Amongst the movement of health-minded individuals trying to derive the perfect algorithm for optimal health, there has been a resurgence of consuming raw, or unpasteurized, unhomogenized milk. For more on their perspective, you can peruse http://www.realmilk.com/ - in summary, they push that it's 'natural' dairy and that is therefore better, making a number of claims that I'll address below.
Besides the obvious naturalistic fallacy and lack of scientific backing, I always find it interesting how humans in modern society love to reinstate previously removed selective pressures. This whole camp of raw milkers also seems, to me, to be of the same mindset as the anti-vacciners. I guess everyone's a bit concerned their immune systems were getting off easy? #YODO.
Anyway, do any of these claims stand up to the science?
Claim 1: Pasteurization denatures proteins - sure, pasteurization denatures proteins, so that they are no longer biologically active. This begs the question of whether these biologically active proteins were helpful or harmful in the first place and whether their activity would be preserved in the digestive tract. There are, in fact, bioactive casein-derived peptides that have gotten some recent attention in the literature, but their effect on human health is not known (1,4). Considering these have been studied using mixtures of pasteurized milk and casein extracts, i'm doubtful that pasteurization is destroying anything too beneficial. If any peptide residue differences exist, it remains to be seen how, and which of, these are crossing the gut into the bloodstream to exert biological effects (2). Many make claims, stating that alkaline phosphatase denaturation reduces mineral bioavailability (3), but there isn't any data to support this. The European Food Safety Authority determined that claims regarding casein peptides and their role in immunity against specific non-communicable disease (type 1 diabetes, autism) could not be substantiated or seen as causal (7). Overall, the focus of research on the bioactive/cytomodulatory protein residues in milk don't distinguish between pasteurized vs raw - if there isn't research to say raw milk has superior protein residues, are these claims really based in any science? If i had to take an educated guess, I would say that these are mainly important for the immature, developing mammalian gut, and they exert little effect on adults. Plenty of cultures survive, and thrive, without magical proteins/enzymes from raw milk - you can too.
Claims 2: Pasteurization destroys vitamins and reduces calcium bioavailability - As one can see from the figure below, the vitamin content differences between pasteurized, raw, and even Ultra High Temperature treated milk do not vary significantly. As you can see, milk's two major vitamins are b12 and b2 (riboflavin), and these are not significantly effected by heat treatment. Sure, there are losses of vitamins, but this remains insignificant. Vitamins A andD will be refortified after pasteurization. Milk is not a good source of vitamin E or K to begin with (yes, I am aware of vitamin K2 debates, and I will comment on that at another time). As I have discussed before, the riboflavin content is more dependent on milk's packaging, as it is sensitive to light. Milk is a great source of b12, but so are many other animal products and fortified foods. The bioavailability of calcium, generally considered the most important nutrient in milk, is not affected by heat treatment (5) - calcium bioavailability is only effected in Overheated Milk (6), which is processed for 3cycles, 16 minutes in length, at 116 degrees Celsius, significantly more treatment than UHT-milk, which is used in shelf-safe milk, already a more intense processing than pasteurized. For differences in technologies, see here. If you're that concerned with the nutrients in your milk, being concerned with what the cow ate is probably a better use of your efforts/concern.
Claim 3: Pasteurization kills off important immune molecules - All mammalian milk contains enzymes/proteins that function to bolster/mold the immune system of the developing offspring. Raw milk contains lactoperoxidase, lysozyme and xanthine oxidase, as well as immunoglobulins, bacteriocins and lactoferrin. Several of these do retain activity after pasteurization, but not after UHT. One however must question the importance of these, for a human with an already developed/established immune system. There is not data to suggest that drinking raw mammalian milk reprograms the immune system. And, as with humans, many of the beneficial immunoglobulins present in raw milk are only in the colostrum, which is not readily available for commercial consumption. Even if it was to be consumed, the concentrations in bovine milk are irrelevant to human physiology, and the most predominant, IgG is not effected by heat treatment (8, 9). Raw milk does not provide protection against those with milk allergies or asthma (8, 10).
Claim 4: Pasteurization kills off probiotics and causes lactose intolerance - a recent RCT found no beneficial effect of raw milk on lactose intolerance (11). Sure, in theory, there could be bacteria that could secrete lactase to digest lactose - however, raw milk is refrigerated, which would lower the activity of lactase and leave significant portions of lactose behind. If left unrefrigerated, it would be fermented and would spoil. Lactose intolerance is a genetic issue from the inability to produce beta galactosidase/lactase, not a modern creation via pasteurization. There is a major claim in the pro-raw milk world that Bifidobacterium, a common probiotic, is present in raw milk, and allows for raw milk to be considered a probiotic. This is a nice thought. It is true that there are Bifidobacteria in our guts, but the only way that they get into cow's milk is from the cow's gut AKA cross contamination with feces. The presence of Bifidobacteria is actually used as a measure to determine if the milk has been handled in a hygenic manner (12). If the milk is handled hygenically with minimal potential to come into contact with feces, Bifidobacteria content should be minimal. Probiotics should be safely consumed from foods purposefully inoculated with specific strains of human-relevant bacteria, free of pathogens, in controlled manners - not through random 'natural' cross contamination.
