Pregnant Women Can Still Eat (Some) Rice

Dartmouth study found associations between fetal development and consumption of arsenic, which rice often contains.

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Harvesting rice in Thailand: Rice is a staple crop for much of the world, but as a plant, it has a greater affinity for the arsenic naturally found in the ground than other grains. Now a Dartmouth study has linked between arsenic in maternal urine and the birth weight, length and head circumference of the baby, with correlation to maternal weight and the baby's gender.
Harvesting rice in Thailand: People love rice but rice loves arsenic. It now turns out that even low amounts of arsenic can affect birth weight.Credit: Bloomberg

A recent study out of Dartmouth has found that consuming even low levels of arsenic can affect birth weight and length, in overweight women. Separately, the world rediscovered this month that relative to other grains, rice contains relatively high concentrations of this toxic mineral. The worst is brown rice, which may have the highest values of blessed minerals – but also the highest concentration of arsenic.

So should pregnant women abstain from rice? Especially brown rice, despite  its nutritional kick?

"I wouldn't go that far. I think that rice can be part of a healthy diet," Diane Gilbert-Diamond, assistant professor of epidemiology at Dartmouth and lead author of "Relation Between in Utero Arsenic Exposure and Birth Outcomes in a Cohort of Mothers and Their Newborns from New Hampshire", published in Environmental Health Perspectives, told Haaretz. "But I think it's important to eat a varied diet. Rather than only eating rice as a grain, pregnant women should eat a variety of grains and foods, which can help minimize their health risk. It's the best way to get a combination of nutrients as well."

Arsenic sounds like an exotic 19th-century murder weapon but in fact it is a common mineral, is used widely in industry and as a pesticide, it sits in our soil and water, and gets taken up by our crops. Rice in particular seems to take up arsenic.

The website Consumer Reports found measurable levels of arsenic in almost all the 60 rice types it checked, noting that the mineral is also found in rice pasta, drinks and cereals.It cautions: "Regular exposure to small amounts of arsenic can increase the risk of bladder, lung, and skin cancer, as well as heart disease and type 2 diabetes."

Why might arsenic affect fetal development? Because it is a time marked by rapid cell division and differentiation and tissue growth, and is therefore highly sensitive to toxins. Arsenic is one of the toxins that can cross the placenta, as was demonstrated in 1998. Previous studies had mixed results: this one found clear correlations, especially when the mothers were overweight or obese – which can affect arsenic metabolism.

Sugar and spice, and arsenic

The Dartmouth study found that the relationship of arsenic consumption and impact on the baby depended on the weight of the mother and sex of the child.

Even low levels of arsenic consumed by overweight or obese pregnant women can impair the fetal growth of baby girls, the Dartmouth College study on 700 women published this week concluded.

In girls born to overweight or outright obese mothers, each doubling of total urinary arsenic was associated with a nearly 63-gram drop in birth weight, on average.

The study, which was done in New Hampshire, also confirmed the correlation between urinary arsenic levels in overweight or obese mothers - and the birth length of baby boys. The higher the arsenic level in the mother's urine, the longer the baby. Each doubling of total urinary arsenic was associated with an 0.28 centimeter increase in length.

Yet another association was found with the ponderal index, a measure of the baby's leanness (a relationship between mass and height), also known as the Rorh's Index. The higher the arsenic concentration in the mother's urine, the leaner the baby – again, only in the case of overweight or obese mothers, but not normal-weight ones. 

And finally, the researchers found that higher levels of arsenic in the mothers' urine during the second trimester was related to decreased head circumference at birth.

"That head circumference finding was found in everybody," says Gilbert-Diamond. The changes were very small, she clarified – "Each doubling of arsenic was associated with a 0.1 centimeter different in head circumference." (That is not microcephaly, which involves greater diminishment of the head dimensions because of problems with brain development.)

At this stage, the medical establishment does not know if this diminishment in head circumference has any clinical significance, she said.

Although rice is a diet staple for a lot of people, water tends to be the greater concern. Bangladeshis famously suffered when deep-dug wells, intended to solve one whole set of problems, turned out to produce arsenic-rich water, resulting in the largest mass poisoning of a population in history.

The findings regarding fetal impact are a particular concern in rural regions where many people rely on private, unregulated drinking water, stated senior author Margaret Karagas, professor and chair of Geisel's Department of Epidemiology at Dartmouth. "People who use private wells need to have them tested for arsenic and other contaminants as recommended by their local public health agency."

Tip to reduce arsenic in cooked rice: Rinse the rice a lot before cooking, discard any foam that rises during cooking, and re-rinse the rice after cooking.