Vitamin D Deficiency

Written by Dr. Steve Chaney on . Posted in Health Current Events, Healthy Living, Supplements and Health, Vitamins and Health

What Is The Real Vitamin D Story?

Author: Dr. Stephen Chaney

 

Vitamin DIf you are like most people, you probably don’t know what to believe about vitamin D deficiency. Some experts tout vitamin D as a miracle nutrient that will help you lead a longer, healthier life. They leave you with the impression that everyone should be supplementing with vitamin D.

Other experts tell you that the supposed benefits of vitamin D are all hype. They tell you not to waste your money on vitamin D supplements.

When you pull back the curtain and look at the clinical studies behind the headlines, a pattern begins to emerge.

Most of the studies that support a role for vitamin D in preventing heart disease, preventing cancer and extending life have been population studies. They have compared populations with low vitamin D intake with populations with adequate vitamin D intake. While population studies are good for suggesting associations, they have their limitations:

  • Population studies are good at suggesting associations, but they do not prove cause and effect.
  • With population studies it is also very difficult to eliminate what scientists call “confounding variables”. Let me give you an example. Suppose someone had low 25-hydroxyvitamin D levels in their blood because they sat around all day watching TV and never got out in the sun. If they got sick you wouldn’t really know whether it was due to low 25-hydroxyvitamin D levels or due to inactivity. In this case, inactivity would be a confounding variable.

On the other hand, most of the studies that fail to find any benefit of vitamin D are double blind, placebo-controlled intervention studies in which one group was given supplemental vitamin D and the other group was given a placebo. While these studies are considered the most reliable clinical studies, they have their limitations as well.

  • In the case of vitamin D many of these studies were done with a cross section of the population in which most of the participants already had adequate blood levels of 25-hydroxyvitamin D at the start of the study. Those studies are incapable of telling us whether correcting a vitamin D deficiency would have been beneficial.
  • Even when the intervention studies focus on participants with low vitamin D status at the start of the trial they have another significant limitation. They are all short term studies. Typically, the best of these studies last no more than a couple of years. Longer term studies are far too expensive. In contrast, diseases such as heart disease and cancer take decades to develop. A one or two year intervention with vitamin D simply may not be sufficient to correct the damage caused by decades of vitamin D deficiency

This is the current dilemma that is creating all of the confusion in the vitamin D story. For the most part, population studies and intervention studies are coming to very different conclusions. And both kinds of studies have inherent limitations that are difficult to overcome.

Fortunately, a new kind of clinical study has been developed in recent years that overcomes the limitations of both population studies and intervention studies.

A New Kind of Clinical Study

Bad GenesThe new approach is something called mendelian randomization. I apologize for the scientific jargon, but let me explain. In this case you are separating your population based on genetic variation rather than on the basis of biochemical or behavioral differences.

 

For example, in the clinical study I will describe in a minute the population was separated into groups based on genetic variations in the DHCR7 and CYP2R1 genes. The first gene is involved in the biosynthesis of cholesterol, which is a precursor of vitamin D, and the second gene converts vitamin D to 25-hydroxyvitamin D. Both genes affect blood levels of 25-hydroxyvitamin D.

This kind of study has several unique strengths:

  • Genetic variations are unaffected by confounding variables such as sun exposure, obesity, smoking, inactivity, and poor diet. If the study population is large enough, those confounding variables will be equally distributed among groups that are selected solely on the basis of genetic variations.
  • These studies are long term by definition. If someone has a genetic variant that lowers their 25-hydroxyvitamin D level, it will do so for their entire lifetime. They can increase their vitamin D status by sun exposure, for example, but their blood levels of 25 hydroxyvitamin D will always be less than someone with equal sun exposure who does not have that genetic variant.
  • Because these studies reflect lifelong exposure to 25-hydroxyvitamin D they are ideally suited for measuring the effect of vitamin D status on mortality and diseases that take decades to develop.

Do Vitamin D Genes Affect Mortality?

This study (S. Afzal et al, The British Medical Journal, 2014;p 349:g6330 doi: 10.1136/bmj.g6330) combined the data from three clinical studies conducted in Copenhagen between 1976 and 2013. The age of the participants ranged from 20 to 100 years and the follow-up was 6-19 years. 95,766 participants in these studies were genotyped for variants in the DHCR7 and CYP2R1 genes which were known to affect 25-hydroxyvitamin D levels. 35,334 of those participants also had blood 25-hydroxyvitamin D levels determined. By the end of the study 10,349 of the participants had died.

  • The individual genetic variants included in this study caused a relatively small (1.9 nmol/L) decrease in blood levels of 25-hydroxyvitamin D. However, because this was a very large study and the participants with those genetic variants were exposed to lower 25-hydroxyvitamin D levels for their entire lifespan, the decreased 25-vitamin D levels were associated with significant increases in all cause mortality and cancer mortality, but not with increased cardiovascular mortality.
  • When they extrapolated to a genetically caused 20 nmol/L decrease in 25-hydroxyvitamin D, the decrease in 25-hdroxyvitamin D was associated with a 30% increase in all cause mortality and a 30% increase in cancer mortality.

