Tuesday, October 9, 2012

A Higher Intake of CLA and Vaccenic Acid from Dairy, Beef, Veal and Lamp Could Prevent Subtle Weight Gain in Healthy Middle-Aged Individuals. Is 1.5g/day the Magic Number?

A dairy cow: Does her stomach hold the key to a leaner, healthier life or are CLA and vaccenic acid, the ruminant trans-fatty acids just as bad as their grainy cousins?
There are supplements that work and supplements that don't work and then there are those supplements, where nobody can actually tell, whether they belong to the former or the latter category. Conjugated linoleic acid, the ruminant omega-6 trans-fat you will find at particularly high concentrations in milk and meat products from grassfed dairy, unquestionably belongs to the latter category. While we do actually have plenty of in parts almost unsettlingly impressive rodent data (e.g. "CLA Destroys Body Fat & Increases Endurance! But at Which Costs?"), the outcomes of independent  controlled human studies are equivocal; with results ranging from "total failure", to "promising, but not half as impressive as we have expected based on previous rodent studies".

That being said, I was quite intrigued, when I hit onto a recently published study that takes a novel angle on the whole CLA for weight loss issue. One I usually don't like, as it involves a lot of statistical shenanigan, but still appears appropriate in this particular case, where the controlled small scale trials are failing us.

The Nordic Men (and women) love their full-fat dairy - rightly so?

If you are a loyal reader of the SuppVersity, who does not just read the detailed elaborations here on www.suppversity.com, but is also following the latest short news on the SuppVersity Facebook Wall, it probably won't surprise you that the study which is going to be published in the October issue of the European Journal of Clinical Nutrition has been conducted in Northern Europe. After all, you will have noticed that many of the interesting short news items relating to (larger scale) studies on the effects of one or another of the "bad fats" are conducted at universities and research centers in Sweden, Finland, Norway and, as in this case, Denmark - at the Aarhus University, to be precise, where Hansen and his colleagues datasets from the Diet, Cancer and Health study from December 1993 to May 1997. The participants, 160,725 men and women, aged 50–64 years, who were all born in Denmark and had been living in the greater Aarhus or Copenhagen areas, had all completed detailed food frequency questionnaire (FFQ) and a self-administered lifestyle questionnaire, before they underwent a physical examination and a follow up 5-6 years later.

How did the scientists know how much CLA and vaccinic acid the individual food items contained? unfortunately, they didn't. The way by which they calculated / estimated it,  i.e, by combining the content of r-TFAs in milk fat (data based on another Danish study) with the content of milk fat in dairy products given by the Danish food composition tables and using the values of r-TFA content in ruminant meat products representative of the supply in Denmark, does however make sense to me. The resulting averages should therefore be relatively reliable.
Based on the 77 food items of the food frequency questionnaires which contained ruminant trans-fatty acids R-TFA (this includes both CLA, as well as vaccinic acid which can be converted to CLA in the human body; cf. Turpeinen. 2002), i.e.
  • dairy products (n=63), 
  • ruminant meat products (beef, veal or lamb) (n=2), and
  • composite recipes containing both dairy and ruminant meat (n=12) 
Hansen et al. calculated the average r-TFA intake of each of the 57053 subjects with complete datasets and correlated them with the participants changes in body weight and waist circumference (WC) over the 5-year period to the follow-up.

