Dairy: food of the Gods or neolithic agent of disease?
on February 8, 2011 by Chris Kresser 54 comments
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One of the most contentious issues in the Paleo nutrition community is whether dairy products are health-promoting or disease-causing.
On one end of the spectrum you have Loren Cordain and his group, who claim that dairy is not fit for human consumption for two reasons: 1) because it’s a neolithic food and not part of our evolutionary heritage, and 2) because of proposed physiological mechanisms by which dairy causes harm when consumed. On the other end of the spectrum you’ve got folks like Kurt Harris, Stephan Guyenet, Chris Masterjohn and the Weston A. Price Foundation who have pointed out the many health benefits of dairy and are generally in favor of its consumption.
My answer to the question of whether dairy is healthy are harmful is, in short: it depends. But before we get into the factors I think the answer depends on, I want to briefly address why I don’t take the evidence against dairy very seriously at this point.
Paleo re-enactment isn’t the goal
I agree with Dr. Kurt Harris on this one. We can look to the Paleo era to determine what was evolutionarily normal for humans, but it doesn’t follow that anything that falls outside of that norm is automatically harmful. The argument that we shouldn’t eat dairy now because we didn’t eat it 2 million years ago – without supporting clinical evidence – is not convincing.
There’s also the inconvenient (for the anti-dairy set) matter of people like the Masai and Loetschental Swiss that Weston A. Price studied, who were free of modern, degenerative disease despite receiving a large percentage of calories from dairy products.
Human evidence is more convincing than proposed mechanisms
Cordain’s group has published and reviewed several papers proposing various physiological mechanisms by which dairy causes harm. One recent example is a paper by Melnik called Milk Signalling in the Pathogenesis of Type 2 Diabetes. The theory presented is that milk consumption beyond the weaning period may overstimulate pancreatic beta-cells and promote beta-cell apoptosis. Since proliferation and apoptosis of beta-cells are hallmarks of type 2 diabetes (T2DM), it follows that milk consumption must contribute to T2DM.
Or does it?
If that theory were true, we might expect to see increased rates of T2DM in people consuming dairy products. But in fact we see just the opposite.
This study looked at serum levels of trans-palmitoleic acid, a fatty acid found in milk, cheese, yogurt and butter, and correlated them with risk factors for diabetes. Here’s what they found:
At baseline, higher circulating levels of trans-palmitoleic acid were associated with healthier levels of blood cholesterol, inflammatory markers, insulin levels, and insulin sensitivity, after adjustment for other risk factors. During follow-up, individuals with higher circulating levels of trans-palmitoleic acid had a much lower risk of developing diabetes, with about a 60% lower risk among participants in the highest quintile (fifth) of trans-palmitoleic acid levels, compared to individuals in the lowest quintile.
Translation: people with the highest trans-palmitoleate levels had 1/3 the risk of developing diabetes over the three years volunteers were followed. Not only that, after adjusting for confounding factors trans-palmitoleate levels were associated with smaller waist circumfrence, lower triglycerides, higher HDL and lower C-reactive protein.
Since trans-palmitoleic acid is a fatty acid found in the – you guessed it – fat of milk, the study also supports the idea that full-fat, whole dairy products are beneficial. This directly contradicts the low-fat hysteria we’ve been brainwashed with for so many years. But I digress.
Stephan Guyenet blogged about this study and re-wrote the authors’ conclusion in more straightforward terms:
Our findings support eating as much butter as possible****. Don’t waste your money on low-fat cream, either (half-n-half). We’re sorry that public health authorities have spent 30 years telling you to eat low-fat dairy when most studies are actually more consistent with the idea that dairy fat reduces the risk obesity and chronic disease.
Since this was an observational study, it doesn’t prove that dairy fat reduces the risk of T2DM. But it does suggest that the converse isn’t true.
Another study found that people with the highest levels of milk fat biomarkers, suggesting they consumed the most dairy fat, were actually at lower risk of heart attack; for women, the risk was reduced by 26 percent, while for men risk was 9 percent lower.
Another study showed that people who ate the most full-fat dairy had a 69% lower risk of cardiovascular death than those who ate the least.
Finally, this literature review of 10 studies found that milk drinking is associated with a small but significant reduction in heart disease and stroke risk.
I could go on, but I think you get the point. Which is this: evidence of what happens when people actually consume dairy products is a lot more convincing to me than proposed mechanisms of how dairy may effect humans.
The problem with isolating certain effects of a nutrient or food, and then making predictions based on those effects, is that we might miss some other quality about that food that negates the proposed effect. That’s a mouthful, so let me explain.
T. Colin Campbell is (in)famous for his research linking casein, a protein in dairy products, with cancer. He then made the huge and unsupportable leap to concluding that all animal proteins cause cancer and should be avoided. Most of you know the rest of that story.
However, what Campbell neglected to notice, or mention, is that whey, another protein found in dairy, has anti-cancer effects that completely cancel out the cancer-promoting effects of casein. Oops! This is why it’s so important to study whole foods, not just nutrients.
So let me finish this section by saying that I believe the weight of the evidence on dairy consumption suggests that it is not only not harmful, but quite beneficial.