What Kind Of Studies Are Needed Next?

The authors noted that this is the first study of its kind, so it obviously needs to be confirmed by other large mendelian randomization studies that test the link between vitamin D status and mortality.

Ideally, it should also be verified by double blind, placebo controlled intervention studies, but that may not be possible. If one really wanted to verify this study, the intervention study should start with a population group with 25-hydroxyvitamin D levels at least 20 nmol/L below what is considered adequate and provide them with enough supplemental vitamin D to increase their 25-hydroxyvitamin D to the adequate range. That is difficult, but doable.

However, the intervention study would also need to be long enough (decades perhaps) to prevent cancer from developing. That kind of study will probably never be done.

 

The Bottom Line

  • The relationship between vitamin D status and mortality has been investigated with a new type of clinical study based on what is called mendelian randomization. Population groups were segregated based on genetic variations in two genes that affect blood 25-hydroxyvitamin D levels (a measure of vitamin D status).
  • This study concluded that a genetically determined decrease of 20 nmol/L in blood 25-hydroxyvitamin D was associated with a 30% increase in all cause mortality and a 30% increase in cancer mortality, but had no significant effect on cardiovascular mortality.
  • This kind of study is particularly strong because it measures the affect of lifelong exposure to 25-hydroxyvitamin D. This is important when assessing the effect of vitamin D status on mortality and diseases such as cancer that take decades to develop. In contrast, the double blind, placebo controlled intervention studies that are consider the “Gold Standard” for clinical studies may be too short term to adequately assess the effect of vitamin D status on cancer or all cause mortality.
  • This study supports the benefit of maintaining optimal vitamin D status, but it is the first clinical study of its kind and needs to be confirmed by other studies.
  • In the meantime, there is no harm to in maintaining your blood levels of 25-hydroxyvitamin D in the optimal range through diet, sun exposure and supplementation. This study suggests it just may help you live a longer, healthier life.

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)

  • Doreen Harrison

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    Love your newsletter, Health Tips From The \professor. I am on you list and want to continue to be so. Thank you for the work you do. I would like to include some of your work in my monthly newsletters if that is OK with you,

    greetings from Canada

    Doreen

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Latest Article

Can Plant-based Diets Be Unhealthy?

Posted September 10, 2019 by Dr. Steve Chaney

Do Plant-Based Diets Reduce Heart Disease Deaths?

Author: Dr. Stephen Chaney

 

plant-based diets vegetablesPlant-based diets have become the “Golden Boys” of the diet world. They are the diets most often recommended by knowledgeable health and nutrition professionals. I’m not talking about all the “Dr. Strangeloves” who pitch weird diets in books and the internet. I am talking legitimate experts who have spent their life studying the impact of nutrition on our health.

Certainly, there is an overwhelming body of evidence supporting the claim that plant-based diets are healthy. Going on a plant-based diet can help you lower blood pressure, inflammation, cholesterol and triglycerides. People who consume a plant-based diet for a lifetime weigh less and have decreased risk of heart disease, diabetes, and cancer.

But, can a plant-based diet be unhealthy? Some people consider a plant-based diet to simply be the absence of meat and other animal foods. Is just replacing animal foods with plant-based foods enough to make a diet healthy?

Maybe not. After all, sugar and white flour are plant-based food ingredients. Fake meats of all kinds abound in our grocery stores. Some are very wholesome, but others are little more than vegetarian junk food. If you replace animal foods with plant-based sweets, desserts, and junk food, is your diet really healthier?

While the answer to that question seems obvious, very few studies have asked that question. Most studies on the benefits of plant-based diets have compared population groups that eat a strictly plant-based diet (Seventh-Day Adventists, vegans, or vegetarians) with the general public. They have not looked at variations in plant food consumption within the general public. Nor have they compared people who consume healthy and unhealthy plant foods.

This study (H Kim et al, Journal of the American Heart Association, 8:e012865, 2019) was designed to fill that void.

 

How Was The Study Done?

plant-based diets studyThis study used data collected from 12,168 middle aged adults in the ARIC (Atherosclerosis Risk in Communities) study between 1987 and 2016.

The participant’s usual intake of foods and beverages was assessed by trained interviewers using a food frequency questionnaire at the time of entry into the study and again 6 years later.

Participants were asked to indicate the frequency with which they consumed 66 foods and beverages of a defined serving size in the previous year. Visual guides were provided to help participants estimate portion sizes.

The participant’s adherence to a plant-based diet was assessed using four different well-established plant-based diet scores. For the sake of simplicity, I will include 3 of them in this review.

