If you’re a dual fan of coffee and cashew nuts, take comfort in knowing that you don’t necessarily have to pick one over the other. Rather, the link seems to lie in the simultaneous consumption of coffee and food items that are high in iron, like cashews. This was evidenced in an early 1983 clinical trial published in The American Journal of Clinical Nutrition, in which participants with healthy iron levels experienced a 39% drop in iron absorption when a cup of coffee was consumed with a hamburger meal. However, this was not the case when participants drank coffee 60 minutes prior to eating, indicating that staggering our coffee consumption might bypass this potential effect. That being said, inhibition of iron absorption was observed in association with drinking coffee one hour after a meal.
If you think you might be better off if you switch from coffee to tea, the study findings also showed that simultaneous ingestion of tea with a hamburger meal decreased iron absorption to an even greater degree by 64%.