An ethnographic study of salt use and humoral concepts in a Latino farm worker community in California’s Central Valley

The concept of humoral pathology, or humoral medicine, is widespread, with several major variants existing throughout Asia, Latin America, and Europe in both historical and contemporary times [1‐6]. All variants are based on a model of balance between key material or metaphoric elements necessary for health, with disease or illness resulting from imbalance of these elements [1, 2]. Major European variants are based on the Hippocratic System, which has its origins in ancient Greco-Roman medicine. The Hippocratic System was based on the theory that all substances were made up of four elements – earth, air, fire, and water – in varying amounts. As a result substances possessed the qualities of two uni-dimensional concepts each comprised of two polar opposites: cold versus hot, and wet versus dry. This theory presented the idea that a healthy body is in a state of equilibrium or balance in each of these oppositions. Illness is equilibrium lost, oppositions out of balance: the body becomes too hot, too cold, too wet or too dry [2, 9, 10]. In the context of health, these properties do not refer to the physical temperature or wetness of these elements or substances, but rather to intrinsic qualities, metaphorical and symbolic, in substances such as food or medicines, and in particular environmental conditions [9, 10]. Various authors have examined the existence of similar, or complementary, concepts in the Americas pre-Conquest as well as the transmission of these concepts to Latin America post-Conquest, where the hot-cold dimension has become dominant and the other axes less prominent [9‐20].

Throughout recorded history, sodium chloride (NaCl), commonly known today as table salt, has played an important role in Mesoamerican and Latin American culture, in both cooking practices and healing. Salt has been an essential component in the preparation and enjoyment of Mexican and Central American foods since Mayan and Aztec times [21, 22]. By the time the Spaniards arrived in the early sixteenth century, the Mayans had a vast salt industry and were trading in salt and salted (preserved) goods such as salted fish [23‐25]. In addition to salt as a culinary item, it was a necessary part of daily life. “In the Maya area, for example, dietary salt needs were considerable because the tropical climate and hard work caused abundant salt loss through sweat. People who live in these conditions usually require a minimum of 8–10 g of salt a day” [24]. In ancient Mesoamerica, the Mayans also used salt, in combination with other elements, for other perceived health values; for example, as a form of birth control, in controlling epilepsy and in reducing the pain of childbirth [25].

For the Aztecs, after corn, chili peppers and salt were the most important food ingredients [24, 26]. The Aztecs believed in four young goddesses: sun, maize, fresh water, and salt (Huixtochiuatl, the Lady of Salt) [27]. Sahagún (cited in [26]) provides a rich description of the market of Tlatelolco in pre-Columbus times with vendors selling a variety of salt-cured fish and “squashes and chiles in varied colors from bright red and yellow to deep green… Most gorgeous of all were the edible flowers of cacao, squash, and maguey (Agave) plants… Nearby rose mountains of salt…” ([26], pp. 8–9). Chili peppers, which have been part of the Mexican diet for thousands of years ([28], p. 46), citrus fruit, introduced at the time of the conquest ([28], pp. 52–53), and salt for seasoning, used for millennia [24], are today frequently used to bring out flavors in Mexican food.

Like the Mayans, the Aztecs used salt as an element in healing. Salt was combined with concentrated maguey syrup (agave) to prevent infection in wounds, a practice later examined and claimed to be effective [29]. Historians suggest that the Aztecs had a view of causes and cures for disease that included supernatural (religious, magical) and natural (physical) elements ([18], p. 3). This duality in health beliefs was reflected in Aztec cosmology, which conceived of a universe of permanent conflict between oppositional forces; light and darkness, north and south, heat and cold [14, 18]. Perceived natural causes of illness (excesses, accidents, deficiencies, exposure to sudden temperature changes and contagions) were inextricably connected with the intervention of non-human beings with “more than normal power” [18].

To better understand the long traditions, major continuities and controversies discernable in humoral medicine in Latin America, especially in relation to salt, we present next a summary of major concepts, beliefs and practices as described by seminal (mainly anthropological) authors since the 1950s. These works expand our knowledge of the concepts discussed thus far, and allow us to see how the fundamental theory of humoral medicine resulted in many apparently distinct local practices from a fairly unified set of principles. Understanding this variability underscores the value of understanding humoral concepts in migrant communities and demonstrates how migrants adapt, manipulate, mobilize, transport and meld these belief systems into practical schema. These practical schema also incorporate biomedical concepts and therapeutics, and so become mechanisms that provide literal as well as ‘symbolic’ relief from illness.

