Not all olive leaf extracts are created equal

After years of using olive leaf extract (Olea europaea folia) in clinical practice, and getting quite variable results, the reason is clear – most olive leaf extracts used by practitioners have quite low levels of some key active constituents.

Olive leaf extract (OLE) can be made from either fresh or dried leaves from the wonderful olive tree. Long regarded as a useful treatment and preventative medicine for some types of respiratory infections, and also a valuable medicine for certain cardiovascular issues such as high blood pressure, I felt in my practice that it did not seem to be living up to its reputation. Upon talking to other practitioners, it turns out I’m not the only one with this feeling.

Yet so many people swear by its benefits – and they are almost always buying it over the counter in a health food store or pharmacy, and not getting it from their herbalist or naturopath. So what is going on?

Well, I am pleased to tell you that we now have a better idea. I recently published research conducted by myself and Claudia Guillaume from the Modern Olives laboratory, and funded by the Olive Wellness Institute. And the results might surprise some people. Read below for a summary of the key points, or read the full paper published in Molecules by clicking

What was the Research?

To cut a long story short, we took 5 olive leaf extracts (OLE) from over-the-counter companies, and another 5 OLE’s from practitioner-only companies, in Australia. We analysed those extracts in the Modern Olives laboratory, quantifying the amount of key active phytochemicals in each product, and then comparing the results between products, but also between the group over-the-counter versus practitioner-only products. The key phytochemicals we examined included oleuropein, hydroxytyrosol, and the total biophenols profile, as well as minor constituents such as oleacein, oleocanthal, maslinic acid and oleanolic acid.

What Were the Results?

The degree of chemical variability between some of the extracts was quite concerning. Whilst a small degree of natural variation in herbal medicines is bound to occur and is quite acceptable, what we found was far more than this. For oleuropein across the 10 extracts sampled, the results ranged from a maximum concentration of 13.635mg/mL, to a minimum concentration of 0.382mg/mL – equating to a 35-fold variation! Similarly a hydroxytyrosol showed a 31-fold variation, and total biophenols an almost 5-fold variation. What was interested in examining the results was the fact that in many of the cases, a product low in oleuropein was higher in hydroxytyrosol, and vice-versa, indicating that in some products the oleuropein was breaking down to form hydroxytyrosol.

Looking a comparing product categories, over-the-counter OLE products had on average 2.4 times more oleuropein that practitioner-only extracts. This led me to examine the results more deeply, resulting in the observation that 4 out of 5 practitioner products were made from dried leaves, whereas for over-the-counter products 4 out of 5 of them were made from fresh leaves. When the chemical profile was compared between products made from fresh versus dry leaves, I observed the following shown in Figure 1.

Chemical profile of OLE's from fresh versus dry leaves

Figure 1: Ranges and mean concentrations of oleuropein, hydroxytyrosol, and total biophenols in extracts made from fresh leaf compared to the dry leaf. The vertical colored bars represent the ranges, and the horizontal labeled white bars represent the means.

Another interesting observation was around dosage. Even though their oleuropein concentrations were lower, most practitioner products had lower dosage ranges than the over-the-counter products, which is surprising given that they are supposed to be dispensed by a trained professional in the context of a health care consultation.

What Does This Mean Clinically?

Human studies on OLE for blood pressure control, insulin sensitivity and respiratory infections have usually utilised OLE preparations standardised between 51-136mg oleuropein per day. Unfortunately, even at the maximum recommended daily dosage, none of the practitioner-only products provided 51mg oleuropein per day. 

However 4 out of 5 over-the-counter products provided more than 51mg oleuropein per day at the maximum recommended dose, and 2 of 5 products provided more than 100mg per day.

No wonder myself and other professionals have been puzzled by the lacklustre results from OLE from practitioner companies, whilst patients swear by the value of the over-the-counter products!

In short, regardless of whether it is over-the-counter or practitioner-only, look for a product made from fresh leaves rather than dry leaves. Also, products should ideally declare the level of key phytochemicals on the label. If your practitioner-only company doesn’t declare this on their labels (all of the over-the-counter products sampled did, but none of the practitioner products had this information), ask them for copies of test results.

As clinicians caring for patients with sometimes serious health issues, we need to be able to trust that the medicines we prescribe are of suitable quality. This research has demonstrated that – at least in the case of olive leaf – just because it is practitioner-only does not mean that it is stronger or better.










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Copyright Ian Breakspear, 2014