Calcium and Breast Cancer Prevention

Written by Dr. Steve Chaney on . Posted in Calcium and Breast Cancer, Supplements and Health, Vitamins and Health

Author: Dr. Stephen Chaney

 

calcium and breast cancerIs there a connection between calcium and breast cancer prevention?  There has been lots of confusion about calcium supplements lately. Just a few years ago most health professionals were recommending calcium supplementation for women to prevent osteoporosis. Now that recommendation has become controversial. That’s because some studies have suggested that increasing calcium intake doesn’t actually prevent osteoporosis. Other studies have suggested that calcium supplementation may actually cause heart disease.

As if all this wasn’t confusing enough, the latest headlines are claiming that increased calcium intake will reduce breast cancer risk. What are we to believe about the value of calcium for our health? Should we take that calcium supplement we threw away out of the trash can and start using it again?

I have previously evaluated the studies behind the previous headlines and debunked the headlines. For example, I reported that previous studies suggesting that calcium supplementation might increase heart attack risk were followed by a much larger, better designed study showing that, if anything, calcium supplementation actually decreases heart attack risk in Do Calcium Supplements Increase Heart Attack Risk?. I also reported that the study claiming calcium supplements did not prevent osteoporosis was fatally flawed in Do Calcium Supplements Prevent Bone Fractures?.

Now it is time to evaluate the study behind the latest calcium headline. Is this headline myth or is it true?  What is the connection between calcium and breast cancer.

 

Calcium and Breast Cancer Risk Reduction

calcium reduces breast cancer riskThis study (Hidayat et al, British Journal of Nutrition, 116: 158-166, 2016) was a meta-analysis of 11 previous clinical studies published between 2002 and 2013 with a total of 872,895 women subjects which measured calcium intake and breast cancer. Follow up ranged from 7 to 25 years in these studies, during which time 26,606 of the women developed breast cancer.

Dietary plus supplemental calcium intake was determined at the beginning of each study using either a 24-hour diet recall or a food frequency questionnaire. Calcium intakes ranged from 203 mg/day to 1,750 mg/day.

In short this was a very large and well done study. Because of the large number of subjects and the large number of cancer cases, this study had the sensitivity to detect even small effects of calcium on breast cancer risk – something that was not possible in previous studies. In addition, the investigators were able to conduct a dose-response evaluation of the effect of calcium and breast cancer risk reduction. This was also had not been possible in previous studies.

When the women with the highest calcium intakes were compared to the women with the lowest calcium intakes:

  • Calcium reduced breast cancer risk by 8%.
  • The effect was much larger for premenopausal women than postmenopausal women:
  • Calcium reduced breast cancer risk by 25% in premenopausal women.
  • Calcium reduced breast cancer risk by 6% in postmenopausal women.
  • The dose response effect was fairly linear over the entire dose range with a 2% decreased risk of breast cancer for every 300 mg/day increase in calcium intake.

 

What Does This Study Mean For You?

As I said in the beginning, when you read the headlines proclaiming that increasing your calcium intake could decrease your breast cancer risk, you probably had two questions:

Is it true?  The answer appears to be yes. This was a very large, very well done study and it showed there is a connection between calcium and breast cancer risk reduction. It was capable of detecting even small effects of calcium on breast cancer risk – something that previous studies simply could not do.

Does it matter?  Here the answer is more complicated. If you’re a postmenopausal woman, increased calcium intake only decreases your risk of breast cancer by 6%.  If you are a premenopausal woman, increased calcium intake decreases your risk of breast cancer by a more robust 25%. However, in both cases you should think of calcium as only one component of a holistic approach to reducing breast cancer risk – something I’ll discuss in more detail below.

Now that you know the answer to those two questions you probably have a third question:

How much calcium do I need?   That’s pretty simple. The calcium DV for adults is 1,000 mg/day, increasing to 1,200 mg/day for women over 50.

How Can You Reduce Breast Cancer Risk?

In a previous article Preventing Osteoporosis,  I reported that while calcium supplementation alone had only a very modest effect on reducing osteoporosis risk, it played an important role as part of a holistic bone-healthy lifestyle. The role of calcium in reducing breast cancer risk is no different.

Most experts estimate that between 30 and 60% of breast cancer cases could be prevented by diet and lifestyle changes. In addition to calcium, both the Mayo Clinic  and the American Cancer Society make the following recommendations for reducing breast cancer risk:

  • calcium supplementsLimit or avoid hormone therapy. This is the single most important step you can take to reduce breast cancer risk.
  • Eat a plant-based diet with plenty of fresh fruits and vegetables, whole grains, legumes and nuts. Use fats in moderation and choose healthy fats such as olive oil and omega-3 fats. Limit the amounts of red meat and processed meats.
  • Control your weight.
  • Be physically active.
  • Don’t smoke
  • Limit alcohol intake.
  • Avoid exposure to radiation and environmental pollution.
  • Breast feed.

