Does rice really contain harmful quantities of arsenic? Dr Michael Mosley of Trust Me, I’m A Doctor investigates.
Many of us are regular consumers of rice – UK consumption is on the rise, and in 2015 we ate 150m kg of the stuff. But there have been reports about rice containing inorganic arsenic – a known poison – so should we be worried?
Arsenic occurs naturally in soil, and inorganic arsenic is classified as a category one carcinogen by the EU, meaning that it’s known to cause cancer in humans.
The consequences of arsenic poisoning have been seen most dramatically in Bangladesh, where populations have been exposed to contaminated drinking water.
The result has been described as a “slow burning epidemic” of cancers, heart disease and developmental problems.
Because arsenic exists in soil, small amounts can get into food, though in general these levels are so low that they’re not a cause for concern.
Rice however, is different to other crops, because it’s grown under flooded conditions. This makes the arsenic locked in the soil more readily available, meaning that more can be absorbed into the rice grains.
This is why rice contains about 10-20 times more arsenic than other cereal crops. But are these levels high enough to do us any real harm?
“The only thing I can really equate it to is smoking,” says Prof Andy Meharg of Queen’s University Belfast, who has been studying arsenic for decades. “If you take one or two cigarettes per day, your risks are going to be a lot less than if you’re smoking 30 or 40 cigarettes a day. It’s dose-dependent – the more you eat, the higher your risk is.”
He believes that the current legislation isn’t strict enough, and that more needs to be done to protect those who eat a lot of rice.
Eating a couple of portions of rice a week isn’t putting an adult like me at high risk, but Prof Meharg is concerned about children and babies.
“We know that low levels of arsenic impact immune development, they impact growth development, they impact IQ development,” he says.
Because of this, the legislation is stricter around products specifically marketed at children – but many other rice products that they may also eat, such as puffed rice cereals, can contain adult levels of arsenic.
It sounds quite scary, even if you don’t eat lots of rice, but there’s an easy solution – a way to cook rice that dramatically reduces the arsenic content.
Now, some ways of cooking rice reduce arsenic levels more than others. We carried out some tests with Prof Meharg and found the best technique is to soak the rice overnight before cooking it in a 5:1 water-to-rice ratio.
That cuts arsenic levels by 80%, compared to the common approach of using two parts water to one part rice and letting all the water soak in. Using lots of water – the 5:1 ratio – without pre-soaking also reduced arsenic levels, but not by as much as the pre-soaking levels.
So, while I would now think twice about feeding young children too much rice or rice products, I’m not going to stop eating rice myself. I will, however, be cooking it in more water and, when I remember, leave it to soak overnight.