Potential impact of restricted caribou (Rangifer tarandus) consumption on anemia prevalence among Inuit adults in northern Canada

Anemia is a major international health issue affecting an estimated 1.62 billion people globally (95% CI: 1.50–1.74 billion), almost a quarter (24.8%) of the world’s total population [1]. Moreover, anemia is disproportionately represented in people of lower socioeconomic strata [2], and Indigenous Peoples in various global regions [3]. Among Inuit (Arctic Indigenous People) in northern Canada, the prevalence of anemia is several times higher than the average prevalence documented in many developed countries (approximately 8%) [4], and corresponds to a moderate (25–30% prevalence) to severe (40–43% prevalence) public health problem [5–7].

Approximately half of all cases of anemia on a global scale are assumed to be caused by dietary iron deficiency, related to inadequate iron intake, poor iron bioavailability, high iron needs, or high loss of iron [8]. However, the etiology of anemia is multifactorial and context-specific (e.g. population, region, and general environmental), with nutrient deficiencies, malaria, infections, inflammatory disorders, blood disorders, and low socioeconomic status, counted among its most frequent causes [8].

The declining consumption of country foods (i.e. wild foods harvested by Inuit using cultural knowledge, and traditional practices) may place Inuit at increased risk for both iron deficiency and anemia [9]. Country foods obtained from hunting, fishing, and trapping, remain fundamental to the Inuit food system, despite rapid sociocultural and economic changes in Inuit communities over the last several decades [10]. While Inuit harvest and consume a diversity of local species (including both plant, and animal species) for culture and subsistence, dietary studies show that caribou (Rangifer tarandus) generally represents the most frequently, and abundantly, consumed country food [11, 12]. Over 90 % of participants in the Inuit Health Survey reported consuming caribou over the previous year, with a mean annual consumption of 29.6–122.8 kg of caribou per person, according to sex, and region [12]. Caribou is also the number one source of iron (up to 36.5% of total population iron intake) and several micronutrients (including zinc, copper, vitamin B₆, and vitamin B₁₂) involved in erythropoiesis reported in contemporary Inuit diets [11, 13].

Many caribou populations across the circumpolar north, however, have experienced dramatic declines (70–97%) in recent decades [14–17], prompting restrictions on Inuit subsistence harvest in several regions of the Canadian north [11]. While Inuit have long adapted to fluctuating cycles of species abundance and migration patterns, the declining use of country foods – which may be related to, or exacerbated by, species declines – may place communities at increased risk of food insecurity and public health issues. Barriers to country food harvest and consumption, whether through species decline (i.e. availability), harvest regulations (i.e. accessibility), and/or other sociocultural, economic and environmental factors that restrict availability and access, are of concern to human health, including (but not limited to) food security and the decline of critical nutrients in the diet. Although many nutrients (e.g. protein) may be provisioned from consumption of alternate country food species [18–20] and/or healthful market foods, certain micronutrients may be limitedly available and/or “unaffordable” in the northern food supply [21]. For instance, when caribou is substituted for other country food species (e.g. muskox (Ovibos moschatus)), intake of zinc, and in some cases iron and vitamin D, is markedly reduced [19]. Furthermore, the high price of animal-source foods in remote northern community stores, may favour the substitution of caribou with lower-cost high-energy density but low nutrient-density foods such as starches and simple carbohydrates [21].

The human health impacts of wildlife declines and harvest restrictions among Arctic Indigenous Peoples are unknown. The goal of this research is to examine the potential human health impact of restricted caribou consumption for Inuit adults in northern Canada. As caribou is a major source of nutrients important in the prevention of anemia, the specific objectives of this research are to: (i) examine the relationship between caribou consumption, hemoglobin (Hb), and blood biomarkers of nutrient status and contaminant exposure; and (ii) examine the theoretical public health impact of restricted caribou consumption, by modelling the response of Hb to caribou intake using multivariable regression. We hypothesize that caribou consumption is positively associated with blood Hb concentrations; thus, restricting caribou intake will lead to an increased prevalence of anemia in the study population.

Inuit have witnessed climate-related changes on various aspects of their traditional food systems, including changes in the accessibility, availability, and condition, of key country food species [18, 32]. In light of emerging livelihood and public health concerns related to caribou declines across northern Canada [33, 34], we have modelled the role of caribou consumption in the maintenance of nutritional adequacy (anemia) for Inuit adults in northern Canada. Previous studies among Inuit adults have reported a positive association between country food consumption, serum ferritin [24], and Hb [6]. The positive association between average daily (annual average) caribou consumption (g/day), serum ferritin, and Hb suggests that barriers to consuming caribou (whether through species decline, associated harvest regulations, and/or other socioeconomic factors that limit subsistence harvests) may represent a concern for public health, including nutrient deficiencies (such as zinc deficiency, associated with diseases such as diabetes and immunological effects [35]) and anemia. While caribou may be substituted for other country food species (e.g. moose or geese), micronutrient levels in the alternate diet may be diminished and result in deficiencies in some individuals [18, 19]. It is important to note, however, that no empirical research has examined changes in nutrition, food security, or public health status, in relation to caribou (or other wildlife) declines and/or related wildlife conservation measures (e.g. harvest quotas) in the Arctic [11]. Given the already high prevalence (up to 68.8%) of food insecurity (i.e. the state of inadequate access to sufficient, safe/nutritious and culturally preferred foods, including country foods) among Inuit in Northern Canada [36], and its adverse association with dietary quality (e.g. higher intake of carbohydrates, and lower intakes of key nutrients such as vitamins C and D, calcium, magnesium, iron, fibre and folate) and blood biomarkers of nutritional status (e.g. lower hemoglobin and serum ferritin levels) documented among Inuit [37], wildlife declines, harvest restrictions, and other factors limiting country food access for Inuit need to be approached (i.e. monitored and responded to, through by appropriate policies and interventions) from a public health perspective.

