Nutritional nuts come with a Christmas bonus

Now new research appears to confirm that the Brazil nut’s good standing is well deserved and, if anything, underplayed.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the VKTA – Radiation Protection, Analytics & Disposal Rossendorf Inc in Germany carried out a study of the minerals, essential amino acids and unsaturated fatty acids present.

Brazils are known to contain high levels of selenium, with a single nut providing the recommended daily requirement of 55-70 micrograms, which aids the immune system and guards cells against the threat of oxidative stress.

However, with the aid of nuclear magnetic resonance spectroscopy (NMR) the researchers identified that the main form of selenium present is an amino acid that is particularly efficiently absorbed by the body: selenomethionine,

“Our study confirms the extremely high selenium content in Brazil nuts. At the same time, we were also able to show that around 85 percent of the selenium is released during digestion and can then be taken up by the body,” says Dr. Astrid Barkleit from the Institute of Resource Ecology at HZDR.

Writing in the International Journal of Molecular Sciences, the scientists also concluded that the presence of two potentially harmful metals in Brazil nuts may posit less risk than expected.

Low calcium soils in which Brazil nut trees live result in chemically similar barium and radium partially replacing the calcium, giving rise to concern regarding radioactivity, bone damage and cancer risk.

Investigation demonstrated that almost 98% of the barium and radium in the nut’s kernel is not released into the digestive tract, with just a tiny percentage bioavailable stated VKTA’s Dr. Diana Walther.

“The calculations show that, due to the very low bioavailability, a daily consumption of one Brazil nut would result in a radiation dose of about 2.4 microsieverts per year,” she said.

Walther added that was equivalent to just one thousandth of the natural annual radiation exposure in Germany, measured at 2.1 millisieverts per year on average by the Federal Office for Radiation Protection.

“Of this, about 10% are ingested with food. Therefore, the radiation exposure caused by radium in Brazil nuts is significantly less than previously assumed,” she explained.

Other elements are bioavailable in larger percentages: Strontium at around 50% and lanthanum and europium around 25%. All, though, are present in minute amounts that strontium especially is toxicologically irrelevant.

“Our results confirm that Brazil nuts are a valuable food – especially as a natural source of selenium,” Barkleit commented.

“At the same time, they show that, thanks to their low solubility, the potentially harmful elements they contain hardly affect the body when the nuts are consumed.”

Techniques employed for the research included mass spectrometry to determine the concentrations of the elements, gamma and alpha spectrometry for radioactive isotopes, and NMR and laser fluorescence methods for characterising the chemical binding form of the elements.

Pic: Schroder/HZDR