A massive amount of data suggest minimal amounts of r-TFA are necessary

As the subheading to this paragraph already reveals, the result of the all this statistical shenanigan suggest that the ruminant trans-fatty acid intake from foods, not supplements, does have a beneficial effect on the change in total body weight (an ameliorating effect on weight gain, to be precise).
Figure 1: Absolute intake of ruminant R-TFA (in g/day) and changes in weight; adjustment for sex, age, height, baseline weight, smoking, alcohol intake, education, weighted intake of foods containing high amounts of I-TFA (g/day) and in women, menopausal status and hormone replacement therapy (Hansen. 2012).
A brief glance at the graphs in figure 1 will yet also tell you that their effect on body fatness (as indicated by changes in visceral adipose tissue), is negligible, not to say non-existent. In a way you may say that this is a good thing, because the turning point at a daily r-TFA intake of >1.5g/day, where the restricted cubic spline (that's a statistical fit into the data; figure 1, solid lines) seems to indicate that r-TFA intakes of more than 1.5g/day would precipitate weight gain, is thus absent as well.
Figure 2: Relative intake of R-TFA (in % of total energy intake) and changes in waist circumference. Solid lines: restricted cubic spline with five knots; Dashed lines: 95% confidence interval; same adjustments as in figure 1(Hansen. 2012)
In addition, if we do also consider total energy consumption and the contribution of r-TFAs to the latter (see figure 2), it becomes obvious that we cannot neglect the profound widening of the 95% confidence interval in figure 1 (dashed lines), which tells us that some of the high r-TFA consumers did get even leaner, while others did gain a significant amount of weight. Adjusted for caloric intake and the other confounding variables this effect vanishes and a trend towards lower / even no body weight gain in high r-TFA consumers becomes visible (even within the higher intakes, where the confidence interval widens, due to the lower number of participants, but does not change the general trend). The beneficial effect on waist circumference, however, remains negligible.

So what, if anything, can we learn from these results?

At first sight, the results of the study at hand seem to stand in line with what you have read in "Fat Advantage: 61% Lower Rates of Metabolic Syndrome in High Fat Dairy Lovers", here at the SuppVersity exactly one week ago. It even appears to provide a mechanism by which the high fat dairy products could exert their highly desirable anti-obesity effects, if the high CLA + vaccenic acid (r-TFAs) consumers in the Hansen study were not just the subjects who gained the least weight (measured against their nutrient intake and adjusted for all sort of other confounding factors), but also those with the lowest increase in visceral adipose tissue.  

If that were the case, however, the graph on the right hand side of figure 2 should have at least some kind of slope. Since it hasn't, we must assume that the beneficial health effects of r-TFAs are either (a) not brought about by changes in visceral obesity, (b) the latter are not appropriately quantified by simply measuring the waist circumference or (c) in view of the fact that we are not talking about "weight loss", but rather a prevention of the (partly probably age induced) increase in weight gain a stable waist circumference has to be considered a "success", already.

The scale is an unreliable tool to judge visceral obesity. And even a measuring tape can be misleading, if you are really "skinny fat".
Personally, I tend towards a combination of all three. First of all even moderate weight gain has been shown to increase the risk of impeding metabolic syndrome. The weight stability over >5years in the high r-TFA consumers must therefore be considered to be prognostic of a lower risk of metabolic syndrome. Secondly, visceral does not necessarily equal abdominal fat. Especially in older individuals the gynoid fat areas contribute to visceral obesity, as well. Moreover, we all know the skinny fats, men and women with a relatively large amount of highly inflammatory visceral fat and normal or even low waist circumferences also known as "normal weight obese"; cf. Romero-Corral. 2010).

And thirdly and most importantly: Weight loss is mainly an issue for people who are already overweight or obese. For best-agers who are still in form (and in Denmark there are such people ;-), success is better defined by maintaining the muscle mass you have, not accumulating additional (visceral) body fat and leading an overall healthy lifestyle. That ruminant trans-fatty acids can, maybe even should be a part of the dietary side of this healthy life-style is therefore the main take home message of this study.

What should not be forgotten, however, is the fact that this study was at least in parts supported by the Danish Dairy Research Foundation, certainly not an organization with a particular interest in "bad news" on vaccenic acid, conjugated linoleic acid and dairy products in general, right?


References:
  • Hansen CP, Berentzen TL, Halkjær J, Tjønneland A, Sørensen TI, Overvad K, Jakobsen MU. Intake of ruminant trans fatty acids and changes in body weight and waist circumference. Eur J Clin Nutr. 2012 Oct;66(10):1104-9. doi: 10.1038/ejcn.2012.87.
  • Romero-Corral A, Somers VK, Sierra-Johnson J, Korenfeld Y, Boarin S, Korinek J, Jensen MD, Parati G, Lopez-Jimenez F. Normal weight obesity: a risk factor for cardiometabolic dysregulation and cardiovascular mortality. Eur Heart J. 2010 Mar;31(6):737-46.
  • Turpeinen AM, Mutanen M, Aro A, Salminen I, Basu S, Palmquist DL et al. Bioconversion of vaccenic acid to conjugated linoleic acid in humans.Am J Clin Nutr2002;76: 504–510.