Changes in plasma phospholipid fatty acid profiles over 13 years and correlates of change: European Prospective Investigation into Cancer and Nutrition-Norfolk Study

Abstract

Background: Little is known about changes in blood fatty acid compositions over time and the correlates of any changes in a general population.

Objective: The aim of this study was to estimate changes in 27 individual plasma phospholipid fatty acids and fatty acid groups over time, and to identify potential correlates of these changes.

Methods: Plasma phospholipid fatty acids were profiled at 3 time-points (1993-1997, 1998-2000, 2004-2011) among 722 participants in the European Prospective Investigation into Cancer and Nutrition-Norfolk Study, UK. Linear regression models were used to estimate both 1) mean changes over time in 27 individual fatty acids and 8 prespecified fatty acid groups and 2) associations of changes in dietary and lifestyle factors with changes in the 8 fatty acid groups, mutually adjusted for dietary/lifestyle factors and other confounders. The prespecified fatty acid groups were odd-chain saturated fatty acids (SFAs), even-chain SFAs, very-long-chain SFAs, marine n-3 polyunsaturated fatty acids (PUFAs), plant n-3 PUFA, n-6 PUFAs, monounsaturated fatty acids (MUFAs), and trans-fatty acids (TFAs).

Results: Adjusted for confounders, fatty acid concentrations decreased for odd-chain SFAs (annual percentage difference in mol percentage: -0.63%), even-chain SFAs (-0.05%), n-6 PUFAs (-0.25%), and TFAs (-7.84%). In contrast, concentrations increased for marine n-3 PUFAs (1.28%) and MUFAs (0.45%), but there were no changes in very-long-chain SFAs or plant n-3 PUFA. Changes in fatty acid levels were associated with consumption of different food groups. For example, a mean 100 g/d increase in fatty fish intake was associated with a 19.3% greater annual increase in marine n-3 PUFAs.

Conclusions: Even-chain SFAs and TFAs declined and marine n-3 PUFAs increased over time. These changes were partially explained by changes in dietary habits, and could potentially help interpret associations of baseline fatty acid composition with future disease risk.

Keywords: change; correlates; n–3 polyunsaturated fatty acids; plasma phospholipid fatty acids; repeated measurement; saturated fatty acids; trans-fatty acids.

FIGURE 1

Annual percentage change in 27 plasma phospholipid fatty acids and fatty acid groups in the EPIC-Norfolk study over 13 y. Error bars represent 95% CIs. In the mixed-effects linear regression models, percentage changes in each fatty acid or fatty acid group were adjusted for year of recruitment, sex, and baseline variables of age, BMI, physical activity, smoking status, alcohol drinking, educational level, social class, total energy intake, fish oil supplements, and intakes of 23 food groups (fruit, vegetable, legume, total dairy, eggs, white fish, fatty fish, red meat, white meat, processed meat, liver potatoes, cereal, bread, sweets, nuts and seeds, tea, coffee, fruit juice, sugar-sweetened beverage, alcohol, margarine, and vegetable oil). The column on the left lists the baseline levels of fatty acids and fatty acid groups.

FIGURE 2

Associations between changes in food groups and changes in plasma fatty acid groups from 1993–1997 to 1998–2000 (between study health checks 1 and 2): European Prospective Investigation into Cancer and Nutrition-Norfolk Study. Mixed-effects linear regression models were used in the analyses. Each value represents a mean relative difference (%) in change/y in mol% of each fatty acid group, per 1-standard serving/d/y increase in food groups (*P < 0.05 and **P < 0.01). Red and blue boxes indicate positive and negative associations, respectively, of change/y in food consumption with change/y in mol% of fatty acids. Mean annual changes in mol% of each fatty acid group are presented in the top row (above the box). Serving sizes were defined as 10 g/d for margarine, liver, nuts, and seeds; as 1 g/d for vegetable oil and 10 units/wk for alcohol; and as 100 g/d for the other food groups. All the estimates were mutually adjusted for changes in food groups and baseline consumption levels of those foods, and adjusted for baseline levels of the given fatty acid and other potential confounders (see Methods text for detail). TFA, trans-fatty acids.