When dairy may not be beneficial
However, as in most things, there are exceptions. Many of you reading this are probably sensitive to dairy and don’t tolerate it well. I certainly have patients that this is true for, and it’s not at all uncommon.
What’s the deal? Why does it seem to benefit some, but cause problems for others? In my opinion the answer boils down to the health of the gut. If someone has compromised intestinal permeability, or “leaky gut”, it’s more likely that their immune system will respond to potentially allergenic components in milk such as alpha- and beta-casein, casomorphin and butyrophillin.
This is especially true for people who are gluten intolerant, because it has been shown that milk proteins commonly cross-react with gluten. Put another way, if you react to gluten, it’s more likely that you’ll also react to milk.
Along these same lines, people with small intestine bacterial overgrowth (SIBO) – which is one of the major causes of irritable bowel syndrome (IBS) – may be more likely to react to milk because the bacteria in their small intestine aggressively ferments lactose, the sugar in milk, causing gas, bloating and other G.I. symptoms.
Not all milk is created equal
Something that irritates me is that raw and pasteurized dairy is often discussed as if it’s the same thing. It’s not. Raw dairy is a whole food, and pasteurized dairy is a processed food.
While it’s true that some people (described above) react to the proteins in milk, most who are sensitive are reacting to the sugar in milk: lactose. The enzyme lactase must be present to hydrolyze lactose into its constituent compounds, glucose and galactose. Somewhere between 1% – 95% of people don’t produce lactase on their own, depending on race and ethnicity.
In a sign of nature’s wisdom, raw milk contains lactase, the enzyme needed to digest lactose. Pasteurization, however, kills lactase. So if you don’t produce your own lactase, you’ll have a hard time digesting pasteurized milk. But that doesn’t mean you can’t tolerate raw milk. I can’t tolerate pasteurized dairy myself, but I don’t seem to have any problems with raw dairy.
So the answer to the question I posed in the title of this article isn’t so simple, and it depends on several factors:
•	The status of your gut barrier 
•	Whether or not you have SIBO or IBS 
•	Whether or not you’re gluten intolerant 
•	Whether you’re eating raw or pasteurized dairy
If you’re not sure where you stand with dairy, the best approach is to remove it for 30 days and then reintroduce and see what happens. Elimination/reintroduction is still the gold-standard for determining sensitivity to a particular food.
But if you tolerate it well, I haven’t seen any evidence in the literature that convinces me you shouldn’t be eating liberal amounts of full-fat dairy.
Animal Protein and the Cancer Promoter IGF-1
Written by: Michael Greger M.D. on February 14th, 2013 

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For years we didn’t know why eating a plant-based diet appeared to so dramatically improve cancer defenses within just a matter of weeks. But researchers recently figured it out: eating healthy lowers the level of the cancer promoting growth hormone IGF-1. This saga was detailed in my last four blog posts:
•	Cancer-Proofing Your Body 
Treating an Enlarged Prostate With Diet 
How Do Plant-Based Diets Fight Cancer? 
Vegan Men: More Testosterone But Less Cancer
What is the mechanism by which a simple dietary change can alter the levels of this cancer promoter? Imagine you’re a kid with some tinker toys. Then for your next birthday you get one of those huge tinker toy sets dumped down in front of you. All excited with this new load of raw building materials, you may really start scaling up. Basically it’s the same with your liver and insulin-like growth factor 1.
When we dump a load of protein in our body, our liver’s like, “Whoa, look at all this! What are we going to do with it all? We can’t just waste it, we’ve got to do something with it!” So our liver starts pumping out IGF-1 to tell all the cells in our body “It’s growin’ time! Be fruitful and multiply. Spare no expense, go crazy—look how much excess protein we got to work with!”
The problem is that some of the new additions spurred by this growth hormone may be tumors. When you’re a fully-grown adult, cell growth is something we want to slow down, not accelerate. The goal, therefore, would be to maintain adequate, but not excessive, overall protein intake.
Wait a second, though. As I show in my 3-min. video Protein Intake and IGF-1 Production, studies have found no association between total protein intake and IGF-1 levels. But that’s because they didn’t take into account animal versus plant protein. It took a study comparing meat-eaters to vegans to show that higher IGF-1 levels were only associated with animal protein intake. In fact, plant protein seemed to decrease IGF-1 levels. Animal protein appears to send a much different signal to our livers than most plant proteins. Even vegans eating the same amount of protein as meateaters still had lower levels of the IGF-1, so it’s apparently not about excessive protein in general, but about animal protein in particular. To understand why, see my 3-min. video Higher Quality May Mean Higher Risk.
If the reason animal proteins raise IGF-1 levels is because they resemble our own proteins, what about the few plant proteins that just coincidently happen to have amino acid ratios similar to proteins such as soy? Great question! That will be the subject of my blog post on Tuesday.
For those who haven’t been following along, see IGF-1 as One-Stop Cancer Shop for the reason we’re so concerned about IGF-1 levels and my videos The Answer to the Pritikin Puzzle and How Plant-Based to Lower IGF-1? to learn about the role diet plays in cancer development.
–Michael Greger, M.D.
