One of the most damaging myths in nutrition is the myth that dietary fat clogs your arteries. It’s made a lot of people worry about how the keto diet affects heart health with no scientifically-backed reason.
The myth is absurd. Free fatty acids and triglycerides—the forms of fat circulating in your body—don’t go around jamming up your blood vessels. In fact, we’ve known for decades that arterial plaques are formed through an inflammatory process involving LDL particles and a bunch of immune factors. It’s not fat.
Closely tied to this myth is the myth that saturated fat causes heart disease. At least this myth can be defended, but the defenders lean heavily on observational science from the 1950s. The current science says otherwise.
Even so, the combination of these myths represents a powerful force against high-fat diets like keto. And since heart disease is the number one killer globally, we should take this topic seriously.
For the next few minutes, I’ll review the facts about heart disease, the keto diet, and different types of fat. Then you can decide if keto is healthy for your heart.
What Does Heart Health Mean?
Let’s define heart health by its opposite: heart disease. For optimal heart health, we want to minimize the risk of heart disease.
Heart disease, or cardiovascular disease (CVD), refers to problems with the circulatory system like:
- Insufficient blood flow to the brain (stroke)
- The heart pumping insufficient blood to meet the body’s needs
- A buildup of plaque that narrows the arteries (atherosclerosis)
Atherosclerosis is the crux of heart disease. It’s called the “silent killer” because it progresses over a lifetime with no noticeable symptoms. Then one day, the plaque breaks off and a heart attack occurs. This first heart attack is often fatal.
What drives atherosclerosis? The main risk factors include elevated LDL particles, inflammation, high blood sugar, and high blood pressure. On their own, each of these factors is insufficient to cause heart disease. Taken together, they can.
The LDL particle, for instance, is the cholesterol-carrying particle that slams into the arterial wall, oxidizes, and kicks off the formation of atherosclerotic plaques. But if inflammation is low, the plaques (which are just clumps of immune particles) are less likely to form. And if blood pressure is low, LDL particles are less likely to stick to the arterial wall in the first place.
Diet affects each of these risk factors, along with a number of related risk factors. Let’s talk about the keto diet now.
How Keto Works
The keto diet (or ketogenic diet) is a very low-carb diet that promotes a fat-burning state called ketosis. Here’s how it works, step-by-step:
- On keto, you avoid carbs like an alert chipmunk avoids falcons.
- Avoiding carbs (the nutrient with the largest glycemic impact) keeps blood sugar lower.
- Low blood sugar means that insulin—your blood sugar boss hormone—also stays low.
- Low insulin signals cells in your liver to start burning body fat and producing ketones.
Limiting carbs to around 30 grams per day is the main rule of keto. On keto, most of your calories will come from protein and fat.
When it comes to keto macros, protein is the priority. Too many keto folks don’t get enough protein, making it hard to gain or maintain muscle. We recommend eating 0.8 grams of daily protein per pound of lean body mass (LBM) on normal days, and 1 gram per pound LBM on active days. That’s about 100 to 200 grams protein per day.
After you hit your protein goal, fill in the rest with fat. Fat is a lever. Take it up or down to match your goals.
Different Types of Fat: Which Are Heart Healthy?
There’s a lot of confusion about healthy and unhealthy fats. Most of this confusion centers around saturated fat and polyunsaturated fat, so let’s start with those.
#1: Saturated fat
Saturated fat is high in meat, lard, egg yolks, coconut oil, butter, and palm oil. Since it’s “saturated” with hydrogen bonds, saturated fat holds up well to heat. It’s an ideal cooking fat.
Many people worry that eating saturated fat is bad for your heart. This fear has roots in the 1950s, when a physiologist named Ancel Keys presented population data linking saturated fat consumption to heart disease. He noted, for instance, that the Japanese ate less saturated fat than other countries and also had better cardiovascular health.
But correlation doesn’t prove causation, and more rigorous science has largely debunked Keys’ claims. For instance, two recent meta-analyses analyzing data from nearly one million people found no link between saturated fat consumption and heart disease[*][*]. If saturated fat caused heart disease, it would have shown up in this data.
#2: Polyunsaturated fat
In the 1970s, food manufacturers began promoting polyunsaturated fat (PUFA) as heart healthy. There was lots of money to be made, since high-PUFA vegetable oils like soybean oil, safflower oil, sunflower oil, cottonseed oil, and peanut oil were becoming staples of the American diet.
