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Research has shown that if you have cancer, getting enough dietary protein can help prevent the loss of muscle mass that is common during treatment.

In an expert group opinion published in the journal Clinical Nutrition, a panel of nutritional experts recommended that patients undergoing treatment for cancer get at least 65% of their protein from animal-based sources.

Katherine L. Ford, RD, a doctoral candidate in nutrition and metabolism at the University of Alberta in Edmonton and the lead author of the opinion piece, told Verywell that animal-based proteins contain more of the building blocks of proteins (amino acids) than plant-based proteins do.

The availability of different amino acids in proteins varies depending on the food. The experts said that meat, fish, eggs, and dairy products are the best foods for building and maintaining muscle.

Carla Prado, PhD, RD, a professor of nutrition, food, and health at the University of Alberta and another author of the piece, told Verywell that muscle mass is important for people being treated for cancer.

Muscle is an independent predictor of a variety of important health outcomes.

“The great majority of people with cancer may have low muscle mass,” said Prado. “Because of the disease itself or the treatment they may lose muscle. And muscle is an independent predictor of a variety of important health outcomes.”

For example, Prado said that “if you have more muscle, you can tolerate more chemotherapy. If you have surgery, you’re going to have fewer complications.”

Additionally, Prado said that survival is often longer for people with greater muscle mass.

People being treated for cancer lose muscle mass for several reasons.

For example, they may not feel hungry or may have nausea and vomiting from treatment. They may not be able to exercise or get much physical activity. The stress of chemotherapy and surgery can also play a role.

To combat the loss of muscle, people being treated for cancer need more protein in their diets. The current recommendation for protein intake for people having cancer treatments is 1.2 to 1.5 grams of protein for every kilogram of body weight.

If you’re being treated for cancer, try to get 1.2 to 1.5 grams (g) of protein for every kilogram (kg) of your body weight per day.

Not sure how much that would be? Here’s how to do the math:

Since that’s only the minimum, your provider might encourage you to increase that amount to help with muscle mass during your cancer treatment.

Ford said that there is a lack of research on the effects of different sources of protein on muscle building or retention for patients being treated for cancer.

There are a lot of misconceptions about animal protein—and even what animal protein is.

“We had to draw from the literature on this topic in other areas,” said Ford. “That is why this is an opinion paper and is hypothesis-generating. It’s essentially a call for more research into this area.” 

The 11 authors of the study are experts in protein metabolism, nutrition, and cancer.

“We’re very careful because we need more research to show exactly the amount [of protein during treatment] is,” Prado said. “We don’t know what that amount is.”

What’s more, Prado said that “there are a lot of misconceptions about animal protein—and even what animal protein is.”

Many people choose to follow a diet low in meat, fish, and other animal products as a form of cancer prevention. However, Prado said that a diet that helps prevent cancer may not be the best one to follow while you’re being treated for cancer.

Prado said that by making the recommendation, the authors had a key message: “We’re not trying to go against veganism or people who are vegetarians.”

A person who is a vegetarian or vegan can still get enough of the right types of plant-based protein while they’re being treated for cancer as long as they’re following a well-balanced and planned diet.

However, Prado said that the experts “also recommend that professional nutrition support be done so that they can be sure that they are meeting this recommendation.”

Nutritional goals probably shift from cancer prevention to cancer treatment.

According to Prado, if you’re vegetarian or vegan, you might be OK “if you have a dietician working with you who knows how to design your diet in a way that you can get all these essential amino acids.”

However, Prado added that “if you want to have a balanced diet that is actually promoting muscle anabolism, a combination of animal protein and plant proteins is more likely to be optimal.”

Ford pointed out that not everyone being treated for cancer has access to a provider who can work with them on nutrition. Even if they do, having to pay for a consultation out of pocket might prevent them from using the support.

Cancer patients, regardless of the diet they follow, have unique nutrition needs. Without help, it can be difficult to navigate those decisions. However, patients aren’t always offered guidance.

“What happens is that patients have to be quite nutritionally compromised,” said Ford. “Even having malnutrition or at high risk for malnutrition before they’re given the opportunity to see a dietitian.”

According to Ford, “what seems to be happening is that patients are taking nutritional matters into their own hands. And nutrition is quite complex.”

As such, Ford said that experts worry that if patients are making choices on their own, “they might not have all the available information in order to inform their decisions.”

The bottom line? A diet that supports your body when you don’t have cancer—and one that may even help prevent it—might not be the one you need if you have cancer and are trying to “muscle” through treatment.

“Nutritional goals probably shift from cancer prevention to cancer treatment,” said Ford. “Coming from the lens of a focus on muscle.” 

To promote muscle mass, experts recommend that patients undergoing cancer treatments should get at least two-thirds of their dietary protein from animal-based sources, such as meat, fish, dairy, and eggs.

Vegetarians and vegans being treated for cancer can get the amino acids they need for muscle building from plant sources, but they should talk to a nutritionist or dietitian to make sure their diet is adequate.

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American Cancer Society. Nutrition for the person with cancer during treatment: a guide for patients and families.

Ford KL, Arends J, Atherton PJ, et al. The importance of protein sources to support muscle anabolism in cancer: an expert group opinion. Clin Nutr. 2022;41(1):192-201. doi:10.1016/j.clnu.2021.11.032

Arends J, Bachmann P, Baracos V, et al. ESPEN guidelines on nutrition in cancer patients. Clin Nutr. 2017;36(1):11-48. doi:10.1016/j.clnu.2016.07.015

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