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Breast cancer risk – lifestyle choices

The myths about cancer risk are both sad and dangerous. Too many times, I read about supplements or diets that stop “cancer” as if it’s one disease (it is not) that a handful of blueberries will destroy. Like almost every cancer, reducing breast cancer risk really boils down to a handful of lifestyle choices.

In 2015, there will be 232,000 new breast cancer cases in the USA (pdf). Worldwide in 2012, it was estimated that there were over 1.7 million new cases of breast cancer. There is evidence that the rate of breast cancer is increasing, but that may be a result of better diagnostic tools that give earlier diagnoses (and this is a discussion left for another day).

Breast cancer has become a part of our culture, partially because the disease moved from a disease that was only mentioned in whispers to one that has some of the highest awareness for cancers.

Using a review article, by Max Dieterich et al.  about breast cancer risk and lifestyle influence as a template, I thought it would be prudent to list out some of the major influencers on breast cancer risk. And no, smoking weed has no known influence on the risk of breast cancer.

Breast cancer risk – obesity


There is good evidence that there is an association between a higher risk of developing breast cancer and obesity. Adult weight gain and body fatness, defined as a BMI (body mass index) above 25 kg/m2, have been shown to increase breast cancer risk.

This relationship between risk and obesity has remained consistent among most studies examining the link. Moreover, there is strong evidence that the relative risk is approximately 1.5 for overweight women (BMI > 25 kg/m2) and 2.0 for obese women (BMI > 25 kg/m2) compared to normal-weight women (18.5–25 kg/m2).

Yes, I understand that there is a rabid cultural “war” about weight (and the BMI measurement), but the evidence is clear regarding obesity and cancer – skinny reduces the risk of cancer. And if you throw in evidence about BMI and other chronic diseases like cardiovascular diseases and type 2 diabetes, I personally ignore the cultural backlash against the get rid of fat strategy.

However, and there’s always an “however,” the role of obesity (or lack of it) in breast cancer risk is not completely clear. It could be growth regulators implicated in obesity that may increase the risk. Or it could be other lifestyle choices that lead to obesity that themselves increase the risk.

But there’s too much evidence linking obesity and breast cancer to ignore. There’s even solid data from research on the reduction of breast cancer risk after significant weight loss (> 4.5 kg). It’s pretty clear that research shows that avoiding adult weight gain and maintaining a normal BMI is strongly associated with reducing the risk of breast cancer.

Breast cancer risk – smoking


You might think that smoking is associated with lung cancer. That’s true. But actually smoking increases the risk of lots of different cancers, including breast cancer. Tobacco is associated with about 21% of cancer mortality worldwide – we could get close to winning the war on cancer just by eliminating smoking.

Dieterich et al. report that “an estimated 10% increased BC risk for women with a history of smoking.” Think about that if you’re a woman who smokes – you instantly reduce your risk of breast cancer risk by 10% (a huge number in relative risk reduction) when you stop smoking. No kale blueberry shake is going to do that.

To be fair, older evidence showed a lack of association between breast cancer and smoking, but more recent evidence, as described by Dieterich et al., states that “enough evidence exists to show that smoking should be regarded as a possible risk factor for BC.”


Breast cancer risk – alcohol


Ethanol itself is not carcinogenic. You could bathe in ethanol every day, and the compound itself wouldn’t increase your risk of cancer. Unfortunately, it’s the metabolites of ethanol that increase risk of cancer.

Moreover, ethanol hampers the liver’s ability to clear compounds out of the bloodstream. And it has a synergistic effect with tobacco to increase risk of breast cancer.

Recent research found a reduced risk of breast cancer at and below alcohol consumption of around 10 g of ethanol a day. Just for comparison’s sake, 10 grams of ethanol is what one would find in a small glass of beer or wine.

Breast cancer risk – diet


As I’ve written previously, a well balanced diet contributes to lower risks across all cancers. However, the evidence is strongly confounded by the close relationship between diet and normal body weight, which may have an association itself with breast cancer risk. It’s almost impossible to separate diet from obesity, so there’s no good evidence that links diet (and diet behavior) to breast cancer risk.

