Dietary enrichment of eggs with omega-3 fatty acids: A review

Abstract

The health benefits of omega-3 polyunsaturated fatty acids (n−3 PUFA) are generally recognized. Unfortunately, in most western countries, the recommended daily intake of these compounds is rarely met. Therefore, enrichment of commonly occurring foods can boost intake of these fatty acids. In this regard, eggs are an interesting target, as they form an integral part of the diet. Their n−3 PUFA profile can be modified through feed supplementation. A traditional n−3 PUFA source to be added to hens' diet is flaxseed, a plant source rich in α-linolenic acid. Alternatively, hens are often fed fish oil, which is rich in long chain n−3 PUFA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). A more recent trend is feed supplementation with microalgae as a source of EPA and/or DHA. In this paper, recent scientific literature concerning n−3 PUFA enrichment in eggs is reviewed, giving an overview of advantages and disadvantages of the different approaches.

Manipulating dietary PUFA in animal feed: implications for human health

“…Are resulting eggs (a) acceptable and (b) offering a health benefit to consumers? A recent review article on dietary enrichment of eggs with n-3 fatty acids Fraeye et al (6) compares twenty-six studies using linseed, fish oils and/ or micro-algae as the source of n-3 PUFA, conducted between 1991 and 2011. One striking feature of the studies covered in this review is the diversity in the PUFA content reported in eggs from hens on the control treatments, reflecting variability in what might be considered as baseline diets, with respect to both n-3 and n-6 supply.…”

“…The response to supplementation, especially with linseed feeding, was greater if the control diet produced eggs low in n-3. Fraeye et al (6) suggest that dietary n-6 supply is also important as was the type or strain of hens, since their ability to convert ALA to longer chain n-3 varies with genetics and the age of the birds, as well as the relative competition between n-3 and n-6. Most studies covered in the present paper supplemented or substituted diets with linseed (high in ALA), fish oil (high in long-chain n-3 such as EPA and DHA) and/or heterotrophic micro algae (cultured 'seaweeds' also high in long-chain n-3 such as EPA and DHA), all of which appear to increase the n-3 content of eggs and reduce their n-6 concentrations.…”

“…Micro-algae was fed in ten comparisons giving responses similar to fish-oil, with a small increase in ALA (1-fold (SE 0.1)) and a greater rise in DHA content of eggs (4-fold (SE 0.5)). Unfortunately, the effective increase in n-3 content of eggs is only part of the overall story; eggs produced from supplementation often have a 'fishy taint' unacceptable to consumers and the elevated PUFA content may makes them prone to oxidation, although Fraeye et al (6) report micro-algae (especially when fed intact rather than by using an extracted lipid product) is less marked in these respects. In reality, moderate levels of linseed (<10 % of the diet) or the addition of <1·5 % of fish oil might be a tolerable compromise and can elevate DHA content to 40 g/kg total FA.…”

“…Explanations for these differences might be found in a larger European study (20) , which also highlights national variation in milk quality outwith the scope of the local retail study. Under a European research project investigating Quality and Safety in LowInput Food milk quality was compared within Italy, Changes in α-linolenic acid (no fill) and DHA (grey columns) content of egg yolk following linseed supplementation (6) . Columns depict 2nd and 3rd percentiles, with median values and error bars representing the range.…”

“…If attempting to manipulate the fat content of animal-derived food to benefit our health the consensus appears to aim for: (a) reducing SFA, (b) increasing PUFA, (c) increase n-3 PUFA especially long-chain n-3 fatty acids such as EPA (20 : 5 n-3), docosapentaenoic acid (22 : 5 n-3) and DHA (22 : 6 n-3) rather than n-6 PUFA and hence reduce the n-6:n-3 ratio and (d) increase the conjugated linoleic acid (CLA) and possibly vaccenic acid (VA; trans-11-18 : 1) content of ruminant-derived foods (4)(5)(6)(7) . Activity to raise CLA and VA content is a relatively long-standing target for improvement despite the lack of official guidelines for their consumption.…”