Although there were prior studies examining humoral beliefs in Latin America [30‐34], anthropologist George M. Foster is often cited as the early major proponent of the idea that humoral beliefs found in Latin America can be traced back to ancient Greco-Roman humoral theory [9, 12, 14, 15, 35]. In a paper summarizing his 50 years of research on traditional medicine in the village of Tzintzuntzan, Michoacan in Mexico, Foster [9] states that upon the arrival of the Spanish conquistadors, different ways of interacting with the environment, foods and disease theories were introduced to the local populations including the Hippocratic humoral system. Among the Tzintzuntzan villagers, balancing hot and cold qualities could be naturally or materially manifest, but were mainly symbolic or metaphoric [9]. According to Foster, in humoral health practices decisions about treatments depended on various factors: symptoms, parts of the body affected, diagnosis of the cause of the illness, and prior experience with different treatments. He speaks of how illness caused by an “offending heat or cold may be neutralized or countered by mean of internal remedies” ([9], p. 812). Such remedies can be tea infusions, coffee and sometimes foods “of humoral qualities” that are opposite to the cause of the symptom [9].

Another well-known humoral scholar from that era was Madsen [10] who worked in San Francisco de Tecospa, a village at the southern end of the Valley of Mexico. The indigenous people of Tecospa also believed that the universe was ordered by a balance of opposites, two halves of one whole (sickness and health, war and peace, hot and cold). Regaining health was achieved by reestablishing the balance of the body - by consuming food and taking medicine with hot/cold properties perceived to be opposite to those producing sickness. Unlike Foster, however, Madsen argues that this “opposite” system was the same as the Aztec concept of the universe, and at least in part existed pre-Conquest. The Greco-Roman humoral concept of wet/dry was not found in Tecospa beliefs, but a system of ranking qualities by intensity was found in both pre-Conquest and the Hippocratic systems. A new category among the Tecospa had also been introduced: fresh and very fresh, which appeared to some degree to be in opposition to hot. Thus, food was classified as hot and very hot, cold and very cold, and fresh and very fresh [10]. The concept of “temperate” was also present, the result of balanced mixing of hot and cold. The mixing of cold and hot dishes, for example, creates temperate food. When in balance (i.e., when healthy), the human body is temperate [20]. Under the Tecospan system, chili and spicy foods are hot, whereas vegetables such as cucumbers and tomatoes are cold. Certain fruits are classified as fresh for the water that they contain (e.g., apples, grapes, grapefruit, lemon, lime and melon). The most important measure for determining the hot or cold classification of any food was its perceived effect upon the metaphoric temperature or balance of the body. Madsen observes that in situations of work in extreme heat in Tecospa, including work in the fields, fresh foods were perceived to be good because these help to return the body to its normal temperate state [10]. Similarly, in the hot and cold classification of the Zapotec people in Mitla, Oaxaca, Messer [11] reported that lemon is consistently classified as “very cold”, “cold” or “cool.” Taken internally or applied externally as part of a poultice, it was believed to “cool” overheated bodies, to relieve inflammation and to “cool” hot spicy dishes.

Authors since Foster and Madsen have differed on the degree to which they felt the Greco-Roman humoral theory matched, supplanted or complemented indigenous health beliefs. Ortiz de Montellano claimed the Aztecs were receptive to European humoral theories because it mirrored their own system and there was a fusion of cultural beliefs around the hot/cold duality, but the duality of wet/dry was rejected [18]. Other authors, such as Lopez Austin [20], concluded that indigenous hot/cold beliefs pre-dated Hispanic influences and persisted in spite of, and alongside, the introduction of outside influences.

