Local country food sources of methylmercury, selenium and omega-3 fatty acids in Nunavik, Northern Quebec ☆
- Under a Creative Commons license
Open Access
Highlights
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- More than half of childbearing-age women in Nunavik have at-risk blood Hg levels.
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- Country foods' consumption has declined markedly over recent decades.
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- Most country foods presently consumed in Nunavik are low in Hg.
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- Even if not a staple of the Nunavik diet, beluga meat contributes to most Hg intake.
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- Marine mammal fats, beluga mattaaq and Arctic char are key to omega-3 and Se intakes.
Abstract
Country foods are central to Inuit culture and replete in selenium (Se) and long-chain omega-3 polyunsaturated fatty acids (n − 3 PUFA). However, some marine country foods bioaccumulate high concentrations of methylmercury (MeHg). Se and n − 3 are associated with several health benefits in Nunavik, Northern Quebec, but, recent studies show that prenatal MeHg exposure is associated with visual, cognitive and behavioral deficit later in childhood.
The study objectives are to identify contemporary country food sources of MeHg, Se and long-chain n − 3 PUFA in Nunavik, particularly among childbearing-age women, taking into account regional differences in consumption profiles. The contribution of different country foods to daily MeHg, Se, long-chain n − 3 PUFA intake (μg/kg body weight/day) was estimated using: (i) country food consumption and blood biomarkers data from the 2004 Nunavik Health Survey (387 women, 315 men), and (ii) data on MeHg, Se, long-chain n − 3 PUFA concentrations found in Nunavik wildlife species.
In the region where most traditional beluga hunting takes place in Nunavik, the prevalence of at-risk blood Hg (≥ 8 μg/L) in childbearing-age women was 78.4%. While most country foods presently consumed contain low MeHg, beluga meat, not a staple of the Inuit diet, is the most important contributor to MeHg: up to two-thirds of MeHg intake in the beluga-hunting region (0.66 of MeHg intake) and to about one-third in other regions. In contrast, seal liver and beluga mattaaq – beluga skin and blubber – only mildly contributed to MeHg (between 0.06 and 0.15 of MeHg intake), depending on the region. Beluga mattaaq also highly contributed to Se intake (0.30 of Se intake). Arctic char, beluga blubber and mattaaq, and seal blubber contributed to most long-chain n − 3 PUFA intake.
This study highlights the importance of considering interconnections between local ecosystems and dietary habits to develop recommendations and interventions promoting country foods' benefits, while minimizing the risk of MeHg from beluga meat, especially for childbearing-age women.
Abbreviations
- CDC, Centre for Disease Control and Prevention;
- DHA, docosahexaenoic acid;
- DPA, docosapentaenoic acid;
- EPA, eicosapentaenoic acid;
- FFQ, food frequency questionnaire;
- GM, geometric mean;
- long-chain n − 3 PUFA, long-chain omega-3 polyunsaturated fatty acids;
- LOAEL, Lowest Observable Adverse Effect Level;
- NOAEL, No Observable Adverse Effect Level;
- NCDS, Nunavik Child Development Study;
- NRBHSS, Nunavik Regional Board of Health and Social Services;
- NNHC, Nunavik Nutrition and Health Committee;
- Hg, mercury;
- MeHg, methylmercury;
- Se, selenium;
- pTDI, Provisional Tolerable Daily Intake;
- U.S. EPA, U.S. Environmental Protection Agency
Keywords
- Methylmercury;
- Selenium;
- Long-chain omega-3 polyunsaturated fatty acids;
- Country foods;
- Childbearing age women;
- Nunavik
1. Introduction
Traditional Inuit knowledge passed down through generations emphasizes the importance of wild animals and plants to Inuit diet, medicine, and culture (Cuerrier and the Elders of Kangiqsualujjuaq, 2012a and Cuerrier and the Elders of Kangiqsualujjuaq, 2012b). These country foods, including fish, caribou, birds, whales, seal, seafood and berries, represent Inuit values and identity, as well as their intricate relationship with surrounding ecosystems. For Inuit communities, the hunting, harvesting and sharing of country foods is fundamental to social cohesion and cultural continuity. From an Inuit perspective, despite the increasing presence of market-imported foods in the modern Inuit diet, country foods remain essential for a healthy spirit, mind, intellect and body ( ITK and ICC, 2012).
Scientific research endorses traditional Inuit knowledge regarding the health benefits of country foods. They are replete in proteins, vitamins, minerals and phytochemicals, and those of marine origin, are exceptionally rich in selenium (Se) and long-chain omega-3 polyunsaturated fatty acids (n − 3 PUFA) (Blanchet et al., 2000 and Kellogg et al., 2010). However, Arctic ecosystems have changed markedly over recent decades, and the safety of some country foods may be compromised since they bioaccumulate high concentrations of environmental contaminants, in particular methylmercury (MeHg) (AANDC, 2012).
