Matt Metzgar

Turning to diets that actually increase vascular health, I wanted to focus on the recent hazelnut study.  This study increased flow-mediated dilation by 56%!  There are a number of interesting things about this study.

First, look at the baseline diet:

In the control diet, there is already a very high unsaturated-to-saturated fat ratio.  If you calculate it, it is 3.27:1.  Based on my previous posts, this should by itself lead to a high level of flow-mediated dilation.  So does it?  Yes!

In this study, the baseline FMD on the control diet was 15.2!  That’s very high.  Compare it to the numbers in a previous post that compared a low-carb versus a low-fat diet.  Those FMD numbers were between 6 and 9.  Now with a high level of unsaturated fat to saturated fats in the diet, the FMD is 15.2%.

So then hazelnuts are incorporated into the diet, which boosts fat intake and reduces carbohydrate intake.  The ratio of unsaturated/saturated fats goes even higher to 5.5:1.  The result: FMD increases to 21.8%!

This is one of the highest levels of FMD I have ever seen!  So what would this change do for a person, health-wise?

A recent meta-analysis showed that for every 1% increase in FMD, the risk of a cardiovascular event is lowered by 13%.  So in this study the increase of 6.6% in FMD would reduce the risk of a cardiovascular event by 86%!

Not bad for swapping some carbs for hazelnuts in your diet!

Here’s one more study on the Atkins diet and flow-mediated dilation.  This one was for 52 weeks.  The result: “FMD decreased in LC (5.7 +/- 0.7% to 3.7 +/- 0.5%” (LC = low-carbohydrate).

So at some point you have to ask, why are people signing up for a diet that directly impairs vascular health?

Time for another butter-buster.  This study (full-text) compared a low-fat diet to an Atkins diet.  It was a six-week study that looked at various markers.

The result: the Atkins diet significantly reduced flow-mediated dilation (FMD).

“But it wasn’t a true low-carb diet”.  Grams of carbohydrate were kept under 25 grams per day over the whole course of the six-week study.  “But they weren’t low-carb adapted”.  Then why did FMD get worse as the study went on, not better?

This study also has some other interesting points that I will circle back to.

Here’s one new study in press on the importance of the unsaturated-to-saturated fat ratio.  What they did was reduce saturated fat and add macadamia nuts in order to improve the ratio.  At baseline, the ratio was 1.33:1, and after 6 weeks with the diet it was 1.89:1 (very close to the 2:1 Paleolithic ratio).

The result: flow-mediated dilation improved.

To test my idea about the unsaturated-to-saturated fat ratio being important for cardiovascular health, I wanted to focus in on this study.  This study, unlike other ones I’ve cited, directly compares oil to oil.  It tests butter versus olive oil in diabetes patients.

So there you have it, butter substantially reduces flow-mediated dilation (FMD), while olive oil is generally neutral.

If you calculate the unsaturated-to-saturated fat ratio for the two meals used in the study, you get:

• Butter  0.5:1
• Olive Oil  5.8:1

Very different ratios, and very different results on vascular health.

Here’s a paper I’ve been puzzled about for a while.  The paper concludes that “bison consumption results in a reduced atherogenic risk compared to beef”.  In the paper, they show that regular consumption of beef (but not bison) reduces flow-mediated dilation.

First of all, I think this is very note-worthy, and I am surprised that most people have been ignoring this finding.  But that’s another story.

The study claims that regular consumption of bison does not statistically lower FMD, but I’m not so sure.  You be the judge (trend in bold).

Anyways, this shows that regular consumption of store-bought beef lowers FMD over time.  This is not a one-meal study.  This is over a period of weeks, and it shows that there is no adaptation.

So you have a couple conclusions: 1) beef lowers FMD, and 2) beef lowers FMD more than bison.  But why?

As I said, I’ve been puzzling over this for a while.  Here’s a table showing the differences in fat consumption:

Okay, so beef has more fat than bison.  But is that the main reason it is worse?  Seems unlikely.

How about the n-6/n-3 ratio?  Again, the ratio for beef is worse, but they aren’t substantially different from each other.

How about the ratio of unsaturated to saturated fat?  If you calculate it for the steaks, you get:

• Beef  1.18:1
• Bison 1.51:1

Both fall short of the 2:1 ratio seen in Paleo diets.  The ratio for bison is closer to 2:1, and is less damaging to FMD than beef is.

There could be multiple factors at work here.  But in my mind, it shows the importance of the fatty acid composition for vascular health.

I’ve been thinking more about the study I previously referred to that shows how butter lowers flow-mediated dilation.  I mean, it’s right there in black-and-white (and free full-text) that consuming butter everyday for 3 weeks led to lower flow-mediated dilation.

However, the monounsaturated and polyunsaturated conditions led to no change in FMD.  The MUFA and PUFA diets had nuts and margarine.  Based on the idea of whole foods, I would suggest that the nuts being whole foods contributed to the better FMD result.  But still, these two diets did contain oil, so that muddies the waters.

My refined thinking on this is that while the nuts probably played a role, I think the overall unsaturated to saturated fat ratio may play an even bigger role.  Here are the diet stats from the paper:

In the previous post, I showed how the Paleo diet has a ratio of 2:1 for unsaturated to saturated fats.  Let’s calculate the ratios for the three diets in the table:

• PUFA   2.7:1
• MUFA   3.3:1
• SFA   0.8:1

Quite a difference!

So could the unsaturated to saturated fat ratio make that much of a difference, that it affects FMD and possibly heart disease?  Stay tuned for the next posts.

I was looking some more at the East African Paleo diet paper.  Specifically, I was looking at the ratios of saturated fat, monounsaturated fat, and polyunsaturated fat.

The paper presents various models, but if you take the “median of the medians”, then you get the following percentage of total calories going to each category:

• Saturated fat – 11.7%
• Monounsaturated fat – 12.1%
• Polyunsaturated fat – 11.9%

So roughly you have a ratio of 1:1:1 for saturated, monounsaturated, and polyunsaturated fat.  In more general terms, you have a ratio of 2:1 for unsaturated to saturated fat.

Also, the omega-3/omega-6 ratio was roughly 1:1.

I will refer to these ratios in upcoming posts.

I thought I would point out this interesting study on a Mediterranean version of a ketogenic diet.

I am not a big fan of ketogenic diets, but in this study they went from 100% of patients having the metabolic syndrome at baseline to 0% twelve weeks later.  By anyone’s definition, those are good results!

There is some discussion of the Paleo diet and other interesting aspects near the end of the paper.