Autumn Wellness: Extra Virgin Olive Oil, the Mediterranean Diet & Immune Health
As autumn settles in, the familiar coughs, colds and seasonal bugs begin doing the rounds. It's also the time of year when we're bombarded with products promising to “boost” our immune system. But supporting our health isn't about one miracle food, supplement or quick fix. Our immune system is extremely complex, and good nutrition is just one part of supporting its normal function.
The Mediterranean diet and immune health
The Mediterranean diet isn't really a “diet” as such, it’s a traditional pattern of eating built around vegetables, fruits, beans and lentils, nuts, whole grains, herbs, fish with extra virgin olive oil as the principal source of added fat.
Research has linked this dietary pattern of eating with a wide range of positive health outcomes. More recently, researchers have also been exploring its relationship with immune function, inflammation and the gut microbiome. The scientific research suggests that the nutrients and bioactive compounds provided by the Mediterranean diet may influence immune health both individually and collectively, with the gut microbiota thought to play an important role.
In the 12-month NU-AGE Mediterranean diet intervention involving older adults across five European countries, greater adherence to the diet was associated with specific changes in the gut microbiome and lower levels of inflammatory markers including C-reactive protein and interleukin-17. Read the NU-AGE Mediterranean diet and gut microbiome study
It isn't that eating one particular Mediterranean food will suddenly make us immune to the winter bugs, it's about giving our bodies a diverse range of nutrients and plant compounds as part of an overall healthy dietary pattern.
Research from the UK arm of the NU-AGE trial has also examined immune cell characteristics and innate immune responses following a one-year Mediterranean-style dietary intervention in healthy older adults, illustrating how researchers are beginning to look beyond individual nutrients to the wider relationship between dietary patterns and immune function. Read the NU-AGE immune function study
So where does extra virgin olive oil fit in?
Extra virgin olive oil is fascinating because it is much more than simply a source of fat. Its principal fatty acid is oleic acid, a monounsaturated healthful fat. EVOO also naturally contains vitamin E, an antioxidant vitamin that contributes to the protection of cells from oxidative stress. The amount naturally present can vary between olive oils.
But genuine high quality extra virgin olive oil also contains hundreds of minor components, including a family of naturally occurring plant compounds commonly referred to as polyphenols.
And this is where things become particularly interesting with a high-phenolic extra virgin olive oil.
Human research has also compared high- and low-polyphenol olive oils: in the double-blind OLIVAUS crossover trial, a high-polyphenol EVOO was associated with improvements in some measures of antioxidant status, although the researchers found no significant between-treatment differences across the full study population and observed stronger effects in certain higher-risk subgroups. Read the OLIVAUS randomised controlled trial
Among the phenolic compounds and their derivatives found in EVOO are:
- Oleocanthal: one of the compounds associated with the distinctive peppery sensation that a high-quality EVOO can produce at the back of the throat. It has attracted considerable scientific attention for its interaction with inflammatory pathways.
- Oleacein: another important secoiridoid found in EVOO and studied for its antioxidant and anti-inflammatory activity.
- Hydroxytyrosol: a phenolic compound particularly recognised for its antioxidant properties.
- Tyrosol: another naturally occurring phenolic alcohol found in olive oil.
- Oleuropein derivatives: compounds originating from the olive fruit that contribute to the complex phenolic profile of extra virgin olive oil.
These compounds help explain why researchers are interested in extra virgin olive oil as something quite different from simply another culinary fat.
A 2021 scientific review of olive-oil polyphenols examined evidence from laboratory, animal and human research and described several potential mechanisms through which compounds including hydroxytyrosol, oleocanthal and related phenolics interact with oxidative and inflammatory pathways. Read the review: Olive Polyphenols – Antioxidant and Anti-Inflammatory Properties
Polyphenols, oxidative stress and inflammation
To understand why these compounds are being researched in relation to immune health, it helps to understand two processes: oxidative stress and inflammation.
Both are normal biological processes.
Our immune system actually uses inflammation as part of its response to infection or injury. Problems can arise, however, when inflammatory processes become persistently dysregulated.
Oxidative stress occurs when the balance between reactive molecules produced within the body and our antioxidant defences becomes disrupted.
EVOO polyphenols have been extensively investigated for their antioxidant and anti-inflammatory properties. Laboratory and preclinical research suggests that compounds such as oleocanthal, oleacein and hydroxytyrosol can interact with molecular pathways involved in oxidative stress and inflammatory responses. Researchers have consequently become interested in whether these compounds might also have immunomodulatory effects, essentially, interactions with mechanisms involved in regulating immune responses.
A review specifically examining EVOO polyphenols and immune-mediated inflammatory disease concluded that experimental evidence supports antioxidant, anti-inflammatory and immunomodulatory activity, while also stressing that the available evidence is not sufficient to establish specific nutritional recommendations for treating immune-mediated disease. Read the review on EVOO polyphenols and immune-mediated inflammation
Research involving The Governor has also explored some of these inflammatory mechanisms: in a 2019 preclinical study, an oleocanthal-rich The Governor EVOO intervention in an Alzheimer's mouse model was associated with reduced neuroinflammation through inhibition of the NLRP3 inflammasome, although this was an animal study and not a trial of immune protection in people. Read the Governor-related NLRP3 inflammasome study
What can we say with confidence about olive oil polyphenols?
There is one particularly important health effect of olive oil polyphenols that has been formally evaluated and authorised.The permitted health claim states:
“Olive oil polyphenols contribute to the protection of blood lipids from oxidative stress.”
For an olive oil to carry this claim, it must contain at least 5mg of hydroxytyrosol and its derivatives — including oleuropein complex and tyrosol — per 20g of olive oil. The beneficial effect is obtained with a daily intake of 20g of olive oil. And not every olive oil will contain enough of these compounds to qualify.
Why are some extra virgin olive oils higher in polyphenols?
Olive variety, climate, growing conditions and the maturity of the fruit all matter. So do harvesting techniques, how quickly the olives reach the mill, extraction conditions, temperature and subsequent storage.
Generally, harvesting olives earlier, while they are still green can result in an oil with a higher concentration of phenolic compounds, although the oil yield from the fruit is lower.This is one of the reasons early-harvest oils can have such a distinctive sensory profile.
As olive oil sommeliers, when we taste a fresh EVOO we aren't simply looking for whether it tastes “nice”. We assess its fruitiness, bitterness and pungency. That bitterness and the characteristic peppery sensation at the back of the throat aren't faults. In a well-made EVOO, they are considered positive sensory attributes, and phenolic compounds are among the contributors to these sensations.
What makes The Governor different?
The Governor is produced on Corfu from the Lianolia olive, harvested early while still green. The olives are taken quickly to the mill and cold extracted, with considerable attention given to preserving the naturally occurring phenolic compounds.
Each harvest is independently analysed to establish its phenolic profile. This testing allows us to see the concentrations of individual compounds such as oleocanthal and oleacein, as well as the wider phenolic composition of the oil, and to establish whether it meets the conditions for the authorised olive-oil-polyphenol health claim.
The Governor itself has also been used in published scientific research: in a 2022 randomised controlled trial, people with mild cognitive impairment consumed 30ml of The Governor EVOO daily for six months, while earlier preclinical work had used the same oleocanthal-rich oil to investigate inflammatory and blood-brain-barrier mechanisms; neither study was designed to show protection from seasonal infections, but they provide product-specific evidence that The Governor has been directly studied rather than simply discussed by association. Read the 2022 human trial involving The Governor EVOO
So this autumn, fill your plates with a little more of the Mediterranean and don't forget the EVOO!