The rise of vegetable oils, unfortunately, paralleled the rise of obesity in America. These oils are high in a polyunsaturated fat called linoleic acid—an omega-6 fat shown to create inflammation and drive obesity in animal models. Not so good for the heart.
Vegetable oils are especially dangerous when cooked. At high heats, the fragile fats denature, creating compounds called oxidized lipids. Oxidized lipids, the data suggests, are highly atherogenic.
By now you might be wondering about omega-3 fatty acids, another polyunsaturated fat. Omega-3s are mostly found in marine life, and consuming them helps offset the inflammatory effects of excess omega-6s.
Most people consume too many omega-6s and not enough omega-3s. The key is to strike a balance.
#3: Monounsaturated fat
You’ll find monounsaturated fat in olives, olive oil, avocados, and nuts. These fats have been linked to lower blood pressure, better blood sugar, and other cardiovascular benefits. We like monounsaturated fat. Not much controversy here.
#4: Trans fat
Trans fats are vegetable oils that underwent a process called hydrogenation to gain a greater shelf life. Basically, they went from being unsaturated to saturated.
Trans fats are bad news. They’ve been linked to nearly every chronic disease, and the World Health Organization has ordered them banned from the global food supply. You won’t find trans fats in many products these days, but if you see something with “hydrogenated” or “partially hydrogenated” on the label, avoid it like poison.
How Keto Might Improve Heart Health
You just learned about the heart healthiness of various fats. The practical takeaway? Get most of your fat calories from monounsaturated and saturated fats, while consuming limited portions of omega-3 and omega-6 polyunsaturated fats in roughly equal proportions.
Putting fats aside for now, how might a well-formulated keto diet help reduce heart disease risk?
One way is by helping folks lose weight. Obese people are at higher risk for CVD, and any intervention that stimulates weight loss in this population is desirable. When fat mass decreases, other heart disease risk factors like blood pressure, LDL particles, and blood sugar tend to improve too. Let’s look at a published example.
In a 2004 study published in Experimental & Clinical Cardiology, researchers put 83 obese people with high blood glucose and high LDL on 24-week ketogenic diet. By the end of the study, the participants had lost weight and had lower blood sugar, LDL cholesterol, and triglycerides—all improvements in heart disease risk.
Keto for obesity is closely linked to keto for type 2 diabetes. Type 2 diabetics have a constellation of heart disease risk factors—high blood sugar, high insulin, obesity, high blood pressure, etc.—and a keto diet has improved all of them in clinical trials.
One 2018 study, for instance, found that one year of keto dieting improved most CVD risk markers in patients with type 2 diabetes. One of these markers was C-reactive protein, a measure of inflammation closely tied to heart disease risk. But don’t dive in all willy-nilly. It's very important for those on blood sugar medications like metformin and insulin to be supervised by a doctor when trying keto.
A keto diet can lower inflammation by several mechanisms:
- By preventing inflammatory high-blood sugar levels (hyperglycemia)
- By suppressing the NLRP3 inflammasome (ketones have anti-inflammatory properties)
- By reducing excess body fat
Still, every risk factor doesn’t always improve on a keto diet. One in particular sometimes goes in the wrong direction.
Concerns With Keto For Heart Health
A subset of people who eat a keto diet see a dramatic rise in LDL cholesterol (LDL-C) and LDL particle number (LDL-P). Elevations in these metrics—especially the LDL particle count—are linked to higher heart disease risk in a variety of populations.
To be clear, the risk brackets aren’t based on keto dieters. We don’t have that data.
And also to be clear, elevated LDL isn’t the only heart disease risk factor. You also have inflammation, high blood sugar, high blood pressure, and a handful of others.
Does this mean we should dismiss a keto-related spike in LDL particles? I don’t think so, and my friends in lipidology agree. For folks who see large LDL spikes on keto, I suggest consuming 100-150 grams of carbs per day to bring lipids back into normal ranges.
Is Keto Good For Heart Health?
As with most nutritional quandaries, this quandary doesn’t lend itself to a yes or no answer. The answer depends on many factors.
It depends what types of fat you eat on keto. It depends on your weight and metabolism going in. And it depends how keto affects your LDL particles.
Check your blood work regularly. If your CVD risk factors are improving, it’s a fairly safe bet that keto is helping your heart.
An even safer bet? The olive oil from your dinner salad isn’t clogging your arteries.