A couple months ago I was asked to look into the issue of arsenic in rice. I hesitated because I was concerned about raising undue concern among those with celiac disease who must follow a gluten-free diet. I looked at my own gluten-free diet which I don’t consider to be rice based. The cereal, crackers, and waffles (which I use as bread) are rice based and I frequently eat rice at lunch or dinner. This got me wondering whether I needed to be concerned about the arsenic levels in my own diet. Arsenic in rice may be an important issue for people who follow a gluten-free diet if it is largely rice based. Fortunately, gluten-free diets do not have to be rice based. There are so many other gluten-free grains and flours to choose from and so many ready-made cereals, bread products, and pastas made from grains other than rice. It is a good idea to not eat too much of any food. As poet William Cowper said, “Variety’s the very spice of life, That gives it all its flavor.”
Arsenic is a naturally occurring element that is found in both organic and inorganic forms. It may be present in soil, water, and air. Inorganic arsenic is a known carcinogen and ingestion may cause an increased risk of certain cancers.
In the United States, arsenic standards have been set for water but not food. The Environmental Protection Agency allows no more than 0.01 milligrams of total arsenic per liter of drinking water. The Food and Drug Administration has the same standard for bottled water. No standards have been set for arsenic in food in the United States.
The European Food Safety Authority is in the process of conducting a risk assessment for arsenic in food. EFSA is also assessing:
“the typical ratios between inorganic and organic arsenic forms in different groups of foodstuffs; the contribution of different foodstuffs to human exposure for total arsenic and inorganic arsenic, including the contribution from drinking water; and the exposure of specific population groups (e.g. high consumers, infants and children, people following specific diets, etc.) and to provide an indication of the age group in which children would be most exposed to the toxic effects of arsenic.”
According to the EFSA, several foods may contain inorganic arsenic and contribute to an individual’s exposure, including rice and rice-based products. Recent studies have assessed the arsenic content of baby rice cereal, rice milk, and rice products.
The abstract from the study entitled, “Inorganic arsenic levels in baby rice are of concern” (Meharg AA, et al. Environ Pollut. 2008 Apr;152(3):746-9. Epub 2008 Mar 12) reads as follows:
“Inorganic arsenic is a chronic exposure carcinogen. Analysis of UK baby rice revealed a median inorganic arsenic content (n=17) of 0.11 mg/kg. By plotting inorganic arsenic against total arsenic, it was found that inorganic concentrations increased linearly up to 0.25 mg/kg total arsenic, then plateaued at 0.16 mg/kg at higher total arsenic concentrations. Inorganic arsenic intake by babies (4-12 months) was considered with respect to current dietary ingestion regulations. It was found that 35% of the baby rice samples analysed would be illegal for sale in China which has regulatory limit of 0.15 mg/kg inorganic arsenic. EU and US food regulations on arsenic are non-existent. When baby inorganic arsenic intake from rice was considered, median consumption (expressed as microg/kg/d) was higher than drinking water maximum exposures predicted for adults in these regions when water intake was expressed on a bodyweight basis.”
The abstract from the study entitled, “Inorganic arsenic levels in rice milk exceed EU and US drinking water standards” (Meharg AA, et al. J Environ Monit. 2008 Apr;10(4):428-31. Epub 2008 Mar 7) reads as follows:
“Under EU legislation, total arsenic levels in drinking water should not exceed 10 microg l(-1), while in the US this figure is set at 10 microg l(-1) inorganic arsenic. All rice milk samples analysed in a supermarket survey (n = 19) would fail the EU limit with up to 3 times this concentration recorded, while out of the subset that had arsenic species determined (n = 15), 80% had inorganic arsenic levels above 10 microg l(-1), with the remaining 3 samples approaching this value. It is a point for discussion whether rice milk is seen as a water substitute or as a food, there are no EU or US food standards highlighting the disparity between water and food regulations in this respect.”
A study entitled, “Survey of arsenic and its speciation in rice products such as breakfast cereals, rice crackers and Japanese rice condiments” (Environ Int. 2009 Apr;35(3):473-5. Epub 2008 Sep 4) was recently published. This study assessed the total arsenic level in 40 rice-based products (3 crisped rice cereals, 2 puffed rice cereals, 3 rice malts, 6 rice noodles, 5 rice-based sweets, 11 rice crackers, 1 amazake, 3 rice bran oils, 4 rice vinegars, 2 mirins). Average arsenic levels were highest for rice crackers (0.28 mg/kg), puffed rice (0.24 mg/kg), crisped rice (0.21 mg/kg), and rice malt (0.21 mg/kg). Lower levels were found in rice-based sweets (0.14 mg/kg) and rice noodles (0.12 mg/kg).
For those products with the highest arsenic levels, investigators looked at the specific type of arsenic. They found that the percentage of inorganic arsenic ranged from 75.2 to 90.1 percent.
Study investigators concluded the following:
“It is the diets that comprise of numerous sources of rice or rice based products, such as in macrobiotic, vegan, gluten and dairy intolerance regimens that the cumulative inorganic As exposure is likely to be highest and thereby of greatest concern.”
Dr. Andrew Meharg from the Institute of Biology and Environmental Sciences, University of Aberdeen, Aberdeen, UK and investigator in all 3 above mentioned studies graciously agreed to answer some questions about arsenic and rice.
Why does rice contain higher levels of inorganic arsenic than other cereal grains?
Rice is grown under flooded conditions that lead to high mobilization of soil arsenic into the plant.
What other foods are likely to contain inorganic arsenic?
Seafood has high arsenic, but the species present are organic, which have low toxicity, unlike inorganic arsenic found in rice.
Is there any data available on the threshold level of tolerance for inorganic arsenic? In other words, what amount of inorganic arsenic must be consumed on a daily basis long term in order to cause health problems?
At the low levels found in foodstuffs it is a chronic carcinogen – at higher doses it is an acute toxin.
Are there more arsenic poisonings reported in countries like China and Japan that presumably would have a higher per person rice intake than the general population in the U.S.?
This type of epidemiology takes decades to research, and the problem has just been identified – only detailed study will link food intake from arsenic to observed cancers. Based on US risk assessments, elevated cancers due to rice consumption should be observed.
Are there any steps that can be taken to reduce the inorganic arsenic levels in rice?
1. Growing aerobic rice – cultivated under none-flooded conditions.
2. Source rice from low arsenic regions.
3. Breed rice for low arsenic.
4. High water to rice volumes and discarding the water during cooking moves a large portion of the inorganic arsenic.
What recommendations do you have for individuals with celiac disease who may consume a lot of rice and rice-based products?
Switch to using other grains if possible, or at least to not have such a strong dependence on rice products, and source rice from low arsenic regions – i.e. Californian rice is lower in arsenic that South Central rice.
Thank you Dr. Meharg!
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