CLAIM: 

An Instagram reel claims that exercising 30 minutes daily lowers the risk of 13 cancers and improves survival after diagnosis in breast, prostate and colon cancer. The speaker also says exercise brings natural killer cells into tumours, cutting off their blood supply and stopping cancer from spreading further. 

FACT: 

Research and experts suggest regular physical activity is linked to a lower risk of 13 types of cancer and to better survival in some cancers, including breast, prostate and colorectal. However, much of the evidence shows an association, not proof that exercise alone is the cause. Exercise also supports cancer care but is not a substitute for standard medical treatment. 

An Instagram reel is going viral with claims that people who exercise for at least 30 minutes a day have a decreased risk of 13 types of cancer. 

“If people start to exercise after a cancer diagnosis, their survival rate increases.”  she says, adding that she found this association in three cancers: breast, prostate and colon cancer. 

Explaining how exercise may affect cancer, she says that “tumours have a blood supply. They’re hungry.” According to her, tumors need to produce more blood vessels to grow and, once they are “strong enough,” they can spread to other sites, a process known as metastasis.

The speaker then claims that this process can be countered by cutting off the tumor’s blood supply. “You need to cut off the blood supply. How do you do that? With natural killer cells,” she says, adding that exercise helps natural killer cells reach tumors. “Well, how do you get the natural killer cells in there? It’s via exercise.”

The reel was posted by the Instagram account louisanicola, which has more than 734,000 followers. It has received more than 323,000 likes, over 1,500 comments and more than 250 reposts.

What has research found?

A study published in the British Journal of Sports Medicine in 2025 examined the link between physical activity and cancer risk among 85,394 people in the UK Biobank, a large health database. The participants, whose median age was 63, wore wrist devices for seven days to track their movement. They were followed for an average of 5.8 years, during which 2,633 were diagnosed with cancer. The researchers looked at 13 cancers that earlier questionnaire-based studies had linked to low physical activity.

People in the most active 20% had a 26% lower risk of cancer than those in the least active 20%. Walking 9,000 steps a day was linked to a 16 per cent lower risk than walking 5,000 steps. Sedentary time was not linked to risk. 

 “There was no significant association between stepping intensity (peak 30-minute cadence) and cancer after adjusting for step count,” the study said.

A review published in Clinical and Experimental Medicine in 2025 summarised existing research on molecules called long non-coding RNAs, or lncRNAs, which help control how cells behave.

The review said, “More research has been done on the correlation between exercise and cancer, which has revealed several ways that physical activity decreases the risk of developing the disease.”

 It noted that regular exercise changes the levels of several lncRNAs that are generally raised in cancer. These molecules are involved in processes such as cell growth and cell death.

The author also pointed out that several lncRNAs can either promote or prevent cancer, depending on the setting, which makes the changes hard to interpret. 

“To understand the complex impacts of exercise-induced lncRNA regulation in cancer biology, more study is required,” the review said.

What are doctors suggesting?

Dr Vaishnavi Joshi, consultant in medical oncology and haemato-oncology at Aster CMI Hospital, Bengaluru, said regular exercise is linked to a lower risk of several cancers but cannot fully prevent the disease.

“Physical activity is just one of the factors that can affect the probability of a person developing cancer,” she said. “Physical activity is linked to a lower risk of 13 cancers, including breast, colon, rectal, endometrial, kidney, bladder, liver and lung cancers. But smoking, alcohol, infections, genetic predisposition, age and hormonal changes can matter more than exercise.

Dr Joshi, however, pointed out that physical activity following a cancer diagnosis has been linked with improved survival rates in some cancers like breast, prostate and colorectal cancers. She cautioned that much of the evidence comes from observational studies. “It means that there is a possibility to observe a correlation between increased physical activity and better outcomes; however, it might be hard to prove that exercise alone is a causal factor,” she said.

Dr Joshi said the amount of exercise a person can safely do during cancer treatment depends on the type and stage of cancer, the treatment being given, symptoms and the individual’s overall physical fitness.

“The amount of exercise one can safely do while under treatment for cancer will depend on the cancer type, treatment, cancer staging, symptoms, and overall physical fitness of the individual,” she said.

She stressed that exercise should not replace medical treatment. “Exercises are not an alternative to cancer treatment,” she said.

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