Use of a low carbohydrate diet is becoming increasingly popular. In addition, various organizations who once recommended against low carbohydrate diets now recommend them.
So it’s not surprising that we’re seeing more and more studies looking at the effects of these diets. There are many potential concerns with long term use due to their high saturated fat content. One concern in particular is how they impact risk of cardiovascular disease.
A new paper published last week investigated the effect of a low carbohydrate diet on blood lipids. The results were ultimately positive for the low carb diet wing. However, many took to social media to claim this study shows that low carb diets are superior to low fat diets(It didn’t).
Today we’ll take a look at this study and discuss what it’s findings tell us about the safety of a low carbohydrate diet on cardiovascular disease risk.
A low carbohydrate diet and cardiovascular disease risk
The design of this study is pretty interesting. Participants underwent a 16 week run-in diet where they lost an average of around 25lbs. The macronutrient breakdown of this diet was 45% carbohydrate, 35% fat, and 25% protein.
Those with adequate weight loss after the run-in diet (Average 10% weight loss) were randomized to 1 of 3 diet groups:
- Low carbohydrate (20% carb, 60% fat) Approx 105g carbs
- Mod carbohydrate (40% carb, 40% fat) Approx 205g carbs
- High carbohydrate (60% carb, 20% fat) Approx 305g carbs
Protein was held constant at 20% of calories for all groups. Participants followed each diet for 3 weeks and had to maintain their weight; they were told not to lose it.
In essence, this paper looks at how varying carbohydrate content in the diet alters lipoprotein markers at weight maintenance. Ultimately, they found better results for the low carb diet.
But digging into the data, the results are actually a little wonky. Let’s dig in!
Sample diet meal plans
Below is a sample meal plan for each of the 3 diet options:
Upon first glance, the low carb diet used in this study is the superior diet. It contains more vegetables and uses olive oil as the primary added fat(11g vs 0g in the other groups).
Furthermore, the moderate and high carb diets add bread to every meal for some reason. Not that bread is bad per se, but there are a lot better options for carbs. I’d much rather see something like potatoes, bananas, sweet potatoes, or some other whole food mixed in than 3 different types of bread.
In terms of macronutrient breakdown, my current diet is like the high carb diet. Quality and diversity of food-wise, my diet is more like the low carb diet.
Consequently, this is a good time to point out that diet quality isn’t in lockstep with macronutrient breakdown. You can have a low carb diet that is much higher in quality than a moderate or high carb diet, or vice versa.
Finally, I’m not altogether sure the low carbohydrate diet in this study really represents what a normal person eating a low carbohydrate eats. They’re not eating vegetarian sloppy joes, and probably not a lentil salad. They’re certainly not drinking orange juice, and probably not having 2 salads a day.
Overall, I think there are way more polyphenols and fiber(25g/day) in this low carb diet vs a standard low carb diet. This is probably not by accident; both polyphenols and fiber have been shown to reduce cardiovascular disease risk.
This sample low carb diet is actually a pretty good example of what I would call healthy low carb. Though, I’d ditch the OJ and replace it with a whole food.
Results of the study: Is the low carbohydrate diet better?
Let’s start off by saying I don’t like how this study reports the results. They report the results as the change in biomarkers from the start of the maintenance diet to the end. You have to dig deep into the data to get the raw results. It makes sense conceptually, but it’s not really practically useful.
Let me explain. First, the low carbohydrate diet saw the biggest improvement in lipoprotein insulin resistance (LPIR) score during the 3 week maintenance phase. Changes in LPIR were as follows:
- Low carbohydrate -5.3 pts(~15% drop)
- Moderate carbohydrate -0.02 pts(0% drop)
- High carbohydrate diet +3.6 pts(10% increase)
But this doesn’t really tell the story. First, all groups saw around a 10 point drop during the weight loss phase, which was 45% carbohydrate. Clearly, weight loss matters more than carbohydrate content.
Second, despite seeing a greater drop during the maintenance phase, there really wasn’t much of a difference in the absolute LPIR score between low and moderate carb at the end.
