At the Diadema campus of the Federal University of São Paulo, chemist Angerson Nogueira do Nascimento and his team made a discovery that reframes how we think about nutritional labels: just because a nut contains a mineral doesn't mean your body can actually use it. In a study published in Química Nova, researchers discovered that the total amount of copper, magnesium, manganese and zinc packed into Brazil nuts and cashews tells only part of the story—the body can access surprisingly small fractions of these valuable elements during digestion.
This distinction matters because consumers often assume that eating foods rich in minerals automatically delivers those nutrients to their bloodstream. The reality is more nuanced. The Brazilian team investigated bioavailability, the fraction of a mineral actually released during simulated gastrointestinal digestion and potentially available for absorption. What they found challenges the simplistic notion that nutritional value is simply the sum of a food's chemical components.
The researchers conducted rigorous laboratory experiments that mimicked the human digestive system, controlling temperature, agitation, pH and enzymatic composition as food particles moved through simulated gastric and intestinal environments. When they tested cashews, they found that 56% of the copper and 52% of the magnesium became bioaccessible—available for the body's absorption. Brazil nuts performed less efficiently, releasing just 50% of their copper and only 28% of their magnesium. For manganese and zinc in both nuts, the amounts remained below the detection limit of their instruments, effectively negligible for nutritional purposes.
"The results demonstrated that assessing a food's nutritional value shouldn't be limited to total nutrient concentration," Nascimento explains. "It's also essential to investigate how these elements behave under conditions that simulate the digestive system to estimate their actual availability for absorption." This reflects a broader shift in nutritional science toward understanding not just what's in food, but what our bodies can actually extract and use from it.
The research is especially significant in Brazil, where both cashews and Brazil nuts hold considerable economic importance and occupy prominent places in the national diet. Rather than dismissing these oilseeds as nutrient sources, however, the findings suggest a more balanced perspective. The nuts remain valuable contributors to a diverse, balanced diet—they simply shouldn't be viewed as exclusive sources of these minerals.
The distinction between bioaccessibility and bioavailability itself reveals the sophistication required to understand nutrition. Bioaccessibility, which the team measured through laboratory simulation, refers to how much nutrient is released from the food's structure. Bioavailability, the true measure of what the body absorbs and uses, would require animal or human studies—far more resource-intensive and ethically complex. This study's careful focus on simulated digestion provides a practical middle ground, offering insights into actual nutritional value without the barriers of human trials.
For anyone reaching for a handful of cashews or Brazil nuts expecting a mineral boost, the takeaway is neither dismissive nor overly optimistic. These foods contain genuine nutritional value, but your digestive system will unlock only a portion of what the label promises. In nutrition science, as in health itself, the full picture often emerges only when we look closer.