Where Should You Get Your Calcium?

Many experts recommend that you get your calcium only from food. Is that the best advice?  I always like to start with food as the source of essential nutrients, but in the case of calcium that usually isn’t sufficient. Here are some facts to ponder:

  • Plain, nonfat yoghurt is the calcium champion, with an 8 ounce serving supplying 42% of the DV (the calcium DV = 1,000 mg/day). However, most yoghurt cups in the market these days are 4 ounces or less.
  • Milk and a few cheeses supply around 30% of the DV. However, many people can’t or don’t consume the 3 or more servings needed to reach the DV.
  • Green leafy vegetables are often mentioned as another good food source. However, a serving of them only provides around 10% of the DV, and many leafy greens contain oxalates which decrease calcium absorption.
  • Beyond that,  most food sources of calcium supply only 1-8% of the DV for calcium. If you don’t drink lots of milk, you need to be a dietitian with an advanced degree to figure out how to get enough calcium from foods alone.
  • If that isn’t bad enough, many foods contain substances that interfere with calcium absorption. In addition to the oxalates in leafy greens, these substances include phytates from whole grains, phosphate from sodas, and saturated fat from red meats.

 

Experts often also recommend getting calcium from calcium fortified foods such as calcium fortified orange juice. That can help you reach the recommended calcium intake, but in my opinion calcium-fortified foods are likely to be more expensive and no better than regular foods plus a calcium supplement.

I recommend getting as much calcium as possible from food and adding a calcium supplement for the rest. Here are my tips on calcium supplementation:

  • If you do use a calcium supplement, make sure it is complete. Don’t just settle for calcium and vitamin D. At the very least you will want your supplement to contain magnesium and vitamin K. I personally recommend that it also contain zinc, copper, and manganese as well.
  • Your calcium supplement will be best utilized if taken between meals.
  • Your calcium supplement will be best utilized if you don’t take more than 500 mg at a time.
  • In most cases there is no need for more than the DV of calcium.

Let’s review the connection between calcium and breast cancer risk reduction.

 

The Bottom Line

  • A recent study has shown that increasing calcium intake reduces the risk of breast cancer. The effect of calcium intake on breast cancer risk was much greater for premenopausal women (25% risk reduction) than it was for postmenopausal women (6% risk reduction).
  • While the effect of calcium alone on breast cancer risk was relatively modest,  it is likely to be an important component of a holistic approach for reducing breast cancer risk.  Additional recommendations of the Mayo Clinic and American Cancer Society for reducing breast cancer risk are contained in the article above.
  • While many experts recommend getting your calcium from food alone, a careful analysis of food sources of calcium clearly shows how difficult that is for most people.
  • Calcium supplements are a safe and effective way to make sure you are getting the calcium you need. In the article above, I describe the optimal design of a calcium supplement and how to take a calcium supplement for optimal utilization.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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Comments (1)

  • douglas

    |

    Gracias muy interesante, se lo dificil que es obtener el calcio en los alimentos cuando se es algo vegetariano-

    Reply

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Latest Article

Is Our Microbiome Affected By Exercise?

Posted November 6, 2018 by Dr. Steve Chaney

Microbiome Mysteries

Author: Dr. Stephen Chaney

is our microbiome affected by exerciseIn a recent post,  What is Your Microbiome and Why is it Important,  of “Health Tips From The Professor” I outlined how our microbiome, especially the bacteria that reside in our intestine, influences our health. That influence can be either good or bad depending on which species of bacteria populate our gut. I also discussed how the species of bacteria that populate our gut are influenced by what we eat and, in turn, influence how the foods we eat are metabolized.

I shared that there is an association between obesity and the species of bacteria that inhabit our gut. At present, this is a “chicken and egg” conundrum. We don’t know whether obesity influences the species of bacteria that inhabit our gut, or whether certain species of gut bacteria cause us to become obese.

Previous studies have shown that there is also an association between exercise and the species of bacteria that inhabit our gut. In particular, exercise is associated with an increase in bacteria that metabolize fiber in our diets to short chain fatty acids such as butyrate. That is potentially important because butyrate is a primary food source for intestinal mucosal cells (the cells that line the intestine). Butyrate helps those cells maintain the integrity of the gut barrier (which helps prevent things like leaky gut syndrome). It also has an anti-inflammatory effect on the immune cells that reside in the gut.