That being said, Dieterich et al. report that there is weak evidence that a Mediterranean diet (high in vegetables, fruits, whole grains, fish, and olive oil) and a diet rich in fruits, vegetables and high fiber have an association with lowering breast cancer risk. But a caveat – we have no idea whether it’s the diet itself or the weight control that might be the result of such diets.

Here’s the thing – if maintaining these diets help maintain a normal body weight, that’s probably a good thing for lowering breast cancer risk (and risks of all cancers, along with other chronic diseases). If having some other diet (like all sushi, every day), helps maintain your weight, go for it.


Breast cancer risk – physical activity


Physical activity is associated with lower cancer risks, including breast cancer. Once again, it may not lower risk itself, but be a part of the lifestyle choices that lead to normal weight.

However, since increased physical activity may have an effect on endogenous steroid hormone metabolism and inflammation. Of course, increased physical activity may lead to the reduction of body fat, improvement of immune system regulators, and alterations in free-radical generation.

A review of 73 studies (that’s very powerful on the hierarchy of scientific evidence) indicates that increased physical activity, across all ranges of that activity, decreases the risk of breast cancer by 25-30%. And if normal weight is an independent variable on breast cancer risk, the combination of the two could be critical to actual breast cancer risk reduction.

If this data is accurate (and a systematic review of 73 other studies would indicate it is), physical activity could be one of the most important breast cancer risk reduction choices one could make.


Breast cancer risk – hormone therapy


Hormone therapy after menopause (HTMP) is a therapy for women who suffer from some menopausal symptoms like hot flashes. HTMP has other value like reducing the risk of coronary heart disease, osteoporosis, and dementia.

Unfortunately, many studies have concluded that there is an association between HTMP and breast cancer risk. A Cochrane Review of 23 studies, involving 42,830 women, established that there was a significantly increased risk of breast cancer after 5.6 years of HTMP. This risk can be almost eliminated soon after stopping HTMP.

However, estrogen-only HTMP (most HTMP also includes progesterone) has not been associated with a significant increase in breast cancer risk.

Breast cancer risk – implants


There have been a lot of studies examining links between silicone breast implants and breast cancer risk. The majority of these studies did not uncover any correlation between breast cancer and breast implants.

A five year follow up of a breast implant device showed that there was no increased risk of cancer. This was repeated in other studies. In addition, studies are consistent from both Europe and the USA that there is no increased risk of breast cancer from implants.

There seems to be a link between breast implants and a very rare form of a cancer of the immune system, ALCL (anaplastic large cell lymphoma), which is completely unrelated to breast cancer. Although the data seems to indicate that the relative risk of ALCL is much higher in women with breast implants compared to those who don’t, the absolute risk is tiny, with less than 1000 cases per year in the USA.

The authors also discuss the link between breast cancer and some other issues like type 2 diabetes (which is close linked to the same lifestyle choices listed above) and stress. But I think the ones I’ve listed here are more in line with the evidence.


Summary recommendations


Based on the evidence in this review, Dieterich et al. recommended the following:

  • Start taking preventive measures early in childhood
  • Eat several servings of vegetables and fruit per day
  • Consume a diet rich in fiber (e.g. cereals and soy products)
  • Maintain an ideal body weight (BMI = 20–25 kg/m2)
  • Avoid animal fat – replace with unsaturated vegetable fat or fish oil
  • Limit consumption of red meat to 140 g/day
  • Avoid supplements in the form of vitamins, minerals, and trace elements (editor’s note – they’re worthless)
  • Exercise regularly (2–3 h/week of moderate exercise)
  • Abstain from alcohol and smoking
  • Avoid unnecessary postmenopausal hormone use

Nothing about consuming kale shakes. Or downing vitamin C by the handful. Or seeing a chiropractor.

Stop smoking. Eat better. Don’t drink. Get exercise. Keep your weight at normal levels.

Easy. More or less.




Michael Simpson
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