Wednesday, November 30, 2011

Pimp My Olive Oil! When Virgin is not Phenol-Rich Enough: The Pharmacokinetics of Phenol-Enriched Virgin Olive Oil.

Image 1:  "If we have not somehow pimped it, it can never be good enough!" appears to be one of the credos with which mankind approaches almost every health-remedy nature has provided for us. In the past this approach was not particularly healthy, though... is phenol-enriched olive oil going to be the exception to the rule?
Being the health-conscious person you obviously are (why else would you visit the SuppVersity ;-), chances are that olive oil, or, to be specific, extra virgin olive oil is one if not primary source of of mono- and polyunsaturated fats in your diet. But do you actually know why? I mean why olive oil? And why extra virgin? What? "Mediterranean diet", "high MUFA content", "lower incidence of coronary heart disease and cancer"? All right, you have done your homework on olive oil, but what about the "extra virgin"? The polyphenols, right. The phenolic content is in fact what distinguishes a "good" olive oil. The phenolic alcohols, the secoiridoid derivatives, the phenolic acids, the lignans and the flavonoids in concert have been reported to have anti-oxidant, anti-inflammatory, anti-atherogenic and anti-carcineogenic properties and are probably as, if not more important for the beneficial health effects of the Mediterranean gold than its fatty acid profile (Covas. 2007; Covas. 2008).

So, if those polyphenols are the "active ingredients" in olive oil, wouldn't it be nice if we had an oil that had even more of these beneficial healthy secondary plant metabolits in our oils, right?

Now we have tons of polyphenols, but does that make a difference?

The thought, that a souped up version of the already phenol-rich virgin olive oil would be an even more potent health promoter must have occurred to a group of researcher from Spain, as well. Back in 2010 already, Manual Suárez and his coworkers published a paper in the Journal of Argiculture and Food Chemistry in which they describe the development of a "phenol-enriched olive oil with phenolic compounds from olive cake" (Suárez. 2010). In essence, the scientists just put back some of the pulp (an extract to be precise) that is produced when the oil is squeezed from the olives into the end-product. In a more recent study the scientists did now try to evaluate how much of these (additional) health promoters in 30ml of regular virgin olive oil (VO) and the enhanced virgin olive oil (EVOO) actually make it into the blood of 16 (8 men, 8 women) healthy subjects in a randomized, controlled, cross-over trial (Suárez. 2011).
Figure 1: Compositional differences (phenol-enriched vs. standard virgin olive oil) in polyphenol content (data calculated based on Suárez. 2011)
If you take a look at the compositional differences between the regular and the "phenol-enriched" virgin olive oil, it is quite obvious that, from a mere quantitative point of view, Suárez' product with on average 3.3x more secondary plant metabolits should be the more potent health promoter. After all, numerous previous studies have shown that those olive oils with (naturally!) particularly high phenol-content exhibit the most pronounced beneficial health effects (Samanego Sanchéz. 2007). This would yet require adequate absorption of the respective compounds from a now obviously more dense solution, which, according to the results of this study, does not seem to be the case for all compounds - and more importantly, all subjects:
The in vivo study showed that the concentration of fourteen of twenty-four compounds detected was higher in the plasma samples from the EVOO than after ingestion of VOO. Among these, two of them, hydroxytyrosol sulphate and vanil-lin sulphate, were statistically significant in attending their pharmacokinetic parameters, demonstrating the suitability of enrichment. In general, a displacement of the time to reach the maximum concentration is observed in the samples, which indicates that more time is needed to absorb the higher phenolic content. However, inter-individual variability in the concentration of the plasma phenol metabolites shows that it is difficult to show statistically significant differences between the VOO and the EVOO.
The scientists thusly conclude that the "metabolism of phenols is affected first by the individual". So until we actually know which influence these are, the label "phenol-enriched" on olive oils and other products has little meaning for you as an individual. And even if you belong to the "lucky" high-absorbers, only two, namely vanillin sulphate and hydroxytyrosol sulphate will reach what the scientists call "pharmocokinetic" levels, if you ingest two tablespoons of the super-potent "phenol-enriched" virgin (and still relatively natural) olive oil.
Figure 2: Changes in total antioxidant activity (TAA) of experimental oils subsequent to heat treatment (from Pellegrini. 2001)
Note: Common Internet wisdom would suggest that you have to be particularly cautious with those "phenol-enriched virgin olive oils", when respective products hit the market (and I bet this won't take long). After all, you will all have heard how heating those oils damages the healthy polyphenols - and while that may to some extend be the case, a 2001 study by Nicoletta Pellegrini et al. found that the total antioxidant value of olive oil does not only increase with increased polyphenol content, but that those polyphenols are also "stabilizers of R-tocopherol during olive oil heating, thus contributing to the nutritional value of cooked foods" and "the prevention of antioxidant activity decay in olive oil during realistic heating conditions" (Pellegrini. 2001), which ranged from 30min at 160°C to 120min at 190°C. The latter happens to be at the upper end of the regular deep-frying temperature and would thus suggest that the commonly heard recommendation not to use extra virgin olive oil for frying is not valid, at least when we focus exclusively on its total antioxidant capacity as measured by Trolox essays (cf. figure 2). In that it should be mentioned that, with its relatively high content of highly oxidizable omega-6 fats, olive oil still isn't the "ideal" frying oil - notwithstanding that frying does not constitute the healthiest way of preparing your food anyways ;-)
And though a recent study has shown that the latter conjugates with LDL and thusly protects it from oxidative damage (González-Santiago. 2010), it remains to be verified whether the consumer variety of the olive oil in this study will actually provide any health benefits. And this is particularly true in view of the fact that the food giants will, as they already do it in the case of "normal" virgin olive oil, minuscule amounts this probably expensive ingredient into their otherwise unhealthy convenient products, just to be able to put the highly marketable "contains phenol-enriched virgin olive oil" on the label... but, hey! I guess, this is just the never-ending story of complete nutritional idiocy ;-)