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

Do Omega-3s Lower Blood Pressure in Young, Healthy Adults?

Posted August 14, 2018 by Dr. Steve Chaney

What Is The Omega-3 Index And Why Is It Important?

Author: Dr. Stephen Chaney

 

Do omega-3s lower blood pressure in healthy adults?

omega-3s lower blood pressure young adultsThe literature on the potential health benefits of omega-3s is very confusing. That’s because a lot of bad studies have been published. Many of them never determined the omega-3 status of their subjects prior to omega-3 supplementation. Others relied on dietary recalls of fish consumption, which can be inaccurate.

Fortunately, a much more accurate measure of omega-3 status has been developed and validated in recent years. It’s called the Omega-3 Index. Simply put, the Omega-3 Index is the percentage of EPA and DHA compared to 26 other fatty acids found in cellular membranes. Using modern technology, it can be determined from a single finger prick blood sample. It is a very accurate reflection of omega-3 intake relative to other fats in the diet over the past few months. More importantly, it is a measure of the omega-3 content of your cell membranes, which is a direct measure of your omega-3 nutritional status.

A recent extension of the Framingham Heart Study reported that participants with an Omega-3 Index >6.8% had a 39% lower risk of cardiovascular disease than those with an Omega-3 Index <4.2% (WS Harris et al, Journal of Clinical Lipidology, 12: 718-724, 2018 ). Although more work needs to be done, an Omega-3 Index of 4% or less is generally considered indicative of high cardiovascular risk, while 8% or better is considered indicative of low cardiovascular risk. For reference, the average American has an Omega-3 Index in the 4-5% range. In Japan, where fish consumption is much higher and cardiovascular risk much lower, the Omega-3 Index is in the 9-11% range.

Previous studies have suggested that omega-3 fatty acids lower blood pressure to a modest extent. Thus, it is not surprising that more recent studies have shown an inverse correlation between Omega-3 Index and blood pressure. However, those studies have been done with older populations, many of whom had already developed high blood pressure.

From a public health point of view, it is much more interesting to investigate whether it might be possible to prevent high blood pressure in older adults by optimizing omega-3 intake in a young, healthy population, most of whom had not yet developed high blood pressure. Unfortunately, there were no studies looking at that population. The current study was designed to fill that gap.

 

How Was The Study Done?

omega-3s lower blood pressure young healthy adultsThe current study (M.G. Filipovic et al, Journal of Hypertension, 36: 1548-1554, 2018 ) was based on data collected from 2036 healthy adults, aged 25-41, from Liechtenstein. They were participants in the GAPP (Genetic and Phenotypic Determinants of Blood Pressure) study. Participants were excluded from the study if they had been diagnosed with high blood pressure and were taking medication to lower their blood pressure. They were also excluded if they had heart disease, chronic kidney disease, other severe illnesses, obesity, sleep apnea, or daily use of non-steroidal anti-inflammatory medications.

Blood samples were collected at the time of their enrollment in the study and frozen for subsequent determination of Omega-3 Index. Blood pressure was also measured at their time of enrollment in two different ways. The first was a standard blood pressure measurement in a doctor’s office.

For the second measurement they were given a wearable blood pressure monitor that recorded their blood pressure over 24 hours every 15 minutes during the day and every 30 minutes while they were sleeping. This is considered more accurate than a resting blood pressure measurement in a doctor’s office because it records the variation in blood pressure, while you are sleeping, while you are exercising, and while you go about your everyday activities.

 

Do Omega-3s Lower Blood Pressure In Young, Healthy Adults?

omega-3s lower blood pressure young adults equipmentNone of the participants in the study had significantly elevated blood pressure. The mean systolic and diastolic office blood pressures were 120±13 and 78±9 respectively. The average Omega-3 Index in this population was 4.6%, which is similar to the average Omega-3 Index in the United States.

When they compared the group with the highest Omega-3 Index (average = 5.8%) with the group with the lowest Omega-3 Index (average = 4.6%):

  • The office measurement of systolic and diastolic blood pressure was decreased by 3.3% and 2.6% respectively
  • While those numbers appear small, the differences were highly significant.
  • The 24-hour blood pressure measurements showed a similar decrease.
  • Blood pressure measurements decreased linearly with increasing Omega-3 Index. [In studies of this kind, a linear dose-response is considered an internal validation of the differences observed between the group with the highest Omega-3 Index and the group with the lowest Omega-3 Index.]

The authors concluded: “A higher Omega-3 Index is associated with statistically significant, clinically relevant, lower systolic and diastolic blood pressure in normotensive, young and healthy individuals. Diets rich omega-3 fatty acids may be a strategy for primary prevention of hypertension.”

