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

Best Diet For Heart Disease Prevention

Posted July 9, 2019 by Dr. Steve Chaney

Are The American Heart Association’s Recommendations Correct?

Author: Dr. Stephen Chaney

 

What is the best diet for heart disease prevention? 

diet for heart disease preventionHeart disease is a killer. It continues to be the leading cause of death – both worldwide and in industrialized countries like the United States and the European Union. When we look at heart disease trends, it is a good news – bad news situation.

  • The good news is that heart disease deaths are continuing to decline in adults over 70.
  • The decline among senior citizens is attributed to improved treatment of heart disease and more seniors following heart-healthy diets.
  • The bad news is that heart disease deaths are starting to increase in younger adults, something I reported in an earlier issue, Heart Attacks Increasing in Young Women of “Health Tips From the Professor.”
  • The reason for the rise in heart disease deaths in young people is less clear. However, the obesity epidemic, junk and convenience foods, and the popularity of fad diets all likely play a role.

Everyone has a magic diet for reducing heart disease risk. The American Heart Association tells us to avoid fats, especially saturated fats. Vegans tell us to avoid animal protein. Paleo and keto enthusiasts tell us carbs are the problem. Who is correct?

Of course, we don’t eat fats, carbohydrates, or proteins. We eat foods. That is why a recent study (T Meier et al, European Journal of Epidemiology, 34: 37-45, 2019) is so important. It reported which foods increase and which decrease the risk of premature heart disease deaths.

How Was The Study Done?

diet for heart disease prevention studyThe authors of the current study analyzed data from the “Global Burden of Diseases (GBD) Study”, a major world-wide effort designed to estimate the portions of deaths caused by various risk factors.

The current study focused on the impact of 12 dietary risk factors on heart disease deaths between 1990 and 2016 for 51 countries in four regions (Western Europe, Central Europe, Eastern Europe, and Central Asia).

The dietary risk factors were:

  • Diets low in fiber, fruits, vegetables, legumes, nuts and seeds, polyunsaturated fatty acids, omega-3 fatty acids, and whole grains.
  • Diets high in sodium, processed meats, sugar-sweetened beverages, and trans fatty acids.

Saturated fat and meat were not explicitly included in the GBS Study data. However, diets low in polyunsaturated fats and omega-3 fats are likely high in saturated fats. Similarly, diets low in fruits, vegetables, whole grains, and legumes are likely higher in meats. The study also did not include dairy, and some recent studies suggest that some dairy foods may decrease heart disease risk.

For simplicity I will only consider the findings from Western Europe because their diet and heart disease death trends are similar to those in the United States.

 

Best Diet for Heart Disease Prevention?

plant-based diet bestThe study found that in 2016 (the last year for which data were available):

  • Dietary risk factors were responsible for 49.2% of heart disease deaths.
  • 6% of all diet-related heart disease deaths occurred in adults younger than 70, and that percentage has been increasing in recent years.

When they looked at the contribution of individual foods to diet related heart disease deaths, the percentages were:

  • Diets low in whole grains = 20.4%
  • Diets low in nuts and seeds = 16.2%
  • Diets low in fruits = 12.5%
  • Diets high in sodium = 12.0%
  • Diets low in omega-3s = 10.8%
  • strong heartDiets low in vegetables = 9.0%
  • Diets low in legumes = 7.0%
  • Diets low in fiber = 5.7%
  • Diets low in polyunsaturated fats = 3.7%
  • Diets high in processed meats = 1.6%
  • Diets high in trans fatty acids = 0.8%
  • Diets high in sugar-sweetened beverages = 0.1%

So, what is the best diet for heart disease prevention?

In short, this study concluded:

  • A primarily plant-based diet is the best protection against premature death due to heart disease.
  • All plant-based food groups (whole grains, nuts and seeds, fruits, vegetables, and legumes) play an important role in reducing heart disease deaths.
  • Meat was not included in the analysis, but it is likely that most people’s diets in this region of the world contained some meat. The most likely take-away is that meat does not affect heart disease risk in the context of a primarily plant-based diet.
  • Dairy was not included in the analysis either, but some studies suggest dairy, particularly fermented dairy foods, reduce heart disease risk.
  • Finally, the study concluded: “Compared to other…modifiable risk factors (physical inactivity, drug and alcohol abuse, tobacco smoking, obesity, etc.), an altered diet is the most effective means of preventing premature deaths from cardiovascular disease in Western Europe.”

While every study has its weaknesses, this study is consistent with multiple previous studies showing that primarily plant-based diets are best for reducing heart disease risk. You will find a more complete discussion of these studies in my book “Slaying The Food Myths.”

 

Are the American Heart Association’s Recommendations Correct?

With this study’s results in mind we can now ask whether the recommendations of the American Heart Association and other popular diets are correct. Are they likely to reduce heart disease deaths?

  • The American Heart Association Recommends a dietary pattern that emphasizes a variety of fruits and vegetables, whole grains, nuts and legumes, skinless poultry and fish, and low-fat dairy products. This study supports those recommendations.
  • This study also supports the heart-health benefits of the Mediterranean and DASH diets.
  • Meat and dairy were not explicitly considered in this study. Thus, the results of this study are also consistent with vegan and semi-vegetarian diets.
  • However, low carb diets like Paleo and keto eliminate some of the key food groups (whole grains, fruits, and legumes) that appear to be essential for reducing heart disease risk. 40% of the heart-health benefits in this study came from those 3 food groups. Thus, this study does not support claims that those two diets are heart-healthy long term.

 

The Bottom Line

 

Everyone has a magic diet for reducing heart disease risk. The American Heart Association tells us to avoid fats, especially saturated fats. Vegans tell us to avoid animal protein. Paleo and keto enthusiasts tell us carbs are the problem. Who is correct?

A recent study provides some important clues. It looked at dietary patterns associated with reduced risk of premature death from heart disease in Western Europe. The study concluded:

  • A primarily plant-based diet is the best protection against premature death due to heart disease.
  • All plant-based food groups (whole grains, nuts and seeds, fruits, vegetables, and legumes) play an important role in reducing heart disease deaths.
  • Meat did not appear to affect heart disease risk in the context of a primarily plant-based diet.
  • Dairy was not included in the analysis, but some studies suggest dairy, particularly fermented dairy foods, reduce heart disease risk.
  • Finally, the study concluded: “Compared to other…modifiable risk factors (physical inactivity, drug and alcohol abuse, tobacco smoking, obesity, etc.), an altered diet is the most effective means of preventing premature deaths from cardiovascular disease.”

While every study has its weaknesses, this study is consistent with multiple previous studies showing that primarily plant-based diets are best for reducing heart disease risk. You will find a more complete discussion of these studies in my book “Slaying The Food Myths.”

With this study’s results in mind we can now ask whether the recommendations of the American Heart Association and other popular diets are correct. Are they likely to reduce heart disease deaths?

  • The American Heart Association Recommends a dietary pattern that emphasizes a variety of fruits and vegetables, whole grains, nuts and legumes, skinless poultry and fish, and low-fat dairy products. This study supports those recommendations.
  • This study also supports the heart-health benefits of the Mediterranean and DASH diets.
  • Meat and dairy were not explicitly considered in this study. Thus, the results of this study are also consistent with vegan and semi-vegetarian diets.
  • However, low carb diets like Paleo and keto eliminate some of the key food groups (whole grains, fruits, and legumes) that appear to be essential for reducing heart disease risk. 40% of the heart-health benefits in this study came from those 3 food groups. Thus, this study does not support claims that those two diets are heart-healthy long term.

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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