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Understanding the PURE Study: Can Carbs Kill?

Have you heard that high-carb diets can kill you? Or that low-fat diets are deadly? These are just some of the headlines that have come out in the evaluation of the recent Prospective Urban Rural Epidemiology (PURE) study. I was just as shocked as you are when I saw these articles, so today I want to dive into the science behind the study to help you uncover the facts.

Low Carb, Low Fat, High Carb, High Fat

To be honest with you, I have never thought of any of these concepts to be important in terms of decision making. As far as I’m concerned, it has always been about the quality of the fuel that you feed into your body – as opposed to the ratios of your fuel.

When the PURE study came out (1), though, I felt that if there was hard data to substantiate these ratios in one way or another, I definitely needed to listen. I have never been a fan of dismissing studies based purely on the idea of it contradicting my beliefs up until this point – if my views need to change, they will always change when the science backs it up.

The PURE Study

So, let’s get into it. Here is what we can take away from the PURE study, what it is all about, and what you need to leave with – information-wise – to make the right choice for your health…

First and foremost, the PURE study is a prospective study (so much so that it is right in the time). This means that the terms of the study were defined in advance, and then they watched the results over the course of years. It also encompassed a large number of people, covering 18 different countries.

They took a look at the ratio of carbs and fats in diets across the world, and also the types of fats (like saturated, polyunsaturated, monounsaturated). Ultimately, they evaluated how these things affected:

  • Total Mortality, and
  • Cardiovascular Mortality

There were conclusions that showed that the highest carb groups in the study simply had higher rates of mortality. They also saw that the lowest fat groups also had the highest rates of mortality. They also saw that the lowest saturated fat group had the highest risk of cardiovascular disease (2).

Bottom Line: The study’s results were honestly fascinating, and I completely take them at face value. When good epidemiology is conducted, and you need to respect the numbers – unless better numbers come along to prove a different point.

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The Central Disconnect

What I noticed from this study helped inform the central disconnect that I think we can see at work here. The study was looking at 18 countries, mostly Asian, and these countries had lower rates of both cardiovascular disease and mortality than we do in the west.

At the same time, these are countries that eat quite differently than we do. The typical American consumes between 35 – 37% of their total overall calories from fat, 10 – 15% calories from protein, and typically 40 – 50% calories from carbohydrates. That’s the average American diet.

Key Insight: When this study was talking about low-fat diets being bad, they were not talking in terms of an American diet specifically. Instead, it was within the context of Asian diets.

Do High Carbs Kill?

One of the main things that I have seen from this study, and the reporting on it, is people really focusing in on the idea of a diet that is high in carbohydrates being linked to a higher rate of mortality. But, what does this all mean? Can this kind of diet be deadly?

As I mentioned before, the typical American diet is made up of 40 – 50% total calories from carbohydrates. As per the PURE study, the high-carb diets that were most “deadly” were in the 67 – 74% range of carbohydrates (with some pushing all the way to 78%).

Key Insight: What does 78% calories from carbohydrates look like in a meal? That looks like a base of noodles, rice, or bread, with some light greens sprinkled on. There’s not much variety, and not much quality to find.

Basically, if you are having any substantial amount of:

  • Vegetables
  • Cooking Oil
  • Nuts and Seeds
  • Poultry
  • Seafood

Any reasonable amount of any of these different categories would make it virtually impossible to make your diet 78% carbohydrates. It just would not be possible. Basically, you have to go out of your way to consume this many carbs, while also denying all of these other aforementioned food categories.

As it happens, in terms of this study, the group with the lowest amount of mortality was actually eating between 55 – 60%. That was the sweet spot low mortality, and it is currently higher than the average American diet. With popular diets like low-carb or Paleo (3), that is even lower.

Bottom Line: Basically a high-carb diet, in terms of this study, is a starch-only diet. I would not recommend that, and nor would many others. Does that mean a diet that is high in carbs is deadly? Only if you are cutting out food variety altogether.

Is Low Fat Deadly?

First, we addressed the question of carbohydrates in the PURE study. Now, with everything that we know, it’s time to look at the low-fat section. In this particular study, diets that were lower in fat were related to higher risks of mortality – when you got below 10% of calories from fat.

I have seen lots of people adding coconut oil to things, or adding butter to their coffee, in order to ensure that they are getting adequate amounts of fat. But the problem here is that you could not get that low in fact, even if you were not consuming any fat in your diet, period.

Key Insight: Only the most restrictive fat-free diets are the ones that can even approach that 10% range of overall calories from fats.

This only works if you are completely cutting out:

  • Fatty Fish
  • Nuts and Seeds
  • Cooking Oils
  • Animal Products
  • Dairy Products

When you are getting none of that whatsoever, you are approaching 10% of your total calories. And, of course, this is not something that I would recommend. These are nice foods, that give us a lot of good things, that are important for our bodies.