  • The PDI (Plant-Based Diet Index) categorizes foods as either plant foods or animal foods. A high PDI score means that the participant’s diet contains more plant foods than animal foods. A low PDI score means the participant’s diet contains more animal foods than plant foods.
  • The hPDI (healthy plant-based diet index) is based on the PDI but emphasizes “healthy” plant foods. A high hPDI score means that the participant’s diet is high in healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, coffee and tea) and low in animal foods.
  • The uPDI (unhealthy plant-based diet index) is based on the PDI but emphasizes “unhealthy” plant foods. A high uPDI score means that the participant’s diet is high in unhealthy plant foods (refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts) and low in animal foods.

For statistical analysis the scores from the various plant-based diet indices were divided into 5 equal groups. In each case, the group with the highest score consumed the most plant foods and least animal foods. The group with the lowest score consumed the least plant foods and the most animal foods.

The health outcomes measured in this study were heart disease events, heart disease deaths, and all-cause deaths. Again, for the sake of simplicity, I will only include 2 of these outcomes (heart disease deaths and all-cause deaths) in this review. The data on deaths were obtained from state death records and the National Death Index. (Yes, your personal information is available on the web even after you die.)

 

Do Plant-Based Diets Reduce Heart Disease Deaths?

plant-based diets reduce heart deathsThe participants in this study were followed for an average of 25 years.

The investigators looked at heart disease deaths over the 25 years and compared people with the highest intake of plant foods to people with the highest intake of red meat and other animal foods. The results were:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, coffee and tea) had a 19-32% lower risk of dying from heart disease than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods (refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts) had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

When the investigators looked at all-cause deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had an 11-25% lower risk of dying from any cause than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

What Else Did The Study Show?

The investigators made a couple of other interesting observations:

  • The association of the overall diet with heart disease and all-cause deaths was stronger than the association of individual food components. This underscores the importance of looking at the effect of the whole diet on health outcomes rather than the “magic” foods you hear about on Dr. Strangelove’s Health Blog.
  • Diets with the highest amount of healthy plant foods were associated with higher intake of carbohydrates, plant protein, fiber, and micronutrients, including potassium, magnesium, iron, vitamin A, vitamin C, folate, and lower intake of saturated fat and cholesterol.
  • Diets with the highest amount of unhealthy plant foods were associated with higher intake of calories and carbohydrates and lower intake of fiber and micronutrients.

The last two observations may help explain some of the health benefits of plant-based diets.

 

Can Plant-Based Diets Be Unhealthy?

plant-based diets unhealthy cookiesNow, let’s return to the question I asked at the beginning of this article: “Can plant-based diets be unhealthy?” Although some previous studies have suggested that unhealthy plant-based diets might increase the risk of heart disease, this study did not show that.

What this study did show was that an unhealthy plant-based diet was no better for you than a diet containing lots of red meat and other animal foods.

If this were the only conclusion from this study, it might be considered a neutral result. However, this result clearly contrasts with the data from this study and many others showing that both plant-based diets in general and healthy plant-based diets reduce the risk of heart disease deaths and all-cause deaths compared to animal-based diets.

The main message from this study is clear.

  • Replacing red meat and other animal foods with plant foods can be a healthier choice, but only if they are whole, minimally processed plant foods like whole grains, fruits, vegetables, nuts, legumes, coffee and tea.
  • If the plant foods are refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts, all bets are off. You may be just as unhealthy as if you kept eating a diet high in red meat and other animal foods.

There is one other subtle message from this study. This study did not compare vegans with the general public. Everyone in the study was the general public. Nobody in the study was consuming a 100% plant-based diet.

For example:

  • The group with the highest intake of plant foods consumed 9 servings per day of plant foods and 3.6 servings per day of animal foods.
  • The group with the lowest intake of plant foods consumed 5.4 servings per day of plant foods and 5.6 servings per day of animal foods.

In other words, you don’t need to be a vegan purist to experience health benefits from adding more whole, minimally processed plant foods to your diet.

 

The Bottom Line

A recent study analyzed the effect of consuming plant foods on heart disease deaths and all-cause deaths over a 25-year period.

When the investigators looked at heart disease deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had a 19-32% lower risk of dying from heart disease than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

When the investigators looked at all-cause deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had an 11-25% lower risk of dying from any cause than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

The main message from this study is clear.

  • Replacing red meat and other animal foods with plant foods can be a healthier choice, but only if they are whole, minimally processed plant foods like whole grains, fruits, vegetables, nuts, legumes, coffee and tea.
  • If the plant foods are refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts, all bets are off. You may be just as unhealthy as if you kept eating a diet high in red meat and other animal foods.

A more subtle message from the study is that you don’t need to be a vegan purist to experience health benefits from adding more whole, minimally processed plant foods to your diet. The people in this study were not following some special diet. The only difference was that some of the people in this study ate more plant foods and others more animal foods.

For more details on the study, 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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