I recently discussed the emerging black market for raw (unpasteurized) milk and the FDA’s crackdown on California farmers. Soon after I posted my comments, a reader asked some detailed questions about heat, enzymes, and milk’s nutritional value. At the same time I received an email from the Vice President of Nutrition Affairs-Health Partnerships at the National Dairy Council, offering to connect me with a dairy product scientist to further the discussion. Isn’t it nice when all the stars align correctly?
I just interviewed Gary Rogers, Ph.D., the Editor-In-Chief of the Journal of Dairy Science and Professor of Animal Science and Dairy Extension Leader at the University of Tennessee in Knoxville. You may listen to the podcast, or enjoy my synopsis below:
Dr. Val: What is pasteurization?
Dr. Rogers: Pasteurization is the heating of milk to a specific temperature for a specified period of time to kill harmful bacteria that may be living in the milk.
Dr. Val: Raw milk enthusiasts argue that pasteurization decreases the health benefits of milk. What exactly is lost when milk is pasteurized?
Dr. Rogers: There are really no important changes that occur (from a nutritional standpoint) to milk when it’s pastuerized. Heat treatment is simply used to kill the bacteria that may present a health risk to those of us who consume milk. Research over the years has shown that there are no significant nutritional benefits to raw milk, but there are risks associated with exposure to bacteria.
Dr. Val: Some people say that raw milk is easier to digest than pasteurized milk. Is that primarily a myth?
Dr. Rogers: Yes, that’s a myth. There is no scientific evidence to suggest that raw milk is easier to digest than pasteurized milk. In fact, many people who have digestive difficulty with fluid milk can eat cheese and yogurt without any difficulty.
Dr. Val: I’ve heard some people claim that there are certain beneficial enzymes in raw milk that are destroyed in the pasteurization process. Is there any truth to that?
Dr. Rogers: There are dozens of enzymes in milk, but most of them are proteases that are involved in the break down of milk proteins and fats. While it’s true that heating can destroy some of these enzymes, they really have no role in human digestion. The enzymes are responsible for milk spoilage, so removing them extends the shelf life of the milk.
Dr. Val: Tell me about UHT milk (the boxed milk that is stored at room temperature) – does it differ -nutritionally and chemically – from pasteurized milk?
Dr. Rogers: UHT (or “ultra-high temperature”) milk undergoes a pasteurization process at a much higher temperature than regular milk. This increases its shelf life, but nutritionally and chemically it’s no different from regular pasteurized milk. It contains all the calcium, phosphorus, and protein of regular milk. However, UHT milk does have a different flavor that some Americans don’t like. In Europe, though, they really enjoy the flavor of UHT milk and often prefer to drink it over pasteurized milk. In the U.S. we use it for flavored milk products, and for military personnel who can’t keep their milk refrigerated as easily.
Dr. Val: I think the key confusion that people have here is that they think of heating milk like heating vegetables. We all know that when we boil vegetables for a long time the nutritional value decreases because their vitamins are removed in the water. However, with milk we’re essentially heating it without removing the “water” part.
Dr. Val: Are US cows exposed to antibiotics and hormones that could find their way into milk?
Dr. Rogers: I know that consumers are very concerned about these issues, but they need to know that every milk tanker is required by law to be tested for antibiotics. There’s a huge incentive for milk producers not to include milk from cows that may have been sick and treated with antibiotics because any tanker that’s found to have any trace of antibiotic in the milk will have its milk discarded. Not only that, but since tankers usually carry milk from multiple producers, one small contribution of contaminated milk will cause all the neigboring farms’ milk to be destroyed. So there’s a lot of peer pressure to keep the milk supply clean. Farmers who contribute milk from cows on antibiotics are fined for the losses of other producers’ milk as well.
As far as “hormones” are concerned, you’re talking about RBST (recombinant bovine growth hormone) to enhance milk production in cows. Although no lab test was ever able to distinguish milk from RBST treated cows from non-treated cows, consumers expressed such concerns about the practice that few milk producers use RBST anymore. I’d say that maybe 10-15% of dairy producers use it, and then it’s not for fluid milk sale, but rather cheese and other dairy products. Those numbers are continuing to decline.
Dr. Val: What does it mean when milk is labeled “organic?” Given the high price of groceries, are there advantages to purchasing organic milk?
Dr. Rogers: I work with both conventional dairy producers and organic dairy producers in my “day job” so I have friends on both sides. As far as nutrition and healthfulness is concerned, organic and conventional milk are equal. The “organic” label has to do with the production practices on the farms that produce the milk, not the properties of the milk itself. On organic farms, they do not use chemical fertilizers or pesticides to raise the crops that they feed to their cows. Some people like the idea of supporting organic farmers and consumers have every right to do that. But both organic milk and conventional milk are safe and equivalent nutritionally.
Milk is heavily regulated and controlled so that even on conventional farms, the pesticides do not get into the milk. All milk is tested for pesticides, and in my experience it has always contained far lower levels than the standard set for safety by the FDA.
Dr. Val: But isn’t it possible that the organic milk might have an even lower level of pesticides in it than conventional milk?
Dr. Rogers: Actually the tests that I’ve seen have not been able to distinguish organic from conventional milk as far as pesticide levels are concerned. However, I haven’t received results from all the organic farms in the U.S. But keep in mind that pesticides exist in such small quantities in milk that usually we can’t even detect them with the most sensitive instruments that we have in the laboratory.
Dr. Val: Is soy milk a good substitute for cow’s milk?
Dr. Rogers: It’s really hard to replicate the nutrition that comes from traditional milk sources. The calcium absorption, amino acids, vitamin, and mineral contents of milk provide a distinct advantage over soy milk, unless you have a specific dairy allergy. In a large recent study on baby formula, for example, there was no advantage to using soy based formulas over cow’s milk. People may prefer to use soy milk for its flavor, or because they support vegetarian food sources. But most soy milk is processed by dairy farms anyway.