5 Foods to Avoid When Taking Letrozole

Letrozole (Femara) is a medication that’s FDA approved to treat certain types of breast cancer. It stops an enzyme called aromatase from converting androgen hormones into estrogen. This can help slow down or stop hormone-sensitive breast tumor growth.

Unlike some medications, letrozole doesn’t interact with any foods or drinks. There’s no food or drinks you have to completely avoid while taking this medication. Food doesn’t impact your body’s ability to absorb letrozole. 

But what you eat still matters while taking letrozole. Certain foods can worsen letrozole side effects. Avoiding these foods can make it easier to tolerate letrozole. 

Letrozole can also affect other parts of your body, especially your bones. Avoiding certain foods can help you stay healthy and lower your risk of complications like high cholesterol and low bone density.

Here are five foods and drinks to avoid while taking letrozole. 

1. Alcohol

While you can consume alcohol while taking letrozole, you may want to limit alcohol intake to an occasional drink or avoid it altogether.

Letrozole can cause side effects like confusion and sleepiness. Alcohol can make these side effects worse. 

Also, letrozole can have an impact on your bone health. People who take letrozole are at risk for developing osteoporosis. Letrozole lowers estrogen levels in the body. Low estrogen levels will lead to lower bone density, which increases the risk of developing osteopenia and osteoporosis. 

It’s best to avoid foods that can lower your bone density or affect your bone health while taking letrozole, like alcohol. There’s some evidence that even one alcoholic drink per day can increase the risk of developing osteoporosis. 

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Your healthcare team may also recommend DEXA tests, and vitamin D and calcium supplements to support your bone health. 

2. High-fat foods

Letrozole can increase your cholesterol and lipid levels. Letrozole lowers your estrogen levels, which in turn can increase your levels of low-density lipoprotein (LDL) cholesterol or “bad” cholesterol, and lower your levels of high-density lipoprotein (HDL) cholesterol or “good” cholesterol. 

The good news is that these effects may not be permanent. Your lipid levels may return to baseline over time, especially if you stop taking letrozole. But experts recommend following a heart-healthy diet while taking letrozole. This can help keep your lipid levels in a healthy range and lower the risk of developing complications from high cholesterol. 

A heart-healthy diet is one that’s high in fruits, vegetables, and whole grains. Some examples of a heart-healthy diet include the Mediterranean and DASH diets. You also want to limit or avoid:

• Fried foods

• Red meat

• Processed meat like bacon, sausages, and ham

• Full-fat cheese and milk

• Butter

• Ice cream

• Coconut and palm oils

• Baked goods

• Processed snacks like chips and microwave popcorn

Your healthcare team may also recommend regular blood tests to check your cholesterol levels and medication to help keep your lipid levels in a healthy range. 

3. Soy and other phytoestrogens

Phytoestrogens are compounds found in soy and certain plants. They have a similar structure to estrogen. There’s some evidence that a specific type of phytoestrogen, called isoflavone, can make letrozole less effective and even counteract its effects. 

But these findings were only shown in lab studies. It’s unclear if isoflavone levels in regular soy foods would have a similar effect in humans. And there’s some evidence that a plant-based diet containing moderate amounts of soy can lower the risk of breast cancer recurrence. 

So you don’t have to cut soy out of your diet altogether. But experts recommend that people taking letrozole and those with a history of breast cancer stick with whole soy foods, like tofu or tempeh. And they recommend eating soy-based food products in moderation as part of a varied diet.

They also recommend avoiding high-concentrated soy products like:

• Soy supplements

• Soy pills and powders

• Isoflavone-based supplements 

• Concentrated isoflavone products

• Phytoestrogen supplements

4. Spicy food

Letrozole can cause side effects including upset stomach and nausea. It can also trigger vasomotor symptoms of menopause, like sweating, flushing, and hot flashes. 

Spicy foods can make these symptoms worse. Spicy foods contain chemicals that cause your blood vessels to widen. This can trigger flushing, sweating, and hot flashes. 

Chemicals in spicy food can also irritate your stomach lining. This can trigger nausea, vomiting, and cramping. They can also trigger heartburn and cause burning during bowel movements in certain people.   

You may want to limit or avoid spicy food completely if you’re experiencing vasomotor syndromes or stomach upset while taking letrozole. 

5. Cinnamon

Cinnamon is a spice added to many foods and drinks in small amounts. 

Cinnamon is broken down into other compounds by the body. One of these compounds can stop the breakdown of letrozole. In lab studies, this led to high levels of letrozole in the body. 

It’s probably safe to consume small amounts of cinnamon, like what you find added to baked goods or sprinkled on a beverage. But you want to avoid ingesting large amounts of cinnamon or cinnamon-containing supplements while taking letrozole. 

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Written by:

Jennifer Sample, MD

After a fellowship, Dr. Sample worked as the medical director at the University of Kansas Hospital Poison Center (The University Of Kansas Health System Poison Control Center), which served the state of Kansas for poison exposures. In 2007, she returned to Children’s Mercy Hospital in Kansas City, Missouri, as a consultant in clinical pharmacology and medical toxicology.

Edited by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

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