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After chewing their cud in pastures all summer, cows that are designated grass-fed will dine on cut grass in barn over the winter.

Gregory Bergman/Getty Images/iStockphoto

Question

What are the differences between grass-fed, organic and regular milk? Is one type more nutritious?

Answer

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Move over almond milk. Thanks to the appearance of grass-fed dairy in grocery stores, cow's milk could be making a comeback with health-conscious consumers already looking for nearly-natural foods. While all types of milk are equivalent when it comes to calcium and vitamin D, it turns out grass-fed milk has other nutritional advantages.

The main differences between grass-fed, organic and conventional milk has to do with the diets the cows are fed. And it certainly seems that the adage "you are what you eat" holds true for cows. Milk from cows that graze on grass – versus eating a grain-based diet on feedlots – is a better source of heart-healthy fats and certain antioxidants.

Grass-fed cattle feed on pasture until the winter months when they're fed cut grasses inside the barn. A diet based on grass results in cow's milk that's higher in an essential fatty acid called alpha-linolenic acid (ALA), an omega-3 fat that reduces inflammation in the body and has been tied to a lower risk of heart disease, stroke and type 2 diabetes. Grass-fed milk has double the omega-3 fat content as conventional milk.

Dairy cattle that produce organic milk are given some access to pasture; at least 30 per cent of their diet must come from grass. When they don't pasture, they're given organic feed that is free of antibiotics, hormones, synthetic pesticides and herbicides and genetically modified ingredients.

Most regular, or conventional, milk from large industrial providers comes from cows that predominantly live inside barns, either indoor pens or tethered to individual stalls, and eat a non-organic feed that includes grain, corn, soy and alfalfa. Corn and soy are high in omega-6 fatty acids, essential fats also needed for health.

The health benefits of essential fatty acids are achieved by getting a proper balance of omega-6 and omega-3 fats. Omega-3 fats can't do their job if they're crowded out with a surplus of omega-6 fats, found in many processed foods. A ratio that's associated with good health is four parts omega-6 to one part omega-3. An even lower ratio, achieved by eating more omega-3s or fewer omega-6s, may be more desirable. Research suggests a omega-6:omega-3 ratio of 2:1 to 3:1 may guard against certain cancers and reduce inflammation in people with rheumatoid arthritis.

The problem is the typical North American diet contains up to 20 times more omega-6 fats (mainly from processed vegetable oils) than omega-3 fats, an unfavourable ratio that's thought to increase the risk of heart disease, diabetes and cancer.

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According to data from the University of Toronto, Ontario-produced Rolling Meadow Grass Fed Dairy's whole milk has an omega-6:omega-3 ratio of 1.8:1 compared with conventional milk that tested as high as 6:1. Some research shows that organic milk also has a more favourable balance of the two fatty acids than conventional milk.

Milk from grass-fed cows also has five times more conjugated linoleic acid (CLA) than conventional milk. CLA, a fatty acid found in dairy and beef, is linked to protection from colorectal and breast cancers, diabetes and heart disease. A 2010 study from the Harvard School of Public Health found people with the highest levels of CLA in their body had a 36-per-cent lower risk of heart attack than those with the lowest levels.

Some data suggest grass-fed milk surpasses conventional milk when it comes to vitamin E, selenium and beta-carotene – antioxidants that protect cells from free-radical damage.

In Canada, dairy milk in general (grass-fed, organic, conventional) does not contain antibiotics or growth hormones. All types of milk are also pasteurized (heated at a high temperature) to destroy illness-causing bacteria. Filtered milk goes through an extra-fine filtration system, which increases its shelf life by 15 days when refrigerated and unopened. (Filtration does not affect nutrient content.)

Many organic and grass-fed milk producers pasteurize at the lowest allowable temperatures to preserve enzymes and enhance taste, resulting in a shorter shelf-life (22 days unopened versus 40 or more). Grass-fed milk comes with a higher price tag though: $5.99 for two litres compared with $3.99 for conventional milk. (High filtered milk is, on average, $4.99 per two litres; organic milk $6.49.)

While milk produced from cows that eat only grass may have a healthier mix of fatty acids, all types of milk are excellent sources of protein, B12 and calcium. And all are fortified with vitamin A and vitamin D.

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Dairy milk by the numbers

Nutrient values are for one cup (250 ml)

Skim (fat-free)

83 calories, 8 g protein, 0.2 g fat (including 0.1 g saturated fat), 12 g carbohydrate, 1.2 mcg B12, 500 IU vitamin A, 100 IU vitamin D, 299 mg calcium

1%

102 calories, 8 g protein, 2.3 g fat (including 1.5 g saturated fat), 12 g carbohydrate, 1.2 mcg B12, 478 IU vitamin A, 100 IU vitamin D, 305 mg calcium

2%

122 calories, 8 g protein, 4.8 g fat (including 3 g saturated fat), 12 g carbohydrate, 1.3 mcg B12, 464 IU vitamin A, 100 IU vitamin D, 293 mg calcium

Whole (3.25%)

149 calories, 7.7 g protein, 8 g fat (including 4.5 g saturated fat), 12 g carbohydrate, 1.1 mcg B12, 395 IU vitamin A, 100 IU vitamin D, 276 mg calcium

Leslie Beck, a registered dietitian, is based at the Medisys clinic in Toronto. She is a regular contributor to CTV News Channel; lesliebeck.com.

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