Nutrition - Intermittent Fasting

Friday 04 May 2018

Some weeks ago there was a Horizon programme on the television focussing on Fasting. It was narrated by Michael Mosely, some of you may remember it. It was well done and very positive about the impact that intermittent fasting has on health, longevity and weight. I did promise to get back to you over this particularly as I have been inundated with questions about this and should it be adopted by people with cancer.

Fasting and cancer

Well it has taken me a little while to respond because I wanted to do some thorough research into this before commenting one way or the other.

There has been quite a bit of research into the  benefits of fasting and cancer but first it is important to understand the thinking behind the idea of fasting and what research has been done to support it.

The potential benefits  of fasting appear to be;

  • Modified fasting lowers blood sugar levels and insulin production. This in turn burns fat and not muscle. (perhaps to be avoided if you are already losing weight as a result of cancer)
  • This reduces levels of insulin growth like factor (IGF-1) and by doing this it is said to extend life and reduce disease.
  • So what is insulin growth like factor?  IGF-1 keeps our bodies in the go go mode with cells driven to reproduce, this is fine when you are growing but not so good later in life. It seems that when our bodies do not have access to food and very low insulin levels as a consequence, they switch from growth mode to repair mode. As levels of IGF-1 drop a number of repair genes appear to get switched on.
  • A lack of nutrients seems to spur the activity of cell repair mechanisms which helps to slow the accumulation of cell damage. Boosting the bodies repair mechanisms seems to protect healthy tissues and make cancer cells easier to treat.
  • Scientists have known since 2007 that intermittent fasting can help cancer patients withstand higher doses of chemotherapy and reduce side effects and protect normal cells against much of the damage done by the drugs.
  • In one case a lady of 51 with breast cancer did her first round of chemotherapy in a fasted state of 140hours. Other than a dry mouth and hiccups she felt fine and carried on working. For the next 2 rounds of chemo she did not fast and the side effects were extremely pronounced- severe fatigue, diarrhoea, weakness, and nausea which prevented her from returning to work. For the 4th round of chemo she fasted and the side effects again were minimal. To add to this her total white blood cell count and platelet counts were all highest after the fasting regime. Interesting I think. Certainly food for thought.
  • In 2008 a group led by Valter Longo, a biologist at a University in USA published a paper
    ‘Modified alternate day fasting regimes reduce cell proliferation rates to a similar extent as daily calorie restriction’, suggesting that a short sharp course of fasting, not eating at all for a few days could make ordinary non cancer cells more resistant to side effects of chemotherapy, at least in mice.  This made news in the Daily Mail on 8th Feb 2008 with the headlines ‘Fasting combats cancer and boost effectiveness of treatments’, reporting that cancer cells respond differently to the stress of fasting compared to normal cells. Instead of entering a dormant state similar to hibernation, the cancer cells kept growing and dividing, in the end destroying themselves.
  • Another paper by Longo, ‘ Fasting cycles retard the growth of tumours and sensitize a range of cancer cell types to chemo therapy’, showing that again in mice, fasting can make cancerous cells more susceptible to chemo than they otherwise might not be. Cancerous calls treated with a combination of fasting and chemo had less chance of survival and resulted in smaller tumours than those treated with either fasting or chemo alone.  All of this would suggest that the explanation for this that in lean times normal cells switch their attention away from reproduction and towards preservation, boosting their repair mechanisms. He suggested that normal cells become resistant to the drugs while cancer cells do not.
  • We must remember that these experiments were done on mice and not humans but if fasting had the same effects on humans with cancer then the attraction is obvious. Human trials are underway, I found one human trial from  2009 (there are probably more) which showed promising results. 10 patients underwent fasting prior to chemotherapy, times ranged from 48-140 hours before treatment and 5 – 56 hours after treatment. All found it effective at reducing side effects of chemo, which is all very favourable.

So what do we think?
The evidence is definitely persuasive. However experts believe it will take several years of trials to confirm if human cancer patients really benefit from calorie restriction.

The bottom line

This all sounds very exciting BUT we must remember that fasting is not for the faint hearted. It is quite challenging and not suitable for everyone with cancer. The best advice is to run it past your oncologist and get their opinion first. Ideally it should be undertaken under medical supervision.

It is also worth considering that it has been found that 2:5 fasting has much the same benefits as total fasting PHEW!!!!  That means that 2 days of the week you have no more than 500 calories if you are a woman and 600 for men and on the other 5 days you eat normally. This is based on research by Dr. Krista Varady from the University of Chicago, a much gentler approach. While planning this, Horizon recommended eating less animal forms of protein and focussing on vegetarian protein sources like peas, beans and lentils. This is often recommended in books focussing on cancer and diet. This is because animal protein naturally contains insulin growth like factor (IGF-1) and by reducing this level seems to be the fundamental effect and benefit  of fasting or 2:5 fasting.

Blog originally writtnen by Caroline November 2012

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