PS: If you haven’t yet, you can subscribe to my videos for free by clicking here and watch my full 2012 – 2015 presentations Uprooting the Leading Causes of Death, More than an Apple a Day, From Table to Able, and Food as Medicine.
10 Common Arguments Against Dairy Consumption Explored 

I’ve celebrated the goodness of dairy fat quite enthusiastically in recent weeks. If you were just joining us, you might have gotten the wrong impression that you’d stumbled into a PR wing of the dairy industry, and that the streets of Mark’s Dairy Apple run whitish-yellow with grass-fed milk fat. No, children aren’t busting open fire hydrants on warm days to dance around in the effervescent spray of kefir, and on winter days it doesn’t rain milk and snow globs of thick Greek yogurt in these parts.
I’m well aware of the darker side to dairy, and today I’ll be exploring the common arguments against dairy consumption. Let’s jump right in:
Grok didn’t drink milk.
True, but the evolutionary argument cannot prove the suitability or unsuitability of a food – it can only generate hypotheses that we can then test or research. The same goes for grain consumption, nighttime artificial light exposure, sedentary living, or any other evolutionary novel activity. It has to be tested.
Takeaway? The relative newness of dairy in the human diet definitely raises concerns about its healthfulness, but it’s not a resounding argument in and of itself.
We’re the only species that drinks the milk of other mammals.
It does seem a bit weird. That’s mankind, though: we do weird things that no other animal could ever conceive of doing. That’s what makes us the top of the food chain. We’re smart and dominant enough to impose our will on nature. It gets us into trouble – see industrial agriculture and artificial trans-fats – but it also improves our station – see the decision of hominids three million years ago to “see how this dead herbivore flesh tastes.” Like the previous argument, this one can only raise hypotheses.
Takeaway? Our species’ departure from, or modification of mammalian norms isn’t always bad. Or good. The specifics matter.
Dairy raises insulin.
It’s true, it does. Both the lactose and dairy proteins exert an insulinogenic effect that when taken in concert rival that of many carbohydrate sources. I actually covered this topic in a post several years ago and found that acute dairy-induced spikes of insulin don’t seem to be related to body fat gain or insulin resistance in healthy people, and that the studies showing a connection between dairy and insulin resistance used skim or low-fat milk, rather than whole. And in athletes trying to recover from training, these insulin spikes may actually promote recovery. Hyperinsulinemia, where insulin is chronically elevated, is another story. If you’re already insulin-resistant, dairy could be problematic.
Takeaway? Dairy’s insulinogenic effect is good for some groups (lean, insulin-sensitive, athletes or trainees looking for muscle recovery), bad for others (insulin-resistant). Context is important.
The betacellulin in dairy can increase cancer.
Betacellulin is a growth factor found in whey that plays an important role in infant growth. In some in vitro studies, isolated betacellulin has been shown to contribute toward the growth of cancer cells. Chris Masterjohn takes apart this argument fairly well, explaining how similar in vitro studies that incorporate conjugated linoleic acid (a trans-fatty acid especially abundant in pastured dairy fat) show that CLA has an inhibitory effect on the promotion of cancer by betacellulin; how most epidemiological studies show no relationship between commercial milk and cancer; how some only support a relationship between low-fat dairy and ovarian and prostate cancer, but not high-fat dairy; and how whole fat milk is actually associated with a lower risk of colorectal cancer.
Takeaway? If betacellulin has cancer-promoting tendencies, it’s probably only when isolated from protective dairy compounds such as CLA and saturated fat. Stick to full-fat, pastured dairy.
Dairy is a general growth promoter and can increase cancer.
Loren Cordain and Pedro Bastos (with a couple other collaborators) released a very interesting paper in which they suggest that rather than being just food, milk is an “endocrine signaling system” whose various components – particularly the proteins – are meant to stimulate hormonally-driven growth in a “species-specific” manner. So human breast milk is perfect for how human babies are supposed to grow and tissue differentiate, cow milk is ideal for calf growth, goat milk for kid growth, and so on. Milk proteins stimulate growth by activating the mTOR pathway and stimulating IGF-1 release. Cordain and Bastos link dairy-induced mTOR activation and IGF-1 release with prostate cancer, citing in vitro and epidemiological evidence that milk consumption during certain developmental phases (prenatal, immediately postnatal, and adolescence) can predispose developing prostates to cancer later in life.
More generally, IGF-1 is a growth promoter which is elevated in childhood – because that’s when people are growing at a fairly steady rate – and in certain types of cancer – because that’s another kind of growth, only unwanted. Since dairy protein consumption is pretty consistently linked to increased IGF-1, it’s easy to assume that dairy can increase cancer risk. Good for growing bodies, bad for growing cancer cells.
So, people with cancer or at risk of cancer should avoid dairy, right? I’m not sure. This study found that a whey protein supplement actually increased the vulnerability of cancer cells to chemotherapy among patients with carcinoma. Another study identified several potential roles for milk proteins in cancer prevention. And there’s the classic tale of Campbell’s rats, where high-casein diets were protective against the development of aflatoxin-induced cancer but increased cancer progression once initiated.
