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Keto Diets and Heart Health: Harmful or Helpful?

April 17, 2023

A young woman stops running when she injures her knee. Her coach attends her.

Ketogenic (keto) and keto-like diets — such as very low carb diets (VLCD) and low carb, high fat (LCHF) diets — have been gaining popularity in recent years. But are they safe?

A new study says keto and keto-like diets may be linked to a higher risk for heart disease, raising LDL (“bad”) cholesterol levels and doubling the risk of cardiovascular events, like heart attacks and strokes.

Atlantic Health System cardiologist Brian Forrestal, MD offers the following information about the popular diet and how it affects your heart health.

What is a ketogenic or keto-like diet and how does it affect your body?

A typical ketogenic diet contains 60-80% fat, 20-30% protein and only 10% carbohydrates. This means cutting out almost all sources of carbohydrates, including fruit and starchy vegetables, grains like pasta, bread and cereal, beans and legumes, sugar and alcohol, and instead relying on fat sources (like nuts, oils, butter, cream and cheese) to keep you full.

To put this in perspective, the current dietary guidelines for Americans suggests eating less than 10% of your total calories from fat. A keto diet requires 6-8 times that amount.

When you eliminate or drastically restrict carbs, your body goes into ketosis, a metabolic state where your body burns fat for energy instead of its usual fuel source, glucose (which comes from carbs). Ketosis is also what your body does when it’s fasting or starving. The result of ketosis can be weight loss and improved insulin sensitivity.

What does the science say?

The ketogenic diet has been used medically since the 1920s as a way to manage epilepsy and control seizures in children who don’t respond well to other treatment methods.

However, previous research has shown that a low carb, high fat (LCHF) keto-like diet (defined as 25% of total calories from carbs, 45% from fat and 30% from protein) can lead to elevated LDL (or “bad”) cholesterol levels. Too much LDL is associated with atherosclerosis (a build up of plaque in your coronary arteries), which is a known risk factor for heart disease.

In this latest study, researchers worked with people following a low carb, high fat (LCHF) keto-like diet and found that over a nearly 12-year period, they had significantly higher levels of LDL cholesterol and twice the rate of experiencing a major cardiovascular event, including heart attacks, strokes, peripheral artery disease (blocked leg arteries) and clogged heart arteries requiring stent surgery.

Safe ways to keto – and who should avoid it

Dr. Forrestal cautions that a keto diet isn’t right for everyone. If you already have heart disease or high cholesterol, a past history of heart events or surgery, an eating disorder or are pregnant, a keto diet may not be safe for you.

If you are still thinking about starting a keto or keto-like diet — maybe to lose weight or for other reasons — take the following steps to do so safely:

  1. Consult with your doctor or health care provider
  2. Know your family history with heart disease
  3. Address any additional risk factors you may already have, such as diabetes, high blood pressure, inactivity, poor sleep and smoking
  4. Have your cholesterol levels monitored throughout
  5. Keep the duration short (this type of diet should not be a long-term diet)

Alternative heart-healthy diet options

Dr. Forrestal suggests a better-balanced, Mediterranean-style diet for heart health, focused on fresh vegetables and low glycemic fruit, lean fish and white meat, whole grains and a moderate amount of fat from sources like nuts and olive oil. Limiting sugar, salt, alcohol, red meat and processed foods is also recommended.

While this newest research does not prove that a keto diet leads to heart disease, it does show a strong correlation between following a ketogenic or keto-like diet and developing heart disease.

“In the short term, following a keto-like diet can help you lose weight, which will improve your overall health,” says Dr. Forrestal. “But it’s not sustainable and should not be done by people with high cholesterol or established heart disease. A better approach is to make lifestyle changes — exercise daily, eat a Mediterranean diet, manage stress — for long-term heart health. And always talk to your doctor.”

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