Fish and fish oil intake in relation to risk of asthma: a systematic review and meta-analysis

Diet and asthma: an update

PURPOSE OF REVIEW

Our objective was to provide an overview and discussion of recent experimental studies, epidemiologic studies, and clinical trials of diet and asthma. We focus on dietary sources and vitamins with antioxidant properties [vitamins (A, C, and E), folate, and omega-3 and omega-6 polyunsaturated fatty acids (n-3 and n-6 PUFAs)].

RECENT FINDINGS

Current evidence does not support the use of vitamin A, vitamin C, vitamin E, or PUFAs for the prevention or treatment of asthma or allergies. Current guidelines for prenatal use of folate to prevent neural tube defects should be followed, as there is no evidence of major effects of this practice on asthma or allergies. Consumption of a balanced diet that is rich in sources of antioxidants (e.g. fruits and vegetables) may be beneficial in the primary prevention of asthma.

SUMMARY

None of the vitamins or nutrients examined is consistently associated with asthma or allergies. In some cases, further studies of the effects of a vitamin or nutrient on specific asthma phenotypes (e.g. vitamin C to prevent viral-induced exacerbations) are warranted. Clinical trials of 'whole diet' interventions to prevent asthma are advisable on the basis of existing evidence.

Fish consumption and risk of myeloma: a meta-analysis of epidemiological studies

PURPOSE

The relationship between fish consumption and multiple myeloma (MM) risk has not been consistent across epidemiological studies. We quantitatively assessed the aforementioned association through a systematic review and meta-analysis.

METHODS

PubMed was searched through the end of March 2015 for eligible studies. Fixed or random effects models were used to pool risk estimates. Five case-control studies that involved 1,366 cases and 8,259 controls were identified. Three studies had high methodological quality, and two studies had low quality based on the Newcastle-Ottawa Quality Assessment Scale.

RESULTS

After pooling all risk estimates, a significant inverse association was found between the highest category versus lowest category of fish consumption and MM risk (relative risk = 0.65, 95% confidence interval = 0.46-0.91), with relatively high heterogeneity (I(2) = 55.6%). No evidence of publication bias was detected. The inverse association persisted in all subgroups according to study quality, type, location, and whether there were adjustments for confounders, although statistical significance was not detected in all strata. The dose-response analysis suggested a nonlinear dose-response relationship for the association, with the lowest risk linked to fish consumption once per week.

CONCLUSION

This meta-analysis suggests that the highest versus lowest category of fish consumption is inversely associated with MM risk. Furthermore, a nonlinear dose-response relationship was suggested for the association. Because this evidence is based on a small number of retrospective studies with mixed quality and because high heterogeneity was detected, further prospective studies are warranted to validate our findings and better characterize the relationship.

Women who take n-3 long-chain polyunsaturated fatty acid supplements during pregnancy and lactation meet the recommended intake

The aim of the current study was to estimate total intake and dietary sources of eicosapentaenoic acid (EPA), docosapentanoic (DPA), and docosahexaenoic acid (DHA) and compare DHA intakes with the recommended intakes in a cohort of pregnant and lactating women. Twenty-four-hour dietary recalls and supplement intake questionnaires were collected from 600 women in the Alberta Pregnancy Outcomes and Nutrition (APrON) cohort at each trimester of pregnancy and 3 months postpartum. Dietary intake was estimated in 2 ways: by using a commercial software program and by using a database created for APrON. Only 27% of women during pregnancy and 25% at 3 months postpartum met the current European Union (EU) consensus recommendation for DHA. Seafood, fish, and seaweed products contributed to 79% of overall n-3 long-chain polyunsaturated fatty acids intake from foods, with the majority from salmon. The estimated intake of DHA and EPA was similar between databases, but the estimated DPA intake was 20%-30% higher using the comprehensive database built for this study. Women who took a supplement containing DHA were 10.6 and 11.1 times more likely to meet the current EU consensus recommendation for pregnancy (95% confidence interval (CI): 6.952-16.07; P<0.001) and postpartum (95% CI: 6.803-18.14; P<0.001), respectively. Our results suggest that the majority of women in the cohort were not meeting the EU recommendation for DHA during pregnancy and lactation, but taking a supplement significantly improved the likelihood that they would meet recommendations.

Fish intake and risk of chronic obstructive pulmonary disease in 2 large US cohorts

BACKGROUND

Despite mechanistic data that linked fish and omega-3 (n-3) PUFAs with lower risk of chronic obstructive pulmonary disease (COPD), epidemiologic data remain scarce. Fish and n-3 PUFAs are an important component of the prudent dietary pattern that is thought to be protective in the onset of COPD.

OBJECTIVE

We examined the role of fish and PUFA intakes on risk of developing COPD while taking into account the overall dietary pattern.

DESIGN

We investigated the objective in 120,175 women and men from the Nurses' Health Study and Health Professionals Follow-Up Study. Over the study period (1984-2000), there were 889 cases of newly diagnosed COPD. Cumulative average intakes of fish, eicosapentaenoic acid, docosahexaenoic acid, n-3 PUFAs, n-6 PUFAs, and the n-3:n-6 ratio were calculated from repeated food-frequency questionnaires. Because fish is a food group included in the prudent pattern, we derived a new prudent pattern without the contribution from fish, and we termed this pattern the "modified prudent" pattern. We performed multivariable Cox proportional hazards models.

RESULTS

Before the dietary pattern was taken into account, and with 14 factors controlled for, we showed that more-frequent fish intake (≥4 servings/wk) was inversely associated with risk of COPD [adjusted pooled HR for the highest intake compared with the lowest intake (<1 serving/wk): 0.71; 95% CI: 0.54, 0.94]. After additional adjustment for the dietary pattern (modified prudent and Western patterns), the association was NS (0.84; 95% CI: 0.63, 1.13). No significant associations were shown between PUFA intakes and risk of COPD.

CONCLUSION

Although COPD-prevention efforts should continue to focus on smoking cessation, these prospective findings support the importance of promoting a healthy diet in multi-interventional programs to prevent COPD instead of focusing on changes in an isolated food or nutrient.

Asthma

Asthma is the most common inflammatory disease of the lungs. The prevalence of asthma is increasing in many parts of the world that have adopted aspects of the Western lifestyle, and the disease poses a substantial global health and economic burden. Asthma involves both the large-conducting and the small-conducting airways, and is characterized by a combination of inflammation and structural remodelling that might begin in utero. Disease progression occurs in the context of a developmental background in which the postnatal acquisition of asthma is strongly linked with allergic sensitization. Most asthma cases follow a variable course, involving viral-induced wheezing and allergen sensitization, that is associated with various underlying mechanisms (or endotypes) that can differ between individuals. Each set of endotypes, in turn, produces specific asthma characteristics that evolve across the lifecourse of the patient. Strong genetic and environmental drivers of asthma interconnect through novel epigenetic mechanisms that operate prenatally and throughout childhood. Asthma can spontaneously remit or begin de novo in adulthood, and the factors that lead to the emergence and regression of asthma, irrespective of age, are poorly understood. Nonetheless, there is mounting evidence that supports a primary role for structural changes in the airways with asthma acquisition, on which altered innate immune mechanisms and microbiota interactions are superimposed. On the basis of the identification of new causative pathways, the subphenotyping of asthma across the lifecourse of patients is paving the way for more-personalized and precise pathway-specific approaches for the prevention and treatment of asthma, creating the real possibility of total prevention and cure for this chronic inflammatory disease.