Plus, the mTOR pathway is also where muscle growth happens, which may be why GOMAD (gallon of milk a day) is a popular tactic for strength trainees.
Takeaway? Dairy is a growth promoter, which can be good (muscle) or potentially bad (cancer, particularly prostate when consumed at certain developmental stages). It’s unclear if dairy actually promotes tumorigenesis or promotes growth only once the cancer has been established – or neither.
Dairy increases intestinal permeability, thus allowing proteins and other bioactive compounds entrance into the bloodstream. This can precipitate or exacerbate autoimmune diseases.
For years, I’ve heard that “dairy is designed to increase intestinal permeability.” After all, infants need a bit of a leaky gut to allow absorption of large things like colostrum. It would make sense for milk to increase permeability so this could happen. But it turns out that infant guts are innately permeable, not permeable because of dairy. If anything, it looks like dairy might actually make guts less permeable. I didn’t find any human research to this effect, but I did find some interesting studies with surprising results:
Hydrolyzed casein restored intestinal barrier function and prevented diabetes in a diabetes-prone rat. A later study confirmed these results. A specific casein peptide was also shown to reduce intestinal permeability in another study, and beta-lactoglobulin (another protein component of dairy) had similar effects on intestinal tight junction function. And finally, a component of whey has also been shown to reinforce tight junction integrity.
Yeah, I was surprised too.
That doesn’t mean there aren’t connections, even causal, between dairy consumption and autoimmune diseases like type 1 diabetes, but the presence of leaky gut may be a prerequisite. This would jibe with the observations that people with type 1 diabetes, multiple sclerosis, rheumatoid arthritis, and other autoimmune diseases sometimes linked to dairy intake have higher intestinal permeability.
Takeaway? Although these were either rodent or in vitro studies using isolated components of dairy, it seems like the evidence points toward dairy upholding intestinal integrity, if anything. Given existing permeability, dairy proteins can slip through and obviously cause problems, but I’m unaware of evidence showing they increase leaky gut or autoimmune disease on their own absent intestinal permeability.
Dairy has a high acid load, which can lead to bone calcium loss.
I’ve always been skeptical of this one because using the same criteria, meat also has a high acid load on the body. Should we forgo eating meat, which has been shown to improve bone mineral density? Plus, one recent study found that dairy doesn’t actually make the body acidic. Milk and dairy products “neither produce acid upon metabolism nor cause metabolic acidosis.” Further, dairy is a good source of calcium and – particularly in the case of gouda cheese – vitamin K2, both important co-factors in bone metabolism.
Takeaway? Dairy consumption may not ensure or be necessary for good bone health, but it doesn’t seem to negatively impact it.
Dairy contains ample amounts of bioactive hormones which can have negative health effects.
Since a common practice nowadays is the milking of pregnant cows in order to maximize production and estrogen goes up during pregnancy, it seems reasonable to expect elevated levels of estrogen in dairy. Most studies I came across found that some estrogen is present in dairy, with skim milk containing the most bioavailable form of estrogen (conjugated estrogen, the same kind used in oral hormone replacement therapy). For the most part, the amount of active estrogen found in dairy seems too low for physiological relevance. We have too much already in circulation for it to be impacted by dietary sources, some of which will be nullified by digestion.
Dairy proteins can certainly increase IGF-1 (as shown previously) in people, but it’s unclear whether the actual IGF-1 found in dairy has an effect on serum levels. If you’re worried about IGF-1, fermentation takes care of most of it. Stick to fermented dairy like yogurt, kefir, or cheese (which already has health benefits over regular unfermented dairy).
Takeaway? Hormone levels in dairy vary according to production method, pregnancy status of the animal being milked, and chance. For the most part, the amount of hormones in dairy pales in comparison to the endogenous amounts circulating in our bodies at any given time, so even if we had the leakiest gut in the world and everything we ate was absorbed directly into our blood, it would likely have minimal impact on our hormone levels.
Dairy causes acne.
Among food-sensitive acne sufferers, dairy is probably the most commonly reported offender. Indeed, recent studies suggest a connection between skim milk consumption and acne in teenage boys (less so for whole milk) and in girls. Researcher Bodo Melnik points the finger at the mTOR/IGF-1 activating qualities of dairy (and the Western diet at large) as the culprit. It’s a compelling line of argument.
However, one recent study found that fermented dairy enhanced with lactoferrin reduced the incidence of acne, suggesting that dairy isn’t always antithetical to skin health. Raw dairy might work better than pasteurized dairy, since pasteurization destroys the natural lactoferrin content of milk.
Takeaway? Dairy is a common aggravator of acne and is worth removing or avoiding if you have it.
That bovine serum albumin in dairy resembles human collagen type 1 and can increase rheumatoid arthritis through molecular mimicry.
Rheumatoid arthritis patients do seem to produce antibodies to bovine serum albumin, and one case study found that an RA patient achieved relief with cessation of milk consumption and saw symptoms return with resumption. Still, another more recent paper found that BSA antibodies weren’t associated with disease progression or activity (flare-ups) in rheumatoid arthritis, so it’s still theoretical. I would imagine that the problem (if extant) is exacerbated by the presence of leaky gut.
