More evidence that dairy foods contain agents with antiinflammatory and antioxidant properties is presented in a study published recently in The American Journal of Clinical Nutrition showing reductions in damaging inflammatory biomarkers. The authors state:

“Oxidative and inflammatory stress are elevated in obesity and are further augmented in metabolic syndrome. We showed previously that dairy components suppress the adipocyte- and macrophage-mediated generation of reactive oxygen species and inflammatory cytokines and systemic oxidative and inflammatory biomarkers in obesity…The objective of this study was to determine the early (7 d) and sustained (4 and 12 wk) effects of adequate-dairy (AD) compared with low-dairy (LD) diets in subjects with metabolic syndrome.”

Their forty overweight or obese subjects with metabolic syndrome were randomly assigned to receive either an ‘adequate dairy diet’ (defined as 3.5 daily servings) or ‘low dairy diet’ (less than half a daily serving) form of weight-maintenance diet for 12 weeks. They measured oxidative and inflammatory biomarkers at the start and after 1, 4, and 12 weeks as primary outcomes, along with body weight and composition to start and after 4, and 12 weeks as secondary outcomes. Their data showed a dramatic difference for the ‘adequate dairy’ diet:

“AD decreased malondialdehyde and oxidized LDL at 7 d (35% and 11%, respectively), with further decreases by 12 wk. Inflammatory markers were suppressed with intake of AD, with decreases in tumor necrosis factor-α at 7 d and further reductions through 12 wk (35%); decreases in interleukin-6 (21%) and monocyte chemoattractant protein 1 (14% decrease at 4 wk, 24% decrease at 12 wk); and a corresponding 55% increase in adiponectin at 12 wk. LD exerted no effect on oxidative or inflammatory markers. Diet had no effect on body weight; however, AD significantly reduced waist circumference and trunk fat, and LD exerted no effect.”

While these findings don’t obviate the need to attend to the possibility of dairy allergies or the quality of dairy foods consumed, this is strong evidence that there agents in an ‘adequate dairy’ diet that can do more than a low dairy diet even when the same amount of weight is lost.

“Data from this study show that an increase in dairy intake from suboptimal to adequate levels (≈3.5 servings/d) significantly attenuates both oxidative and inflammatory stress in metabolic syndrome. Notably, although these effects may result, in part, from reductions in adiposity on higher dairy diets, the rapid onset (within the first 7 d of dietary change) suggest that there is an adiposity-independent effect as well. This is further supported by our previous evidence that showed direct effects of dairy components on adipocyte cytokine expression and secretion.”

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Original research published recently in the Annals of Internal Medicine offers evidence that trans-palmitoleate, a fat present in milk, is responsible for metabolic benefits observed with dairy consumption. The authors set out to…

“…To investigate whether circulating trans-palmitoleate is independently related to lower metabolic risk and incident type 2 diabetes.”

They examined 3736 adults in the Cardiovascular Health Study for plasma phospholipid fatty acids, blood lipids, inflammatory markers, and glucose–insulin and dietary habits, taking into consideration relevant demographic, clinical, and lifestyle factors. They then determined how trans-palmitoleate related to major metabolic risk factors. Their data tell an interesting story of a helpful fat:

“In multivariate analyses, whole-fat dairy consumption was most strongly associated with higher trans-palmitoleate levels. Higher trans-palmitoleate levels were associated with slightly lower adiposity and, independently, with higher high-density lipoprotein cholesterol levels, lower triglyceride levels, a lower total cholesterol–HDL cholesterol ratio, lower C-reactive protein levels, and lower insulin resistance. Trans-palmitoleate was also associated with a substantially lower incidence of diabetes…Protective associations with metabolic risk factors were confirmed in the validation cohort.”

Of course, this study does address the widespread problem of dairy allergy, nor does it discriminate between the widely varying qualities of dairy (organic from grass-fed free-range animals versus industrial dairy). But it does caution against the wholesale discrimination against fats in general and the dairy food group in particular. As always, clinical and lifestyle decisions depend on the needs of the individual which can be verified by objective outcome markers. Practitioners and health conscious individuals can consider the authors’ conclusion:

“Circulating trans-palmitoleate is associated with lower insulin resistance, presence of atherogenic dyslipidemia, and incident diabetes. Our findings may explain previously observed metabolic benefits of dairy consumption and support the need for detailed further experimental and clinical investigation.”

