Working Night Shift and it’s Link to Breast Cancer

Breast cancer is the leading cause of illness and death for women in both developed and developing nations. (It may not be the predominant cancer diagnosed in men, men do get breast cancer as well.) While researchers may not still know all causes of breast cancer there is convincing evidence that excessive alcohol intake, increased weight and decreased physical activity can increase your risk.

Another risk factor that doesn’t seem to be discussed as much is working night shift.  The International Agency for Research on Cancer has classified shift work as carcinogenic to humans.  While more studies need to be done in this area so far the research seems to conclude that the risk of developing breast cancer increases with the number of years a woman does night shift (1, 2, 4).  So what is the link?  Our body has a natural circadian rhythm wanting to be active during the day and sleep at night.  The production of melatonin (our sleep hormone) occurs in the evening and throughout the night.  Melatonin is hypothesized to protect cells from cancer and to send a potent anti-cancer signal to existing cancer cells (5).

Virtually no melatonin is produced during daylight hours when we are active and thus lack of melatonin production while working night shift appears to be the link to increased risk of breast cancer for women working night shift.

Carrying excess weight is also of concern and has been studied amongst the nursing population who work shift work (4,5).  When nurses work night shift they are working in opposite pattern of their circadian rhythm.  They are working when they should sleep and eating at times when their intestinal tract is not interested in digesting food.  The longer nurses work night shift the higher the risk for becoming overweight.

So let’s get rid of night shifts! If only it were that simple; shift work is a vital part of our economy and doing away with it is likely never going to happen.  So what can we do? Here are a few recommendations based on what is known so far:

  1. It appears working 1-2 consecutive nights versus 3-4 is less likely to interrupt your circadian rhythm.
  2. Even though you are working night shift, very little food should be consumed after 7pm.  I have worked with a lot of people who work shift work and once I get them eating at similar times to what they would on day shift they notice they lose weight- while it’s not a randomized control trial but rather just 16 years of practice!
  3. Eat regular balanced meals and ensure you are getting adequate vegetables to meet your daily fibre goals.  If you fuel your body properly you will be less likely to crave the carbs later in the evening.  A simple strategy is to use the divided plate concept at meals.  Fill half of your plate with vegetables, ¼ with grains/carbs and ¼ with meat/meat alternative/fish/chicken.
  4. Don’t fuel on Double Doubles!  Sorry Tim but the medium Double-Double has over 200 calories and the extra large Double-Double has over 300 calories.  I’ve had people tell me they have 2-3 Double-Double coffees per night shift to stay awake! You may want to consider cutting back on the frequency, decreasing the added cream and the sugar, switching to  milk and skipping the sugar or just drinking it straight up.
  5. Stay active.  Physical activity is imperative in maintaining and building lean muscle mass.  It’s pretty simple- the more muscle you have, the more calories you can consume AND maintain your weight.
  6. Limit your alcohol consumption. Women are at higher risk for developing breast cancer when they consume alcohol.

Given that breast cancer is the most common cause of illness or death for women it seems plausible to assume each and every one of us is going to be touched in some way by this disease during our lifetime.  As with any disease the more we learn about it will only continue to help improve the diagnosis, treatment and hopefully the cure one day.