Posted by kathryn in Myths

We’re starting today’s Q & A Thursday with a curly one – does drinking coffee affect your absorption of other nutrients?

This is actually a tough one to answer and at the moment there’s conflicting evidence. In the early 1980s a study was published in the American Journal of Clinical Nutrition which found a cup of coffee could reduce the absorption of iron from a hamburger by 40%. Concern has also been expressed about coffee affecting the absorption of magnesium, zinc, potassium, calcium and B vitamins. However, not every study has reproduced these results and significant nutritional deficiencies have not been found in coffee drinkers .

As is often the case with nutrition, there may be more complex factors at work when it comes to coffee drinking. In the case of calcium, while consuming caffeine leads to increased calcium losses in your urine, there seems to be a compensatory mechanism whereby you absorb more of the calcium from your diet, to maintain your calcium status quo. So, for moderate coffee drinkers there isn’t an increased risk of osteoporosis, unless your dietary intake of calcium is low (and you’re not replacing the caffeine-induced losses).

To sum up

At the moment the general advice is – moderate coffee consumption (less than four cups per day) is not harmful and doesn’t affect the intake of nutrients from your diet enough to be a concern.

I would add a word of caution to this though – if you’re stressed, having sleeping problems, or suffering from anxiety I would strongly recommend reducing your coffee intake. I think for many people coffee can become a crutch – you start to “need” it to get through the day or wake up in the morning and your intake can edge up higher and higher.

The other point to remember – in terms of overall health, smoking, a lack of exercise, not eating enough vegetables and excessive alcohol intake are far more harmful than the odd cup of coffee . You would be better to work on improving those areas, rather than worrying about the couple of capuccinos you have each day.

For more information

• ABC caffeine fact file
• Coffee and health: a review of recent human research
• Choice report: caffeine

14 June, 2007