So what does change with milk? It's organoleptic profile AKA it's taste and smell. And this is largely dependent upon the fat content that you're drinking. If you're following the skim milk recommendations, this isn't an issue (8).
In response to realmilk.com, a group of public health advocates have gotten together and created http://www.realrawmilkfacts.com/ - a site that tracks outbreaks from Raw Milk. The fact still stands that pasteurization has drastically reduced the number of food borne illnesses related to raw milk (13), and is considered a public health success story. Sure, many will claim that there are few deaths related to raw milk consumption per year - but how much of the current population is consuming raw milk regularly? It's a 'minimal' risk, right up until the moment your child becomes infected - then it's a preventable tragedy.
I think it's always a nice reminder that, while little data suggests milk is bad for you, there are other sources of calcium, with other/more bone relevant nutrients (vitC,K, magnesium). I always encourage individuals to aim for at least a third of their calcium requirements to come from low, oxalate, dark leafy greens, like collards and kale. And don't forget about exercise.
UPDATE: The CDC has released a recent study (14) showing that the number of raw milk-associated outbreaks between 2007 and 2012 has increased relative to those documented in 1993-2006; they attribute this to 8 additional states since 2004 allowing the sale of raw milk legally.
1.http://www.ncbi.nlm.nih.gov/pubmed/23576048
2.http://www.karger.com/Article/Abstract/61797
3. http://www.naturalnews.com/z028799_pasteurized_milk_raw.html
4. http://www.sciencedirect.com/science/article/pii/S0958694609001071
5. http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2621.1985.tb13021.x/pdf
6. http://www.ncbi.nlm.nih.gov/pubmed/21094734
7. http://www.efsa.europa.eu/en/efsajournal/doc/231r.pdf
8. http://www.sciencedirect.com/science/article/pii/S095671351200535X
9. http://www.fda.gov/food/foodborneillnesscontaminants/buystoreservesafefood/ucm247991.htm
10. http://onlinelibrary.wiley.com/doi/10.1111/j.1398-9995.1988.tb00404.x/abstract
11. http://www.annfammed.org/content/12/2/134
12. http://www.ncbi.nlm.nih.gov/pubmed/10777066
13. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1508307/
14. http://wwwnc.cdc.gov/eid/article/21/1/14-0447_article
Besides the obvious naturalistic fallacy and lack of scientific backing, I always find it interesting how humans in modern society love to reinstate previously removed selective pressures. This whole camp of raw milkers also seems, to me, to be of the same mindset as the anti-vacciners. I guess everyone's a bit concerned their immune systems were getting off easy? #YODO.
Anyway, do any of these claims stand up to the science?
Claim 1: Pasteurization denatures proteins - sure, pasteurization denatures proteins, so that they are no longer biologically active. This begs the question of whether these biologically active proteins were helpful or harmful in the first place and whether their activity would be preserved in the digestive tract. There are, in fact, bioactive casein-derived peptides that have gotten some recent attention in the literature, but their effect on human health is not known (1,4). Considering these have been studied using mixtures of pasteurized milk and casein extracts, i'm doubtful that pasteurization is destroying anything too beneficial. If any peptide residue differences exist, it remains to be seen how, and which of, these are crossing the gut into the bloodstream to exert biological effects (2). Many make claims, stating that alkaline phosphatase denaturation reduces mineral bioavailability (3), but there isn't any data to support this. The European Food Safety Authority determined that claims regarding casein peptides and their role in immunity against specific non-communicable disease (type 1 diabetes, autism) could not be substantiated or seen as causal (7). Overall, the focus of research on the bioactive/cytomodulatory protein residues in milk don't distinguish between pasteurized vs raw - if there isn't research to say raw milk has superior protein residues, are these claims really based in any science? If i had to take an educated guess, I would say that these are mainly important for the immature, developing mammalian gut, and they exert little effect on adults. Plenty of cultures survive, and thrive, without magical proteins/enzymes from raw milk - you can too.
Claims 2: Pasteurization destroys vitamins and reduces calcium bioavailability - As one can see from the figure below, the vitamin content differences between pasteurized, raw, and even Ultra High Temperature treated milk do not vary significantly. As you can see, milk's two major vitamins are b12 and b2 (riboflavin), and these are not significantly effected by heat treatment. Sure, there are losses of vitamins, but this remains insignificant. Vitamins A andD will be refortified after pasteurization. Milk is not a good source of vitamin E or K to begin with (yes, I am aware of vitamin K2 debates, and I will comment on that at another time). As I have discussed before, the riboflavin content is more dependent on milk's packaging, as it is sensitive to light. Milk is a great source of b12, but so are many other animal products and fortified foods. The bioavailability of calcium, generally considered the most important nutrient in milk, is not affected by heat treatment (5) - calcium bioavailability is only effected in Overheated Milk (6), which is processed for 3cycles, 16 minutes in length, at 116 degrees Celsius, significantly more treatment than UHT-milk, which is used in shelf-safe milk, already a more intense processing than pasteurized. For differences in technologies, see here. If you're that concerned with the nutrients in your milk, being concerned with what the cow ate is probably a better use of your efforts/concern.