Takeaway? Seems worrisome enough that people with RA might try avoiding dairy, at least as a trial to see how it affects their symptoms. One confounder is that bovine serum albumin is also found in beef muscle meat. RA patients who are reading this: do you notice problems with beef?
Overall, it appears that dairy has both benefits and risks, and that where you fall depends on several factors, like gut health, insulin sensitivity, activity level, age, as well as the quality and form of the dairy (which though I didn’t really get into are implicit when discussing dairy). In other words, it’s extremely variable and personal.
What do you think, folks? Any other anti-dairy arguments out there? Let me know in the comment section!

Read more: http://www.marksdailyapple.com/10-common-arguments-against-dairy-consumption-explored/#ixzz4FN6mxAGq

Insulin-like growth Factor 1 (IGF-1)
Insulin-like growth factor 1 (IGF-1) is a hormone produced in the liver and body tissues of mammals. One important role for IGF-1 is to promote cell growth and division, this is important for normal growth and development. It plays an important role in childhood growth and continues to have anabolic effects (the building up of organs and tissues) in adults.
IGF-1 from cows is identical to human IGF-1 in that the amino acid sequence of both molecules is the same. Amino acids are the building blocks of proteins and there are 20 different amino acids. All proteins consist of amino acids joined together like beads on a string and the nature of the protein (how it behaves) is determined by the order in which the amino acids occur along the string. In both human and bovine IGF-1 the same 70 amino acids occur in exactly the same order, which may or may not have a significant impact on human health (see below). As previously stated, the use of recombinant bovine somatotrophin (rBST) in cows increases levels of IGF-1 in their milk, however, it should be noted that cow’s milk from cows that are not treated with rBST also contains IGF-1. Again, the significance of this is discussed below.
It has been suggested that IGF-1 is not destroyed during pasteurisation. Furthermore it has also been suggested that it is not completely broken down in the gut and that it may cross the intestinal wall in the same way that another hormone, epidermal growth factor (EGF), has been shown to do. EGF is protected from being broken down when food proteins (such as the milk protein casein) block the active sites of the digestive enzymes. This allows the molecule to stay intact and cross the intestinal wall and enter the blood. This raises a theoretical concern that IGF-1 from cow’s milk could increase normal blood IGF-1 levels and so increase the risk of certain cancers linked to IGF-1.
However, Professor Jeffrey Holly, Professor of Clinical Sciences at the University of Bristol says that although bovine IGF-1 is identical to human IGF-1 and in theory some of the IGF-1 that is present in ingested milk may be absorbed un-degraded, it is implausible that this would affect the systemic levels of IGF-1 in humans. Holly states that the dynamics of the IGF-1 system (with a huge circulating reservoir and a large flux primarily due to production from the liver) means that even assuming the extreme estimates of what could be absorbed and not metabolised it would still require consumption of something like 60 litres of milk a day to increase serum levels by the least amount that could be measurable. However, he goes on to say that there are many small peptides and amino acids that are present in milk that potently stimulate hepatic IGF-1 expression and pituitary growth hormone release. In other words, drinking milk increases IGF-1 production from the liver which in turn leads to an increase in the levels present in the blood.
Milk is designed as the only food between birth and weaning and is designed to sustain the rapid growth that occurs at this stage of life. Holly states that his studies and those of others have consistently found that, of all the components of human diet, milk and dairy products have the greatest effects on IGF-1 levels. So it is not the presence of IGF-1 in milk that matters but rather the impact of milk on stimulating human IGF-1 production within individuals who consume milk and dairy products. He also points out that there is similar confusion over dairy cows treated with rBST (in the US), the milk from such cows has higher levels of bovine growth hormone and bovine IGF-1 but neither are likely to alter the effects on humans consuming such milk.
Whether cow’s milk ingestion increases IGF-1 levels in humans by bovine IGF-1 crossing the gut wall, or (as seems more likely) other components in milk initiating a rapid rise in human IGF-1 production from the liver, the net effect is the same; if you drink cow’s milk, you end up with higher levels of IGF-1 in your blood. 
As stated, IGF-1 regulates cell growth, development and division; it can stimulate growth in both normal and cancerous cells. Even small increases in serum levels of IGF-1 in humans are associated with increased risk for several common cancers including cancers of the breast, prostate, lung and colon. The link between IGF-1 and cancer is becoming increasingly apparent in the scientific literature.
In the first prospective study to investigate the relationship between the risk of breast cancer and circulating IGF-1 levels, researchers at Harvard Medical School analysed blood samples originally collected from 32,826 women aged between 43 and 69 years during 1989 and 1990. From this group, 397 women were later diagnosed with breast cancer. Analysis of IGF-1 levels in samples collected from these women compared to samples from 620 controls (without breast cancer) revealed a positive relationship between circulating IGF-1 levels and the risk of breast cancer among premenopausal (but not postmenopausal) women. It was concluded that plasma IGF-1 concentrations may be useful in the identification of premenopausal women at high risk of breast cancer.
