Does Green Feed Result in Healthier Dairy Products? How can dairy products contribute to a healthy and sustainable diet?

Lifestyle diseases such as cardiovascular disease (CVD) and type 2 diabetes mellitus (T2DM) are a growing problem in the Western world. Dairy products comprise a food group containing a high amount of saturated fat, which has been linked to an increase in CVD risk. However, a recent metaanalysis including 611.430 subjects failed to find any association between dairy product consumption and CVD risk. Consequently, there is less focus on the consumption of saturated fatty acid. However, many attempts have been made to prevent and reduce complications from CVD and T2DM and one strategy is the use of bioactive agents in foods. Phytanic acid (PA), produced by the
degradation of the chlorophyll molecule, is a fatty acid (FA) uniquely found in ruminant fat. PA has been suggested to have beneficial properties with regard to metabolic disorders, due to agonist ctivities for nuclear receptors with central roles in among others the lipid and glucose metabolism.
The content of milk fat PA has been shown to increase with the content of green feed fed to dairy cows. Hence, increasing green feed has the potential to modify the content of this FA in commercially sold dairy products.
The objective of the first part of this PhD thesis was to examine if dairy products (represented by cheese and butter) from cows fed green feed would affect the human concentration of plasma PA differently as compared to dairy products from cows fed conventional feed, and, further to examine the health effects of PA. A second objective was to examine the health effects of dairy products (represented by butter) produced from milk delivered from mountain-pasture grazing cows. This was evaluated on the basis of two human intervention studies where risk markers of CVD and T2DM were assessed.
We found that it is possible to increase human plasma PA concentration after four weeks of intervention with butter and cheese containing even a traditional content of PA, which agrees with observational studies. No significant difference in plasma PA concentration between treatment groups was found; therefore, investigating any effect of PA on metabolic parameters was not possible. However, considering the strong correlation between plasma PA at baseline and total cholesterol and low density lipoprotein cholesterol (LDL-C), it may be suggested that PA have a specific LDL-C rising effects. We found no health beneficial effect on CVD and T2DM risk
markers of butter delivered from mountain-pasture grazing, which had, among other differences, increased PA content compared to butter from conventionally fed cows. As no other study has been published regarding the health of milk delivered from grazing cattle, we cannot compare our findings directly with other studies and further evidence is needed.
During the past few years climate change has been recognized as the major environmental problem facing the world. In the European Union about one third of all emissions are related to the food production. Animal based products are generally associated with relatively large greenhouse gas emissions (GHGE) on a per kg basis compared to vegetable products. Therefore, a change toward a less animal-dependent diet is also one of the solutions often suggested to reduce GHGE. However, products of animal origin also have an important place in a healthy diet because of their high
nutritional value. In addition, when discussing the need to reduce the GHGE caused by the food sector, it is crucial to consider the nutritional value of alternative food choices.
The objective of the second part of this PhD thesis was to elucidate the role of dairy products in overall nutrition and furthermore to clarify the effects of dietary choices on GHGE by creating dietary scenarios with different quantities of dairy products. This was evaluated on the basis of one theoretical study based on national intake data and carbon footprint data of 71 widely consumed food items. Furthermore, an index was used to estimate nutrient density in relation to climate impact
for difference solid food items.
Our dietary scenarios including meat and different quantities of dairy products ranged from 3.6 to 4.8 kg carbon dioxide equivalents (C02e) per day, and 3.1 and 2.4 kg CO2 e per day for the vegetarian and vegan diet, respectively. This result seems to be consistent with other studies. The main contributor to diet-related GHGE was meat and meat products. Our results demonstrate that reducing or eliminating consumption of food items with high or relative high GHGE such as dairy products is not necessarily the best approach to decrease diet-related GHGE. In addition, the effect
on diet-related GHGE depends very much on the substitutions made, as both the GHGE per kg of the substituted product but also its energy density influence the results. We found that reducing or eliminating dairy products from the diet may have nutritional consequences regarding certain nutrients such as calcium. Moreover, our results also indicate an important role of dairy products with regard to vitamin D, riboflavin, and selenium. Beef, polished rice and bananas was low in nutrients compared to their climate impact resulting in a low index value. Interestingly, the index value for pork, chicken, cod and cheese, which generally have a high GHGE per kg product, was more similar to plant based products. This indicates that these products provide key nutrients to a reasonable climate cost. Nutrient profiling combined with climate impact is a new field of research which is essential to encompass nutrition in the climate debate.