The final LPIR score for low carb was 29.3 and in the moderate carb group it was 31.5. This is because the moderate carb group ended the weight loss phase at a lower LPIR than the low carb group.
Oddly enough, this makes the low carbohydrate diet inferior to the moderate carbohydrate diet for reducing inflammation. The low carbohydrate diet group saw a 9.9% drop in hsCRP while the moderate carb group saw a 20.6% drop. Again, weight loss produced a much larger effect than carb composition.
However, the group randomized to the low carb diet ended with a lower hsCRP because they started maintenance with a lower overall number(1.1 vs 1.5). This is important because cardiovascular disease risk is dictated by those numbers, not the change in those numbers.
So the low carb diet actually had a better CVD risk based on hsCRP if you look at the numbers rather than the change in numbers. The same would hold for LPIR score.
For example, my LPIR score is 20, which is much better than both groups. From a macronutrient perspective, my diet is more like the high carbohydrate diet.
If I maintain my diet for 3 weeks I’ll see a 0 point drop in my LPIR, certainly not better than a 5 point drop. But at the end of the day, my cardiovascular disease risk is lower because my score is lower. So switching to a low carbohydrate diet would make no sense.
In fact, it could increase my risk.
What this study tells you about low carbohydrate diets
So what does this study tell us about low carbohydrate diets and cardiovascular disease risk? After a period of weight loss, maintaining your weight loss on a low carb diet probably doesn’t increase your cardiovascular disease risk. It may even reduce it.
Based on Lp(a), the low carbohydrate diet was better. But Lp(a) is a wonky number. In fact, Lp(a) increases with weight loss in the obese, and an increase in Lp(a) worsens cardiovascular disease risk. However, weight loss is clearly beneficial to cardiovascular disease risk
Unfortunately, the most important lipoprotein measure for cardiovascular disease risk is ApoB and it wasn’t measured. Overall, this paper shows that one can formulate a low carbohydrate diet that is just as good or better long term for heart health than a moderate or high carb diet.
I don’t think it shows they’re better. Weight loss appears to be more important for lowering LPIR, so whichever diet leads you to maintain a healthy weight, be it low or high carb, is more important.
Don’t guess, test
It’s probably not a good idea to just assume your low carbohydrate diet is fine for your cardiovascular disease risk based on this paper. Particularly if your diet is lower in polyphenols and fiber than this diet. Truth be told, most moderate and high carb diets that the average person eats would have lower polyphenols and fiber than this one.
Whether you are low carb or high, it makes sense to have these numbers assessed to see if changing your diet will improve your cardiovascular disease risk. Currently, the best available option is the Precision Health Report from…Precision Health Reports.
They assess the same lipoprotein measures used in this study including LPIR, as well as ApoB particles. They also assess inflammation with GlycA, which is a more stable marker than hsCRP.
I recently had mine assessed, and covered the results in a blog and video you can check out by clicking the links. My 10 year risk for CVD was half someone my age, and my inflammation was super low(bottom 2.5th percentile). My LPIR score was also excellent at 20.
It’s clear from my numbers that I don’t need to switch to a low carbohydrate diet, but the results of this study as reported imply that I should. However, for most, eating any diet that maintains a healthy weight that also contains a good dose of polyphenols and fiber will minimize cardiovascular disease risk.
The takehome for those on a low carbohydrate diet
The low carb diet in this study is a cleverly constructed one. It’s not super low carbohydrate, which actually improves insulin sensitivity vs a diet with fewer carbs. Any low carber who’s done an oral glucose tolerance test can attest.
It also has more polyphenols and fiber than a standard diet. And even though it contains double the recommendation for saturated fat, it still led to benefits in lipoprotein markers for CVD.
If you eat a low carbohydrate diet and it looks like this one, you can feel pretty confident that you’re not negatively impacting your cardiovascular health. In fact, you’re likely improving it if you’re moving from a standard American diet.
However, it does make sense to assess your risk using a test like Precision Health Reports.