The principal biological role of α-linolenic acid (αLNA; 18:3n-3) appears to be as a precursor for the synthesis of longer chain n-3 polyunsaturated fatty acids (PUFA). Increasing αLNA intake for a period of weeks to months results in an increase in the proportion of eicosapentaenoic acid (EPA; 20:5n-3) in plasma lipids, in erythrocytes, leukocytes, platelets and in breast milk but there is no increase in docosahexaenoic acid (DHA; 22:6n-3), which may even decline in some pools at high αLNA intakes. Stable isotope tracer studies indicate that conversion of αLNA to EPA occurs but is limited in men and that further transformation to DHA is very low. The fractional conversion of αLNA to the longer chain n-3 PUFA is greater in women which may be due to a regulatory effect of oestrogen. A lower proportion of αLNA is used for β-oxidation in women compared with men. Overall, αLNA appears to be a limited source of longer chain n-3 PUFA in humans. Thus, adequate intakes of preformed long chain n-3 PUFA, in particular DHA, may be important for maintaining optimal tissue function. Capacity to up-regulate αLNA conversion in women may be important for meeting the demands of the fetus and neonate for DHA. n-3 polyunsaturated fatty acids / humans / α-linolenic acid / metabolism

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Conversion of alpha-linolenic acid to longer-chain polyunsaturated fatty acids in human adults.

https://www.dur-a-avaler.com/wp-content/uploads/2013/02/Red%20meat%20consumption%20An%20overview%20of%20the%20risks%20and%20benefits.pdf

Red meat consumption: an overview of the risks and benefits.

Increasing the concentrations of beneficial polyunsaturated fatty acids in milk produced by dairy cows in high-forage systems

Inflammation is a stereotypical physiological response to infections and tissue injury; it initiates pathogen killing as well as tissue repair processes and helps to restore homeostasis at infected or damaged sites. Acute inflammatory reactions are usually self-limiting and resolve rapidly, due to the involvement of negative feedback mechanisms. Thus, regulated inflammatory responses are essential to remain healthy and maintain homeostasis. However, inflammatory responses that fail to regulate themselves can become chronic and contribute to the perpetuation and progression of disease. Characteristics typical of chronic inflammatory responses underlying the pathophysiology of several disorders include loss of barrier function, responsiveness to a normally benign stimulus, infiltration of inflammatory cells into compartments where they are not normally found in such high numbers, and overproduction of oxidants, cytokines, chemokines, eicosanoids and matrix metalloproteinases. The levels of these mediators amplify the inflammatory response, are destructive and contribute to the clinical symptoms. Various dietary components including long chain omega-3 fatty acids, antioxidant vitamins, plant flavonoids, prebiotics and probiotics have the potential to modulate predisposition to chronic inflammatory conditions and may have a role in their therapy. These components act through a variety of mechanisms including decreasing inflammatory mediator production through effects on cell signaling and gene expression (omega-3 fatty acids, vitamin E, plant flavonoids), reducing the production of damaging oxidants (vitamin E and other antioxidants), and promoting gut barrier function and anti-inflammatory responses (prebiotics and probiotics). However, in general really strong evidence of benefit to human health through anti-inflammatory actions is lacking for most of these dietary components. Thus, further studies addressing efficacy in humans linked to studies providing greater understanding of the mechanisms of action involved are required.

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Inflammatory disease processes and interactions with nutrition

Association between trans fatty acid intake and 10-year risk of coronary heart disease in the Zutphen Elderly Study: a prospective population-based study.

Objective: To assess the intake of trans fatty acids (TFA) and other fatty acids in 14 Western European countries. Design and subjects: A maximum of 100 foods per country were sampled and centrally analysed. Each country calculated the intake of individual trans and other fatty acids, clusters of fatty acids and total fat in adults and/or the total population using the best available national food consumption data set. Results: A wide variation was observed in the intake of total fat and (clusters) of fatty acids in absolute amounts. The variation in proportion of energy derived from total fat and from clusters of fatty acids was less. Only in Finland, Italy, Norway and Portugal total fat did provide on average less than 35% of energy intake. Saturated fatty acids (SFA) provided on average between 10% and 19% of total energy intake, with the lowest contribution in most Mediterranean countries. TFA intake ranged from 0.5% (Greece, Italy) to 2.1% (Iceland) of energy intake among men and from 0.8% (Greece) to 1.9% among women (Iceland) (1.2-6.7 g/d and 1.7-4.1 g/d, respectively). The TFA intake was lowest in Mediterranean countries (0.5 -0.8 en%) but was also below 1% of energy in Finland and Germany. Moderate intakes were seen in Belgium, The Netherlands, Norway and UK and highest intake in Iceland. Trans isomers of C(18:1) were the most TFA in the diet. Monounsaturated fatty acids contributed 9-12% of mean daily energy intake (except for Greece, nearly 18%) and polyunsaturated fatty acids 3-7%. Conclusion: The current intake of TFA in most Western European countries does not appear to be a reason for major concern. In several countries a considerable proportion of energy was derived from SFA. It would therefore be prudent to reduce intake of all cholesterol-raising fatty acids, TFA included. Sponsorship: Commission of the European Communities (AIR 2421); National Funds; European Industries supported the chemical analyses.

A. H. Rimestad

Papers

Intake of fatty acids in western Europe with emphasis on trans fatty acids: the TRANSFAIR Study.

Trans fatty acids in French fries, soups, and snacks from 14 European countries: The TRANSFAIR study