Vitamin D and Cancer Risk?

Written by Dr. Steve Chaney on . Posted in Vitamin D and Cancer Risk

Does Vitamin D Reduce Cancer Risk?

Author: Dr. Stephen Chaney

 

vitamin d and cancer riskThe relationship between vitamin D and cancer risk is controversial. Some studies suggest that vitamin D reduces cancer risk. In those studies, the risk reduction was strongest for colon cancer, lung cancer, and breast cancer. However, other studies have found no association between vitamin D status and cancer risk.

Most previous studies have been conducted in European and American populations. Very few of the studies have been done in Asian populations. So, the authors of the current study (S. Budhathoki et al, BMJ 2018; 360:k671, doi: 10.1136/bmj.k671 ) focused their attention on the Japanese population.

How Was The Study Done?

vitamin d and cancer risk studyThe data for this study were drawn from the much larger Japanese Public Health Center (JPHC) Study. THE JPHC Study is an ongoing study investigating the role of lifestyle and other factors on the risk of cancer and other diseases. The study began in 1990 and enrolled 140, 420 participants aged 40-59.

All participants in the JPHC study filled out a detailed food frequency questionnaire at the time of entry into the study. A subset of participants also donated blood upon entry into the study for determination of 25-hydroxyvitamin D levels (the most reliable measurement of vitamin D status). It is this subset of participants who formed the basis of the current study.

There were 33,736 participants in this study. Based on plasma 25-hydroxyvitamin D levels at entry into the study, the participants were divided into four groups of around 1000 participants.

  • Group 1 had a median serum 25-hydroxyvitamin D level of 36.9 nmol/L.
  • Group 2 had a median serum 25-hydroxyvitamin D level 48.4 nmol/L.
  • Group 3 had a median serum 25-hydroxyvitamin D level of 56.9 nmol/L.
  • Group 4 had a median serum 25-hydroxyvitamin D level of 72.6 nmol/L.

For reference, the NIH considers < 30 nmol/L to be deficient, 30 to < 50 nmol/L to be insufficient for bone and overall health, > 50 nmol/L to be sufficient, and > 150 nmol/L to be potentially associated with adverse effects. By these criteria, group 1 had insufficient serum levels of 25-hydroxyvitamin D, group 2 was borderline, and groups 3 and 4 had sufficient serum levels of 25-hydroxyvitamin D.

The participants were followed for a total of 19 years. During this time 3301 participants developed cancer. The cancer incidence in groups 2, 3 and 4 were compared to the cancer incidence in group 1 to determine the effect of vitamin D status on cancer risk.

 

Vitamin D and Cancer Risk

 

vitamin d and cancer risk study resultsThe results of the Vitamin D and cancer risk study were:

  • Vitamin D reduced total cancer risk by up to 25%.
  • Vitamin D reduced the risk of liver cancer by up to 55%.
  • Vitamin D reduced the risk of pre-menopausal breast cancer by up to 44%.
  • There was a trend towards reduction of colon, liver, and prostate cancer by vitamin D, but the results did not quite reach significance.
  • There were too few cases for most other cancers to assess whether vitamin D status had any effect.
  • Risk reduction was not linear. Except for liver cancer, risk reduction for group 4 (72.6 nmol/L) was not greater than the risk reduction for group 3 (56.9 nmol/L). The significance of this observation will be discussed below.

The authors concluded: “Our findings support the hypothesis that vitamin D may confer protection against cancer. Nevertheless, the lower risk associated with higher circulating vitamin D concentrations seemed to show a ceiling effect, which may suggest that although maintaining an optimal 25-hydroxyvitamin D concentration is important for prevention of cancer, having a concentration beyond this optimal level may provide no further benefit.”

 

Why Is The Association of Vitamin D And Cancer Risk So Confusing?

 

vitamin d and cancer risk confusionSo why do some studies demonstrate confusing data on Vitamin D and cancer risk?  The “ceiling effect” mentioned by the authors of this study may explain much of the variation in results from previous trials. As I say in my upcoming book, “Slaying The Supplement Myths” , supplementation is most likely to be effective when the subjects are deficient in that nutrient at the beginning of the study. If they are starting with adequate levels of the nutrient, supplementation is unlikely to provide additional benefit.