The hot/cold classification process itself has at times been considered to be a “hard” classification; a particular food or type of food is always hot or cold, and differences were considered to be “discrepancies.” At other times, such discrepancies have been explained as resulting from a classification that is based not on the hotness or coldness of an element itself but on its successful use against an illness that is classified as hot or cold; i.e., a food that works to improve or re-balance a hot condition is, by definition, cold [9‐13]. While some researchers discard the need for a full accounting [10], many others have concluded that varying contexts or domains of influence help determine classification. Mathews [36], for example, describes a complex system present in one community in Oaxaca, Mexico in which food items were classified in three ways: for their possible “dangerous” role in meal preparation, their ability to neutralize or moderate sexual behavior, and for their healthfulness in the treatment of illness. She recorded how certain items might be subject to classification as hot or cold in terms of their possible toxicity as a foodstuff, but have no classification in the dimensions of neutralization of sexual behavior, or healthfulness. She also documented how items can possess opposite classifications concurrently. White beans, for example are “considered to be ‘hot’ with respect to the ‘food danger’ dimension” and is therefore served with cold foods, but are ‘cold’ in terms of neutralizing ‘hot’ sexual states.” ([36], p. 838). Mathews’ approach emphasizes the need to understand belief and action in context and to not search for invariant classifications.

In summary, with regard to local health practices in the Americas, disagreements abound with respect to how much empirical evidence, sensory evidence, abstract symbolism, or any combination thereof are incorporated in hot/cold medical theory and practice. In addition, authors have disagreed with regard to how hot/cold beliefs are conceptualized and applied, or how rigidly systematized these are or even need to be [37‐39]. Further, the degree of overlap with biomedical categorizations of disease or dis-order are imperfect: not every indigenous malady has an equivalent in the biomedical system of thought, and not every biomedically-defined disease is recognized within any local humoral system. Moreover, while it is generally accepted that indigenous healers and practitioners have a larger, more complex, more systematized system of knowledge than lay people in their communities, not every healer holds the same beliefs to the same degree [38]. While the basic conceptual apparatus and practice is recognizably and similar, the implementation of these differs somewhat from healer to healer and one circumstance to another. As Messer stated, “Even if they accept different traditional classifications for individual items or follow different paths to classification, they [humoral systems] still share a basic set of rules for classification, and faith in a common system” ([11], p. 139).

California is a major agricultural state with high proportions of Latino migrant and non-migrant farmworkers. This qualitative research study took place in Mendota, Fresno County, a Latino farmworker community in California’s Central Valley (see map [45]). The community’s permanent resident population of 11,148 in 2010–2013, the period during which data were collected, was 97% Latino-origin, comprising primarily first-generation, but also some second-generation, immigrants from Mexico and other Latin American countries [46]. Non-livestock agriculture is the main economic enterprise, especially the growing of cantaloupes and tomatoes, as well as rice, fruits and other vegetables. Approximately 46% of the population lives in households with incomes at or below the United States (US) federal poverty level, defined in 2012 as an annual income less than or equal to $23,492 for a family of four [47, 48]. This high level of poverty is partly due to high seasonal unemployment, the continuing long-term impact of the nationwide economic downturn in 2007–2008, as well as the current drought [49].

People in this farmworker community, like migrant farmworkers generally, experience a range of chronic illnesses. In addition to cardiovascular disease and respiratory disease, these include diabetes, dermatological conditions, high blood pressure, anemia, poor dentition and oral health [42‐44, 50‐53]. Some of these conditions are directly associated with agricultural occupations and some are exacerbated by excess dietary consumption of salt. Environmental exposures (e.g., to pesticides) and climate extremes, especially excess heat, exacerbate many of the illnesses to which members of this population are prone [54]. During the summer and harvest times, daytime temperatures in this region regularly approach 100 °F. Heat waves, which can last for several weeks, at times bring temperatures exceeding 110 °F [55‐57]. Under these conditions, minimizing fluid and sodium losses helps to prevent heat-associated illness for field workers by maintaining thermoregulation [58]. Significant impacts of excess heat can be seen for several disease categories, including cardiovascular disease, respiratory disease, dehydration, acute renal failure, heat illness, and mental health [55]. Thus far the literature contains little documentation of the practices in which Latino fieldworkers engage to establish rehydration, or the ways in which humoral concepts play a role in this.

