Wednesday, April 1, 2015
My milk manifesto
Folks, grab a few of your favorite cookies—I recommend these—pour yourself a glass of … well, whatever; and settle in. This won't take you nearly as long as it took me, but it's a bit of a commitment just the same.
Working ourselves up into an ideological fervor, and frothing at the mouth in disparate passions over topics in nutrition that could, and frankly should, be a matter of calm, evidence-based consensus, is simply what we do.
So, for instance, it's not enough to agree that we consume a large excess of added sugar, and then come together to do something about it. We need an unending parade of self-proclaimed Messiahs to carry on as if each was the first to discover that we consume an excess of sugar, and that it's a bad idea, despite the Jack La Lanne videos telling us just that some 70 years ago (and he was not the first). Sugar can't just be bad, it has to be poison, and then we have to bog down in spirited arguments over which sugar is worst, creating cover for Big Food to celebrate much ado about nothing.
It's not enough to agree that a sizable minority in the population is gluten sensitive, and should avoid gluten for that reason, while still deriving health benefits from a variety of natively gluten-free whole grains. We have to throw gluten under the bus for everybody, then wheat, then all grains, renouncing even the distinction between whole and refined grains, and ignoring the weight of evidence simply because it proves, well, inconvenient to the argument.
And of course it's not nearly enough to acknowledge that not all saturated fat is created equal, and that we have known so for a long time. It's not enough to note that some saturated fatty acids appear to be innocuous, while others still appear to be otherwise, and to date none is demonstrably beneficial. It's certainly not enough to concede that when an excess of saturated fat is replaced with an excess of refined starch and sugar (or perhaps not even replaced, but compounded by them), health does not improve. No, we have to take just such evidence and pretend it suddenly means lard is Manna from heaven.
As far as I can tell, though, no nutrition topic is in a more constant state of vitriolic froth than dairy. The vegans are pretty much appalled by the whole category, and in a very rare confluence, the true Paleo devotees agree. Mom's was the only milk in the Stone Age, after all.
A mass of nutrition moderates can take dairy or leave it. The scientists involved in the DASH studies have naturally drunk rather deeply of their own work, as we are all somewhat prone to do, and generally espouse the virtues of milk, and quite effectively, I might add. Good public relations and the imprimatur of the NIH are likely why DASH wins the US News and World Report Best Diet competition every year.
Mediterranean diet proponents advocate for the inclusion of dairy in the diet, but don't tend to emphasize it, finding that other attributes of the diet seem to matter much more. When they do talk about it, they don't generally mention the fat content at all. Scientists working for the dairy industry understandably circulate flattering studies preferentially. And what we might call the non-vegan New Age enthusiasts, are adamant that dairy should be full fat at least, and possibly raw.
As a result, it's a rare day when I am not lobbied, prodded, chided, stirred, and shaken down by some faction or another over some claim or another about dairy. I am taken to task for views I do hold and shouldn't, or don't hold but should, via email, tweets, and blogs.
Well enough of that. From atop my tuffet, here's what I think about dairy, and why.
1. Isn't it true we simply aren't adapted to consume dairy other than in infancy? Isn't it “unnatural?”
Only if the very same logic is applied to iceberg lettuce, whole grains, refined grains, tangerines, beefsteak tomatoes, grain-fed beef, salami, baloney, pepperoni (figure any “oni” is on the list, there were, apparently, no Stone Age “onis”); coffee, chocolate, wine, beer, nectarines, zucchini, Idaho potatoes (after all, Idaho wasn't there yet … ); and, well, you get the idea. Almost nothing we eat today existed in its current form in the Stone Age. If we need to have been consuming something for more than 15,000 years to grant it entry into our diets, well, folks, enjoy the hunger strike.
It is true, of course, that in general mammals are adapted to consume milk only in infancy. Throughout the mammalian family, the gene that encodes for the enzyme lactase, required to break down the complex milk sugar lactose, turns off at the time of weaning. Were that true of all humans, we might convincingly argue that it isn't “natural” for adult humans to consume dairy.
But it isn't true. In some human populations, notably, those with the longest traditions of dairying, the gene stays turned on permanently in almost everyone. Why? Evolution by natural selection. Apparently, there was a survival advantage conferred upon those who could continue to consume dairy when it was available and other foods scarce, so they adapted and passed on their fortuitous genes, or didn't adapt, and consigned their alternative genes to oblivion.
If lactose tolerance among human adults is a product of adaptation, and it clearly is exactly that (populations without long traditions of dairying remain predominantly lactose intolerant, never having experienced dairy digestion as a survival advantage), then it represents the very argument we generally invoke about the Stone Age: it's good for us because we are adapted to it. By just such logic, every lactose tolerant human SHOULD consume dairy routinely.