 

What Does This Mean For You?

omega-3s lower blood pressure young adults questionPerhaps I should first comment on the significance of the relatively small decrease in blood pressure observed in this study.

  • These were young adults, all of whom had normal or near normal blood pressure.
  • The difference in Omega-3 Index was rather small (5.8% to 4.6%). None of the participants in the study were at the 8% or above that is considered optimal.
  • Liechtenstein is a small country located between Switzerland and Spain. Fish consumption is low and omega-3 supplement consumption is rare.

Under these conditions, even a small, but statistically significant, decrease in blood pressure is remarkable.

We should think of this study as the start of the investigation of the relationship between omega-3 status and blood pressure. Its weakness is that it only shows an association between high Omega-3 Index and low blood pressure. It does not prove cause and effect.

Its strength is that it is consistent with many other studies showing omega-3 fatty acids lower blood pressure. Furthermore, it suggests that the effect of omega-3s on blood pressure may also be seen in young, healthy adults who have not yet developed high blood pressure.

Finally, the authors suggested that a diet rich in omega-3s might reduce the incidence of high blood pressure by slowing the age-related increase in blood pressure that most Americans experience. This idea is logical, but speculative at present.

However, the GAPP study is designed to provide the answer to that question. It is a long-term study with follow-up examinations scheduled every 3-5 years. It will be interesting to see whether the author’s prediction holds true, and a higher Omega-3 Index is associated with a slower increase in blood pressure as the participants age.

 

Why Is The Omega-3 Index Important?

 

The authors of this study said: “The Omega-3 Index is very robust to short-term intake of omega-3 fatty acids and reliably reflects an individual’s long-term omega-3 status and tissue omega-3 content. Therefore, the Omega-3 Index has the potential to become a cardiovascular risk factor as much as the HbA1c is for people with diabetes…” That is a bit of an overstatement. HbA1c is a measure of disease progression for diabetes because it is a direct measure of blood sugar control.

In contrast, Omega-3 Index is merely a risk factor for cardiovascular disease. However, if it is further validated by future studies, it is likely to be as important for predicting cardiovascular risk as are cholesterol levels and markers of inflammation.

However, to me the most important role of Omega-3 Index is in the design of future clinical studies. If anyone really wants to determine whether omega-3 supplementation reduces cardiovascular risk, high blood pressure, diabetes or any other health outcome they should:

  • Start with a population group with an Omega-3 Index in the deficient (4-5%) range.
  • Supplement with omega-3 fatty acids in a double blind, placebo-controlled manner.
  • Show that supplementation brought participants up to an optimal Omega-3 Index of 8% or greater.
  • Look at health outcomes such as heart attacks, cardiovascular deaths, hypertension, stroke, or depression.
  • Continue the study long enough for the beneficial effects of omega-3 supplementation to be measurable. For cardiovascular outcomes the American Heart Association has stated that at least two years are required to obtain meaningful results.

These are the kind of experiments that will be required to give definitive, reproducible results and resolve the confusion about the health effects of omega-3 fatty acids.

 

The Bottom Line

 

An accurate measure of omega-3 status has been developed and validated in recent years. It’s called the Omega-3 Index. Simply put, the Omega-3 Index is the percentage of EPA and DHA compared to 26 other fatty acids found in cellular membranes.

Although more work needs to be done, an Omega-3 Index of 4% or less is generally considered indicative of high cardiovascular risk while 8% or better is considered indicative of low cardiovascular risk.

Previous studies have shown an inverse correlation between Omega-3 Index and blood pressure. However, these studies have been done with older populations, many of whom had already developed high blood pressure.

From a public health point of view, it is much more interesting to investigate whether it might be possible to prevent high blood pressure in older adults by optimizing omega-3 intake in a young, healthy population, most of whom had not yet developed high blood pressure. Until now, there have been no studies looking at that population.

The study described in this article was designed to fill that gap. The participants in this study were ages 25-41, were healthy, and none of them had elevated blood pressure.

When the group with the highest Omega-3 Index (average = 5.8%) was compared with the group with the lowest Omega-3 Index (average = 4.6%):

  • Both systolic and diastolic blood pressure were decreased
  • Blood pressure measurements decreased linearly with increasing Omega-3 Index.

The authors concluded: “A higher Omega-3 Index is associated with statistically significant, clinically relevant, lower systolic and diastolic blood pressure in normotensive, young and healthy individuals. Diets rich omega-3 fatty acids may be a strategy for primary prevention of hypertension.”

Let me translate that last sentence into plain English for you. The authors were saying that optimizing omega-3 intake in young adults may slow the age-related increase in blood pressure and reduce the risk of them developing high blood pressure as they age. This may begin to answer the question “Do omega-3s lower blood pressure in young, healthy adults?”

Or even more simply put: Aging is inevitable. Becoming unhealthy is not.

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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