Thank you for reading my newsletter! If you’re newly subscribed, let me tell you a bit about what content you can expect to find here.
I’m a cardiologist by training and a COVID doctor by necessity. This newsletter covers topics related to my work.
While most of my focus is on heart disease and the pandemic, I also discuss media coverage of science and healthcare as well as health policy (especially as it relates to the pandemic and cardiovascular disease). You can also expect to find coverage of nutrition, exercise, and other aspects of preventive medicine, in particular diabetes and metabolic syndrome.
I welcome your questions and opinions regarding my writing. You can always reply directly to these emails to contact me directly.
The beginning of a New Year always leads to inevitable renewed interest in diet and exercise. I’ve noticed that the January gym influx is in full force despite the pandemic, and I suspect that many of us are thinking about how to lose the COVID-15 that crept up over the past few months.
I’ve been somewhat surprised by just how many keto diet questions that I’ve been getting from both patients and friends over the past few weeks.
If you aren’t familiar with it, keto is short for ketogenic, which means that your body produces something called ketones (or ketone bodies) for fuel. When you aren’t eating enough carbohydrate calories to fuel your organs, your body must rely on other energy sources, so it breaks down fat to produce ketones as an energy supply.
In other words, keto is essentially a super low carb diet.
To be “keto” doesn’t specify the specific foods that you consume; you can be keto and totally vegan, you can be keto and on a carnivore diet, you can be keto and eat only processed food, and so on and so forth.
Keto just means that you produce ketones to use for energy.
While keto is increasingly popular, there is a backlash from many conventional nutrition sources (as well as many cardiologists) about keto causing heart disease. Many of my patients are asking about the health impact of a keto diet, in no small part because of a worry about their heart.
“Is keto unhealthy?” is the wrong question
US News and World Report puts out a list every year of the “Best” and “Worst” diets for your health. Keto consistently ranks as either the worst or near worst every year.
This is such a dumb list and such a dumb way to discuss diet.
As I’ve written before, I believe that the future of personalized nutrition is based on how different diets impact our own individual biomarkers of chronic disease - things like continuous glucose monitoring and serial cholesterol testing.
The question isn’t whether some abstract idea of a keto diet is “bad for you,” but how a keto diet in practice impacts markers of disease.
What’s the concern about keto and heart disease?
On the surface, this concern seems pretty simple: a keto diet probably means you eat more saturated fat —> saturated fat can increase blood levels of LDL cholesterol —> increased levels of LDL cholesterol increase your risk of heart disease.
But when you dig into the details, as with almost anything in biology, there’s more than meets the eye. I can think of a handful of objections why this line of thought may be mistaken:
There’s more to heart disease risk than just LDL cholesterol (and LDL cholesterol is probably the wrong cholesterol metric to be tracking anyway)
A keto diet doesn’t necessarily mean you’re eating more saturated fat
Going keto may reduce blood pressure, improve diabetes, and lower triglycerides which all reduce heart disease risk
It’s possible that your LDL cholesterol won’t be impacted even with a high saturated fat intake
The biggest flaw in the keto —> heart disease hypothesis, however, is the increasing doubt that saturated fat increases heart disease risk
Expert opinion on this has been changing recently.
Take a look at this review of the evidence in the Journal of the American College of Cardiology. Or this analysis in the British Medical Journal.
The cardiovascular reputation of saturated fat has really undergone quite a change in the last few years. Many experts no longer believe that increased saturated fat in the diet increases heart disease risk.
Unfortunately, saturated fat = good is also oversimplifying things
There is a subset of the population that has a huge rise in their LDL cholesterol levels on a keto diet or even after just dramatically cutting carbs.
Some people in the low-carb community describe these folks as “lean mass hyper-responders” which just means that their LDL cholesterol levels shoot up super high when they cut carbs.
The LDL cholesterol and heart disease connection is made out by skeptics to be more complicated than it is (and there are a fair number of complete cholesterol deniers out there).
Getting into the weeds here is probably beyond the scope of this newsletter installment, but even though I acknowledge that there are many other aspects to the biology of heart disease, I don’t find the cholesterol deniers persuasive.
So what does all this mean about keto diets and our heart?
I think about this very simply: if you go on a keto diet and your lipid numbers (not just LDL cholesterol, but LDL-P or apolipoprotein B) shoot up super high, it’s hard to imagine that this doesn’t impact your risk of heart disease.
Of course, we need to balance the cholesterol impact with the impact on other things - blood pressure, glucose, insulin resistance - but all things being equal, higher levels of these LDL metrics mean higher risk.
I mentioned before that not all keto diets are the same.
So if you happen to be one of the people who have this type of response on your bloodwork, I really do think that you’re gambling with your heart disease risk living with these super high levels of cholesterol carrying particles circulating in your blood.
After all, just look at the data on familial hypercholesterolemia patients and see the heart attacks and strokes that happen in young people who were born with defects in LDL metabolism that leads to really high levels of these markers at an early age.
Ultimately, you need to be your own advocate here
There’s so much variation from person to person in how folks respond to diet.
The advice I give to all my patients is similar: you need to experiment to find out what works for you and use both hard and soft metrics to evaluate that.
Hard metrics are things like blood pressure, waist size, cholesterol, glucose, and insulin levels. Soft metrics are things like sleep, energy, mood, and subjective well being.
You can make basically any type of diet either healthy or unhealthy.
The practical advice if you go keto, feel great, and have your LDL-cholesterol levels shoot up is to change the composition of the keto foods you’re eating to reduce saturated fat levels.
More fish, less red meat. More avocados and less coconut.
Then recheck your numbers and see if it makes a difference.
I’m frankly not all that interested in the diet wars that tend to become almost religious in nature. And so I always recommend to my patients that you should make these decisions more about how you respond and less about what’s right for everyone.
Thank you for reading! If you’re enjoying my newsletter, please consider sharing with your friends and family and encouraging them to subscribe!
I always appreciate any feedback or thoughts you might have. You can reply directly to this email to reach me directly.