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Studies examining the epidemiological effect of a food rarely disclose its quality and source. Do you ever wonder if a study on meat, for example, might give different results if the subjects consumed only organic grass-fed meat rather than meat from hormone and antibiotic-laced feedlot animals fed on grain silage and offal? A study recently published in the European Journal of Clinical Nutrition came up with a surprise when it investigated the effect of full-fat dairy on cardiovascular disease in Australian adults.

“Dairy foods contain various nutrients that may affect health. We investigated whether intake of dairy products or related nutrients is associated with mortality due to cardiovascular disease (CVD), cancer and all causes.”

The authors studied 1529 adult Australians over 16 years, correlating habitual intakes of dairy products with mortality and cause of death. When the numbers were analyzed an unexpected finding emerged:

“…compared with those with the lowest intake of full-fat dairy, participants with the highest intake had reduced death due to CVD after adjustment for calcium intake and other confounders.”

The data compelled them to record conclusions contrary to popular dogma:

“Overall intake of dairy products was not associated with mortality. A possible beneficial association between intake of full-fat dairy and cardiovascular mortality needs further assessment and confirmation.”

Perhaps it has something to with what the cows were eating. A study published just last month in the journal Veterinary Research Communications compared the effect of grass hay versus grain (maize = corn) on the properties of the milk to promote cardiovascular disease.

“14 Holstein dairy cows were fed…either grass hay (GH) or maize silage (MS). Milk samples were collected…and fatty acid (FA) profiles were analyzed…Milk from animals fed the GH-diet contained lower concentrations of saturated FAs and higher levels of polyunsaturated FAs (PUFAs). Feeding additional hay also increased conjugated linoleic acid and n-3 FA levels and decreased C16:0 levels.”

What do these differences in fatty acids mean for cardiovascular disease risk?

“Increases in both PUFAs and n-3 FAs resulted in lower atherogenic and thrombogenic indices in milk from animals fed the GH diet compared with those fed the MS diet. A complete substitution of GH for MS appeared to improve milk FA profiles….”

Too bad the authors of the Australian study weren’t able to specify what those Australian cows ate. But another fascinating study just published in the American Journal of Clinical Nutrition sheds more light on the matter. The authors begin by observing:

“Despite the high saturated fat content of dairy products, no clear association between dairy product intake and risk of myocardial infarction (MI) has been observed. Dairy products are the main source of conjugated linoleic acid (CLA; 18:2n–7t), which is produced by the ruminal biohydrogenation of grasses eaten by cows. Pasture-grazing dairy cows have more CLA in their milk than do grain-fed cows. Some animal models have reported beneficial effects of CLA on atherosclerosis.”

The authors wanted to determine the association between CLA in adipose tissue and risk of MI [myocardial infarction]. They used 1813 individuals with non-fatal heart attacks compared to matched controls, in Costa Rica where people use traditional pasture-grazing for dairy cows. What did their data show?

“Adipose tissue CLA was associated with a lower risk of MI…Dairy intake was not associated with risk of MI, despite a strong risk associated with saturated fat intake.”

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This is a surprising paper just published in the American Journal of Clinical Nutrition. Don’t forget that allergy to casein (dairy protein) is a serious matter, but when that is not a factor note what the investigators found: “The dairy-supplemented diet resulted in significant suppression of oxidative stress and lower inflammatory markers and increased adiponectin, whereas the soy exerted no significant effect.” Just goes to show the importance of the scientific approach and an open mind. The authors conclude: “An increase in dairy food intake produces significant and substantial suppression of the oxidative and inflammatory stress associated with overweight and obesity.” The best dairy is from animals eating alpine grasses or forage rather than grain, whether cow, sheep or yak. [In fact, 'yak' refers to the male of the species; the milk-bearing female is the dru.]

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