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)
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) (which is even below the average of all beers, 0.2mg per liter). (3)
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.”
Is this a significant amount?
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)
- 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. Examples of excellent sources of iron are clams (24mg/3oz), beef liver (5.5mg/3oz), pumpkin seeds (4.2mg/1oz) or cooked lentils (3.3mg/half a cup). For a full list of significant dietary iron sources click here.
Considering all of the above, Guinness beer is an insignificant source of iron.
NUTRITION FACTS VS NUTRITION MYTHS
You will find a summary of the most common nutrition myths and evidence-based nutrition facts here.