Study procedures were approved by the University of California San Francisco’s Institutional Review Board (#10-04246), and conformed to the funder’s approved protocol and Clinical Terms of Award. In addition, all study procedures were informed by and approved by two local community advisory boards. Ethnographic mapping and observations of the community’s access to and use of salt along with interviews with key informants (such as restaurant and store managers, local physicians, civic leaders) occurred first. The study aimed to interview 25 to 30 participants and conduct five confirmatory focus groups with 5–8 participants in each group. In-depth interviews in Spanish with individuals in early 2012 were followed by confirmatory focus groups with individuals who had not previously been interviewed, in November 2012. Inclusion criteria for participants were: self-identification as an adult of Latino origin providing care to a child under age 10, and affiliated in some way with farm work (either as a field or crop worker, ranch hand, spouse of a farmworker, or employed in an allied industry such as produce packing or distribution). Participants were recruited through various child-related and community organizations. Each caregiver received $30 compensation for his or her time in the form of a gift card for food at a locally owned supermarket. Study procedures are also described more fully elsewhere [40].

We explored salt beliefs, knowledge, habits and use at home in cooking and eating, and at work while in the fields. In both interviews and focus groups we asked about concerns about salt consumption and its possible effects on health, especially but not exclusively its negative effects. Interviews and focus groups lasted 1.5–2 h with individual interviews conducted in participants’ homes and focus groups in a local community center. Each individual interview and focus group was audio recorded, translated into English, transcribed and imported into NVivo 10.0® qualitative software program [59]. The broadly social constructivist theoretical approach underpinning this study [60] relies on data collection and constant comparison of themes presented by participants to develop a conceptual model of participants’ ideas in relation to: (a) established views (called a priori codes derived from the literature) and (b) viewpoints emerging directly from the observational and text data (also known as post codes) [61‐63]. Three study researchers independently and iteratively read the transcripts, identified and applied codes, analyzed and connected the emerging broad themes in the data. The first round of coding included six categories of classification: salt, work, health problems, food, children and fluoride. Subsequent more detailed analyses focused on the first three of these large categories and their overlaps, and were primarily conducted by the second author. A refinement of the initial salt code, for example, included differentiation of the term ‘sodium’ and ‘salt’, ‘table salt’ from salt used for other purposes such as in water softening devices. Overlaps between the code “table salt” and “work”, for example revealed the ways and reasons why salt featured in certain work settings. In this fashion, we used coding and interpretive practices similar to those described by Strauss and Corbin, especially when identifying emergent themes [61]. Confirmatory readings and discussion of the coding refinements and main themes/findings then occurred among the authors until a consensus was reached on data interpretation.

Illustrative quotations from unique individuals are included in the Results section. These comments are typical of the entire body of general comments on specific topics or ideas made by respondents.

Table 1 outlines the socio-demographic characteristics of participants. A total of 30 people engaged in individual interviews with another 31 participating in the five focus groups. This sample matched well the population targeted for inclusion. The majority of participants were women from Mexico and Central America. The majority of participants or their partners were involved in farm work, a proportion similar to that reported by Stoecklin-Marois and colleagues in a representative sample of the same community [46]. Our participants described their work as taking place in the cotton, fruit and vegetable fields, harvesting cantaloupe, watermelon, tomato, asparagus, onion, garlic, lettuce and broccoli. Major tasks entailed hoeing, pruning, cleaning, picking, sorting and packing in the produce packing plants and distribution centers or at the tomato cannery. All 61 participants were adults who self-identified as Latino with a low-income, with many also reporting a low educational attainment, the mean educational level of the sample being 6th grade (with a standard deviation of 4 grades). The level of acculturation for this community has been reported as “low” [46, 64].

Explanations of the causes of certain illnesses and efforts to prevent illness and restore health were offered by study participants through stories of their daily lives and through detailed descriptions of the actions they took as individuals and as a group when working in the fields. They told, for example, of sharing lemon, salt, and self-prepared liquid solutions to address issues such as extreme heat that threaten the hot-cold equilibrium of the healthy body. One study participant understood her asthma to be a result of constant exposure to extreme and sudden changes in temperature, going from a very hot environment inside of the tomato cannery to very cold air outside, an explanation consistent with biomedical views.

Study Participant: Look, during winter I went in [the factory] and when I came out it was cold and raining [makes troubled breathing sounds.]

Interviewer: That you couldn’t breathe?

Study Participant: Choking because I was coming from the heat to the cold, and that was the hardest.