Claim 3: Pasteurization kills off important immune molecules - All mammalian milk contains enzymes/proteins that function to bolster/mold the immune system of the developing offspring. Raw milk contains lactoperoxidase, lysozyme and xanthine oxidase, as well as immunoglobulins, bacteriocins and lactoferrin. Several of these do retain activity after pasteurization, but not after UHT. One however must question the importance of these, for a human with an already developed/established immune system. There is not data to suggest that drinking raw mammalian milk reprograms the immune system. And, as with humans, many of the beneficial immunoglobulins present in raw milk are only in the colostrum, which is not readily available for commercial consumption. Even if it was to be consumed, the concentrations in bovine milk are irrelevant to human physiology, and the most predominant, IgG is not effected by heat treatment (8, 9). Raw milk does not provide protection against those with milk allergies or asthma (8, 10).
Claim 4: Pasteurization kills off probiotics and causes lactose intolerance - a recent RCT found no beneficial effect of raw milk on lactose intolerance (11). Sure, in theory, there could be bacteria that could secrete lactase to digest lactose - however, raw milk is refrigerated, which would lower the activity of lactase and leave significant portions of lactose behind. If left unrefrigerated, it would be fermented and would spoil. Lactose intolerance is a genetic issue from the inability to produce beta galactosidase/lactase, not a modern creation via pasteurization. There is a major claim in the pro-raw milk world that Bifidobacterium, a common probiotic, is present in raw milk, and allows for raw milk to be considered a probiotic. This is a nice thought. It is true that there are Bifidobacteria in our guts, but the only way that they get into cow's milk is from the cow's gut AKA cross contamination with feces. The presence of Bifidobacteria is actually used as a measure to determine if the milk has been handled in a hygenic manner (12). If the milk is handled hygenically with minimal potential to come into contact with feces, Bifidobacteria content should be minimal. Probiotics should be safely consumed from foods purposefully inoculated with specific strains of human-relevant bacteria, free of pathogens, in controlled manners - not through random 'natural' cross contamination.
So what does change with milk? It's organoleptic profile AKA it's taste and smell. And this is largely dependent upon the fat content that you're drinking. If you're following the skim milk recommendations, this isn't an issue (8).
In response to realmilk.com, a group of public health advocates have gotten together and created http://www.realrawmilkfacts.com/ - a site that tracks outbreaks from Raw Milk. The fact still stands that pasteurization has drastically reduced the number of food borne illnesses related to raw milk (13), and is considered a public health success story. Sure, many will claim that there are few deaths related to raw milk consumption per year - but how much of the current population is consuming raw milk regularly? It's a 'minimal' risk, right up until the moment your child becomes infected - then it's a preventable tragedy.
I think it's always a nice reminder that, while little data suggests milk is bad for you, there are other sources of calcium, with other/more bone relevant nutrients (vitC,K, magnesium). I always encourage individuals to aim for at least a third of their calcium requirements to come from low, oxalate, dark leafy greens, like collards and kale. And don't forget about exercise.
UPDATE: The CDC has released a recent study (14) showing that the number of raw milk-associated outbreaks between 2007 and 2012 has increased relative to those documented in 1993-2006; they attribute this to 8 additional states since 2004 allowing the sale of raw milk legally.
1.http://www.ncbi.nlm.nih.gov/pubmed/23576048
2.http://www.karger.com/Article/Abstract/61797
3. http://www.naturalnews.com/z028799_pasteurized_milk_raw.html
4. http://www.sciencedirect.com/science/article/pii/S0958694609001071
5. http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2621.1985.tb13021.x/pdf
6. http://www.ncbi.nlm.nih.gov/pubmed/21094734
7. http://www.efsa.europa.eu/en/efsajournal/doc/231r.pdf
8. http://www.sciencedirect.com/science/article/pii/S095671351200535X
9. http://www.fda.gov/food/foodborneillnesscontaminants/buystoreservesafefood/ucm247991.htm
10. http://onlinelibrary.wiley.com/doi/10.1111/j.1398-9995.1988.tb00404.x/abstract
11. http://www.annfammed.org/content/12/2/134
12. http://www.ncbi.nlm.nih.gov/pubmed/10777066
13. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1508307/
14. http://wwwnc.cdc.gov/eid/article/21/1/14-0447_article
My wife and I drink raw goat milk - we feel better when we do
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