To investigate the link between prostate cancer risk and plasma IGF-1 levels, a study was conducted on 152 men with prostate cancer and 152 men without the disease. Analysis revealed a strong positive association between IGF-1 levels and prostate cancer risk. In agreement, a Swedish study compared IGF-1 levels in 210 prostate cancer patients with those in 224 men without the disease and found that there was a strong positive correlation between the risk of prostate cancer and raised serum levels of IGF-1. It was concluded that high levels of IGF-1 may be an important predictor for risk of prostate cancer.
In a study into the link between the risk of lung cancer and IGF-1, serum IGF-1 levels were measured in 204 lung cancer patients registered at the University of Texas M.D. Anderson Cancer Centre and compared to those in 218 people without lung cancer. Results showed that high levels of IGF-1 were associated with an increased risk of lung cancer.
In order to assess colorectal cancer risk in relation to IGF-1, a research group at Harvard Medical School analysed blood plasma samples originally collected from a pool of 14,916 men. In a 14-year follow-up of these men, 193 had been diagnosed with colorectal cancer. Analysis of IGF-1 levels in samples taken from these men and 318 controls revealed an increased risk for colorectal cancer among the men who had the highest levels of circulating IGF-1 and it was concluded that circulating IGF-1 is related to future risk of colorectal cancer. 
In summary, the literature strongly supports a link between high circulating IGF-1 levels and cancer, but what has this to do with the consumption of cow’s milk and dairy products? The answer is a lot: circulating IGF-1 levels are higher in people who consume milk and dairy products. Researchers at Bristol University investigating the association of diet with IGF-1 in 344 disease-free men found that raised levels of IGF-1 were associated with higher intakes of milk, dairy products and calcium while lower levels of IGF-1 were associated with high vegetable consumption, particularly tomatoes. In their study, published in the British Journal of Cancer, it was concluded that IGF-1 may mediate some diet-cancer associations. 
US researchers from Harvard Medical School and Bringham and Women’s Hospital in Boston also investigated the link between IGF-1 levels and diet. They examined circulating IGF-1 levels in 1,037 healthy women. The most consistent finding was a positive association between circulating IGF-1 and protein intake; this was largely attributable to cow’s milk intake. In another study, researchers at the Fred Hutchinson Cancer Research Centre in Washington investigated the link between plasma levels of IGF-1 and lifestyle factors in 333 people thought to be representative of the general population. They too found that milk consumption was linked to IGF-1 levels (Morimoto et al., 2005). One study actually quantified the effect of cow’s milk on circulating IGF-1 levels in 54 Danish boys aged 2.5 years. In this study an increase in cow’s milk intake from 200 to 600ml per day corresponded to a massive 30 per cent increase in circulating IGF-1. In agreement with Holly’s research, it was concluded that milk contains certain compounds that stimulate IGF-1 concentrations. An even earlier study concurred that cow’s milk contains many bioactive compounds such as hormones and cytokines, growth factors, and many bioactive peptides, which may also affect IGF-1 levels.
In conclusion, the research shows that nutrition has an important role in determining serum IGF-1 levels. Whether the increase in IGF-1 caused by cow’s milk occurs directly (by IGF-1 crossing the gut wall), or indirectly (as a result of the action of other factors), the research is clear. The consumption of cow’s milk and milk products is linked to increased levels of IGF-1, which in turn are linked to various cancers. In time, the molecular mechanisms underlying these links will inevitably be teased out. 
The Great Dairy Debate
October 13, 2012 in Categories: Nutrition, Science of AIP Nutrition by ThePaleoMom 

The value (or lack thereof) of dairy products is the second most fiercely debated topic within the paleo community (after carbohydrate intake). Opinions vary dramatically from consumption of no dairy whatsoever, to only consuming dairy fat (such as ghee, butter and heavy cream), to only consuming raw grass-fed dairy, to only consuming fermented dairy or aged cheeses, to including any dairy on a regular basis.
The reason for this diversity of opinions is that the science is not clear cut. There are strong arguments to be made both for and against.
Let’s start with the arguments against dairy. Prof. Loren Cordain dedicates an entire well-cited chapter in his most recent book The Paleo Answer (a fantastic book for describing the nitty gritty scientific details behind the paleo diet) to the many reasons why milk should not be consumed in any form. To summarize, what I view the strongest parts of this argument:
•	Milk is not as nutrient-dense as meat, fruits and vegetables. 
•	Milk is highly insulinogenic, meaning it causes a large spike in blood insulin levels, disproportional to the amount of sugar and protein in milk. This may contribute to the development on insulin resistance, at least in the context of a high carbohydrate diet. Insulin is also pro-inflammatory. 
•	Milk contains active bovine (cow) hormones which have the potential to alter our hormone levels. The effects of dietary intake of most of these hormones have not been studied. However, other hormones have been studied. For example, the milk hormone Insulin-like Growth Factor-1 (IGF-1) has been linked to risk of breast, colorectal and prostate cancer, with the strong indication that consumption of dairy protein is a large contributor to blood IGF-1 levels 1. 
•	Milk contains protease inhibitors which may contribute to the development of a leaky gut (see this post for a more in depth explanation as to why) 
•	Milk increases mucus production. This may aggravate conditions such as asthma but also creates excess mucus in the gastrointestinal tract which may irritate the gut lining and inhibit nutrient and mineral absorption. 
