MEDITERRANEAN DIET AND DEPRESSION INCIDENCE
Sánchez-Villegas A, Delgado-Rodríguez M, Alonso A, Schlatter J, Lahortiga F, Majem LS, and Martínez-González MA. Association of the Mediterranean dietary pattern with the incidence of depression: the Seguimiento Universidad de Navarra/University of Navarra follow-up (SUN) cohort. Arch Gen Psychiatry. 2009; 66:1090–1098.
Depression is a major public health concern, and relatively little is known about potential preventive strategies to reduce the risk of depressive disorders. Lifetime prevalence of depression in US populations is estimated to be approximately 10%, while Northern European populations having slightly lower rates. In Mediterranean countries the prevalence is lower than in northern countries; for example, in Spain the estimated lifetime prevalence is approximately 4–5%. It is proposed that adherence to a traditionally Mediterranean diet may reduce the risk of depression in these countries. The Mediterranean diet is rich in foods that are associated with reduced inflammation, cardiovascular disease, and metabolic perturbations that may be involved with the risk of depression. Intake of olive oil, in particular, may be protective against depression via improvements in serotonin binding affinity. Some research has shown that a higher intake of olive oil was associated with lower risk of severe depression. In the present report, Sánchez-Villegas et al. examined the relationship between the level of adherence to a traditional Mediterranean diet and development of clinical unipolar depression.
Participants included in the present analysis represent a subset of participants enrolled in the Seguimiento Universidad de Navarra (SUN) trial. SUN is an ongoing trial composed of former University of Navarra students, other university graduates, and professionals from other Spanish provinces. Participant recruitment began in 1999 and is continuously open. Participants complete questionnaires every 2 years on exposures and outcomes related to the larger trial. In the present analysis, data were included from 10,094 participants who were generally healthy and without depression at baseline. Dietary intakes were assessed using validated food frequency questionnaires, and adherence to a traditionally Mediterranean diet was scored and categorized into quintiles. Depression was assessed using participants' self-report of medically diagnosed depressive illness or use of antidepressant medication. Median follow-up was 4.4 years for the current analysis. During follow-up, 480 cases (∼4.75% of the sample) of depression were reported, a rate which is consistent with the estimated rates of depression in the general Spanish population. Participants in the lowest quintile of Mediterranean diet adherence had a greater incidence of depression relative to the higher quintiles. Risk of depression was negatively associated with increased adherence up to the highest two quintiles. When intake of individual foods was examined, there were dose-dependent, inverse relationships for fruit and nuts, legumes, and the ratio of monounsaturated- to saturated-fatty-acids. The authors acknowledge limitations of the study design, including the lack of ability to determine causality in the observed relationships, and limitations on the availability of other psychological characteristics in the SUN cohort. The authors suggest that the overall Mediterranean diet pattern may provide synergistic combinations of dietary antioxidants, natural folates and B vitamins, phytochemicals, and unsaturated fatty acids, which together may be protective against the development of clinical depression.
NEIGHBORHOOD RESOURCES AND TYPE 2 DIABETES
Auchincloss AH, Diez Roux AV, Mujahid MS, Shen M, Bertoni AG, and Carnethon MR. Neighborhood resources for physical activity and healthy foods and incidence of type 2 diabetes mellitus: The Multi-Ethnic Study of Atherosclerosis. Arch Intern Med. 2009;169:1698–1704.
The risk for type 2 diabetes increases with central adiposity, lack of physical exercise, and intake of energy-dense/nutrient-poor foods. Considerable research has been focused at the level of the individual, in terms of an individual's behavior or predisposing risk factors in the ontogeny of type 2 diabetes. Environment also plays a role in the risk of overweight and of poor diet. Previous research shows that living in low-income areas where access to fresh produce, “whole” foods (as opposed to highly processed packaged foods), and where outdoor activity is limited by safety or desirability is associated with increased BMI, insulin resistance, and type 2 diabetes; however, these studies were restricted to relatively small samples and limited geographical areas. Auchincloss et al. report on a long-term, multi-neighborhood analysis of risk for type 2 diabetes as a function of neighborhood features that foster an active lifestyle and healthy eating.