The media’s portrayal of this study furthers a message that “if you are not getting enough fat, you are going to die,” without considering just how little fat you would need to consume to even come close to that risky range of 10%.

If anything, the study worked to prove an opposite point. While people were afraid that low-fat diets were going to kill them, they ignored the fact that diets that are high in fat (like typical American diets) are also high in mortality risk. Those who are on low-carb or paleo diets can also be shooting way past these markers for fat intake.

Carbs and Fats, Good and Bad

I think it is about time that we divorced ourselves from this type of thinking. Considering carbs and fats as good or bad is not a productive way of pointing us in the right direction for our health. Instead, I think it is really important that we focus on both.

Key Insight: There’s nothing inherently bad about carbs and fats, and one is not a hero and the other is not a villain. We need both, and we need reasonable amounts of each to lead a happy, healthy, and productive life.

Nobody likes to go to extremes, and it often leads us to a place where we are not doing the right thing for our health. Which leads me nicely into my next point…

Saturated Fats

One of the things that people pulled out from this study was the role of saturated fats in the diet. The study had suggested that a low amount of saturated fat in the diet, led to an increased risk for stroke in participants.

Now, I thought long and hard about this data point. It was surprising to me, so I really wanted to hone in on what it means (and the context of it in the study). So, what were the details? The thing about this part of the study is that the threshold that caused more stroke risk was less than 2% of saturated fat in the diet.

Honestly, if you consume a handful of walnuts each day you are going to hit this marker for saturated fat – without even knowing it! We can get this from wonderful foods, and are naturally-occurring in these foods. They are:

  • Nuts and Seeds
  • Avocados
  • Fatty Fish

Bottom Line: The only possible diets that were lacking in saturated fats, to the point where they could cause stroke risk, were the same as the ones that lacked in these wonderful foods – and I don’t just mean lacking, they would be without them entirely.

Here’s yet another twist with this study. At present, most Americans are running the 15% or more range of saturated fat intake. This study also showed that when you got above 13%, there were higher rates of mortality. Those who subscribe to the paleo or ketogenic diets, they can be in the realm of 20 – 30% or more (which the data has shown is even riskier).

My message is not that saturated fat is bad, and that you should avoid it entirely. There are some great foods with saturated fat in them. What I want you to know is that saturated fat is neither hero, nor saviour, and that the ratio, amount, and quality of saturated fat is what matters more than anything else.

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The Right Diet

You might have heard me say it before, but variety is the spice of life! The same applies when it comes to your food. I believe that a good diet comes from:

  • Healthy Plant Foods
  • Good Carbs (rice, legumes, beans, intact whole grains, vegetable starches, and tubers)

For human history, these have made up the bulk of our calories – and we need to rely on a reasonable variety of them for our overall health. The same PURE study that we have been talking about said the same thing, that those who consumed the bulk of their calories from these types of food had the lowest rates of mortality amongst everyone studied.

This does not mean that you need to eat nothing but carbs, because extreme amounts can cause problems. What you need is variety, and a good variety of everything to ensure that you are feeling good.

The thing that I want you to take away about the PURE study is not that the science was flawed – it’s that it was contextual. Moreover, the headlines that came from it often do not tell the whole story (or tell the story in a flawed way, which can lead to major problems for so many people).

Bottom Line: The PURE study is all about context and ranges. Within the ranges that they set, being high in carbs or low in fats is dangerous – but you need to know just how difficult it would be to eat that many carbs, or cut out all that fat. More importantly, on the other end of each spectrum we might find more issues for traditional American diets. Instead, we have focused on the wrong issues for us, based on a study that does not account for our eating culture.

A Balanced Approach

When it comes down to it, the PURE study turned out to be a vindication towards a more balanced approach – and a diet that appreciates and preaches variety for all. By no means does it suggest that you should be eating in extreme ways, and making massive cuts to certain things that you are eating. Instead, it should be a great reminder that variety and quality are the two main drivers between what you should be eating – and how what you are eating fuels your body.

Bottom Line: We need foods, and we need lots of good foods. Variety is so important to your diet, and to your health. There is no magic ingredient, and no magic food that will make you healthier – instead, it is all the food you eat working together.

More Balance, More Results

The results of the PURE study were so important to understand for those who have not had the chance to dig deep into the science. I hope I helped you understand more about why the headlines you might have seen lately don’t really add up. While you are here, please consider taking the Thyroid Quiz (4), and get to know a little bit more about the science behind your body.

Dr. Alan Glen Christianson (Dr. C) is a Naturopathic Endocrinologist and the author of The NY Times bestselling Adrenal Reset Diet.

Dr. C’s gift for figuring out what really works has helped hundreds of thousands of people reverse thyroid disease, lose weight, and regain energy. Learn more about the surprising story that started his quest.

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