Arsenic and Brown Rice, Putting it In - TopicsExpress



          

Arsenic and Brown Rice, Putting it In Perspective: https://drmcdougall/forums/viewtopic.php?p=470631#p470631 I wanted to research this to see how much of a concern this could be. I eat lots of rice and arsenic doesnt have a nice ring to it. First, lets start by some calculations. uncgirl, you worry about the arsenic in your Lundberg brown rice, which was 3.8 - 5.4 μg per 40 g rice in the report[1], which is equivalent to 95 - 135 μg/kg, whereas a typical average value for brown rice is 210 μg/kg [2]. The FAO has withdrawn its Provisional Tolerable Weekly Intake(PTWI) of 15 μg per kg body weight. Now theres a Benchmark Dose Level(BMDL)[4] instead which is different for various outcomes, but they determined that for lung cancer it was 3 μg/kg b.w[3]. The benchmark dose level they used was 0.5% extra risk(BMDL.5). This was a relative risk, so its just a 0.5% increased risk of the absolute risk(which is 7.4% over a lifetime of getting lung cancer[5]. 0.5% of that is a teeny increased risk of 0.04%, in absolute terms). (I hope Ive understood the definition of BMDL correctly [4].) Lets see what happens if youre eating nothing but brown rice. You eat 2000kcal @ 60 kg b.w. which equates to approx 600 g of brown rice. Given 210 μg/kg, thats an intake of 126 μg per day. The BMDL of 3 μg/kg b.w. equates to 180 μg. Youre still beneath the BMDL.5 for lung cancer from the FAO. And I didnt use the Lundberg rice which approx. has half as much arsenic. Now the BMDL isnt meant to be used as a safe amount. Its a limit to show where theres (pretty) good evidence for adverse effects. So people should ideally be well below this limit. Furthermore, reading parts of the EFSA(European Food Safety Authority) report on arsenic in food, they have a range of BMDL01(using 1% increased risk instead of 0.5%) from 0.3 μg/kg b.w. to 8 μg/kg b.w. for various conditions, with lung cancer having a BMDL01 of 0.3 μg/kg b.w[6]. This is extremely different from FAOs estimate, and the reason for this discrepancy it seems are that they base their estimates on different studies. EFSA based it on a small study from Chile. Reading the EFSA report made it clear to me that the evidence of arsenics carcinogenic effects are pretty convincing, also at moderate to low dosages with high precision (thus the ability to calculate BMDL of .5% and 1%). But the effects are probably very small for typical exposures it seems to me. I believe the most convincing evidence has been produced in areas with high drinking water arsenic content, often much, much higher than exposures in most other areas/countries. I wonder what BMDL01 value would be given to number of cigarettes smoked daily. Maybe 0.1 cigarettes. Or sat.fat intake above 5% for instance or similar. I think there are much more important things to be done before people switch away from rice due to arsenic. Also, I do believe one has had long-lived well-healthed populations in regions of naturally high arsenic content. So its probably one of many minor bad guys in relation to health outcomes in my mind. As the consumerreports link you gave, uncgirl, explained, theres also a lot of ways people can greatly reduce arsenic in their diet. Jeffs rice cooking method is one very effective way. Also, the (inorganic) arsenic in brown rice may actually isnt absorbed as much as in other types[7]: The bioaccessibility of arsenic in rice decreases in the general order of extra long grain, long grain, long grain parboiled, to brown rices. Another interesting study[8] on bioaccessibility (in digestion) of inorganic arsenic says that increasing fat, and lower gastric pH increases bioaccessibility of arsenic. This would favour our WOE, I think. Higher bile salts decreased bioaccessibility. However, I may be wrong about the bioaccessibility of arsenic according to this study[9]: An Asian diet background resulted in a larger As bioaccessibility (81.2%) than a Western diet background (63.4%). On the other hand, incubation of As contaminated rice with human colon microbiota in the presence of a Western type diet resulted in a larger amount of hazardous As species - monomethyl arsonite and monomethylmonothio arsonate - to be formed after 48h. The permeability of these As species (60.5% and 50.5% resp.) across a Caco-2 cell line was significantly higher compared to iAsV and DMAV (46.5% and 28% resp.). We conclude that dietary background is a crucial parameter to incorporate when predicting bioavailability with bioaccessibility measurements and when assessing health risks from As following oral exposure. Hopefully this post wasnt more confusing than it was helpful. [1] consumerreports.org/cro/magazine ... /index.htm [2] Elements in rice on the Swedish market: part 2. Chromium, copper, iron, manganese, platinum, rubidium, selenium and zinc. ncbi.nlm.nih.gov/pubmed/18569003 [3] apps.who.int/food-additives-cont ... hemID=1863 [4] https://pesticideresearch/site/?glossary=bmdl10 [5] cancer.org/cancer/cancerbasi ... rom-cancer [6] EFSA report on arsenic in food efsa.europa.eu/en/efsajournal/pub/1351.htm Table 43, page 141 [7] ncbi.nlm.nih.gov/pubmed/22251206 [8] ncbi.nlm.nih.gov/pubmed/23442116 [9] ncbi.nlm.nih.gov/pubmed/25192650
Posted on: Sun, 04 Jan 2015 03:44:16 +0000

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