Fasting before/during radiotherapy

Hi everyone, I’m new here, second time around with breast cancer and seems rather easier this time - maybe less of the great unknown ten years on…but anyway…

I’m starting radiotherapy next week for a nine days and have been reading about the potential benefits of fasting before treatment. Does anyone have any experience or thoughts about the practicalities or benefits of doing this?

I’ve heard of recommendations to fast before chemo, but this seems easier to do because it’s generally every few weeks. How would pre-radiation fasting work, other than for the first dose (and even then, is there a preferred length of time to fast)? Has anyone fasted all the way through? Or done alternate day fasting, or intermittent fasting?

I can’t get any of medical team to comment one way or the other. I’d be grateful for any views or to hear others’ experience or advice they’ve received on this. Thank you!  

I was scoffing biscuits minutes before every radiotherapy so it seems crazy to fast when you need strength and energy. I’d say fasting is a bad idea. 

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Hi @BPatB  

I would advise you to speak to your Treatment team for advice about this as I’m not sure it’s wise but I see you’ve already tried.

Have you had radiotherapy before - if so how did you feel afterwards ? Like @Bunty B  I found the treatments made me feel a bit tired . When I got on the table I felt fine but every time I got off it I felt like I’d worked a night shift .I dealt with that by sitting down for a good 30 minutes with a coffee and it has to be said , a piece of cake after which I was fine for the rest of the day . I’m certainly not saying that my way of dealing with it was the right one - I know it wasn’t great but it got me through.

 A few days after treatment I experienced fatigue and nausea and couldn’t eat much anyway for about a week so I think you should eat to keep your strength up if I’m honest .

I did find that kombucha especially the ginger flavour seemed to help with the nausea and there’s a lot of evidence that kombucha is good for the immune system so maybe just look into eating an optimal diet rather than either fasting or snacking.

Perhaps you would be able to cope with fasting and radiotherapy both but I have my doubts. I can see that it might be helpful for chemo for reducing nausea / vomitting caused by the medication, but with rads certainly for me the fatigue caused the nausea and although I had no appetite I always felt better after I’d managed to eat something.

Whatever you decide I hope everything goes well for you  x

Hello @BPatB, I’m about to embark on a similar journey and was looking at intermittent fasting sparked by the Nobel Prize that Yoshinori Ohsumi got, even before my (2nd) cancer journey started.

I think I will likely have to do 5 fractions over a week and, from what I read, some form of restricted dieting would be beneficial and increase the positive outcomes of RT: Perspective: Do Fasting, Caloric Restriction, and Diets Increase Sensitivity to Radiotherapy? A Literature Review - ScienceDirect

This might look like fasting before RT and calorie-restriction after (if I can cope well with it). But what protocol and for how long is still a blur to me, and as you said, unfortunately I do not expect my medical team to advise me one way or another on this, although I will definitely ask.

I have done intermittent fasting (IF) before - nothing crazy, basically having dinner at 6pm and breakfast at 11 am the next day once a week, whenever I remembered. I do not recall having any unwanted side-effects, so I expect I could do the same before the RT sessions without major issues. However, I’m not particularly keen on calorie restriction afterwards, unless I could cope with easily and knew that it had strong benefits.

What did you end up doing @BPatB and was it beneficial?

Just to say your appointments might not be at the same time every day . I assumed wrongly that as my first one was around 3pm they all would be but one was as early as 09.30 whilst another was 6pm so you might need to get your schedule first in order to plan around them .


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