However, associations don’t prove cause and effect. We don’t know whether the differences in gut bacteria were caused by differences in diet or leanness in populations who exercised regularly and those who did not. This is what the present study (JM Allen et al, Medicine & Science In Sports & Exercise, 50: 747-757, 2018 ) was designed to clarify.  Is our microbiome affected by exercise?

 

How Was The Study Designed?

is our microbiome affected by exercise studyThis study was performed at the University of Illinois. Thirty-two previously sedentary subjects (average age = 28) were recruited for the study. Twenty of them were women and 12 were men. Prior to starting the study, the participants filled out a 7-day dietary record. They were asked to follow the same diet throughout the 12-week study. In addition, a dietitian designed a 3-day food menu based on their 7-day recall for the participants to follow prior to each fecal collection to determine species of gut bacteria.

The study included a two-week baseline when their baseline gut bacteria population was measured, and participants were tested for fitness. This was followed by a 6-week exercise intervention consisting of three supervised 30 to 60-minute moderate to vigorous exercise sessions per week. The exercise was adapted to the participant’s initial fitness level, and both the intensity and duration of exercise increased over the 6-week exercise intervention. Following the exercise intervention, all participants were instructed to maintain their diet and refrain from exercise for another 6 weeks. This was referred to as the “washout period.”

VO2max (a measure of fitness) was determined at baseline and at the end of the exercise intervention. Stool samples for determination of gut bacteria and concentrations of short-chain fatty acids were taken at baseline, at the end of the exercise intervention, and again after the washout period.

In short, this study divided participants into lean and obese categories and held diet constant. The only variable was the exercise component.

 

Is Our Microbiome Affected By Exercise?

is our microbiome affected by exercise fitnessThe results of the study were as follows:

  • Fitness, as assessed by VO2max, increased for all the participants, and the increase in fitness was comparable for both lean and obese subjects.
  • Exercise induced a change in the population of gut bacteria, and the change was comparable in lean and obese subjects.
  • Exercise increased fecal concentrations of butyrate and other short-chain fatty acids in the lean subjects, but not in obese subjects.
  • The exercise-induced changes in gut bacteria and short-chain fatty acid production were largely reversed once exercise training ceased.

The authors concluded: “These findings suggest that exercise training induces compositional and functional changes in the human gut microbiota that are dependent on obesity status, independent of diet, and contingent on the sustainment of exercise.” [Note: To be clear, the exercise-induced changes in both gut bacteria and short-chain fatty acid production were independent of diet and contingent on the sustainment of exercise. However, only the production of short-chain fatty acids was dependent on obesity status.]

 

What Does This Study Mean For You?

is our microbiome affected by exercise gut bacteriaThere are two important take home lessons from this study.

  • With respect to our gut bacteria, I have consistently told you that microbiome research is an emerging science. This is a small study, so you should regard it as the beginning of our understanding of the effect of exercise on our microbiome rather than conclusive by itself. It is consistent with previous studies showing an association between exercise and a potentially beneficial shift in the population of gut bacteria.

The strength of the study is that it shows that exercise-induced changes in beneficial gut bacteria are probably independent of diet. However, it is the first study to look at the interaction between obesity, exercise and gut bacteria, so I would interpret those results with caution until they have been replicated in subsequent studies.

  • With respect to exercise, this may be yet another reason to add regular physical activity to your healthy lifestyle program. We already know that exercise is important for cardiovascular health. We also know that exercise increases lean muscle mass which increases metabolic rate and helps prevent obesity. There is also excellent evidence that exercise improves mood and helps prevent cognitive decline as we age.

Exercise is also associated with decreased risk of colon cancer and irritable bowel disease. This effect of exercise has not received much attention because the mechanism of this effect is unclear. This study shows that exercise increases the fecal concentrations of butyrate and other short-chain fatty acids. Perhaps, this provides the mechanism for the interaction between exercise and intestinal health.

 

The Bottom Line

A recent study has reported that:

  • Exercise induces a change in the population of gut bacteria, and the change was comparable in lean and obese subjects.
  • Exercise causes an increase in the number of gut bacteria that produce butyrate and other short-chain fatty acids that are beneficial for gut health.
  • These effects are independent of diet, but do not appear to be independent of obesity because they were seen in lean subjects but not in obese subjects.
  • The exercise-induced changes in gut bacteria and short-chain fatty acid production are largely reversed once exercise training ceases.

The authors concluded: “These findings suggest that exercise training induces compositional and functional changes in the human gut microbiota that are dependent on obesity status, independent on diet, and contingent on the sustainment of exercise.”

For more details and my interpretation of the data, read the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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