Last year, I blogged in two separate posts about research into the topic of heart health and the keto diet. Now a follow-up study on this research has been published which sheds some important light on the topic.
Before getting into this new research, it would be worth your time to read (or re-read) my two prior posts on this topic, which can be found by clicking here and by clicking here.
In case you don’t have the time or patience for that, I will briefly summarize those prior posts as follows: keto diets are known to lead to weight loss and work well for many people, and in the majority of cases, they do NOT lead to a big rise in cholesterol. However, in a minority of patients they do. If you go keto and your LDL (“bad”) cholesterol gets worse, but your blood pressure, HDL (“good cholesterol”), triglycerides, glucose markers, inflammatory markers, and waistline all improve, are you really worse off than before you went keto? Moreover, is there something fundamentally different about human metabolism when in a state of ketosis that might change the relationship between cholesterol in the bloodstream and the risk for heart disease and stroke?
Given these questions, a group of grass-roots funded researchers has been trying to gather data on what happens to people who go keto, see their LDL cholesterol levels skyrocket, but in every other way get healthier. Last year they published a baseline study on these folks that showed that they didn’t seem to have increased plaque in their arteries compared to a group of “average” people. Which brings you up to date on the short version of my prior posts.
And now, onto the specifics of this newest study.
Researchers enrolled a group of 100 “Lean Mass Hyperresponders.” These are folks who:
Did not have high total or LDL (the “bad”) cholesterol levels before going keto
Went on a keto diet
Developed sky high LDL cholesterol levels (often over 200, 300, or even 500) once they were keto and
Are in every other way lean and metabolically healthy including having very low triglycerides and very high HDL (“good cholesterol”) levels.
In other words, these 100 people can be documented to a) not have a genetic predisposition to having high cholesterol, and b) have very, very high cholesterol but otherwise no obvious risk factors for heart disease and no evidence of any metabolic dysfunction.
Moreover, these were people in their 50s, all of whom had been keto for at least five years. So this is a great group of patients to study if we want to answer the question of just how dangerous high cholesterol really is in isolation, that is, when combined with no evidence of insulin resistance or other obvious risk factors for coronary disease.
All 100 patients had a baseline coronary artery angiogram, a test in which dye is injected into the coronary arteries and then a high resolution CT scan is performed which can detect even very minimal amounts of arterial plaque. As discussed in my blog post last year and above, on average at that time, these folks did not have any more arterial plaque than would be expected for their age group.
Now in this most recent study, the researchers re-scanned these people one year later, and published data on them. And this is where a controversy has erupted.
The researchers initially publicized the results as being very favorable, with evidence of only minimal plaque progression in the group. However, once the study was published and the data made available, a number of reviewers noted that, on average, most of the participants in the study DID in fact have progression of plaque over the ensuing year that was higher than would be expected for an average group of people. In other words, at least from this study, it does indeed appear that having sky high cholesterol levels on a keto diet might increase the long-term risk of heart disease.
As with all studies, it’s worth recognizing that this study has limitations. These include:
It is just one study.
There is no control group included in the study. This weakens the strength of the evidence and makes it difficult to know with any certainty what the “baseline” rate of plaque progression should be in a comparable non-keto diet group.
This was only one year of follow up. We would presumably learn a lot more by following these folks for 10, 15, or 20 years (which might still happen – but for now it’s obviously too soon to have such data).
The studied population is very specific. These are lean, metabolically healthy, people who developed high cholesterol only as a result of going keto. This study does not provide evidence that is generalizable to the broader population.
With all of that said, this study suggests that caution is advised regarding low-carb diets.
To be honest, since I’ve seen some folks really turn their lives around with low-carb diets during my career, I was hopeful that this study would prove reassuring. But science is science, and we have to acknowledge results even when they are not to our liking. As the famed economist John Maynard Keynes is reported to have said, “When the facts change, I change my mind. Tell me sir, what do you do?” If and when further research is published that shows good outcomes from low-carb diets, I will be more than willing to re-evaluate again. But for now, I plan to proceed with circumspection.
Does this study mean that nobody should ever go low-carb? Not at all. But it does suggest that if you are the kind of person whose cholesterol goes very high on a low-carb diet (again – remember that this does not in fact happen to most people), you might consider coming off the diet. Alternatively, if you chose to continue on keto, either closer periodic monitoring of your cardiac health (such as with cardiac imaging), or using medication to bring your cholesterol down into a more acceptable range would both be worth consideration.
