Polyphenols: Olive Oil’s Secret?

Is there a secret ingredient in olive oil?

Recently there’s been a lot of talk about the near-mythic “Mediterranean diet” and how it can keep us healthy. What makes it special? Is it the olive oil?

What is the Mediterranean diet?

First, the name “Mediterranean diet” is misleading.

There are many local cuisines in the Mediterranean region. Mediterraneans as a group don’t all eat the same things. Indeed, many have wandered off the path and into the local fast food joint.

And as you can see, the “Mediterranean” involves many very different countries.

As photographer Peter Menzel documented in his project Hungry Planet, diets are pretty different across this region. Here, the Manzo family of Sicily (top) versus the Ahmed family of Cairo (bottom). (You can see more of what the world eats here.)

But I guess everything needs a name and “Mediterranean diet” probably evokes exotic fantasies of sun-kissed olive groves and eating fresh-caught fish while wearing an impeccably tailored white linen suit. Or it sounded better than “If you want to live to 100 than you should eat this way diet”.

Regardless of the name, the highlights of the diet are:

• mostly plant-based food (beans and legumes, vegetables, fruits, whole grains)
• eating fish and poultry at least twice a week
• eating primarily olive oil
• limited red meats and sugars (although judging from the bottles of soda in the photos above, that’s changing)

So what makes this diet supposedly so good? Is it the lack of red meat? Or the ample vegetables? Or the quarter-cup of olive oil a day?

Well, my Greek grandma lived to 96 years old without any signs of Alzheimer’s, cancer, heart disease, high cholesterol or high blood pressure and her motto was “You need enough olive oil or the food isn’t tasty.” Enough olive oil meant a good half-cup in her vegetable stew.

If you look at the list above, nothing is too surprising… until you look at the amount of fat in the diet. Up to a whopping 40% of the calories in the Mediterranean diet come from fat (which should have been a clue that a low fat diet might not work out too well in the long run). And most of that fat is olive oil.

Olive oil breakdown

What actually makes up olive oil?

The chart below shows the fatty acid composition of olive oil.

• Palmitic acid and stearic acid are saturated fats (S)
• Palmitoleic acid and oleic acid are monounsaturated fats (M)
• Linoleic acid and alpha-linolenic acids are unsaturated fats (U)

As you can see, oleic acid usually makes up the bulk of olive oil, generally around 55-80%, while linoleic acid is usually about 4-20% of olive oil. You can also see, by the way, that olive oil has a notable proportion of saturated fats — palmitic and stearic acids together usually make up around 15%.

Fatty acid composition varies depending on processing and type. Extra-virgin, cold-pressed olive oil — the good stuff — is basically made by mashing olives. Don’t be fooled by impostors that are chemically treated and heat-processed!

Does NOT count as “health food”…

Yeah, I’m pretty sure my gramma would flip out at the idea of olive oil margarine.

Polyphenols

So, one explanation for olive oil’s health benefits may be the fatty acid type. But another component, polyphenols, may actually be the key to what make olive oil so special. Polyphenols are plant-based antioxidants. In olive oil, tyrosol and hydroytryosol are the two major polyphenols.

This week, I review a study that tries to see whether polyphenols are the magic bullet of the “Mediterranean diet”.

Konstantinidou V, et al. In vivo nutrigenomic effects of virgin olive oil polyphenols within the frame of the Mediterranean diet: a randomized controlled trial. FASEB J. 2010 Jul;24(7):2546-57.

Methods

Ninety men and women between the ages of 20 and 50 years old were randomly assigned into one of three groups. People that were very physically active (>3000 kcal/day), obese or had other possible confounding risk factors (diabetes, hypertension, high cholesterol, celiac) were excluded.

• Group #1 followed the Mediterranean diet, including virgin olive oil.
• Group#2 followed the Mediterranean diet, including washed virgin olive oil. (Yes, washed. More on that in a sec.)
• Group #3 followed their normal diet with no changes (control group).

Washing oil: beyond Shout it out!

Washed virgin olive oil. Um, what?

My first thought when I read this was How do you wash oil? I can’t wash oil out of my shirt!

In a cycle similar to your washing machine, researchers washed the olive oil by mixing it with water (10% water-oil solution) at 70°C while shaking for two cycles, and then cooled it to 40°C for 20 min with more shaking. Then they put it through a spin cycle (centrifugation) to separate the water from the oil. Just to make sure the oil was squeaky clean – hmm, I guess that wouldn’t happen with oil – they did the whole cycle five more times!

So what the heck did they wash out of it? Polyphenols. Unwashed virgin olive oil has 328 mg/kg polyphenols while the washed virgin olive oil has only 55 mg/kg (about 17% of the unwashed oil).