She also attributed her asthma to inhaling hot steam from bags of tomatoes at the factory while they were being processed at high temperature.

Study Participant: I came out sick with asthma from there. I didn’t have asthma before but since you have to cut the bags [of cooked tomatoes]. The [wheelbarrow] they give you is very hot and you have to cut them really fast… cut it, and shake it and we burn our hands even with the gloves from how hot it is and you inhale all of the steam. That’s why there are a lot of sick people. Because you inhale all of the vapors [steam] from the bag.

For several study participants, colds and coughs common in children, were attributed not only to exposure to extreme weather during the summer and winter months, but also to wide or rapid oscillation in temperatures during the day and night. Here, temperature was meant in both a physical as well as a symbolic sense. One grandmother explained how colds and coughs develop by telling a story about her grandchildren:

Study Participant: Well, because sometimes we don’t pay enough attention and they [children] don’t take care of themselves. They take their clothes off when they’re sweating and that’s really bad, or they take off their shoes if you’re not watching them; they get wet.

Extreme exposures to elements in the environment (weather conditions, hot steam from the tomato cannery, pesticides in the soil, and pesticide “contaminated wind”), and situations in which the individual has limited or a complete lack of control over their work, were often described as issues of “too much” or “too little” (too much heat, too much stress, too much labor insecurity, too much worrying… too little rest, too little time to eat, too little money). Rapid changes in conditions such as these ‘shock’ the body and cause illness. Repeated or sustained exposures to these excesses and extremes also had implications for health. Participants talked about many instances in which prolonged excess of, or lack of, one element would provoke the body to become unbalanced, resulting in illness. One woman in our study identified arthritis as a common problem in this population, while another attributed hand pain to her hands being too frequently immersed in cold water or exposed to icy conditions:

Study Participant: … because the older you get, the more pains you get in your hand…I’ve packed the broccoli in mid-winter so much that by lifting the broccoli container you could see the ice underneath.

Participants recognized cardio-vascular disease or hypertension (high blood pressure) as a common health issue in the community (see also [65]). It is, simultaneously, a formally defined medical condition, diagnosed by physicians and treated biomedically and a ‘folk’ illness amenable to other explanatory schema and therapeutics. Members of the community added other symptoms and causes to this category of illness, in effect redefining what hypertension means: it became “high blood pressure”. This redefined condition was attributed to an accumulation of deep sadness, too much tension, too many worries, thinking too much about problems and working too much (especially in the fields), or resting too little. All of these feelings and exposures added up, accumulated in the body, and caused “high blood pressure.” In a recent study by Aroian and colleagues looking at hypertension prevention and beliefs among Latinos, participants identified certain emotions, such as feeling too “stressed out,” “excited,” “worried” or “upset,” as causes of hypertension [66]. The commonality uniting these emotions is that for the study’s participants they were classed as “hot,” a term that expressed a strong reaction.

In our farmworker community, hypertension as “high blood pressure” was seen as being an endemic problem because of the extremes and persistence of stress. “High blood pressure” was attributed to a persistent lack of food and water when needed; not eating enough or at normal times due to too many hours working in the fields (or, alternately, not having enough work due to the drought); having to wait for the foreman to announce a break, and having limited time to eat on breaks. According to one participant: “as you can see, there is no work. They [people in the town] start thinking about the rent coming up. If they don’t have money to pay for it, then they’ll get kicked out to the street. All of that is expressed by people too.”

When asked who suffers more from high blood pressure, one of our study participants said that it was women more than the men “…because we [women] go here and there. When we come home from work we still have to cook, to wash and … well, the pressure we have. Like we have to go to work the next day, we have to make lunch, to get the things for the kids ready.”