Individuals included in the present analysis (n = 2285) are a subset of The Multi-Ethnic Study of Atherosclerosis (MESA). Participants in MESA ranged in age from 45 to 84 years and were free of cardiovascular disease at enrollment. Data were included for participants in three of the six neighborhoods of MESA: Baltimore City/County, MD; Forsyth County, NC; and New York City/Bronx, NY. Baseline examinations, including blood glucose measurements, were collected between 2000 and 2002, and three follow-up examinations were conducted approximately 1.6, 3.1, and 4.8 years later. Type 2 diabetes was defined as a fasting blood glucose level of 126 mg/dL or higher. Use of insulin was also ascertained. Neighborhood resources were ascertained from an independent population-based random telephone survey as part of the MESA Ancillary Neighborhood Study. Neighborhood resource questions included whether or not it was “pleasant” or “easy” to walk in the area, if there were nearby exercise facilities, and if there was a large, “high-quality” selection of fruits, vegetables, and low-fat foods. Neighborhood resources were scored (range 1 to 5, with 1 being the lowest and 5 being the highest) and categorized into tertiles. Over approximately 5 years of follow-up, about 10% of the study population developed type 2 diabetes. Neighborhood scores were less favorable among individuals who developed type 2 diabetes during follow-up. Individuals living in less favorable environments also had lower income levels, lower physical activity levels, increased rates of smoking, and higher baseline blood glucose levels and BMI scores. When adjusting for other cofactors, neighborhood resources remained a protective factor in the development of type 2 diabetes, and this effect was strongest in individuals under the age of 60 years. The authors suggest that communities lacking resources to support physical activity and foods associated with a healthy diet, such as fresh fruits and vegetables, may increase individual risk for developing diabetes. While considerable effort has been focused on fostering behavioral change in individuals, the present observations on neighborhood resources provide a possible target for community-based interventions in the prevention of type 2 diabetes.
Comment: In his accompanying editorial, Dr. Katz underscores the shift in environment seen over the last half-century, which has preceded the increases seen in obesity and rates of type 2 diabetes. Historically, significantly more physical effort was needed to complete work, chores, and food preparation than is required today. He indicates that changes in the environment that make activity and healthy eating easer for individuals could be of benefit in decreasing rates of type 2 diabetes.
Comment: Katz MH. Quality of residential neighborhood: A modifiable risk factor for type 2 diabetes? Arch Intern Med. 2009;169:1653–1654.
PARASITE INFECTION MODIFIES SUPPLEMENT BENEFITS ON INFANT GROWTH
Rosado JL, Caamaño MC, Montoya YA, de Lourdes Solano M, Santos JI, and Long KZ. Interaction of zinc or vitamin A supplementation and specific parasite infections on Mexican infants' growth: a randomized clinical trial. Eur J Clin Nutr. 2009;63:1176–1184.
Child malnutrition and poor infant growth continue to comprise an important problem in poor areas of the developing world. Micronutrient deficiencies, in particular, are associated with growth faltering and stunting in children. Supplementation with individual micronutrients, however, is not uniformly beneficial in improving growth rates. This observation is likely due to the presence of multiple, simultaneous deficiencies that may act together in stunting. For example, zinc is necessary for the transport and metabolism of vitamin A; thus, zinc status affects vitamin A status. Another major factor in growth failure in children is the presence of parasitic infections, some of which are aggravated by micronutrient deficiency. Low vitamin A is associated with increased levels of Ascaris lumbricoides eggs, and low zinc status is associated with increased parasite numbers and survival. To date, relatively little is known about the interaction between parasite burden and micronutrient supplementation in infant growth. The objective of the present randomized, controlled trial was to ascertain the effects of vitamin A and zinc supplementation, both alone and in combination, on growth rates in children with or without concomitant parasitic infections.
Children from Mexico City, aged 5–15 months (N = 584), were randomly assigned to one of four conditions: placebo, vitamin A alone, zinc alone, and combined vitamin A and zinc. Children were excluded from the trial if there were any indications of immunosuppression, or digestive problems that might affect micronutrient absorption. The vitamin A group received retinol supplements every 2 months for 1 year (20,000 IU for children ≤1 year old; 45,000 IU for children >1 year old). The zinc group received 20 mg/d elemental zinc. The vitamin A and zinc group received both supplement treatments, and the placebo group received an inactive solution. Supplements were given in solution either by field researchers or by caregivers. Parasite infections were determined by microscopic examination of stool samples collected on a monthly basis, and infection withA. lumbricoides, Giardia duodenalis, or Entamoeba spp. was defined as the presence of parasite eggs or cysts. Anthropometric measurements included height/length and weight, and were collected at baseline and at monthly intervals throughout the study. At baseline, approximately 19% of children showed stunting, with 8.6% having low weight-for-age scores. Over the period studied, children were most commonly infected with G. duodenalis followed by Entamoeba spp. and A. lumbricoides. There were no interactions for combined vitamin A and zinc supplementation. Supplementation with vitamin A produced growth improvement in infants with any type of parasitic infection, although the rate of growth was slower in these infants than in those without parasitic infection. Zinc supplementation in infants with G. duodenalis or A. lumbricoides was associated with reduced growth relative to non-infected infants. Although there were no biochemical measures of micronutrient status in the present study, nutritional surveys conducted in the region of Mexico City indicate that approximately 37% of children have low serum retinol levels and approximately 36% have low zinc status. The present findings suggest, however, that children with parasitic infections are not benefiting from micronutrient supplementation to the same degree as uninfected children. The authors indicate that elimination of parasitic infection should therefore precede micronutrient supplementation. Additionally, organizers of nutrient interventions should take into account the prevalence of parasitic infections in specific communities and consider linking supplement programs with parasite eradication programs.
