Dietary Strategies for the Treatment of Cadmium and Lead Toxicity - 01 Introduction
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This is such a good paper, so clear, well written and helpful that I have included it in full
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Nutrients. 2015 Jan; 7(1): 552–571. Published online 2014 Jan 14. doi: 10.3390/nu7010552 PMCID: PMC4303853 Dietary Strategies for the Treatment of Cadmium and Lead Toxicity - Qixiao Zhai,1 Arjan Narbad,2 and Wei Chen1,3,*
Heavy metal toxicity is one of the oldest environmental problems and remains a serious health concern today. Cadmium (Cd) and lead (Pb) are common toxic heavy metals in the environment. The general public is exposed to Cd and Pb through the ambient air, drinking water, food, industrial materials and consumer products
Today, it is the developing countries that are facing the most serious Cd and Pb pollution problems. The threshold for blood lead level (BLL) thought to cause toxicity in children was 60 μg/dL in 1960s but this value was lowered to 10 μg/dL in 1991, subsequently the Centers for Disease Control and Prevention in US reported that they no longer consider any blood lead level to be safe for children.
As a consequence of pollution, the blood lead analyses of 15,727, 14,737 and 13,584 Chinese children in 2004, 2005, and 2006, respectively, showed 10.10%, 7.78% and 7.30% of children had BLL above 10 μg/dL]. A study conducted in Pb polluted areas of Egypt between 2007 and 2008 indicated that 44% of tested children had BLL above 10 μg/dL, and 37% of these had cognitive dysfunction.
As reported in 2010, the average BLL of Indian children from a polluted village was 15.11 ± 5.62 μg/dL . The average Cd concentration of rice from polluted areas in Jiangxi Province of China was 0.59 mg/kg in 2006, which is 2.5 times higher than it was in 1987 and significantly higher than the Chinese Hygienic Standard for rice (0.20 mg/kg). A study conducted in a heavy metal polluted village in Vietnam in 2007 showed that the Cd concentration of rice was 0.31 mg/kg, significantly higher than the maximum allowable concentration for Cd in rice (0.20 mg/kg), as published by the Vietnamese Ministry of Health.
Cd and Pb exposure cause a broad range of adverse health effects in humans and animals.
Cd toxicity is associated with pulmonary, renal , hepatic , skeletal , reproductive and cardiovascular dysfunctions . This non-essential metal is also classified as a group I human carcinogen by the International Agency for Research on Cancer .
Pb exposure induces neurologic and haematological dysfunctions, renal and hepatic damage as well as reproductive disorders in the human body. Children are especially at greater risk because they have higher intestinal Pb absorption and more vulnerable nervous systems which are still under development.
Although a number of different routes by which Cd and Pb cause toxicity have been reported, the underlying basic mechanisms can be summarized as the interactions between Cd/Pb and essential metals and the oxidative stress caused by Cd/Pb exposure. To some extent these two mechanisms are still interrelated because the metabolic disorder of essential metals such as zinc and selenium also induces adverse effects in the oxidative and antioxidative systems.
The most commonly used therapeutic strategy for heavy metal poisoning is chelation therapy to promote metal excretion. However, chelators for Cd and Pb toxicity are themselves reported to have a number of different safety and efficacy concerns.
None of the chelation therapies for Cd toxicity have yet been approved for clinical use thus far.
Chelators such as CaNa2EDTA and meso-2,3-dimercaptosuccinic acid (DMSA) have been reported to have protective effects against Pb toxicity. However, CaNa2EDTA can cause renal toxicity (at the proximal tubule particularly), especially during repeated high doses treatment (above 75 mg/kg) and in subjects with previous history of kidney damage. Because of its relative lack of specificity, other essential metals such as zinc, iron and manganese are also reported to be excreted and depleted following CaNa2EDTA therapy. DMSA also has side effects such as appetite loss, nausea and diarrhea. A study of children being treated with DMSA showed that 12% had mild gastrointestinal symptoms and 5% experienced general malaise.
The development of safe and efficient strategies against Cd and Pb toxicity is therefore an area of ongoing research.
Dietary supplements have been reported to play important roles in the alleviation or prevention of Cd and Pb toxicity. Dietary strategies are advantageous, as nutritional ingredients can easily and affordably be added to the daily diet and can overcome the negative side effects of the chelation therapy.
Herein we review the potential dietary strategies for Cd and Pb toxicity of essential metal, vitamin, edible plant and dietary phytochemical supplementation and probiotics, among others.
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Observation contributed by: John Bryant