Probiotic bacteria found in yogurt can protect people from the effects of exposure to heavy metals, particularly in pregnant women and children, a Canadian study suggests.

The researchers at the Canadian Center for Human Microbiome and Probiotics, who found one bacteria, Lactobacillus rhamnosus, was exceptionally effective in binding to toxic heavy metals, set out to determine if regular consumption of the probiotic could prevent heavy metals in the diet from being absorbed into the body.

In a field study in Tanzania, yogurt with L. rhamnosus was distributed to pregnant women and to children in the Mwanza region.

Tanzania has a network of yogurt kitchens set up in communities with the help of scientists to provide a low-cost, locally sourced nutrition product.

The researchers recorded their levels of toxins before and then after the distribution of the new yogurt containing L. rhamnosus, they reported in the American Society of Microbiology journal mBio.

A "significant protective effect" against arsenic and mercury was seen in pregnant women, project leader Gregor Reid says, and "reduction in these compounds in the mothers could presumably decrease negative developmental effects in their fetus and newborns."

Mercury and arsenic are environmental toxins often present in food products, especially fish, and in drinking water.

In countries where regulation of industrial activities like mining and agriculture is limited or not enforced, levels of the contaminants can be particularly high, the researchers say.

Mwanza, near Lake Victoria, is known for its high levels of environmental pollution.

In the reported study, a similar reduction in heavy metal toxin levels was found in children, although the researchers acknowledge that given the small size of the sample, just 44 children, and the duration of treatment, those results could not be considered statistically significant.

Still, Reid says, the results were encouraging, especially among the pregnant women, where the probiotic yogurt increased their protection from further uptake of arsenic by as much as 78 percent and from mercury by 36 percent.

"The findings are exciting for many reasons," he says. "First, they show a simple fermented food, easily made by resource-disadvantaged communities, can provide benefits in addition to nutrition and immunity.

"Second, the results are relevant for many parts of the world, including Canada, where exposure to these toxins occurs daily."

The researchers said they were continuing their research, funded by the Bill and Melinda Gates Foundation, in an effort to identify probiotic lactobacilli with even more specific mechanisms for sequestering mercury to protect people exposed to it.

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