In Canada, artificial growth hormones are not permitted for use in either conventional or organic milk production. Strict measures and best practices with respect to antibiotic use and animal welfare are also in place for all milk produced in Canada, including conventionally produced milk.
In addition to these regulations, organic milk production complies with Canadian Organic Standards.1
In practice
- Significantly higher levels of omega-3 fatty acids and conjugated linoleic acid (CLA) have been found in organic milk products, but it is not clear whether these differences are clinically important;
- There is no evidence to suggest that organic products, including milk, provide health benefits that are different from conventionally produced foods;
- Other than the farming method (i.e., organic vs. conventional), many factors, including the season and the feeding regimen, affect the nutritional content of milk and milk products.
Factors that affect the nutritional composition of milk
The farming method (i.e., organic vs. conventional) is one of the factors that can vary the nutritional profile of milk.
Many other factors may also affect the nutritional composition of milk and milk products, including:2,3
- The season;
- The cattle feeding regimen (which is affected by the season as well as vitamin and mineral supplementation);
- Genetic variability and cattle breed.
What research says about organic milk
To date, several studies have suggested that organic milk may have a more desirable fatty acid composition than conventional cow’s milk. For instance, findings from a meta-analysis published in 2016 indicated that organic milk contained statistically significantly higher concentrations of total polyunsaturated and omega-3 fatty acids, as well as conjugated linoleic acid.4
However, the relevance of these findings from a nutritional and clinical standpoint is unclear:
- Canada’s Food Guide recommends having at least 2 servings of fish per week, which would provide about 0.3 to 0.45 g of EPA and DHA (omega-3 fatty acids) per day.5 According to the meta-analysis, 2 cups (500 mL) of full-fat milk would provide 39 mg if organic, and 25 mg if conventional.4 This represents ~10% and 6%, respectively, of the recommended amount, which is a relatively small proportion.
- Or, in absolute values, switching from drinking 2 cups of full-fat milk that has been conventionally produced to one that is organic would result in a 14 mg increase in omega-3 fatty acid intake.4 This is unlikely to be clinically meaningful when considering the diet as a whole.
- The results may not reflect the Canadian context. Out of the 170 studies included in the meta-analysis, only 7 used Canadian data. The majority (76%) of the studies were conducted in Europe.4
- The difference observed in the fatty acid composition of organic versus conventional milk was mainly due to contrasting feeding regimens rather than the farming method itself.
The high intake of fresh forage by grazing cattle was found to have a desirable effect on the fatty acid contents in milk.4 In fact, it was also observed that cows on organic farms received more fresh forage, which would explain why organic milk had a more favourable nutritional profile in terms of fatty acids. A 2012 meta-analysis suggested that a higher intake of fresh forage by cattle on conventional farms would also drive a higher nutritional quality of the milk produced.3 Another review suggested that the concentration of several nutrients in milk, including the omega-6 to omega-3 fatty acid ratio, can be manipulated through feeding regimens.6
- Most of the studies included in the analyses evaluated raw rather than pasteurized milk, and caution is required when interpreting the results.
- Furthermore, several studies have indicated that the milk production season may affect fatty acid content as much as the farming method.7
Moreover, a systematic review compared the health effects of organic foods to those of conventional alternatives.7 The authors concluded that the published literature lacks strong evidence that organic foods are significantly more nutritious than conventional foods.
Conclusion
Emerging evidence suggests that organic milk products are higher in certain nutrients such as omega-3 fatty acids and CLA. However, it is not clear whether these differences in nutritional composition are important in terms of health benefits.
Future studies that include randomized controlled trials and large, long-term cohort studies should address the clinical relevance of differing nutrient levels in organic versus conventional milk products. These studies should also account for variations in milk composition due to seasonality and feeding regimens.
Additionally, research focused on Canadian milk products is essential to determine whether these differences apply to milk produced in Canada.
References
- Agriculture and Agri-Food Canada. 2012. Organic Dairy Industry in Canada – 2012 Edition. www.dairyinfo.gc.ca. Accessed April 1, 2016.
- Forman J et al. Organic foods: health and environmental advantages and disadvantages. Pediatrics 2012;130:e1406-1415.
- Palupi E et al. Comparison of nutritional quality between conventional and organic dairy products: a meta-analysis. J Sci Food Agric 2012;92:2774-2781.
- Średnicka-Tober D et al. Higher PUFA and n-3 PUFA, conjugated linoleic acid, α-tocopherol and iron, but lower iodine and selenium concentrations in organic milk: a systematic literature review and meta- and redundancy analyses. Br J Nutr 2016;115:1043-1060.
- Dietitians of Canada. 2013. Food sources of omega-3 fats. www.dietitians.ca. Accessed April 13, 2016.
- Haug A et al. Bovine milk in human nutrition – a review. Lipids Health Dis 2007;6:25.
- Smith-Spangler C et al. Are organic foods safer or healthier than conventional alternatives?: a systematic review. Ann Intern Med 2012;157:348-366.
