How nutrition affects cancer treatment for children

When a child is treated for cancer, doctors use powerful medicines called chemotherapy to help fight the disease. But did you know that a child's nutrition—whether they are underweight or overweight—can change how these medicines work inside their body? Let’s explore why nutrition matters so much for kids with cancer, what scientists have learned, and how this could shape the future of care for young patients.

Why nutrition makes a difference in childhood cancer

Children and teenagers with cancer can be undernourished (too thin), have normal weight, or be overweight. Each of these conditions is called a “nutritional status.” Scientists have found that both being underweight and being overweight can affect the body’s ability to handle cancer drugs. This is especially important because these medicines have to be just right: too little and they might not work; too much and they can cause bad side effects. A recent large review published in the British Journal of Cancer explained how nutrition affects the way these medicines move through kids’ bodies and how they do their job (Lovell et al., 2025).

How chemotherapy works in the body

Doctors use special words to describe what happens to medicines after you take them. "Pharmacokinetics" is about how a drug is absorbed, travels through, and leaves the body. "Pharmacodynamics" is about what the drug actually does inside you. When a child is very thin or has a lot of extra body fat, this can make drugs act differently. For example, medicines like vincristine or methotrexate may move more slowly or quickly, or reach higher or lower levels in the blood.

What the research shows

Scientists looked at many studies involving children with cancer who were underweight or overweight. They found that:

• Undernourished kids sometimes had the medicine in their bodies for longer, which could mean more side effects.

• Overweight kids sometimes cleared the drugs faster, which might make the drugs less effective.

• The way doctors usually decide how much medicine to give—using height and weight—doesn’t always work well for kids who are very thin or overweight.

One study found that in children with more body fat, certain drugs like methotrexate stayed in the body longer, which could be risky (de Oliveira Henz et al., 2023). Another study showed that overweight children taking mercaptopurine had lower levels of the drug in their blood, which could reduce its cancer-fighting power (Zuccaro et al., 1991). These findings show that dosing isn’t one-size-fits-all.

Challenges and the need for better guidelines

Even though doctors know nutrition is important, there’s still a lot to learn. Studies use different ways to measure who is underweight or overweight, so it’s tricky to compare results. Also, most research has been done in wealthier countries, but almost 90% of children with cancer live in places where undernutrition is more common. Because of all these differences, experts say that we need more studies with clear, agreed-upon ways to measure nutrition and drug levels.

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What it means for patients and families

If you or someone you care about is going through cancer treatment, it’s OK to ask the doctor how your child’s nutrition might affect their care. Sometimes, children who are very thin or overweight may need their medicine doses checked more closely. This could mean more blood tests or special monitoring to make sure they’re getting just the right amount. Health AI tools, like those developed by SlothMD, are also helping doctors and families keep track of this kind of information in a safe and private way.

The road ahead: More research for safer treatments

Doctors, scientists, and organizations around the world are working together to make cancer treatment safer for all children—no matter where they live or what their size is. They recommend using better ways to measure body composition, like looking at how much fat and muscle a child has, not just their weight or height (Browning et al., 2011). It’s also important to include children from many countries in studies, so new guidelines will work for everyone.

For those interested in how health AI is shaping the future of personalized care, SlothMD offers more insights into privacy and technology, helping families stay informed and secure.

Takeaway

Nutrition plays a big role in how well cancer medicines work for children. Doctors need better guidelines to help every child get the safest and most effective treatment. Until then, families and healthcare teams should work together, ask questions, and use new tools to keep kids as healthy as possible during their fight against cancer.