Arctic populations are especially vulnerable to MeHg exposure (AMAP, 2011 and Donaldson et al., 2010). While no known anthropogenic sources of mercury (Hg) are found in the North, inorganic Hg emissions, primarily now released from coal burning and artisanal and small-scale gold mining in East and Southeast Asia, accumulate at the poles following long-range atmospheric, oceanic, and river transport (UNEP, 2013). In northern aquatic ecosystems, inorganic Hg is transformed into MeHg by microbial action, and further bioaccumulated and biomagnified at the top of the aquatic food chain, primarily in predatory fish and marine mammals, which are often consumed by local populations (AMAP, 2011). In contrast to inorganic Hg, this highly toxic form of Hg is almost completely absorbed by the human intestine and can readily cross the placenta and blood–brain barriers, causing major health effects, particularly on child development (Clarkson, 2002).
Reducing MeHg exposure is a health priority in the Arctic, particularly during pregnancy (AMAP, 2011 and NRBHSS, 2011). The Nunavik Child Development Study (NCDS), a mother-and-child cohort study in Nunavik, Northern Quebec, recently showed that prenatal exposure to MeHg is associated with shorter duration of pregnancy and consequently reduced fetal growth (Dallaire et al., 2013). In addition, prenatal MeHg exposure is associated with several neurological outcomes in school-age children: poorer early process of visual information; altered attentional mechanisms modulating the early processing of sensory information; poorer memory performance; and increased risk of attention problems and Attention Deficit Hyperactivity Disorder of inattentive type (Boucher et al., 2010, Boucher et al., 2012a, Boucher et al., 2012b and Ethier et al., 2012). While none of these visual, cognitive and behavioral outcomes were associated with MeHg exposure during childhood, current exposure to MeHg was associated with lower heart rate variability in school-age Inuit children (Valera et al., 2012), and to lower heart rate variability and hypertension in Nunavik adults (Valera et al., 2008 and Valera et al., 2009).
Some nutrients found in country foods may counterbalance MeHg toxicity (Chapman and Chan, 2000). In Nunavik, high long-chain n − 3 PUFA intake during pregnancy is associated with several benefits including increased birth weight, and child's visual and memory functions (Boucher et al., 2011, Jacques et al., 2011 and Lucas et al., 2004) and a lower prevalence of cardiovascular risk factors among adults (Ayotte et al., 2011, Dewailly et al., 2001b, Valera et al., 2009 and Valera et al., 2011). High dietary Se intake may also contribute to offset some Hg-toxic effects among adults in Nunavik and other fish-eating populations (Ayotte et al., 2011, Fillion et al., 2013, Lemire et al., 2010b, Lemire et al., 2011 and Valera et al., 2009).
Since the 1990's, several authors have pointed to marine mammal consumption or different parts of marine mammals as the predominant source of MeHg exposure in different regions of the Arctic (Dewailly et al., 2001a, Fontaine et al., 2008, Laird et al., 2013, Milman et al., 1994 and Tian et al., 2011). Nonetheless, considering the evolution of Inuit dietary habits in Nunavik (Blanchet and Rochette, 2008), current sources of exposure need to be assessed. Furthermore, because Inuit populations are culturally diverse and live in varying socio-economical contexts and ecosystems, regional differences within the Nunavik territory need to be taken into account in assessing dietary sources of MeHg and nutrients.
The objectives of the present study are to identify contemporary country food sources of MeHg, Se and long-chain n − 3 PUFA in Nunavik, particularly among childbearing-age women, which take into account regional differences in country food consumption profiles and contaminant exposure and nutrient intake patterns. Strategies to balance country food risks and benefits, and develop public health recommendations and community interventions are also discussed.
2. Methods
2.1. Study population
The “Qanuippitaa? How are we?” Nunavik Inuit Health Survey is a cross-sectional study conducted in the fall of 2004 (August 27 to October 1st) among the 14 communities of Nunavik set along the eastern coast of the Hudson Bay (hereafter Eastern Hudson Bay), and the coasts of the Hudson Straight and the Ungava Bay ( Fig. 1). Nunavik lies north of the 55th parallel in Quebec (Canada) and covers a third of the total surface area of the province. This study is based on a large and representative sample of the Inuit population (889 adults aged between 18 and 74 years old), which represented 10% of the Inuit population of Nunavik at that time ( Statistics Canada, 2001). The study design and 2-stage stratified random sampling strategy are detailed elsewhere ( Rochette and Blanchet, 2007), and the participation rate was estimated at 52% for the complete clinical examination ( Valera et al., 2009). Participants were invited on-board the Amundsen research vessel for biological sample collection, and various anthropometric and physiological measurements. Questionnaires were administered to document socio-demographic data, lifestyle habits, and food consumption frequencies. Among the 889 participants, a total of 702 Inuit adults (387 women and 315 men) provided blood samples and completed the anthropometric examination and questionnaires (including general background information, lifestyles and diet), and were included in the present study. Pregnant women were excluded from this analysis (n = 26). Based on our maternal biomonitoring studies in Nunavik, childbearing-age was defined between 18 and 39 years old. Each individual who agreed to participate signed a consent form, which was read to them in their preferred language (Inuktitut, French or English). The study protocol was approved by the Ethics Committee of theCentre Hospitalier Universitaire de Québec (CHU de Québec) and Université Laval.
