Hein van Valenberg is since 2002 ass prof at the dairy science and Technology Group of Wageningen University, the Netherlands. The main teaching activities are for the course Dairy Chemistry & Physics and the supervision of thesis students. Research topics are the causes of variation in milk fat and protein composition on the characteristics of milk and dairy products.
Concentrations of very long chain omega -3 (or n-3) fatty acids, such as EPA, in bovine milk fat and their relations with α-linolenic and linoleic acid.
The very long chain (VLC) omega-3 or n-3 FA, EPA and DHA, can be synthesized by humans from α-linolenic acid. This metabolic pathway does not provide adequate levels of EPA and DHA for optimal human health; additional intake of EPA and DHA is recommended to levels between 250 and 450 mg per day.
Cows can convert dietary ALA and LA into VLC fatty acids via the n-3 and n-6 metabolic pathways. Average concentrations in Dutch bovine milk fat of the n-3 fatty acids ETA, EPA, and DPA are 0.041, 0.067 and 0.086 g per 100 g FA, respectively, whereas DHA concentrations are lower than 0.020 g per 100 g FA. Based on these results, the contribution of milk fat to the daily intake of EPA, DPA and DHA was calculated for human consumption levels. Milk fat contributes around 13 % to the daily intake of EPA and around 28% to the intake of DPA; whereas DHA contribution is marginal.
The sum of the n-3 fatty acids concentrations , derived from ALA, is on average 0.23 mg per 100g FA. The level of these VLC n-3 fatty acids is positively correlated with ALA and negatively with LA concentrations. The negative correlation can be explained by substrate competition between ALA and LA during the first step of the n-3 and n-6 pathways.
At high ALA (0.80 g/100 g of FA) and low LA levels (0.55 g/100 g of FA) in milk fat the quantity of n-3 VLC fatty acids derived from ALA, is twofold higher than average. This quantity is comparable with human milk fat composition, however, DHA levels in human milk are always higher. It can be hypothesized that concentrations of ETA, EPA and DPAn-3 can be increased by feeding cows ratios high in ALA and low in LA content.
Hein van Valenberg. Dairy Science and Technology Group of Wageningen University, the Netherlands.