While that statement seems to be obvious, many previous studies have ignored the beginning nutritional status. Some have not measured 25-hydroxyvitamin D levels at the beginning of the study. Others have measured starting 25-hydroxyvitamin levels but have not considered the starting levels in interpretation of their data.

Group 1 in the current study clearly had inadequate 25-hydroxyvitamin D levels. That may be why the groups with sufficient 25-hydroxyvitamin D levels showed a reduction in risk. The low baseline 25-hydroxyvitamin D is logical because most of Japan lies north of the United States, so sun exposure is less. In addition, the authors stated that food fortification and supplementation with vitamin D is much less in Japan than the US. In contrast, the baseline 25-hydroxyvitamin D status in many US studies is significantly higher.

The authors did a thorough analysis of previous studies. In general, studies with a low baseline level of 25-hydroxyvitamin D showed a reduction in cancer risk by vitamin D. Studies with a higher baseline level of 25-hydroxyvitamin D showed no effect.

This analysis does not permit a definitive conclusion, but it clearly defines how future studies should be designed. Simply put, to reliably test whether vitamin D reduces cancer risk, the experiment must be designed in such a way that the baseline 25-hydroxyvitamin D level is in the inadequate range. Otherwise, there is no reason to expect that higher levels of 25-hydroxyvitamin D will confer any benefit.

 

The Bottom Line:

 

A recent study looked at the effect of vitamin D status (serum 25-hydroxyvitaminD levels) on cancer risk. The study reported:

  • Vitamin D reduced total cancer risk by up to 25%.
  • Vitamin D reduced the risk of liver cancer by up to 55%.
  • Vitamin D reduced the risk of pre-menopausal breast cancer by up to 44%.
  • There was a trend towards reduction of colon, liver, and prostate cancer by vitamin D, but the results did not quite reach significance.
  • There were too few cases for most other cancers to assess whether vitamin D status had any effect.
  • Risk reduction was not linear. Except for liver cancer, risk reduction for group 4 (72.6 nmol/L) was not greater than the risk reduction for group 3 (56.9 nmol/L).

The authors concluded: “Our findings support the hypothesis that vitamin D may confer protection against cancer. Nevertheless, the lower risk associated with higher circulating vitamin D concentrations seemed to show a ceiling effect, which may suggest that although maintaining an optimal 25-hydroxyvitamin D concentration is important for prevention of cancer, having a concentration beyond this optimal level may provide no further benefit.”

The “ceiling effect” mentioned by the authors of this study may explain much of the variation in results from previous trials.

For more details, 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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Comments (4)

  • Kathleen-Marie

    |

    It’s important if we are taking a calcium supplement to be sure we are also getting adequate vitamin D from diet (mushrooms, eggs, fish), sunshine on the exposed skin midday in the summer, or our D3 supplementation. Especially for diets high in vitamin A, D is important too. All possibly affecting the cancer and disease prevention quality of circulating D2/3 in the bloodstream. It’s important to remember that vitamin D is a hormone precursor, or has hormone like affects on metabolism in general as well. In the animal world — reindeer moving North due to hotter temperatures (which means more suffocating flies in their nostrils), the reindeer are beginning to suffer from D deficiencies, even getting rickets and not being able to stand up well as babies. Wise vets and Laplanders have been putting a lot of lichen (which is also what our birds eat in the winter as source for D supplementation) in reindeer feeding areas. It’s so important for good immune function! I notice backyard birds eating lichen on rainy days perching on fallen tree branches around my feeders. Chimpanzes and other research and zoo animals also need D supplementation in their “chow” feed, along with fresh veggies and roots, to keep well and happier.

    Reply

  • Mary Butler

    |

    It asked me if chrome could access all of my files etc and I said no…so it didn’t download.

    Reply

  • Laura Nokes Lang

    |

    Thank you for letting us know the good news about eggs. I have always enjoyed eggs and usually have at least one a day. Now I know I’m not killing myself doing that, I feel better.

    Reply

  • Caroline

    |

    Dr., unfortunately I have seen women young and over age 55 with super low BP and that is dangerous. I chew on two REAL licorice pieces on the days my BP is too low and I am over 80 and I get back my energy and brain working well. I do take the OmegaGuard and sell a lot of it, thank goodness. But then I still have some trust left in Shaklee.

    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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