guinness is indifferent for you

Last yuletide I did a piece about second-day drinking tactics, saying

grasp the fact that you’re not going to eat properly any time soon, so it’s essential to have something that feels like nutriment. To this end, neck a pint of stout.

People will tell you that women on labour wards used to be given stout after childbirth to replace lost iron. The fact is that it’d take gallons of the stuff to get your RDA, but that’s not the point. To you in your mentally pliable state – and, in all likelihood, to those women – it feels true, and that's what counts.

But hang on a minute. I'm basing my assertion that it'd take gallons on what a mate (admittedly a seasoned Irish lifetime career drinker) told me once in the pub. To paraphrase Jermaine Jackson, let's get rigorous. Time to do a bit of number crunching.

How much iron do you need?

The government says

adult men need 8.7mg of iron a day. For women the figure is 14.8mg

A 2003 government report into toxicity (around 100mg of iron can be lethal apparently) says

Estimated average daily iron requirements in the UK are 8.7 and 6.7 mg for males aged 11-18 and 19+ years, respectively. For women in the 11-50 years age group the estimated average daily iron requirement is 11.4 mg, whilst that for postmenopausal (50+ years) women is 6.7 mg.

The American government's page breaks it down into age groups, but it basically says adult men need 8mg a day, pre-menopausal women need 18mg.

A little variation there, then, but we get the general idea. Now we move on to the source.

How much iron is there in stout?

An Irish health insurance company says there is 0.3mg in a pint of Guinness. That's about the same as a bite of wholemeal toast or a solitary dried fig.

A pregnancy nutrition site confirms the figure (well, near enough at 0.28mg a pint), saying there is

0.05mg of iron in 100mls of stout, compared with 0.9mg in 100mls of red wine

Of course, you don't drink equal volume of stout and wine. We need to compare by units of alcohol or drink for drink. But even then, red wine's the clear winner.

By the iron figures they give it works out as:

Stout - 0.28mg/pint or 0.12mg/unit
Red wine - 1.58mg/glass (175ml), or 0.75mg/unit

So whichever way you cut it, red wine provides substantially more iron than stout - 18 times as much per millilitre, or more than six times as much per unit of alcohol. No surprise, then, that red wine is the only booze to make it on to the UK government's dietary iron for dummies page.

How much do you need for your daily iron?

If there's 0.28mg in a pint and if we play with the present government iron numbers (8.7mg for men and 14.8mg for women), to get your recommended daily allowance of iron you'd need to drink:

Men - 31 pints of stout a day
Pre-menopausal women - 53 pints of stout a day

If you slurp the other stuff its;

Men - 967 ml of red wine a day
Pre-menopausal women - 1645 ml of red wine a day

There's another consideration that's been the room-contained pachyderm here, though.

How much iron can alcohol safely provide?

The (unrealistic to expect even if they are actually right about what's good for us) recommended maximum alcohol consumption is 3-4 units of alcohol per day for men and 2-3 for women.

Stout can safely provide a maximum of:
5.5% of a man's iron
2.4% of a woman's iron

Red wine can safely provide a maximum of:
34.5% of a man's iron
15.2% of a woman's iron