•	Lactose is poorly tolerated by adults. Approximately 25% of Caucasians (American and European) are lactose intolerant. 97% of Native Americans are lactose intolerant. This argument does not apply to drinking raw milk since raw milk contains enzymes to help digest lactose. 
•	Dairy is highly allergenic. This is where I believe the chief argument against dairy lies and I will discuss this further below.
There are also some very compelling arguments for including dairy products in our diets. Studies have shown that consumption of dairy, especially full-fat dairy products and fermented dairy products, can protect against Metabolic Syndrome (cheese, full-fat dairy, and fermented dairy), Type II Diabetes (fermented dairy only) and Cardiovasular Disease (cheese, full-fat dairy, and fermented dairy) 2-6.
Grass-fed dairy, especially the fat from grass-fed dairy, is an excellent source of fat-soluble vitamins and Conjugated Linoleic Acid, an anti-inflammatory and healing fat. Fermented dairy is an excellent source of probiotics. There are also some valuable proteins in dairy, such as glutathione (very important for reducing inflammation and protecting against oxidative stress) and whey (which may help prevent cancer).
There is also evidence that dairy proteins are beneficial for children due to their growth-promoting effects. Traditionally, children would have received some breast milk until approximately 5 years of age. In our current society, most children are weaned by age 1. The current scientific view is that, provided cow’s milk is not introduced too early, it is a good substitute for human milk in terms of its growth promotion 7.
Yes, the science is not clear, although there seems to be a good case for including dairy fat in our diets. This is why the standard paleo diet allows for ghee and butter, and in many cases heavy cream and full-fat sour cream. Many people also include fermented dairy in their diets with great success.
However, one thing that is abundantly clear is that milk allergy is common. Beyond lactose-intolerance, which can be treated with the aid of digestive enzymes or consumption of raw milk, allergy to milk proteins is very common. Epidemiological reports of cow’s milk allergy (IgE antibody reactions to cow’s milk proteins) range between 1 and 17.5% in preschoolers, 1 and 13.5% in children ages 5 to 16 years, and 1 to 4% in adults 8. It is not known how prevalent cow’s milk sensitivities are (IgA and IgG antibody reactions to cow’s milk proteins). It’s important to note that goat’s milk is not as allergenic as cow’s milk.
Cow’s milk proteins are also known gluten cross-reactors, which means that those with gluten intolerance may produce antibodies against gluten that also recognize dairy proteins. For these people, eating dairy is the same as eating gluten (more information in this post). Very importantly, for people with allergy, intolerance or gluten cross-reactions to dairy proteins, even the trace dairy proteins in ghee can be a problem.
So, what do I recommend? Caution. I believe that dairy is probably okay for many healthy adults, especially full-fat, grass-fed dairy. In fact, for healthy individuals, the benefits likely outweigh the risks. However, for those battling autoimmune disease or other conditions where a leaky gut is a potential contributing factor, it makes the most sense to omit dairy from your diet for now. As is my standard recommendation for all of the gray-area foods, I suggest leaving it out of your diet for at least 1 month, then try reintroducing it and see if you notice any obvious symptoms (this is the best way to determine if you are allergic or sensitive).
I am still trying to gauge my own tolerance for grass-fed butter. My daughters both seem to do better without cow’s dairy in their diets (except grass-fed butter, which seems okay), but I have reintroduced grass-fed goat mineral whey protein powder into their diets and they seem to do really well with that (especially my oldest). I also have intentions to try them with some grass-fed goat’s whole milk. This is another highly individual aspect of a paleo diet and you really don’t know whether or not milk is good for you until you try living without and then try living with.
1. Crowe FL et al “The association between diet and serum concentrations of IGF-I, IGFBP-1, IGFBP-2, and IGFBP-3 in the European Prospective Investigation into Cancer and Nutrition.” Cancer Epidemiol Biomarkers Prev. 2009 May;18(5):1333-40.
2. Louie JC et al “Higher regular fat dairy consumption is associated with lower incidence of metabolic syndrome but not type 2 diabetes.” Nutr Metab Cardiovasc Dis. 2012 Sep 26. pii: S0939-4753(12)00193-7. doi: 10.1016/j.numecd.2012.08.004. [Epub ahead of print]
3. Warensjö E, et al. “Biomarkers of milk fat and the risk of myocardial infarction in men and women: a prospective, matched case-control study.” Am J Clin Nutr. 2010 Jul;92(1):194-202. Epub 2010 May 19.
4. Sonestedt E et al. “Dairy products and its association with incidence of cardiovascular disease: the Malmö diet and cancer cohort.” Eur J Epidemiol. 2011 Aug;26(8):609-18. doi: 10.1007/s10654-011-9589-y. Epub 2011 Jun 10.
5. Sluijs I et al “The amount and type of dairy product intake and incident type 2 diabetes: results from the EPIC-InterAct Study.” Am J Clin Nutr. 2012 Aug;96(2):382-90. Epub 2012 Jul 3.