2. Should every lactose tolerant human consume dairy routinely?
Only if they want to do so, and even then, not a whole lot. To the best of my knowledge, we have no evidence, zero, that adding dairy to balanced, prudent vegan diets improves health outcomes in any way. On the other hand, we also have no evidence to my knowledge that such optimized vegan diets produce better health outcomes than comparably balanced, optimized Mediterranean diets that do include dairy.
Many studies of dietary intake in the U.S. do suggest benefits of dairy, for children in particular. This may be because dairy is directly beneficial, but it may also be because of the generally ignored pebble-in-a-pond aspect of dietary intake: more of X as a percent of total calories means less of Y. So, perhaps in the context of the typical American diet the inclusion of dairy is consistently beneficial because it tends to mean less soda, among other things. I have seen next to nothing in the literature on how the overall profile of food choices varies between those who routinely include and those who routinely exclude dairy in the U.S., and such studies would answer very interesting questions.
In the interim, we shouldn't pretend to have answers to the good questions we have yet to ask. I know it's horribly nuanced to say this, and I know we seem to hate shades of gray unless handcuffs are involved, but: we have a choice.
You can have an optimal diet that includes or excludes dairy. For that matter, you can have a crummy diet that includes or excludes dairy, too.
3. Shouldn't dairy be full fat?
I don't think we know for sure, but to the extent we do know, I think it's all a matter of dietary context. On the one hand, some studies do suggest that full-fat dairy may confer greater satiety, a lasting feeling of fullness, and thus confer a weight control benefit. But the context here seems again to be the typical American diet, where low-fat junk foods abound. Such foods are often the very opposite of satiating, and high in added sugars. Dairy is subject to the same adulterations, such as non-fat yogurts that, as pointed out by Rob Lustig in his book Fat Chance, serve as delivery vehicles for more added sugar than is found in a soft drink.
Do we have studies that keep all other factors constant, and compare health outcomes based on intake of plain, unsweetened dairy products across a range of fat content? I have not found any, and I have looked harder than most.
When dairy is discussed in the context of the Mediterranean diet, fat content is almost never mentioned. This likely means that the dairy in question is full-fat, but it may also merely mean it doesn't much matter, because dairy is a relatively unimportant contributor to the health effects of such diets.
Overall, my impression is that there may well be some benefit, to satiety at least, of full-fat dairy for those who consume dairy in the first place, and who otherwise work to avoid dietary fat, but don't do it very well, i.e., by eating the fat-reduced junk foods that prevail in our culture. As noted, those who get low-fat eating right, by eating a wide variety of plant foods, derive no established benefit from the addition of dairy, fatty or otherwise.
If, however, one's diet is not restricted in fat, the fat content of dairy is unlikely to confer any proven benefit at all. For one thing, the very best thing that can be said of the saturated fat in dairy is that maybe it does not increase cardiovascular risk much, although I remain very dubious about that claim. But there is no evidence that it reduces risk, and since when is “absence of overtly harmful effects” the standard-bearer of high quality nutrition? We have abundant evidence that natural sources of monounsaturated fats, and a balanced array of polyunsaturated fats including omega-3s, are associated with actual benefit, not the far less propitious “possible lack of serious harm.” So if inclined to liberalize dietary fat intake, there are far better places to get it than in that glass of milk. I recommend you grab a few walnuts, and chew on it.
For another, when protein and fat intake are moderate; and intake of refined starch, added sugar, and hyper-processed, willfully addictive junk low to negligible, there is unlikely to be any satiety problem left to fix. In such context, fat comes from nuts, seeds, olives, avocado, fish, seafood, and for those so inclined, meat. Why add dairy fat? On the basis of available evidence, I have found no good reason.
So here, too, we have a choice. If dairy makes up a small percentage of your calories, as it generally does in the truly wholesome variations on the theme of the Mediterranean diet, it probably doesn't matter much whether it's full-fat, fat-free, or in between. But in the context of such relatively generous fat intake, there is certainly no established advantage to adding more fat from dairy. The only real liability of prioritizing fat-free dairy is the common tendency to conflate fat-free for “nutritious” no matter what else is in the mix. Avoid that mistake, by all means.
If, however, you choose simple, minimally processed dairy; have ample, healthy fat in your diet; and are not struggling with appetite control, I still think fat-free dairy is the way to go. The rather small role of dairy in my own diet is played by just such actors, notably plain, fat-free Greek yogurt to hold together my breakfast of berries, nuts, and whole grain cereals.
