The Irish Cancer Society has urged people to get information on the disease from trusted sources.
It comes as The Happy Pear issued an apology for a social media post that contained claims that were labelled "not true".
A now-deleted Instagram post was shared by the twin brothers to promote a podcast. In it, among other things, they claimed mushrooms could reduce the risk of breast cancer.
The post was criticised by many, with surgeon Dr Liz O'Riordan saying mushrooms, soy and a plant-based diet do not reduce your risk of getting breast cancer.
The Irish Cancer Society's director of advocacy Rachel Morrogh told thethat the majority of cancers occur for reasons outside of anyone’s control.
"While maintaining a healthy and balanced diet can help to reduce cancer risk, there is no strong evidence that consuming one particular food or food group reduces the risk of cancer," she said.
Ms Morrogh said that for about four in 10 people who are diagnosed with cancer, it is possible to link the cause back to known causes of cancer, such as smoking and alcohol.
Addressing diet and cancer, she said: "While having a healthy and balanced diet can help reduce a person’s risk of cancer, it’s important to get information on what steps you can take to achieve this, from a trusted source.
"In the case of diet and food, the best course of action is always to follow dietary advice from registered/licensed dieticians and medical professionals. Their guidance can always be relied upon due to their established professional expertise and reliance on fact-based and verified information."
There are "vast amounts of information" available around diet and cancer which "can be really difficult to navigate", added Ms Morrogh.
She encouraged people with concerns to contact the Irish Cancer Society and speak to a specialist cancer nurse or to listen to its podcast on what cancer advice is trustworthy.
Responding to the criticism of the video, The Happy Pear — which consists of twin brothers Stephen and David Flynn — apologised "for any offence caused", stating "it is never our intention to mislead or to misinform".
"The Happy Pear acknowledges that some of the content in a recent post [on Instagram and Facebook] promoting an upcoming podcast with Dr Nitu Bajekal, Consultant Obstetrician and Gynaecologist from London UK, has caused offence as a few of the statements were not qualified appropriately," they told thein a statement on Monday.
"The Happy Pear partners with many highly qualified and experienced medical practitioners and we always defer to their professional expertise and opinions. The Happy Pear never represents itself as a medical professional or medical expert. Our main purpose serves to highlight some of the health and lifestyle benefits of plant-based eating. We will endeavour to ensure that this does not happen again."