Although country foods remain vital to the health and wellness of Arctic Indigenous Peoples [10], the public health implications of species declines and harvest restrictions in the Canadian north have not been well studied. While hunting pressures by humans can exacerbate caribou declines, they are not generally recognized as the ultimate cause of population declines [16, 33]. Yet, the health consequences of these declines would be experienced directly by Inuit and other northern Indigenous Peoples who rely on caribou for food security and nutritional adequacy. In Madagascar, wildlife consumption (“bush meat”) contributed approximately 0.7 g/dL to Hb levels in children, and a modelled restriction in bush meat access resulted in an estimated 29% increase in the number of cases of childhood anemia [31]. Nevertheless, even at the international scale, studies on the impact of wildlife depletion and harvest restrictions on food security and human health are limited.

It is important to note that the etiology of anemia among Inuit is not fully understood [5], and recent evidence recognizes non-dietary/nutritional factors (e.g. poverty, household crowding, food insecurity, lead exposure, H. pylori infection, inflammation, chronic blood loss, and impaired iron absorption and/or utilization) [6, 38]. There is also concern that exposure to heavy metals (e.g. lead and mercury) from consumption of country foods may expose individuals to unsafe levels of environmental contaminants and represent concern for anemia (e.g. lead interference with heme biosynthesis). Lead exposure among Inuit has been investigated as a potential cause of anemia and has been found to be negatively associated with Hb in men [6]. In this study, most concentrations of blood nutrients and contaminants remained stable between tertiles of caribou consumption. However, we observed that mean concentrations of %EPA, magnesium, selenium, and mercury were lower in the highest tertile of caribou consumption relative to the lowest tertile. It is noteworthy that although country foods are rich sources of heme iron [23], consumption of total other country food meat (i.e. non-caribou country food meat) was negatively associated with Hb in this study. Frequency of marine mammal consumption has been documented as an independent negative predictor of Hb concentrations in the Inuit population of Canada [6]. It is postulated that high red blood cell EPA status, corresponding to higher intake of marine mammals [39], may contribute to anemia in this population [6]. Higher intakes of n-3 fatty acids may alter platelet function and/or hemostasis and lead to increased gastrointestinal blood loss [40]. Thus, high intakes of caribou may reflect lower intakes of marine mammals, contributing to improved iron status and Hb concentrations.

Women of childbearing age, as well as pregnant and lactating women, who are at increased risk of iron deficiency and inadequacies of magnesium and zinc [41, 42] may be at increased risk of adverse health outcomes from restrictions on caribou harvests. This has significant implications for health and social equity, as maternal health and disadvantage have important consequences for intergenerational equity, including child growth and development [43]. In low- and middle-income countries, for example, maternal anemia status is one of the most significant predictors of anemia in children [44]. Although a low prevalence of iron-deficiency anemia has been documented among Inuit children in Nunavut [38], iron depletion was highly prevalent (33%) among Inuit children in Nunavik, where food insecure children also had a greater burden of nutritional deficiencies and slower linear growth [45]. As described above, the human health effects of wildlife depletion have not been well studied, accordingly the public health risks are largely unknown. Public health interventions for the treatment and prevention of iron deficiency anemia generally include iron supplementation and fortification. Nutrient supplementation strategies such as “Sprinkles” [46], for instance, have been included in strategies to prevent anemia in Indigenous children of northern Canada [47, 48]. While anemia among premenopausal Inuit women is largely attributed to low iron /depleted iron stores [6, 7], the vast majority of anemia cases among Inuit men and post-menopausal women are unexplained by iron status [6]. The clinical significance of anemia among Inuit has not, to our knowledge, been established or described in the literature, and requires further study and monitoring – particularly in light of biodiversity declines.

Several important study limitations warrant mention. First, this study is based on cross sectional data which precludes the direct inference of causality. Thus, the relationship between caribou consumption and hemoglobin levels observed in this study warrants further examination through dedicated case studies, that include both epidemiological designs, but also participatory community-engaged methods to capture the many wellbeing and psychosocial impacts of caribou declines on public health. Second, caribou consumption estimated from the FFQ reflects the average diet during the twelve months preceding the interview, while blood biomarkers reflect a single time point (in the late summer/fall). Accordingly, the relationship observed between caribou consumption and blood biomarkers may differ throughout the year. Third, data from the Inuit Health Survey is aggregated at the regional level, which precluded the possibility of linking human health measures to the status of northern caribou populations. Data for all regions was thus combined and modelled at the population level; however, this may have obscured region, age, and sex risk factors [6]. Nevertheless, this is the first study, to our knowledge, that has attempted to establish empirical links between country food consumption and human health status in the Arctic.

The prevalence of anemia is high in the Inuit adult population of Canada and restricted access to caribou has the potential to further exacerbate this issue. Inuit communities and organizations, conservation scientists, and public health practitioners must work together to implement integrated solutions that ensure the sustainability of caribou populations over the long term, while sustaining food security and public health in the interim. Preventing anemia will also necessitate support to address systemic inequalities (e.g. education, food insecurity and infection) among Inuit [6].