6. Bonthuis M et al. “Dairy consumption and patterns of mortality of Australian adults” European Journal of Clinical Nutrition (2010) 64, 569–577; doi:10.1038/ejcn.2010.45; published online 7 April 2010
7. Agostoni C and Turck D. “Is cow’s milk harmful to a child’s health?” J Pediatr Gastroenterol Nutr. 2011 Dec;53(6):594-600.
8. http://www.worldallergy.org/publications/WAO_DRACMA_guidelines.pdf
Chris Kresser has a terrific post Dairy: food of the Gods or neolithic agent of disease?
The Paleo Answer by Prof. Loren Cordain is an excellent resource.
3. Ghee is Suitable for Individuals with Casein and Lactose Sensitivities
Another one of the health benefits of ghee? It’s lactose and casein-free. Some individuals have a milk allergy, which may stem from a heightened sensitivity to casein, and others may be hypersensitive to lactose. For individuals with a casein allergy, the reaction may include swelling of lips, mouth, tongue, face or throat, hives, or congestion.
Lactose intolerance individuals have a difficult time digesting lactose; however, the symptoms are much less dangerous than a casein allergy. Symptoms of lactose intolerance may include bloating, gas, nausea, vomiting, gurgling and cramps. The majority of people who have sensitivities to either casein or lactose don’t have an issue with ghee, as these elements have been removed through skimming and straining.

4. Ghee Made From Grass-Fed Cows Contains CLA
Conjugated linoleic acid or CLA is higher in grass-fed beef and in products made from their milk. This is one of the main reasons I encourage eating grass-fed beef and dairy. While research is still diving into the benefits of CLA, initial studies indicate that it may help to reduce tumors, lower cholesterol and high blood pressure, reduce inflammation, and actually lower body fat.

5. Ghee Contains Butyrate, an Essential Short-Chain Fatty Acid
Butyrate, or butyric acid, is a short-chain fatty acid that acts as a detoxifier and improves colon health. It’s been shown to support healthy insulin levels, is an anti-inflammatory, and may be helpful for individuals suffering from IBS, Crohn’s disease and ulcerative colitis.
A recent study found that “butyrate can prevent and treat diet-induced insulin resistance in mouse.” (2) Researchers agree that more study needs to be conducted to further explore how butyrate affects insulin levels in humans.
7. Ghee Builds Strong Bones With Vitamin K2
Another one of the fat-soluble vitamins, K2 is essential for the body to help utilize minerals, including calcium. In fact, studies show that Vitamin K builds bones better than calcium.
Proper levels of Vitamin K2 help to protect against tooth decay, supports proper growth and development of bones, and protects against the calcification of the arteries, also known as atherosclerosis
9. Ghee Improves Digestion
As mentioned above, the short-chain fatty acid butyrate helps support a healthy digestive tract. It works by stimulating the conversion of fiber into more butyric acid, which is essential for detoxifying as well as the elimination of other fats and toxins. Additionally, ghee benefits include increasing gastric acid and aiding in efficient digestion.

10. Ghee Reduces Inflammation
Ghee’s levels of butyrate play a role in reducing inflammation in the digestive tract and throughout the body. In Ayurvedic practice, ghee benefits the body by creating a more alkaline system that overall reduces inflammation by reducing the leukotriene secretion and reducing prostaglandin in the body. It’s believed that inflammation is at the root of most diseases we face today including Alzheimer’s Disease, some types of cancer, high cholesterol levels, arthritis and asthma.
How to Make Ghee
Yes, anyone can make ghee! And, when made with grass-fed butter, the home process retains more nutrients than ghee made in a centrifuge in commercial products. Here is what you need to get started:
•	1 pound of grass-fed unsalted butter 
•	Deep, wide-bottomed skilled 
•	Wooden spoon or heat-resistant spatula 
•	Cheesecloth 
•	Mesh skimmer 
•	Mesh strainer 
•	Glass jar
Place one pound of butter into a deep skillet over medium-low heat and watch it melt. The key here is to initially melt the butter slowly. Do not try to rush this step. As the butter begins to bubble, it will spatter a bit. Stir with a long-handled spoon and maintain a simmer.
Continue to simmer, stirring occasionally, for 20-30 minutes until the milk proteins have separated from the gold liquid. There will be white foam on the top, and some bits of milk fats on the bottom of the pan. Gently skim the foam off with the mesh skimmer and discard. You may have another “foam up” stage, and this is good. Skim and discard once again. Now, the milk fats on the bottom of the pan will continue to brown. Again, this is a good thing – this is where the distinctive nutty flavor comes from.
Continue to simmer until they are golden brown, but not burnt. Keep a watchful eye because at this stage, the ghee can quickly burn. Remove from heat and allow to cool to room temperature. Place several layers of cheesecloth in the mesh strainer (or use nut milk bags) and slowly pour the butter into the jar. The result? A beautiful golden clarified butter that is liquid gold.
While it will firm up a bit at room temperature,keep in the refrigerator if you desire a spreadable ghee. Ghee will remain fresh at room temperature for several weeks, when sealed properly. It can last months in the refrigerator. Because fats tend to absorb other flavors, it’s essential that ghee is kept properly sealed whether in the refrigerator or on the counter.