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Abstract

Feeding algae to enrich dairy products represents a viable option to substantially increase human intake of long-chain n-3 PUFA. There is however, considerable variation between algal sources in their efficiency of uptake into milk for reasons that are as yet poorly defined. Importantly, very little work has been conducted on the effects of enriched milk on cheese quality, despite this being a key product to enhance human LC n-3 PUFA intake. The inclusion of industrially produced algae may reduce enteric methane production, but few studies have been conducted in this area.

Description

There is a large body of evidence to support the beneficial effects of long chain (LC) n-3 polyunsaturated fatty acids PUFA) on cardiovascular health in humans, and there is increasing evidence for their neurological benefits (Gibbs et al., 2009). The important LC n-3 PUFA are 20:5n-3 (EPA) and 22:6n-3 (DHA),  both of which are naturally found in substantial amounts in oil-rich fish, although this occurrence is a direct result of the consumption of phytoplankton that are the abundant natural producers of LC n-3 PUFA at the base of the food chain (Givens, 2001). It is estimated that the mean current intake of LC n-3 PUFA for UK adults is 244 mg/d (Gibbs et al., 2009), considerably below the recommended intake of 450 mg/person/d (SACN/COT, 2004). Animal-derived foods such as dairy products have been highlighted as having the potential to be altered to enhance their LC n-3 PUFA content. It has for example, been calculated that enriched dairy products (particularly cheese) could supply 71.5 mg LC n-3 PUFA per person/d, second only to poultry and considerably more than enriched beef, lamb, pork or eggs at 10.4, 13.0, 2.7 and 54.3 mg per person/d respectively. Despite oily fish being a rich source of LC n-3 PUFA, consumption has declined markedly over the last 50 years (MAFF 2001), and only 27% of the population are regular consumers. In contrast, consumption of dairy products has remained relatively static over the past 10 years (Defra 2011), and enrichment of these products offers the potential to increase the intake of LC n-3 PUFA without markedly affecting consumption patterns.

There is a distinct lack of dietary sources of LC n-3 PUFA that can be included in animal diets. For example, vegetable sources are very low in LC n-3 PUFA (Givens et al., 2001), whilst there are concerns regarding the sustainability of the continued use of fish oils in animals’ diets. In contrast, the industrial production of algae provides a consistent, traceable and sustainable source of LC n-3 PUFA which can be used to enhance product quality. The LC n-3 PUFA content of marine algae varies with the species and growing conditions (Givens et al., 2001), but their content of EPA and/or DHA can be high.

Enteric methane (CH₄) emissions from livestock account for approximately 38.9% of total anthropogenic CH₄ emissions and 5.7% of global anthropogenic emissions, and there is growing interest in developing practical strategies that will lead to a reduction in these emissions. Recent investigations have shown that dietary fat supplements, especially those containing unsaturated fatty acids, may reduce rumen CH₄ emissions (Beauchemin et al., 2008). It has been proposed that LC n-3 PUFA are particularly potent at reducing enteric CH₄ emissions, with in vitro studies having demonstrated a reduction in CH₄ production of up to 80% (Fievez et al., 2007).

In summary, feeding algae to enrich dairy products represents a viable option to substantially increase human intake of LC n-3 PUFA. There is however, considerable variation between algal sources in their efficiency of uptake into milk for reasons that are as yet poorly defined. Importantly, very little work has been conducted on the effects of enriched milk on cheese quality, despite this being a key product to enhance human LC n-3 PUFA intake. Finally, the inclusion of industrially produced algae may reduce enteric methane production, but few studies have been conducted in this area.