Abstract
SFA intakes have decreased in recent years, both in Ireland and across other European countries; however a large proportion of the population are still not meeting the SFA recommendation of <10% of total energy (TE). High SFA intakes have been associated with increased CVD and type-2 diabetes (T2D) risk, due to alterations in cholesterol homoeostasis and adipose tissue inflammation. PUFA, in particular EPA and DHA, have been associated with health benefits, including anti-inflammatory effects. It is well established that dietary fat composition plays an important role in biological processes. A recent review of evidence suggests that replacement of SFA with PUFA has potential to reduce risk of CVD and T2D. The public health and molecular impact of EPA and DHA have been well-characterised, while less is known of effects of α-linolenic acid (ALA). The current dietary guideline for ALA is 0·5% TE; however evidence from supplementation trials suggests that benefit is observed at levels greater than 2 g/d (0·6-1% TE). This review highlights the gap in the evidence base relating to effects of the replacement of SFA with ALA, identifying the need for randomised controlled trials to determine the optimal dose of ALA substitution to define the efficacy of dietary fat modification with ALA.
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Key Points
High saturated fatty acid (SFA) intakes have been associated with increased risk of cardiovascular diseases (CVD), due to their LDL-cholesterol raising properties. SFA have also been associated with
adverse effects upon key biological processes including insulin sensitivity, inflammation and lipid metabolism. Recommendations have been made to reduce SFA intakes by replacing them with PUFA in particular, omega 3. The aim of this review is to discuss the public health and physiological impact of
replacing SFA with PUFA, with an emphasis on ALA. The review provides an overview of current dietary fat intakes, the evidence from RCT and cohort studies relating to replacement of SFA with PUFA and the associated mechanism of action. A substantial body of evidence supports replacement of SFA with PUFA which would reduce population SFA intakes and ultimately reduce disease risk. The paper reviews strategies to modify the fatty acid composition of beef and dairy products through ruminant grass-based feeding practices. This results in a reduction of SFA and an increase in PUFA concentrations, in particular ALA and conjugated linoleic acid. Consumption of grass-fed meat and milk was estimated to decrease LA intakes and the LA:ALA ratio, and increase intakes of ALA, which consequently improves LC n-3 PUFA precursor bioavailability. The authors conclude that while modification of foods to reduce SFA and replace it with PUFA is an attainable public health strategy to reduce SFA intakes and subsequently disease risk, there are still gaps in the knowledge base as to the adequate dose of PUFA replacement. Research needs to be completed and validated in a number of populations to establish if the replacement PUFA dose varies by age, sex and habitual dietary intakes. The global obesity epidemic is greater than fat quality alone, therefore simultaneous, effective public health strategies are required to achieve a healthy diet and lifestyle, and collectively reduce disease risk.