Wednesday, July 11, 2012

Higher Calcium Intake Greater Fatty Acid Oxidation!? True: Chronic & Acute Effect Size Comparable to Caffeine

Image 1: When people hear they should increase their calcium intake, they either think of pills and tablets or milk and dairy in general. The fact that all greens, nuts and many seeds contain tons of calcium, as well, is commonly overlooked (for more high calcium foods see table 1, below).
"Increase your calcium intake, if you want to lose body fat!" I honestly don't even remember, when I've heard this statement for the first time, but it was way before I started questioning general recommendations on nutrition. Meanwhile, my blind faith in dietary recommendations and expert advice has faded, yet the general advice to "increase your calcium intake" is still so ubiquitous that searching for it on Google returns 373.000 results within 0.24 seconds, searching for the same token yet with "magnesium" instead of calcium does only yield 11,900 results and even "increase your omega-3 intake" will deliver only a meager 17,500 results (4.6% of the results for calcium). The publication of a very recent review by Gonzales, Rumbold and Stevenson in the "early view" section of Obesity Reviews was therefore a very welcome opportunity for me to take another look at the effects high(er) dietary / supplemental calcium intakes exert not just on weight loss, but also on postprandial and 24h fatty acid oxidation.

Will calcium make you lean or at least help you to stay lean?

Calcium intake has been associated with lower body mass index and adiposity (body fatness) for decades and supporting evidence from epidemiological studies is abundant (see references 1-15). If you take a look the highly opinionated paleosphere, the most recent consensus on calcium and the most prominent (I did not say best ;-) dietary calcium source, dairy, is however that dairy is the devil and calcium supplements are made of the devil's excrements... and in fact, at least the latter may be dead-on. After all, one of the purported mechanisms that could explain the associations of high(er) calcium intakes and low(er) body fat levels is directly related to excrements - the fat content of your excrements, to be precise, of which a handful of studies have shown that it is increased (see references 18-21) in response to calcium supplementation / increases in dietary calcium.
Figure 1: When added to a regular calorically reduced diet supplemental and even more dairy calcium ramp up its efficacy (data based on Zemel. 2004).
Sufficiently powered and well-conducted trials support the epidemiological data: As Trowman et al. pointed out in another systematic review of the literature (Trowman. 2006), most trials did not adequately make up for biases that may have been introduced by weak allocation methods and the only "adequately powered" study that was specifically designed to identify the effects of calcium supplementation on weight loss on an energy restricted (-500kcal) diet over a sufficiently long time period (24 weeks) by Zemel. et al. yielded a highly significant increases weight and fat loss for both supplemental and dairy calcium (see figure 1). An effect, of which the researchers state that it is most likely mediated by the inhibition of the 1,25-dihydoxyvitamin D increases with which our body reacts in response to low-calcium diets and thus stimulate adipocyte Ca2+ influx and, as a consequence, lipogenesis, while simulataneously suppressing lipolysis, and increasing lipid accumulation.
The subsequent decrease in fatty acid and thus energy absorption can yet not fully explain the observed weight loss effects. According to Christensen et al. the latter would amount to roughly 2g/day and thus no more than 0.7kg of body fat per year (Christensen. 2009)! The data of the study be Zemel et al. (see red box), on the other hand, shows an absolute increase in weight loss of 4.5kg within no more than 24 weeks, which highlights the importance of other mechanisms such as...
  • the aforementioned (see red box) reduction in 1,25-dihydroxyvitamin D expression and its pro-adipogenic (=promoting fat storage) and anti-adipolytic (=inhibiting fat burn) effects, or
  • lower parathyroid hormone (PTH) levels and subsequently increased insulin sensitivity and sympathetic nervous system activity, which will in turn increase dietary induced thermogensis and fatty oxidation rates, and lastly
  • gastrointestinal effects of dietary calcium (and dairy) on the release of peptides and hormones in the GI tract
all of which interact to increase energy expenditure, decrease the fat balance, increase energy loss (increased mitochondrial uncoupling; e.g. Shi. 2001) and reduce food intake, with the net effect of decreases in body weight and body fat levels.
Figure 2: Effects of chronic (top) and acute (bottom) high calcium intake on fat oxidation, as well as weighed averages (lower right);  Ca2+, calcium; DA, dairy (based on Gonzales. 2012)
The data from the initially mentioned meta-review by Gonzales et al. in figure 2 confirms the significance of these effects. Irrespective of the scenario, i.e. weight loss vs. weight maintenance, calcium sufficient vs. calcium deficient baseline diet and acute vs. chronic, an increase in dietary calcium from supplements or food sources lead to statistical significant increases in fatty acid oxidation, of which the researchers state that they are of "comparable magnitude with that seen with caffeine supplementation" (Gonzales. 2012).

Two reasons why you should prefer dietary (dairy) calcium: Efficacy and safety

Despite the fact that the difference is not statistically significant, the data Gonzales et al. collected and my own cursory review of pertinent studies, both suggest that contrary to the effects on fatty acid oxidation, which are, as Gonazeles et al. point out apparently slightly more pronounced in response to supplemental calcium (could simply be an effect of insufficient adherence in the dietary calcium groups; popping a pill is easier and above all  more convenient than eating 2-3x servings of dairy), dietary calcium sources elicit greater weight- and fat-loss effects than supplements. It stands to reason that part of this may be explained by confounding factors such as
Table 1: High calcium foods with a calcium to phosphorus ratio of 1:0.14 (Turnip) to 1:0.7 (Celery); data adapted from parrottalk.com; eating those foods will also shift your often too low calcium to phosphorus ratio in the "right" direction
If you add to that the already inconclusive evidence that high(er) calcium intake precipitates heart disease (e.g. deBoer. 2008) refer exclusively to supplemental calcium (and most data is from postmenopausal women on synthetic hormone therapy), I suggest you head right over to one of the nutrition analyzers to see if you get at ~900mg-1,300mg of calcium in your diet. What your calcium to phosphor ratio looks like (should be 1:1) and whether another cup of spinach and a glass of milk once in a while could not maybe help you to shed some additional pounds of body fat.

Update: I forgot to mention a previous article of mine on potential toxicity issues with many commercially available calcium supplements which could be a hitherto overlooked confounding factor in the etiology of heart disease - see "Alarmingly High Levels of Lead in Calcium Supplements: Pb Content per Serving Up to 18x Over 'Acceptable Levels'"

References: 
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