iron contents of guinness

Is Guinness beer a good source of iron?

Pawel Malczewski
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Short summary

The only credible information found on the iron contents of Guinness beer is 0.1mg per liter, which was confirmed by the Diageo’s customer information representative. This amount of iron is insignificant in our daily diet, proving that Guinness beer is not a good source of iron. For a quick answer click here.

Explanation

The original myth goes something like this: “Irish women should drink Guinness beer during pregnancy because it is a good source or iron”. Note: there is an increased requirement for iron during pregnancy.  (see recommendations for iron..)

In the first place, since even the experts cannot establish a minimum safe amount of alcohol during pregnancy, drinking alcohol should be avoided while you are expecting. (1)NHS Choices. Alcohol in pregnancy. Available here.

Even if we assume that pregnant women can have one or two alcoholic drinks, how much iron would Guinness beer provide?

How much iron is in Guinness beer?

In the search for answers on the iron contents in Guinness beer, it became clear that another myth was created. Answering the question “Is Guinness beer a good source of iron?” I found many claims stating that a pint of Guinness contains 0.3mg of iron. However, none of the claims has a reference to where this number comes from.

The original myth, that Guinness beer is a good source of iron, is neither claimed by Diageo (the company that produces the Guinness beer) nor shown by any official nutritional information database, such as the USDA. There is also a complete lack of results from independent laboratories.

In fact the contents of iron in Guinness beer are not only low but even lower than the it is claimed (0.3mg per pint) by most of the sites related to this subject.

The only credible information available compares the amount of trace elements in various beers and shows that the iron contents of the Guinness beer is only 0.1mg per liter (2)Alcázar A, Pablos F, Martín MA, González AG. Multivariate characterisation of beers according to their mineral content. Talanta. 2002 Apr 22;57(1):45-52. Available here. (which is even below the average of all beers, 0.2mg per liter). (3)USDA. Basic Report:  14003, Alcoholic beverage, beer, regular, all. Available here.

This amount confirmed the information provided to me by the consumer information at Diageo. The email response was: “The iron content of Guinness is just .011mg per 100ml. In the past, iron brewing vessels and pipe-work added quite a bit but these are no longer used.“

Some calculations to put this matter into perspective:

  • A “standard alcoholic drink” has 10g of alcohol which is equivalent to a 285ml glass of beer. (4)Australian Federal Police. Drink driving. Available here.
  • 1 liter of Guinness beer contains 0.1mg of iron.
  • 285ml of Guinness beer therefore contains about 0.03mg of iron. (285ml * 0.1mg of iron/1,000ml)
  • Assuming that one drinks 1 standard alcoholic drink with 285ml of Guinness, the amount of iron ingested from that beer will be 0.03mg.
  • The recommended dietary intake of iron is 8mg/day for men, 18mg/day for women and 27mg/day for pregnant women.
  • 0.03mg of iron represents: 0.38% of RDI of men, 0.17% of RDI for women and 0.11% for RDI for pregnant women.
  • A good source of iron is considered to be between 10% and 20% of RDI. This means that, to be a good source of iron, a man would have to consume at least 27 glasses, a woman 60 and a pregnant woman 90 glasses of Guinness beer.

Conclusion

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Besides the fact that when pregnant, alcohol should be avoided, drinking 1 standard drink contributes only 0.03mg of iron, which is insignificant.

References   [ + ]

1. NHS Choices. Alcohol in pregnancy. Available here.
2. Alcázar A, Pablos F, Martín MA, González AG. Multivariate characterisation of beers according to their mineral content. Talanta. 2002 Apr 22;57(1):45-52. Available here.
3. USDA. Basic Report:  14003, Alcoholic beverage, beer, regular, all. Available here.
4. Australian Federal Police. Drink driving. Available here.

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