Vitamin C and Diabetes

Written by Dr. Steve Chaney on . Posted in Vitiman-C and Blood Sugar

Author: Dr. Stephen Chaney

 

vitamin c and blood sugar glucose testType 2 diabetes is increasing at an alarming rate. Between 1990 and 2010, the number of people in the US living with diabetes has more than tripled. In 2017 the CDC reported that 30.3 million Americans (9.4% of the population) had diabetes. Another 84.1 million had pre-diabetes, a condition which, if left untreated, will develop into diabetes within 5 years.

That is concerning, because type 2 diabetes can have devastating health consequences. It increases inflammation and oxidative damage. It significantly increases your risk of heart disease, Alzheimer’s Disease and some cancers. Then there is kidney disease, nerve pain, and loss of limbs.

It is the hyperglycemia (high blood sugar levels) associated with diabetes that plays a major role in many of these poor health outcomes. That is why so much effort is focused on helping people with type 2 diabetes gain better control of their blood sugar. Management of blood sugar levels in people with diabetes involves both medications and a healthy lifestyle (weight control, a healthy diet, and exercise). Unfortunately, despite their best efforts and the best efforts of their doctors, millions of Americans with diabetes struggle to control their blood sugar levels.

Is there a positive relationship between vitamin C and diabetes?

What if there were a simple, inexpensive intervention that could help diabetics control their blood sugar levels? Recent research suggests that vitamin C might be that intervention. Nobody is claiming that vitamin C is THE solution to blood sugar control. However, the recent research suggests it may be a useful addition to diabetes drugs and a healthy lifestyle.

 

Does Vitamin C Improve Blood Sugar Control?

 

vitamin c and blood sugar pillsThe idea that vitamin C may improve blood sugar control has been around for decades based on studies showing that vitamin C helps clear glucose from the circulation. Now, however, we are starting to understand how vitamin C does that.

But before I discuss how vitamin C may improve blood sugar control, the professor in me feels a need to explain what I call Diabetes 101. In type 1 diabetes the pancreas has become unable to produce insulin. In type 2 diabetes tissues have become resistant to the effects of insulin. I will focus on type 2 diabetes.

Glucose is the primary sugar in the bloodstream. Whenever blood sugar (glucose) increases, our pancreas responds by producing insulin. Insulin binds to receptors on our tissues and signals them to take up glucose and rapidly metabolize it. As a result, glucose is rapidly cleared from the circulation and blood sugar levels return to normal.

Type 2 diabetes is caused by insulin resistance. Simply put, our pancreas is still producing insulin, but our tissues have become less efficient at responding to it. Initially, the pancreas responds by overproducing insulin. A new homeostasis is achieved. Blood insulin levels are abnormally high, but glucose is still cleared from the circulation reasonably well. We call this pre-diabetes.

Eventually the pancreas loses the ability to overproduce insulin. Because our tissues are still insulin resistant, glucose is cleared from the circulation slowly. We now have trouble keeping blood sugar levels under control. We call this type 2 diabetes.

There are two major theories at present for why vitamin C may help diabetics control their blood sugar levels:

  • One theory holds that oxidative stress reduces the ability of the pancreas to release insulin. This theory suggests vitamin C improves insulin release from the pancreas, and the extra insulin overcomes insulin resistance and improves the ability of our tissues to clear glucose from the circulation.
  • The other theory holds that oxidative stress plays an important role in causing insulin resistance. This theory suggests vitamin C reduces insulin resistance and improves the clearance of glucose from the circulation by this mechanism.

There is some experimental evidence for both mechanisms. It may be that both play a role in vitamin C’s ability to improve blood sugar control.

How Were The Studies Done?

vitamin c and blood sugar studyIn terms of the effect of vitamin C on blood sugar control, there are two recent studies that have provided intriguing results.

The first study (Y. Song et al, Diabetes Care, 34: 108-114, 2011) was designed to see if supplementation with multivitamins or individual vitamin and mineral supplements affected the risk of developing diabetes among older US adults. It utilized data from the National Institutes of Health – American Association of Retired Persons Diet and Health Study.

The study enrolled 566,402 AARP members ages 50-71 in 1995-1996. Upon entry into the program, participants filled out a dietary survey that included supplement usage. In 2004-2006 a follow-up survey was mailed out to surviving participants that asked about occurrences of major chronic diseases.

Because the onset of a major disease is known to affect supplement usage, all participants with pre-existing diabetes or who developed diabetes prior to 2,000 were excluded from this analysis. Of the remaining 232,007 participants, 217,877 did not have diabetes and 14,130 had developed diabetes between 2000 and the end of the study.

The second study (SA Mason et al, Diabetes, Obesity and Metabolism, 21: 674-682, 2019 ) was a double blind, placebo controlled study design to determine whether supplemental vitamin C improved blood sugar control in people who already had type 2 diabetes.

In this study 31 adults (average age 62 years) were enrolled in the study. All the subjects were borderline obese and had type 2 diabetes. Five of the patients were being managed with lifestyle changes only. The other 26 patients were on one or more diabetes medications to help control their blood sugar levels.

The subjects were advised to avoid supplementation prior to the study. They were then given either 1,000 mg of vitamin C (two 500 mg capsules) or a placebo to take for 4 months. After the first 4-month period they were put on a “washout” protocol with no supplementation. Then they were put on a second 4-month regimen in which they received the opposite tablets (Those who received vitamin C during the first 4 months received a placebo during the second 4 months and vice versa.) Compliance with the protocol was determined by measuring blood levels of vitamin C.

The subjects were outfitted with a continuous blood glucose monitor for a 48-hour period at the beginning and end of each 4-month regimen. They were given standardized meals during those 48-hour test intervals and their blood sugar response to the meals was continuously monitored over the next 48 hours.

