Material and methods

This study was conducted in the municipalities of Quibdó, Río Quito, Cantón, Itsmina, and Condoto, all in the Chocó department (figure 1). This department is in the northwest of the country being border with Panamá. This region is one of the most biodiverse and rainiest in the world (average annual precipitation: 8,000 to 13,000 mm) ²³, and its geography is dominated by extensive jungles and the basins of the Atrato, San Juan and Baudó rivers.

Figure 1 Municipalities included in the study (Chocó, Colombia) 

In Chocó there is gold and platinum mining (a high proportion of this activity is informal and illegal) in a context where there is illegal armed groups and criminal organizations ²⁴. In this way it is a clear example of a region where gold mining is associated with poverty and other manifestations of social inequality ²⁵. The five municipalities were selected because of the high number of workers involved in artisanal gold mining.

The department of Chocó is the one with the highest concentration of Afro population in Colombia. This population began to arrive in Colombian territory since the times of the Conquest, in the 16th century. Gold was the reason that led to the appearance of settlements, and the mining extraction of the gold present in the rivers was the main reason for the Afro to arrive in the region. However, in this jungle region there were multiple Afro and indigenous revolts that prevented large-scale mining until the middle of the 17th century. The possession of slaves was a sign of power and wealth, which ended after the Independence from Spain (1810) and the entry into force of the abolition of slavery in 1851 ²⁶.

Freedom allowed the various Afro communities from Chocó and those who immigrated from other regions to mix and disperse throughout the jungle regions, where they began to have subsistence activities, such as fishing, agriculture, and in some cases artisanal gold mining. The isolation of the Andean regions of the country, from where political and economic power is exercised, allowed the emergence of an Afro culture where colonialism, slavery, Catholic religion, African knowledge and traditions were mixed ²⁷. This together with the government abandonment of this region of the country generated a context of very high social vulnerability. Recent econometric studies show that large-scale slavery during the Colonial period is associated with lower gross domestic product and greater poverty today ²⁸. Without a doubt, these are some of the social determinants with more influence on health conditions of the Afro-Colombian population.

Results

Table 1 shows the characteristics of the participants in the study. It is observed that 85.94% are women and that the median age of the participants was 46 years (between 18 and 98 years old). Of the participants, 41.88% were illiterate, with a marked difference concerning the other educational levels. Many people reported having been previously intoxicated with mercury due to their work activity, which is related to the use of this metal through “barequeo” (activity of washing the sand in a tray or “barequera” to extract gold) for artisanal gold extraction, mainly an activity of women. High mercury concentrations were found in hair, which exceeded up to 39 times the permissible limit in one extreme case.

The frequency of selected selenium-rich food consumption is observed in table 2. Note that the main foods with selenium consumed daily were guava, strawberries, spinach, sunflower seeds, and walnuts. In the opposite, those with less consumption were broccoli, sunflower seeds, and puffed wheat. The association between mercury in hair and consumption of strawberries, sunflower seeds, walnuts, whole wheat flour and yeast extract is in table 3. No associations with other foods were observed. The only gradient protective crude association was observed with the strawberries. In the adjusted models, only protective associations with the monthly consumption of walnuts, whole wheat flour, and yeast extract were observed. This is perhaps a consequence of the low proportion of individuals with high consumption of these foods.

Discussion

Findings of this study suggest that walnuts, whole wheat flour and yeast extract can be used to diminish the levels of mercury among Afro-Colombian individuals exposed in mining activities. Although their consumption is not frequent among this population, the fact that they include these foods in their diet is a good starting point for future dietary interventions. Some traditional foods that use nuts are immature banana juice (jugo de guineo), pineapple colada (colada de piña) and borojó (B. patinoi) sorbet (sorbete de borojó); the traditional cookies cucas (made of wheat flour, panela derived from sugar cane, water, eggs, cinnamon baking powder), and the enyucado (cake based on grated cassava) includes nuts and yeast among its ingredients ²⁹. With these foods it is possible to begin a diet rich in selenium, increasing its content and improving its flavor. Note that selenium-rich foods that may also have high concentrations of mercury, nor foods from other regions that involve spending additional money have not been included.

However, restrictions in the consumption of mercury-rich foods can be included in the diets when there is no risk of causing nutritional deficiencies. In this regard, the consumption of carnivorous fish that have shown higher concentrations of mercury should be avoided ^33-35. The exclusion of breast milk in the diet of neonates and young children ⁸ should not be a generalized option and should only be reserved for cases of severe intoxication, and under supervision of health professionals. Deficiencies in micronutrients such as selenium and zinc can increase susceptibility to the adverse effects of mercury and other toxics. Conversely, a diet rich in antioxidants, such as vitamins C and E, can reduce oxidative stress caused by mercury. For this reason, the importance of adequate nutritional status based on a varied and balanced diet, which contributes to reducing the susceptibility of people to the toxic effects of mercury ³⁶.

Food culture is made up of eating habits, what we eat, when and how we eat. Considering the food culture of populations, especially minorities such as indigenous or Afro-descendant population, is necessary to facilitate that food intervention are successful ³⁷. For the population health practice, it is essential to understand the food culture in particular settings and the complex elements that are related to it, in such a way that food interventions can contribute to improving the health and nutritional status of populations ³⁸.

Those interventions could be based on interculturality and respect for diversity. Factors such as illegal mining, drug trafficking and the presence of armed illegal groups have a negative influence on the nutritional status of the Chocó communities. In Colombia, some studies have been carried out related to eating habits and nutritional status in the Chocó population ^39-44, most of them carried out with children. There are no studies on differential food interventions for the adult Afro-descendant population of Chocó.

This study should be understood with some limitations. The main ones are the cross-sectional design used and the possible confusion due to variables not included that prevent defining causality. The sample was not representative of the Afro-Colombian population in Chocó, but we consider it sufficient to explore selenium-rich foods potentially useful in future interventions.

Additionally, in this study we did not ask about other selenium-rich foods such as fish, shellfish, red meat, eggs, chicken, dairy products and derivatives, or grains and cereals because these would not be included in a culturally adapted intervention. Some of these foods accumulate a lot of mercury and others are not traditional food of the region, which would lead to a cost that would not allow the intervention to be maintained in the medium and long term.

Another limitation was the way of measuring food consumption was not detailed enough, and it is possible that it has measurement errors, which are expressed in the lack of an exposure gradient. However, we consider that this approach could be used as a basis to identify the basic elements of an intervention based on diet in this population group. Further intervention studies could include diets based on our findings and include serum/plasma selenium levels among the participants, to find the amount of selenium- rich food required to achieve the chelating action in this population, without increasing selenium to levels that lead to toxic effects. Reducing exposure to mercury in the population, especially in those groups that live in contaminated areas and in people considered susceptible (children, pregnant and lactating women) should represent a priority for health authorities and for decisionmaking in public health.

In conclusion, this study provides culturally acceptable evidence from Afro-Colombian populations for actions that aim to control environmental exposure to mercury through the consumption of selenium-rich food. Further studies will be able to explore in greater depth the number of selenium-rich foods required to control mercury levels in the population participating in this study and use similar methodologies with other vulnerable groups to define the best culturally accepted strategies to reduce mercury concentrations.