«Wild Edible Plant Consumption and Age-Related Cataracts in a Rural Lebanese Elderly Population: A Case control Study By Joelle Zeitouny School of ...»
Obviously, it was not possible to blind the interviewers to each participant’s disease status. Moreover, participants could not be expected to provide themselves written answers to the questionnaires as more than two-thirds were illiterate and around 30% of cases had not had cataract surgery (and thus had poor visual acuity).
Therefore, the interviewers read out all questions clearly, without giving any additional explanations, in order to keep the reliability of the answers to the questions as optimal as possible. There is no reason to suspect that the responses given differed depending on the interviewer as the nutritionist participated in most of the interviews.
Data were collected on the most important potential confounding factors: age, gender, iris color, cigarette smoking and sunlight exposure. These confounders, with their strong interrelations with age-related cataracts, could have had a direct effect on the results obtained, especially that they could have affected the relationship between the intakes of lutein and zeaxanthin as well as other antioxidants and age-related cataracts. Personal field observations revealed that most of the cases had experienced the death of someone close to them, and thus unusually intense and disruptive feelings of grief, before developing age-related cataracts. Hence, cataracts could have 55 been the result of an increased oxidative stress. Further inquiry into the topic was not possible as war broke out in Lebanon a couple of weeks after the fieldwork was completed.
The semi-quantitative food frequency questionnaire used was modified (from a previously validated food frequency questionnaire used by Dr. Malek Batal’s research team to assess food intake -including that of wild plants- in the same area) to include along with staples, local foods particularly rich in lutein and zeaxanthin as well as in other carotenoids (such as β-carotene and lycopene). The semi-quantitative food frequency questionnaire is a widely used tool in dietary assessment. However, it is a relatively crude instrument as it depends on people’s recollection at a given point in time of foods they take over long periods of time; it doesn’t measure accurately what a person actually consumes every day, or how that changes (Van Staveren et al., 1986; Dwyer & Coleman, 1997; Ambrosini et al., 2003), and can overestimate nutrient intake (George et al., 2004). To circumvent the problem of difficulty with portion estimation, food models were used as in previous studies (Moore et al., 1967;
Labadarios, 1999). In addition, the interviewers were trained to ensure the accuracy and consistency of the information obtained.
All twelve common and indigenous wild leafy greens consumed were listed in the questionnaire. In addition, study participants were asked to recall if they consumed any other wild leafy greens and if so, how frequently based on a usual portion size. As mentioned before, wild leafy greens are highly seasonal, and most of them are available only between the months of February and May. The 3-month food frequency questionnaire spread over most of their growing period to capture as much as possible of the yearly intake.
The Food Variety Score (FVS) and the Dietary Diversity Score (DDS), the two measures of dietary diversity used, have both been shown to reflect nutrient adequacy (Ruel, 2002) and dietary quality (Hatløy et al., 1998; Torheim et al., 2004;
Savy et al., 2005) in developing countries. If used alone, the FVS can sometimes give 56 a false favourable impression of the quality of the diet as it counts all the food items consumed, regardless whether they came from the same or different food groups. A high DDS, on the other hand, will reflect a consumption of foods from several of the food groups, and is thus indirectly indicative of a diet of high nutritional quality.
Both the FVS and the DDS have the advantage of being simple, low-cost, and widely used methods for the assessment of the nutritional quality of diets (Ogle et al., 2001).
Measurement periods for FVS and DDS have most commonly ranged from 1 to 3 or 7 days. However, the present study measures FVS and DDS over a period of three months, which makes its comparison to other studies hard and resulted in generalized high DDS.
Some limitations of our study must be acknowledged. First, it was impossible to sort out the contribution of lutein and zeaxanthin from that of β-carotene, vitamin C, α-tocopherol, vitamin A and from plant diversity itself. Moreover, the study did not measure the lens optical density of the cases, or determine the subtype of cataracts that the participants had, which would have drawn a stronger relationship between antioxidant intake and age-related cataracts. In addition, intakes of lutein and zeaxanthin, β-carotene, and vitamin A (the different carotenoids studied) were derived from the consumed food items’ nutrient composition whereas previous research indicates large variations in bioavailability of carotenoids from different plant foods (DePee et al., 1995; Van het Hof et al., 1999b). The nutrient content of the majority of wild leafy greens was estimated using average values from databases (USDA National Cancer Institute Carotenoid Food Composition Database; Calvo, 2005; O’Neill et al., 2001) and may not be accurate. The consumption of wild leafy greens depended not only on the seasonality of supply but also on the accessibility and the availability of these plants on the market (which is often impeded by their short shelf-life). Finally, the study results could not be generalized to the
Age-related eye diseases can be devastating in terms of personal quality of life, as well as national public health and economics. In Lebanon, age-related cataracts are responsible for more than 40% of the causes of blindness (Mansour et al., 1997). The present findings suggest that dietary antioxidants such as lutein and zeaxanthin, β-carotene, vitamin A and vitamin C may contribute to protection against age-related cataracts. Dietary diversity seems to contribute to protection against agerelated cataracts by optimizing nutrient intake. In addition, wild leafy greens seem to substantially contribute to the quality of the diet, especially of those of low socioeconomic status.
In summary, our findings support recommendations to consume a varied diet rich in fruits and vegetables in order to decrease micronutrient deficiencies and health problems that result from a high reliance on refined foods. They also strongly encourage the conservation of traditional knowledge on the identification, collection and consumption of wild leafy greens.
To our knowledge, the present study is the first to look at the relationship between antioxidant intake and age-related cataracts in a developing country. It is also the first study to look at the importance of traditional wild leafy greens in preventing age-related cataracts. Its main strengths are that it was conducted in an ethnically homogeneous population and that it correlated long-term dietary intake and age-related cataracts.
Cataract research is still a fertile field for investigation as few diseases have as great an impact on public health worldwide. Future studies should better elucidate the relation between antioxidant intake and specific opacity subtypes. Relative risk of age-related cataracts in relation to intake of antioxidants could help sort out the contribution of lutein and zeaxanthin from that of other antioxidants after adjusting for confounding variables (Snellen, 2002). The relationship between age-related 59 cataracts and wild leafy greens should be investigated further, particularly in populations that are food insecure. In addition, prospective public health interventions should not undermine the use of wild leafy greens, but should, on the opposite, bolster it and study ways to prolong the period of availability of these plants as they seem to constitute the major source of key micronutrients, especially in the rural areas of developing countries (Humphry et al., 1993; Ogle et al., 2001; Batal & Hunter,
2007) where the rates of cataract are the highest (Xu et al., 2006; Chandrashekhar et al., 2007; Mathenge et al., 2007).
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