4. Shouldn't milk be raw?
I searched Pubmed, the on-line library of peer-reviewed scientific papers, for the very general terms “raw milk health” in the title and came up with 19 citations. I tried “raw milk benefits” and found just 1, a commentary (not a research paper). In contrast, there are 2004 papers with “onchocerciasis” in the title.
In other words, all of the passion about raw milk is just so much foam. There is virtually no science behind it. In fact, the relevant papers have generally concluded the opposite, finding that risks are almost certain to outweigh any theoretical benefits, and that nutritional differences are negligible. Those who think the current generation discovered this preoccupation will be interested to know it was around, and debunked, back in the early 1980s. That, by the way, is the native life cycle of dietary fads; most of them are reheated versions of fads we forgot from a decade or so ago. Raw milk, it turns out, is no exception.
Pasteurization caught on for a reason. There is a real risk of infectious disease with raw milk, and no established benefit. Of course, that doesn't mean there isn't some benefit as yet unproven, but that's a leap of faith. If inclined to leap accordingly, at least look carefully before you do so at the track record of the farm in question. Know your cow, in other words, before putting your lips to an udder.
5. Should dairy be organic?
We don't have “proof” that the antibiotics and hormones that find their way into the milk of “factory farm” bovines are harmful to humans, but the circumstantial evidence is hard to ignore. Besides, the precautionary principle applies: when sense suggests the likelihood of potential harm, the first job of science is not to prove that harm, but to disprove it. In the absence of disproof, adulterations of our dairy may be presumed guilty. When you can choose organic dairy, by all means do.
6. What about the cows?
My friend John Robbins famously renounced the Baskin-Robbins family fortune to which he was heir to become an activist for animal welfare, environmentalism, and plant-based eating. This was prompted by the abuses of cattle he observed first hand, a story he told in The Food Revolution.
The simple fact is that if a population of 7 billion Homo sapiens make dairy, or meat for that matter, a major component of their diets, methods of mass production are applied to the animals involved. This, inevitably, engenders corner-cutting, and wanton disregard for expendable concerns, like decency.
But if you are decent, cruel and abusive treatment of our fellow creatures must matter to you. To keep dairy on the menu and take cruelty off, be sure to know something about the treatment of those cows who gave the milk.
I note that I do get tweets from some who sneer at the idea that how animals are treated matters at all in our decisions about food. All I can say to that group is that you are an embarrassment to the better angels of our nature, and neither the angels, nor I, give a damn what you eat. The angels hope you choke on it.
7. What about the planet?
The husbandry of large herds of cattle for both meat and dairy is a very important source of green house gas emission. Excessive appetites for meat and/or dairy therefore conspire directly against efforts to curtail climate change.
The notion that we humans can eat however we want and ignore the implications for the planet at large is stunningly benighted. The good news, of sorts, is that the thinking is unsustainable, because calamity will put an end to it. Unfortunately, none of us will get the last laugh. We will all be crying together, over spilled milk, and lost opportunity.
In summary, then, vegan claims that healthy diets must exclude dairy are belied where Mediterranean diet meets Blue Zone. Steadfast Paleo opposition to dairy is hoisted on its very own petard, since specific genetic adaptation to dairy consumption is on overt display in hundreds of millions of modern Homo sapiens, with no such obvious adaptations to most of the other stuff they are eating.
We can take milk, or leave it; take milk fat, or leave that. Either way, we can have a good diet of wholesome foods in sensible combinations, or not. But either way, we need to take seriously the reverberations of our dietary choices across the landscape of a shrinking planet, and the legacy of kindness or cruelty by which history will be invited to judge us.
If I may borrow from Taylor Swift, the dairy lovers are gonna’ love, love, love it. The dairy haters are gonna’ hate, hate, hate it. Tweeters gonna’ tweet, tweet, tweet. Everybody's gonna’ stir their particular glass, and shake up the subject as they see fit. Frankly, I think the topic has been milked for much more than it's really worth. So as I continue to encounter the daily attempts to shake me down, I'm just gonna’ shake it off, and carry on.
David L. Katz, MD, FACP, MPH, FACPM, is an internationally renowned authority on nutrition, weight management, and the prevention of chronic disease, and an internationally recognized leader in integrative medicine and patient-centered care. He is a board certified specialist in both Internal Medicine, and Preventive Medicine/Public Health, and Associate Professor (adjunct) in Public Health Practice at the Yale University School of Medicine. He is the Director and founder (1998) of Yale University's Prevention Research Center; Director and founder of the Integrative Medicine Center at Griffin Hospital (2000) in Derby, Conn.; founder and president of the non-profit Turn the Tide Foundation; and formerly the Director of Medical Studies in Public Health at the Yale School of Medicine for eight years. This post originally appeared on his blog at The Huffington Post.
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