Tuesday, December 10, 2013

Dairy - The Good, the Bad or The Ugly? Latest Studies On Heart Disease, Diabetes, Cancer, Obesity and Co. Plus: What Dairy Peptides Do For Your Heart, Gut, Brain, etc.

Do you take Liz Hurley's word and set all warnings about the "non-paleo-ness" of dairy in general and milk in particular at naught? Or do you put faith into the "got milk?" campaign? Personally, I'd suggest not to do one or the other. I'd rather suggest you join me and take a look at a selection of recent studies.
If you've been following the SuppVersity Facebook News and / or have read previous SuppVersity articles on milk and dairy, you will be aware that I am not exactly convinced that the mere existence of allergic reactions and the "fact" that "our ancestors did not drink milk before ..." *put your favorite guesstimate here* allows for the conclusion that we are "not meant" to consume cow's milk. I am nevertheless open to scientific arguments that would convince me that dairy is bad for me - it's just that I don't see this evidence outside of "western diet + dairy makes you fat and that makes you sick" contexts.

What I do see, though, are papers such as the one Sandra Abreu or the recent review by Flávia Galvão Cândido et al. - studies that tell us that the intake of milk is negatively associated with the clustering of cardiometabolic risk factors in adolescents (Abreu. 2013), and reviews which conclude that "the consumption of low-fat dairy products may be an important strategy to prevent and control T2DM [type 2 diabetes]" (Cândido. 2013).

The evidence that dairy is bad for us all is simply not there

But hey, ... let's tackle the evidence one by one. I mean, there is plenty of news-worthy material here and we don't want the fun to be over prematurely, do we? So, let's start with a brief sketch of what Sandra Abreu and her colleagues from the University of Porto base their assessment that the intake of milk, but not total dairy, yogurt, or cheese, is negatively associated with the clustering of cardiometabolic risk factors in Spanish adolescents - shall we?
No! Full-fat dairy is not bad for you: While most of the epidemiological studies with their hilariously unreliable food questionnaires appear to suggest that only low fat dairy was good for your heart, a recent study from the Harvard School of Public Health found a clever way to test the association more objectively. Instead of questioning their subjects, 2837 US adults aged 45 to 84 years, they tested the amount of certain phospholipids in their blood and found that "plasma phospholipid 15:0, a biomarker of dairy fat, was inversely associated with incident CVD [-19%] and CHD [-26%]." (de Oliveira Otto. 2013) The fact that other dairy related phospholipids were not associated (neither positive nor negative) with cardiovascular and coronary heart disease risk does yet, as the scientists rightly point out, warrant further investigation.
"To test th[e] hypothesis [that a higher dairy product intake is associated with lower cardiometabolic risk factor clustering in adolescents], a cross-sectional study was conducted with 494 adolescents aged 15 to 18 years from the Azorean Archipelago, Portugal. We measured fasting glucose, insulin, total cholesterol, high-density lipoprotein cholesterol, triglycerides, systolic blood pressure, body fat, and cardiorespiratory fitness. We also calculated homeostatic model assessment and total cholesterol/high-density lipoprotein cholesterol ratio. For each one of these variables, a z score was computed using age and sex. A cardiometabolic risk score (CMRS) was constructed by summing up the z scores of all individual risk factors. High risk was considered to exist when an individual had at least 1 SD from this score. Diet was evaluated using a food frequency questionnaire, and the intake of total dairy (included milk, yogurt, and cheese), milk, yogurt, and cheese was categorized as low (equal to or below the median of the total sample) or “appropriate” (above the median of the total sample). The association between dairy product intake and CMRS was evaluated using separate logistic regression, and the results were adjusted for confounders." (Abreu. 2013)
I know that sounds really sophisticated, but in the end, it's just standard procedure for cross-sectional studies like this - studies with one unfortunate downside: It's impossible to detect causal relationships. 
Figure 1: Dietary intake in the low and "adequate" dairy-, milk-, yogurt-intake groups (Abreu. 2013)
Keep that in mind, when you take a closer look at the data in Figure 2 which indicates that the average adolescent milk connoisseur of whom you can see in Figure 1 that he / she consumes significantly more energy on a daily basis has a significantly reduced cardiometabolic risk (predicted by cardiometabolic risk score; CMRS):
Figure 2: Cardiometabolic risk in "adequate" vs. low dairy, milk, yogurt and cheese consuming adolescents; adjusted for parental education , pubertal stage, low-energy reporter, energy intake, total fat , protein , and dietary fiber intake.
I personally was surprised to see a statistically significant protective effect only with milk - it's not that I had expected to see that for all forms of dairy, but based on previous studies I would have expected the fermented yogurt products to outperform conventional milk.

