats, taking the drink after a small meal cut absorption by more than half.
What they found
Studies in people
Absorption in people
The proportion of iron absorbed from the drink with ferric orthophosphate plus ascorbic acid was 0.25, from ferric orthophosphate alone 0.24, and from ferrous sulphate 0.23. There were no significant differences between the three drinks.
Ascorbic acid effect
Adding ascorbic acid at 1 mg per gram of powder did not increase iron absorption from the ferric orthophosphate-fortified drink. The authors say the level was not high enough to improve availability further.
Animal and lab studies
Fasting in rats
Rats given the drink shortly after a small meal absorbed less than half as much iron as those given the drink on a fasted stomach. In fasted rats, ferric orthophosphate and ferrous sulphate were absorbed similarly, but after a meal ferrous sulphate was better absorbed than ferric orthophosphate.
Isotope label validity
In rats, iron absorption from wheat flour labelled with the stable isotope 58Fe was not significantly different from flour labelled with 59Fe. This confirmed that 58Fe could be used as an extrinsic label.
Other findings
Solubility test
The ferric orthophosphate used was totally soluble in 0.1 M hydrochloric acid, both on its own and when added to the malted cocoa. The iron naturally present in the cocoa powder was less soluble.
What the authors conclude
“It was concluded that the FePO4 used to fortify the malted cocoa drink was as well absorbed as FeSO4 but that the high levels of absorption were a reflection of the fasting condition of the subjects.”
Also in their conclusions
- They conclude that ferric orthophosphate soluble in 0.1 M hydrochloric acid was as well absorbed as ferrous sulphate in fasting human subjects.
- They say the addition of ascorbic acid had no effect on availability at an ascorbic acid to iron value of 6.
- They anticipate that when taken with or shortly after a meal, absorption would significantly fall and ferric orthophosphate would become less available than ferrous sulphate.
How it was done
Ferric orthophosphate is often used to fortify foods with iron because it does not cause discolouration, rancidity or unpleasant taste, but it is commonly believed to be poorly absorbed compared with ferrous sulphate. The authors wanted to measure iron absorption from a malted cocoa drink fortified with ferric orthophosphate, with and without ascorbic acid, and compare it with ferrous sulphate.
Eleven healthy adults (three women and eight men, average age 28) took a malted cocoa drink fortified with ferric orthophosphate, ferric orthophosphate plus ascorbic acid, or ferrous sulphate, in random order one drink per week, after an overnight fast. Iron absorption was measured by giving a stable isotope label and measuring unabsorbed iron in faeces. A separate rat experiment compared absorption when the drink was given on a fasted stomach or shortly after a small meal.
What it can’t tell you
- The human part of this study measured absorption only when the drink was taken after an overnight fast, so it cannot show how much iron would be absorbed from the drink taken with or after a meal.
- The finding that ferric orthophosphate becomes less available than ferrous sulphate after a meal comes from rats, so it may not be the same in people.
The paper
- Title
- Iron absorption from a malted cocoa drink fortified with ferric orthophosphate using the stable isotope 58Fe as an extrinsic label
- Type
- Randomised controlled trial
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Fairweather-Tait SJ, Minski MJ, Richardson DP (1983). Iron absorption from a malted cocoa drink fortified with ferric orthophosphate using the stable isotope 58Fe as an extrinsic label. The British journal of nutrition. doi:10.1079/bjn19830071Free full textPubMed 6882732DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error