Need more iron in your diet? Start drinking more dark beers.

A new study from the University of Valladolid in Spain reveals that dark beers have, on average, a free iron content of 121 parts per billion compared to the 92 parts per billion in pale beers and 63 parts per billion in non-alcoholic beers.

Iron is a vital part of the human diet as it assists in a number of cellular functions, including food digestion and carrying oxygen from the lungs throughout the body.

In addition to the nutritional value, iron is also a key component in oxidizing the organic compounds in beers, which provide the beverages with their taste.

The researchers believe that the higher iron content in dark beers could come from the hop and malt extracts used make the beers.

In the case of pale beers, a filtering process that uses sedimentary rock of a porous nature may trap the iron in the beer, thus lowering the iron content.

To analyze the 40 beers from 24 countries, including Spain, the researchers used a differential pulse adsorptive stripping voltammetry technique they developed themselves, and refer to it as a "an ultra-sensitive, selective, rapid, reliable and cost-effective method.”

A dark Spanish beer had the highest free iron count, with 165 parts per billion.

A beer from the Netherlands came in last, with only 41 parts per billion.

The study included 17 beers from Spain, and 23 other brands from around the world. There were 28 pale beers, 6 dark and 6 non-alcoholic beers in the study.

The study was published in the Journal of Science of Food and Agriculture.