FRUIT INTAKE PROTECTIVE AGAINST CEREBROVASCULAR DISEASE
Mizrahi A, Knekt P, Montonen J, Laaksonen MA, Heliövaara M, and Järvinen R. Plant foods and the risk of cerebrovascular diseases: a potential protection of fruit consumption. Br J Nutr. 2009;102:1075–1083.
Incidence of stroke and other cerebrovascular diseases are predicted to increase over the next several decades. Although reduced smoking rates and better treatment of hypertension have reduced the risk of stroke in some countries, primary prevention of stroke continues to be a major concern. Cerebrovascular disease, like cardiovascular disease, may be altered by nutritional factors such as intake of fruits, vegetables, and cereal grains. Some research suggests that intake of fruits and vegetables reduce the risk of stroke, other research shows a link between whole grain consumption and reduced risk, while some studies show no association for these foods. In the described study, Mizrahi et al. examined whether intake of fruits, vegetables, and cereal grains would be protective against cerebrovascular disease over a 24-year period.
The cohort data included in the present analysis were obtained from the Finnish Mobile Clinic Health Examination Survey, which was conducted between 1968 and 1972. Individuals in this cohort are representative of a population with traditionally low levels of fruit and vegetable intake and high intakes of whole grains, although the Finnish diet has changed in the intervening time. A subset of the cohort, including men and women (N = 3932) aged between 40 and 74 years and free of cardiovascular disease at baseline, was used in the present study. Baseline assessments included dietary history, activity levels, BMI, blood pressure, cholesterol levels, and medication use. Dietary intakes were re-estimated at 4–8 months and 4–7 years after baseline. Primary outcome measures included stroke, ischemic or hemorrhagic stroke, or other cerebrovascular incidents. Morbidity and mortality data were obtained from the Finnish Hospital Discharge Register and from death certificates indexed in Statistics Finland. Incidence of stroke during follow-up was positively associated with older age, higher BMI, higher cholesterol, and higher blood pressure at baseline. Older age was associated with lower intakes of fruits, berries, and vegetables. A higher intake of fruits and berries was associated with a lower incidence of cerebrovascular diseases. This relationship was primarily driven by intake of citrus fruits. Total vegetable consumption was not related to incidence of cerebrovascular disease. When vegetables were analyzed separately, intake of cruciferous vegetables was associated with reduced risk for cerebrovascular disease, and intake of root vegetables and legumes reduced the risk for ischemic stroke. No relationship was seen between intake of whole or refined grains and cerebrovascular disease. The authors acknowledge several limitations associated with longitudinal cohort designs; they also describe how the Finnish diet has changed over the past 24 years. Year-round availability of fresh fruits and vegetables in Finland has increased, and dietary intake of fruits and vegetables increased 2- to 3-fold during the period studied. As older individuals in the cohort were at higher risk for stroke and consumed the lowest levels of produce, it is appreciably difficult to determine the degree to which baseline consumption of fruits conferred a benefit, or if the increase in available produce lent ongoing benefits to younger members of the cohort. The strengths of this study include the long period of follow-up, detailed dietary histories, and comprehensive outcome measures. Intake of fruits, particularly citrus fruits, and intake of cruciferous vegetables may be protective against stroke and cerebrovascular disease.
Comment: Drs. Martínez-González and Lamuela-Raventos commend the authors for obtaining detailed diet histories and comprehensive morbidity and mortality data as well as conducting a long-term follow-up of a large cohort. They note the protective effects of citrus fruits and cruciferous vegetables could be attributable to synergistic effects among vitamin C and flavanones or isothiocyanates. They also urge caution when evaluating data from cohort studies. In nutrition studies, it is difficult to determine whether specific foods provide protective effects, or whether overall lifestyle is the protective factor. Still, cohort studies can hold some advantages over randomized trials, particularly when follow-up is conducted over several decades.
Comment: Martínez-González MA and Lamuela-Raventos RM. The unparalleled benefits of fruit. Br J Nutr. 2009; 102:947–948.