Vitamin C and Diabetes

 

vitamin c and blood sugar glucose meterThe results of the first study were:

  • Multivitamins and most of the individual supplements tested had no effect on the risk of developing diabetes over the next 10 years. The only supplements that reduced the risk of developing diabetes were vitamin C and calcium.
  • Vitamin C reduced the risk of developing diabetes by 9%.
  • The benefits of vitamin C appeared to be limited to individuals who did not use multivitamins and who had low dietary intake of vitamin C (No surprises there. Supplementation is usually most effective when it is filling in nutritional gaps).

This study has several obvious limitations:

  • It is an association study, so it does not prove cause and effect.
  • It does not tell us whether vitamin C prevents diabetes or simply improves blood sugar control in people who are borderline diabetic.
  • It did not measure how much supplemental vitamin C people were taking. However, based on what is available in the marketplace, it is probably safe to assume it was between 500 and 1,000 mg/day.

However, this study did lay the groundwork for the second study.

The results of the second study were that 4 months of vitamin C supplementation reduced:

  • The blood sugar response to standardized meals by 36%.
  • The duration of high blood sugar following a standardized meal by 1.7 hours.
  • The amount of time during the day with high blood sugar levels by 2.8 hours.

These are all important improvements for anyone with type 2 diabetes. In the words of the authors: “The improvement in total daily time spent with hyperglycemia [high blood sugar] is of potential clinical importance as the risk of complications in type 2 diabetes is strongly associated with previous hyperglycemia.”

The authors went on to say: “Compliance in the present study was high [people did not find it difficult to take 2 tablets a day] and the number of reported adverse effects was low, suggesting that vitamin C may be safely and consistently used in addition to [emphasis mine] primary diabetes treatment. Given the potential side effects with common anti-diabetic medications…, the idea that a relatively benign and inexpensive vitamin supplement might play a role in managing diabetes has particular appeal.”

Note: This was a very well-designed study. Its weakness is its small size. While it is consistent with other recent studies, larger clinical trials are needed to confirm this effect. 

What Do These Studies Mean For You?

vitamin c and blood sugar meaningThe idea that vitamin C may help with blood sugar control has been around for decades. These studies provide experimental support for that idea. While both studies have limitations, they are consistent with other recent studies. Much more research is needed, but it is good to finally see the hypothesis being rigorously tested.

So, what do these studies mean for you? Here is the take home message:

  • Although more studies are needed, vitamin C appears to help with blood sugar control.
  • We don’t know how much vitamin C is needed, but the most recent study was done with 1,000 mg/day. That is more than can be obtained from diet alone.
  • The improvement in blood sugar control was significant, but it was not huge. Vitamin C will not replace a healthier weight, a healthy lifestyle, and exercise.
  • You should think of vitamin C as something you add to the treatment plan your doctor recommends for type 2 diabetes. At best it may allow your doctor to reduce the amount of medication they prescribe.

If you have type diabetes, here are my recommendations:

  • If you are overweight, try to attain and maintain a healthier weight.
  • Eat a whole food, primarily plant-based diet. Avoid sodas, sweets, and highly processed foods. Eat a variety of fruits, vegetables, whole grains, and beans in their natural, unprocessed state. Include small amounts of meat, eggs, and dairy. Think of them as the garnish, not the main course.
  • Add a daily vitamin C supplement.
  • If that is not enough, ask your doctor what medications he or she recommends.

Other nutrients that may help are chromium, taurine and alpha lipoic acid. Herbs that may help are bitter melon and gymnema.

 

The Bottom Line

 

What is the association between vitamin C and diabetes? The idea that vitamin C may help with blood sugar control has been around for decades. Two recent studies provide experimental support for this idea. The second study showed that 4 months of 1,000 mg/day vitamin C supplementation reduced:

  • The blood sugar response to standardized meals by 36%.
  • The duration of high blood sugar following a standardized meal by 1.7 hours.
  • The duration of the day with high blood sugar levels by 2.8 hours.

These are all important improvements for anyone with type 2 diabetes. In the words of the authors: “The improvement in total daily time spent with hyperglycemia [high blood sugar] is of potential clinical importance as the risk of complications in type 2 diabetes is strongly associated with previous hyperglycemia.”

While this study has limitations, it is consistent with other recent studies. Much more research is needed, but it is good to finally see the hypothesis that vitamin C improves blood sugar control being rigorously tested.

So, what do these studies mean for you? Here is the take home message:

  • Although more studies are needed, vitamin C appears to help with blood sugar control.
  • We don’t know how much vitamin C is needed, but the most recent study was done with 1,000 mg/day. That is more than can be obtained from diet alone.
  • The improvement in blood sugar control was significant, but it was not huge. Vitamin C will not replace a healthier weight, a healthy lifestyle, and exercise.
  • You should think of vitamin C as something you add to the treatment plan your doctor recommends for type 2 diabetes. At best it may allow your doctor to reduce the amount of medication they prescribe.

For more details and my recommendations 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 (2)

  • Health Lines

    |

    Great newsletter how do I send this to my email contacts

    Doreen

    Reply

    • Dr. Steve Chaney

      |

      Dear Doreen,
      In each newsletter I have a spot at the beginning and the end which says something like “copy this link and send it to a friend”. Click on the word “link” and, once the article comes up, copy the URL and paste it into your email.

      If it is an old copy of the newsletter, go to https://healthtipsfromtheprofessor.com and type the appropriate term in the search box. In the case of this post either vitamin C or diabetes should locate the article for you. Then click on the article. Once it comes up, copy the URL into your email.

      Dr. Chaney

      Reply

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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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