CARDIOVASCULAR HEALTH: Saturates may be good for us, especially dairy derived ones
A major new study just published in the American Journal of Clinical Nutrition (Am J Clin Nutr August 2012 vol. 96 no. 2 397-404) is of interest as it investigated a very important area generally overlooked, namely it worked to establish whether or not all saturated fats might have the same impact on cardiovascular disease risk and moreover, to profile the relative risks or otherwise of each main class.
In other words, is there any reason to imagine that the impact on general cardiovascular health is the same from the consumption of any given quantity of saturated fat, of whatever type and derived from whatever source? Saturates of course predominate in a range of very different food types: salami, beef, butter, eggs, poultry, cheese, milk, coconuts etc.
The study tracked “substitution effects” only, monitoring the impact of getting relatively more of one's saturates from a given saturate source as against another, across the full range of light total saturate to high total saturate eaters. In other words, for any given level of total saturate consumption, it explored what might be the ideal way to split one's nutrition amongst all possible individual saturate sources.
As pointed out in the study intro, findings from many prospective cohort studies have generally not found any significant association between overall saturated fat intake and greater risk of CVD in spite of a generalized assumption amongst the public at large that such is certainly the case. Potentially more worrying still is that all too often a move away from a saturate-rich diet tends to co-occur with a move towards more carbohydrates (the most common scenario in the United States and other populations), which switch in energy source could potentially worsen CVD risk according to many experts (particularly if the carbohydrates are principally nutrient-poor refined grains and/or high in sugar). While higher saturate fat consumption generally increases the so-called bad LDL, saturates also offer several beneficial effects, unlike carbohydrates, such as increasing the “good” HDL, decreasing triglycerides and having little net effect on the ratio of total:HDL cholesterol. There is thus support for wondering if, generally, more saturates in the diet might actually help CVD risk. The really interesting part is to try to establish if certain saturate sources might increase the risk of heart attack and stroke trouble whilst others might actually help in this regard. Such was the subject of this work.
The study involved over 6,000 participants in the “Multi-Ethnic Study of Atherosclerosis (MESA)” who were monitored between 2000 and 2010, ultimately yielding over 36,000 person-years of follow-up. Total CVD events were monitored and participants were monitored in terms of consumption of saturates of various types (dairy, meat incl. fish and poultry, butter, plant sources, mixed animal & plant sources.) Raw data was parsed and 3 multi-variable models were used with increasing correction for possible confounders (moving on from things like age, rage, total calories/day through education level, exercise, smoking, to supplement use, fruit and veg intake, increased dietary Vitamin E etc.) In unadjusted comparisons, there was an association between higher saturate intake and worse CVD risk profile but higher BMI, smoking, no exercise etc. were likely contributors.
In essence, the study showed the following:
TOTAL saturate consumption was modestly associated with lower risk of CVD in the unadjusted model, which association strengthened after adjustment for other behavioral and lifestyle confounders.
Greater DAIRY SF consumption showed a clear significant inverse correlation or lower CVD risk. Whilst no significant association showed in the unadjusted data, in the fully adjusted model, each 5-g/d greater intake was associated with 21% lower risk [HR (95% CI): 0.79 (0.68, 0.92). Similarly, each 5-unit increase in the percentage of energy from dairy SF was associated with 38% lower risk of CVD [HR (95% CI): 0.62 (0.47, 0.82)] Meat Saturate consumption showed a slight positive correlation between greater consumption and greater CVD risk in the unadjusted data, which correlation was attenuated somewhat once confounders were allowed for.
Overall, the data suggests that the substitution of 2% of energy from meat SF with a similar amount of energy from dairy SF was associated with 25% lower CVD risk [HR (95% CI): 0.75 (0.63, 0.91)] At 2000 kcal/d, this substitution would correspond to the exchange of 50 kcal or 5.5 g SF [eg, the replacement of 2 oz beef or half a “quarter pounder” burger with one glass (240 mL) of whole milk .
The authors have rightly wondered about what might be behind their findings. One explanation could be the predominance of medium-chain fatty acids in dairy generally which help boost HDL more than palmitic acid, the main fat in meats. The authors also reference new findings from the Cardiovascular Health Study wherein higher concentrations of plasma trans palmitoleic acid, a fatty acid originating primarily in dairy foods, have been recently associated with higher HDL, lower triglycerides, lower C-reactive protein, lower insulin resistance, and lower incident diabetes. Another possibility is the possible anti-hypertensive effects of the calcium, potassium and phosphorus in milk as against the sodium and nitrates found in certain meats, processed ones in particular, which would tend to drive up blood pressure.
No one study alone can or should provoke major behavioral change; nonetheless, we feel that it would be helpful if the “take-home” from this study began to percolate out into the wider public that NOT ALL SATURATES ARE BAD!
© SmartEatersTM 2012