Researchers find lead in turmeric

It is presented as a health enhancer and a healing agent, but it can be at the origin of cognitive defects and other serious ailments. A new study by Stanford reveals that turmeric – a spice commonly used throughout Southeast Asia – is sometimes adulterated with a lead-based chemical compound in Bangladesh, one of the major regions of the world where turmeric is the most cultivated.

Long banned from food products, lead is a powerful neurotoxin considered dangerous in any quantity. A recently published related analysis confirms for the first time that turmeric is probably the main culprit in raising blood lead levels among Bangladeshi respondents.

"People are unconsciously consuming something that could cause major health problems," said Jenna Forsyth, lead author of the journal, a postdoctoral researcher at the Stanford Woods Environmental Institute. "We know that adulterated turmeric is a source of lead exposure, and we need to do something about it."

A long-standing problem

The first study, available online at Environmental research, includes several analyzes, including interviews with farmers and spice processors in several districts of Bangladesh, which together produce nearly half of the country's turmeric. Many have traced the problem back to the 1980s, when a massive flood made turmeric crops wet and relatively dull in color. The demand for bright yellow curry has prompted turmeric processors to add lead chromate – an industrial yellow pigment commonly used to color toys and furniture – to their products. The practice continued as an inexpensive and quick way to produce a desirable color.

Powerful neurotoxin

As a potent neurotoxin, lead increases the risk of heart and brain disease in adults and interferes with the development of children's brains. About 90% of children with high blood lead levels live in low-income countries, and the resulting cognitive damage is associated with a loss of productivity of nearly one trillion dollars a year.

"Unlike other metals, there is no safe consumption limit for lead, it's a neurotoxin in its entirety," said lead journalist Stephen Luby, a professor of medicine. and director of research at the Stanford Center for Global Health Innovation. "We can not console ourselves by proposing that had the contamination been such and such, it would have been safe."

The related study, published on Sept. 17 in Environmental Science & Technology, examined various potential sources of blood lead contamination in Bangladeshi people. Lead comes in different forms, called isotopes, and the ratios of these isotopes vary depending on the origin of the lead. The researchers were able to identify lead chromate adulterated turcuma as the most likely culprit in comparing it to lead isotopes in people's blood. This research is the first to establish a direct link between lead in turmeric and lead levels in the blood.

Beyond Bangladesh

Researchers have not found direct evidence of the presence of contaminated turmeric beyond Bangladesh. They also pointed out that food safety controls carried out by importing countries had prompted major Bangladeshi spice processors to limit the amount of lead added to turmeric for export. The researchers warned, however, that "the current system of periodic food safety controls only captures a fraction of the adulterated turmeric marketed around the world." In fact, since 2011, more than 15 brands of turmeric, distributed in countries such as the United States, have been recalled due to their excessive lead content.

Although these recalls and previous studies have revealed the presence of lead in turmeric, none has clearly identified the source (some have suggested that it could be related to soil contamination), nor proved the link with the concentrations lead in the blood, nor revealed the omnipresence of the problem and the incentives to perpetuate it.

Towards solutions

Since 2014, Forsyth, Luby and Scott Fendorf, Terry Huffington's professor of the School Earth, Energy and Environment Stanford, co-authors of both articles, have been working in rural Bangladesh to assess lead exposure. With funding from the Stanford Woods Environmental Institute, they first conducted an assessment of the population that revealed that more than 30% of pregnant women had lead levels in the high blood.

Researchers now plan to focus on changing consumer behavior in the consumption of contaminated turmeric and reducing incentives to practice. They suggest more efficient drying technologies for the treatment of turmeric. They also recommend to import inspectors around the world to control turmeric by means of x-ray machines capable of detecting lead and other chemicals.

Although few low-cost responses appear to be available in Bangladesh, the researchers suggested involving consumers, producers, and other stakeholders with a focus on food safety and public health, which could provide the foundation for a solution. To this end, Forsyth, Luby and Fendorf are part of an interdisciplinary project team, funded by the Stanford King Center for Global Development, seeking solutions to reduce lead exposure from turmeric, battery recycling and other sources in Bangladesh and elsewhere.

Among other goals, the team plans to develop business opportunities that reduce lead exposure. A member of the team, bio-engineer Manu Prakash, is developing inexpensive technologies to measure lead in turmeric, blood and other sources. Other collaborators, Shilajeet Banerjee and Erica Plambeck, are exploring ways to change demand and create business opportunities for lead-free turmeric.

"Jenna's outstanding work allows us to work with stakeholders in Bangladesh to target effective prevention," said Luby.