The negative effects of cheese on the other hand are by no means surprising. Food logs do after all include all types of "cheese" including the fake yellow vegetable oil based cheese analogues the kids shovel down with their pizzas, burgers and the rest of the fast food dirt. A high cheese intake has thus (unfortunately) become an indicator of low diet quality and the results of the study at hand hardly a credible marker that cheese is bad for you.

If 95% of your "dairy intake" comes from pizza, you are unlikely to see...

... any of the following benefits of dairy peptides, Blanca Hernández-Ledesma, María José García-Nebot, Samuel Fernández-Tomé, Lourdes Amigo, and Isidra Recio summarized in a soon-to-be-published review in the peer-reviewed scientific journal International Dairy Science:
  • Figure 3: Reduction of systolic blood pressure in mmHg per mg/kg of the said peptide you consume - mind the logarithmic scale(!); data calculated based on rodent studies summarized in Hernández-Ledesma (2014)
    Cardiovascular health effects due to the antihypertensive, anti-inflammatory, general antioxidant and hypocholesterolaemic properties of various dairy peptides
  • Intestinal health effects due to the ability of dairy peptides to modulate and regenerate the gut mucosa, increase mineral absorption, exert local anti-inflammatory effects at the gastrointestinal level
  • Antidiabesity effects that are related to both direct pro-insulinogenic effects of dairy peptides ant their ability to increase satiety. 
  • Central nervous system relaxant and antinociceptive (pain-killing) effects
  • Immune health which is promoted by antimicrobial and immunomodulatory peptides that are either already present in dairy or arise during the digestion process
  • Anticancer effects that are mediated by the overall anti-inflammatory properties of certain dairy peptides, as well as direct anti-proliferative effects of dairy
Now, it goes without saying that you won't see the same effect from eating some goat kefir as Miguel et al. (2010) observed it, when they administered fraction 58-68 of goat casein to their lab rodents, but the data in Figure 3 can explain the well-established blood pressure lowering effects of dairy in general and the whey and casein induced BP reduction Figueroa et al. observed only recently in a study with obese women (Figueroa. 2013; see SuppVersity Facebook News).
Bottom line: You can't expect dairy to fully protect you against diabesity, cancer and a leaky, you can't expect it to lean you out in days, and you can't expect it to build muscle overnight, but you can expect general health benefits not detriments from incorporating a variety of fermented and unfermented dairy products into your diet - as long as you ain't lactose intolerant.

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One thing you should keep in mind, though, is the unfortunate fact that the amount of "non-dairy" cheese, cream and other products is increasing by the day. Especially the former, the fake yellow vegetable oil based cheese analogues is something you want to avoid. The same goes for many of low fat products. While much of the "magic" is in the peptides, most of the commercially available "diet" products contain tons of sugar and all sorts of questionable additive to make up for the loss of color, taste and texture that's brought about by the removal of the fat. And lastly all products that extend the shelf-life to "eternity" by adding questionable preservatives.
  • Abreu, S., Moreira, P., Moreira, C., Mota, J., Moreira-Silva, I., Santos, P. C., & Santos, R. (2013). Intake of milk, but not total dairy, yogurt, or cheese, is negatively associated with the clustering of cardiometabolic risk factors in adolescents. Nutrition Research.
  • Cândido, F.G., Ton, T. S., & Alfenas, R. D. C. G. (2013). Dairy products consumption versus type 2 diabetes prevention and treatment; a review of recent findings from human studies. Nutr Hosp, 28(5), 1384-1395.
  • de Oliveira Otto, M. C., Nettleton, J. A., Lemaitre, R. N., Steffen, L. M., Kromhout, D., Rich, S. S., ... & Mozaffarian, D. (2013). Biomarkers of dairy fatty acids and risk of cardiovascular disease in the multi‐ethnic study of atherosclerosis. Journal of the American Heart Association, 2(4), e000092.
  • Figueroa, A., Wong, A., Kinsey, A., Kalfon, R., Eddy, W., & Ormsbee, M. J. (2013). Effects of Milk Proteins and Combined Exercise Training on Aortic Hemodynamics and Arterial Stiffness in Young Obese Women With High Blood Pressure. American Journal of Hypertension, hpt224. 
  • Freedman, B. J. (1980). Sulphur dioxide in foods and beverages: its use as a preservative and its effect on asthma. British Journal of Diseases of the Chest, 74, 128-134.
  • Hernández-Ledesma, B., García-Nebot, M.J., Fernández-Tomé, S., Amigo, L.,
    Recio, I., Dairy protein hydrolysates: Peptides for health benefits, International Dairy Journal(2014), ahead of print
  • Iammarino, M., Di Taranto, A., Palermo, C., & Muscarella, M. (2011). Survey of benzoic acid in cheeses: contribution to the estimation of an admissible maximum limit. Food Additives and Contaminants: Part B, 4(4), 231-237.