When situations were out of one’s control, and for situations in which distress was constant, it was difficult for the body by itself to restore balance and return to its normal state. In such instances, symptoms can be treated but often balance is restored only temporarily. Symptoms identified as being a result of “high blood pressure” were treated by actions such as talking to a neighbor, or someone one trusted, −“to tell her things, to get it off of your chest”- or going for a walk to distract oneself. Consistent with humoral healing practices, foods with particular characteristics were often used to alleviate symptoms of “high blood pressure” and other health issues. In order to restore balance resulting from “high blood pressure” or blood pressure oscillating from high to low, several participants used “dark soda” (e.g., Coca Cola® or Pepsi®) and a “pinch of salt.” Other therapeutic variations included combining dark soda, lemon and salt, or combining coffee with salt. The physiological symptoms of “low blood pressure,” as expressed by study participants, were low physical energy, vertigo, sweating and vomiting, often occurring in situations of sustained physical exercise and sweating, especially in extreme heat [67]. When referring to “low blood pressure,” one woman said she would also use a “red popsicle” in order to get her “energy to go up.” Madsen, working among the Tecospa in Mexico, noted that dark colors, including black, brown, dark green, purple, and red, were considered hot, with black and red the most important colors for classifying an object’s symbolic temperature [10]. Thus “hot” dark soda, coffee or a red popsicle would counteract the literal and metaphoric “cold” induced by sweating or water leaving the body. Several participants reported combining salt and coffee to prevent or address heat-related symptoms. Foremen would also provide salt and coffee to fieldworkers.

Study Participant: So, they [the foremen] would sometimes give us coffee with salt. According to them [foremen] so that we would feel better. The foreman would sometimes carry coffee. “Oh, I feel dizzy from the heat!” Wait, just wait, let me give you some coffee and salt.

Interviewer: And they would give you that?

Study Participant: They would give us that instead of sugar. You would feel better with that, I’m not going to say we didn’t.

Like “high” and “low blood pressure,” the development of diabetes was also attributed to states that were extreme, such as a persistent state described as ‘hunger,’ said to be caused by events similar to those inducing “high blood pressure”: lack of time to eat while working in the fields and foremen not giving workers a break. Work hours frequently extended from early morning to afternoon, such as 3:00 am to 1:00 pm, or 5:00 am to 4:00 pm, times not conducive to eating meals as a family. Stomach problems – abdominal pain, cramps – were attributed not just to excess heat but also to not eating well in the fields, a result of being too tired to eat, opting for rest during breaks instead of eating, and working too much.

In general, preventing illness, addressing symptoms, restoring and maintaining health through re-establishing equilibrium were important daily goals for study participants who worked in the fields. Getting sick to the point of not being able to work was not an option. Work in the fruit orchards or vegetable fields lasted only part of the year and opportunities for a regular income outside harvest season were severely limited [68].

Not every medical condition recognized as prevalent in this community was subject to humoral explanation. Community members, for example, knew that, in common with many Latino farmworker communities nationwide they - and their children especially - had high rates of dental decay (caries) and unmet dental care needs [69‐71]. Study participants were interested in, even eager to find caries preventive that was safe, effective, easy to use, and low cost. They rejected the usual approach, water fluoridation, for a variety of reasons, importantly the shared belief that the tap water was unsafe and unpleasant to drink. Residents in this community have reported that the city’s tap water commonly smells of sewage and chlorine, and has a yellow appearance particularly in the mornings [41]. Participants expressed a willingness to embrace an effective alternate caries preventive if it were easily available– namely, salt fluoridation [40]. At no point, however, were concepts derived from humoral pathology, diagnostics, treatment or practice invoked in their discussions about caries, its prevention, recognition or treatment.

This qualitative study is limited because it involves a small convenience sample of low-income, Latino individuals in a single, rural site. Caution must therefore be exercised in generalizing results, especially to other Latino groups with different socio-economic backgrounds, migration experiences, greater health literacy or who reside in other geographic areas in the US. Nevertheless, data from our California Central Valley community are robust and consistent with findings from other contemporary studies with Spanish-speaking Latino groups, in both the US and elsewhere. These studies suggest that influences from humoral theory are likely to be found among (rural) migrant Latino groups, and therefore merit continued study. Investigation is needed into the ways Latino farmworkers conceive vulnerability to illnesses, both biomedical and humoral, and what they do to combat, ameliorate or prevent those ailments. The influence of humoral beliefs on rural field and factory workers’ management of occupational exposures, work endurance and health, particularly in conditions of extreme heat are especially worthy of further detailed ethnographic investigation. While empirical observations of the existence, expressions and processes of illness and illness prevention often match the perspective of a contemporary biomedical model, a Latino fieldworker’s understanding of the underlying causes of these expressions and processes can differ dramatically from those of biomedically trained personnel.