I do wonder what else was lost.

Three months later

Researchers took several measures before and after the study. Some, you’ve probably heard of, such as:

• BMI
• blood pressure
• lipid profiles
• blood glucose

Others, not so much:

• IFN-γ (interferon gamma)
• MCP-1 (monocyte chemotactic protein-1).

They also measured changes in how active genes were, or gene expression. When genes are more active, they make more mRNA that eventually becomes functional proteins (like INF-γ). Why not just measure the protein? Technical problems, mostly. For now it’s way easier to find out if there are changes in mRNA compared to proteins.

INF- γ and MCP-1

The proteins INF- γ and MCP-1 can tell us whether someone might develop atherosclerosis (hardening of the arteries).(1)

INF- γ is a key player in immunity. Too much INF- γ has been linked to autoimmune diseases, such as lupus or multiple sclerosis, and diseases caused by auto-inflammation, such as atherosclerosis.

MCP-1 is the siren call for monocytes, so monocytes go to MCP-1. The problem is that monocytes have low-density lipoprotein cholesterol (LDL-C), aka “bad” cholesterol.

Where does MCP-1 come from?

MCP-1 is a protective substance. Sometimes, that’s good… in the right amounts, and at the right times. Sometimes, that’s not so good.

For instance, if you’ve cut yourself, then the damaged cells of your dangling finger make a bunch of MCP-1 to save you from the viruses and bacteria trying to invade your body. (Good.)

But if the cells lining your artery walls have been irritated or damaged, they make MCP-1, which then causes more problems in the end. (Bad.)

If artery cells just made a bit of MCP-1 and that was the end of it, it wouldn’t be a big deal. However, once a monocyte goes to an atherosclerotic lesion, it releases MCP-1 so more monocytes come. Monocytes dump their LDL-C into the lesion, making it bigger.

Don’t be surprised if you see an anti-MCP-1 drug on the market in the next 10 years or so, since they actually have genetically modified mice without MCP-1, who don’t get atherosclerosis. (One small problem… you need to make sure you don’t cut yourself.)

Results

Well, kind of underwhelming.

Although there were differences in the traditional blood measures, they weren’t dramatic. Over 3 months:

• Total cholesterol, HDL-C and LDL-C and INF-γ all decreased in the Mediterranean diet with virgin olive oil.
• There were no changes in the control and Mediterranean diet with washed olive oil.

The decrease in HDL-C goes against the idea that olive oil increases HDL-C, and that increase is part of the reason olive oil protects against atherosclerosis.

No change in MCP-1, which is a bit odd considering how well it seems to correlate to atherosclerosis.

Gene expression

The big headline for this study is “The Mediterranean diet and olive oil modifies genes.” This is misleading, because the genes haven’t been modified; however, the gene activity (or expression) has changed. The difference is similar to saying you’ve changed a recipe when all you did is make more.

Of the 48 genes they looked at, a subgroup of genes linked with inflammation were less active in the Mediterranean diet with olive oil compared to the control. One of the genes was the gene responsible for making IFN-γ, which makes sense, since there was less IFN- γ protein.

Conclusion

The big finding in this study was that the Mediterranean diet with regular virgin olive oil decreased the activity of inflammatory genes, but the Mediterranean diet with washed olive oil (no polyphenols) didn’t change these genes compared to the control group.

The researchers thus concluded that polyphenols are what make the “Mediterranean diet” effective.

While this is statistically true, the real story is that the Mediterranean diet — with or without polyphenols — does reduce inflammatory gene activity — just not enough to be considered “real” statistically. Basically, the Mediterranean diet with polyphenols is a bit better than without, but when you compare it to the control, that bit better makes it statistically significant.

Do polyphenols hold the key Mediterranean diet? Yes and no. Yes the Mediterranean diet group with polyphenols (olive oil) had reduced inflammatory gene activity more than without polyphenols. And no because the Mediterranean diet without polyphenols still reduced inflammatory gene activity.

Bottom line

Polyphenols do help reduce cardiovascular risk, but you can’t guzzle some polyphenols, eat whatever you want, and expect to be safe from a heart attack. You still need to eat along the lines of the Mediterranean diet to get the full health benefits.

And don’t try to convince your Spanish or Lebanese grandmother that olive oil margarine should go into the stew.

Reference

1. Gu L, Okada Y, Clinton SK, Gerard C, Sukhova GK, Libby P, Rollins BJ. Absence of monocyte chemoattractant protein-1 reduces atherosclerosis in low density lipoprotein receptor-deficient mice. Mol Cell 1998;2:275-281.