Metalloids in food: Researchers warn of tellurium contamination from popular foods

06 Aug 2024 --- A new study by researchers from Nagoya University, Japan, found that higher levels of tellurium, a contaminant in plant-based foods, is a strong indicator of developing high blood pressure. The study highlights the importance of closely monitoring tellurium levels in everyday foods.

“Our epidemiological studies targeting the general population showed a positive dose-dependent relationship between tellurium exposure and blood pressure. In addition, our animal studies showed that systolic blood pressure increased first after tellurium exposure, followed by increases in both systolic and diastolic blood pressures with continued exposure,” Takumi Kagawa, a Ph.D. candidate in the Department of Occupational and Environmental Health, Nagoya University and co-author of the study, tells Nutrition Insight.

“These results suggest that hypertension may be further exacerbated with higher tellurium exposure and longer duration of exposure.” 

Tellurium is transferred from mining and manufacturing activities to food, and as levels increase, so does the likelihood of developing or exacerbating hypertension, commonly known as high blood pressure. Better monitoring of tellurium levels in specific foods can reduce high blood pressure in the general population.

“We found that despite raising tellurium levels in the urine, cereal and legume intake did not directly increase the risk of hypertension. Cereals and legumes may contain many diverse nutrients that can mitigate the risk of hypertension despite high levels of tellurium,” says Kagawa. 

Caution against contamination
The researchers say the findings are significant and indicate that tellurium exposure concerns public health. Cereals and legumes such as rice and fermented soybeans (natto) are popular food choices in Japan. While these foods contain high-quality carbohydrates, vitamins and minerals, tellurium can be present. 

“However, considering that increased tellurium exposure is a latent risk factor for hypertension and foods contribute to this association, careful and continuous monitoring of tellurium levels in individual foods may be crucial,” Kagawa explains.

Kagawa notes that they think research on an inexpensive and simple system for measuring tellurium concentration is important. “Currently, tellurium concentration is often measured using an instrument called Inductively Coupled Plasma Mass Spectrometry (ICP-MS), which is expensive and requires specialized knowledge to operate.” 

“During our research, we have confirmed that the concentration of tellurium in urine serves as a biomarker reflecting exposure using the instrument. If we can more easily detect tellurium concentrations not only in urine but also in food, soil, and other environmental samples and elucidate the relationship with various health parameters, it is expected to accelerate research on tellurium and health.”

Tellurium is transferred to food through soil that has been contaminated when dust, ash and slag are released from mining and manufacturing activities. The tellurium is transferred from the soil to crop plants such as cereals, carrots and garlic.

“The results indicate diet was the most significant contributor to increased urinary tellurium levels, compared to other lifestyle factors, such as smoking, working status and physiological factors, such as age and sex. Dietary intake, an important aspect of our lifestyle, plays a significant role in increased urinary tellurium concentrations,” says Kagawa.

Exposure from cerealsResearchers discovered a link between high blood pressure and tellurium.
The study, which recruited 2,592 Japanese adults and found the same results in humans and mice, was published in the Environment International journal. The researchers also studied foods that raise the levels of tellurium in urine. They discovered that consuming cereals and legumes caused high levels of tellurium, but further testing did not establish a direct link to high blood pressure rates.

Masashi Kato, professor in the Graduate School of Medicine Program in Integrated Medicine Social Life Science, Nagoya University and corresponding author, tells us: “The development of cooking and processing methods (washing, peeling and boiling) and materials that reduce dietary tellurium will be an important topic of future food research. The authors are also addressing this issue by developing tableware that absorbs toxic elements and are aiming for its practical application.”

“We administered tellurium to mice in amounts equivalent to what humans might encounter daily and observed an increase in blood pressure,” says Tomoko Misawa, assistant professor at Nagoya University Hospital Anesthesiology and lead author of the study.

“When we stopped the exposure, both the blood pressure and the tellurium levels in their urine decreased. These results directly link tellurium exposure and increased blood pressure, confirming findings in humans.”

Previous studies suggested that tellurium exposure is associated with production of oxidative stress (harmful reactive molecules in the body). Oxidative stress damages blood vessels and increases blood pressure. Therefore, we speculate that tellurium exposure elevates blood pressure via oxidative stress in the cardiovascular system.

“Our findings are important because they highlight a previously unrecognized risk factor for hypertension, a global health issue with rising prevalence. We for the first time provided human and animal evidence that elevated tellurium level is a potential risk for hypertension. Another remarkable part of this study is the finding that dietary intake, an important aspect of our lifestyle, plays a significant role in increased tellurium exposure in general people,” Kato explains.

“Considering that the urinary level of tellurium in this study was comparable with the levels in general populations in other countries, our results indicate an increased potential risk of hypertension by tellurium exposure may be applicable to the global population.”

The researchers say the urinary level of tellurium in this study was comparable with the levels in general populations in other countries. The results indicate an increased potential risk of hypertension by tellurium exposure may apply to general populations worldwide.

Meanwhile, another study found that practicing mindfulness focused on healthy eating helped study participants with elevated blood pressure adhere better to the DASH (Dietary Approaches to Stop Hypertension) diet. Though this diet is known to lower blood pressure, adherence is typically low.

By Inga de Jong