Risk Factors of Prostate Cancer

Written by Dr. Steve Chaney on . Posted in current health articles, Nutritiion, Vitamins and Health

Vitamin D Deficiency?

Author: Dr. Stephen Chaney

Vitamin D

Is vitamin D deficiency one of the risk factors of prostate cancer? What if something as simple as maintaining optimal vitamin D status could decrease your risk of prostate cancer? There is a lot of indirect evidence suggesting that vitamin D deficiency might affect your risk of developing prostate cancer. For example:

  • Prostate cancer incidence and vitamin D deficiency parallel each other. Both are highest in northern latitudes, in African American men, and in older men.
  • Prostate cancer mortality rates are highest for patients diagnosed in the winter and at Northern latitudes.

However, clinical studies looking at the correlation between 25-hydroxy vitamin D (the biologically active form of vitamin D in the blood) and prostate cancer incidence have been inconsistent. Because of this there has been considerable controversy in the scientific community as to whether or not there was any correlation between vitamin D deficiency and prostate cancer.

Vitamin D Deficiency and Cancer

That’s what makes the recent headlines suggesting that vitamin D is associated with decreased risk of aggressive prostate cancer so interesting. Does this study show low vitamin D to be one of the risk factors of prostate cancer? Have the conflicting data on vitamin D deficiency and prostate cancer finally been resolved or is this just another case of dueling headlines? Let’s start by looking at the study itself.

This study (Murphy et al, Clinical Cancer Research, 20: 2289-2299, 2014) enrolled 667 men, aged 40-79 (average age = 62), from five urology clinics in Chicago over a four year period. These were all men who were undergoing their first prostate biopsy because of elevated serum PSA levels or an abnormal DRE (that’s doctor talk for digital rectal exam – the least favorite part of every guy’s physical exam). The clinics also drew blood and measured each patient’s 25-hydroxy vitamin D level at the time of the prostate biopsy.

This study had a number of important strengths:

  • It was conducted at a northern latitude. Because of that 41.2% of the men in this study were vitamin D deficient (<20 ng/ml) and 15.7% were severely vitamin D deficient (<12 ng/ml). That’s important because you need a significant percentage of patients with vitamin D deficiency to have any chance of seeing an effect of vitamin D status on prostate cancer risk.
  • The study had equal numbers of African American and European American men. That’s important because African American men have significantly lower 25-hydroxy vitamin D status and significantly higher risk of prostate cancer than European American men.
  • All of the men enrolled in the study had elevated PSA levels or abnormal DREs. That’s important because it meant that all of the men enrolled in the study were at high risk of having prostate cancer. That made the correlation between vitamin D status and prostate cancer easier to detect.
  • This was the first study to correlate 25-hydroxyvitamin D levels with prostate biopsies at the time of biopsy. That’s important because it allowed the investigators to distinguish between aggressive tumors (which require immediate treatment and have a higher probability of mortality) and slow growing tumors (which may simply need to be monitored).

The results were pretty dramatic:

  • In African American men vitamin D deficiency (<20 ng/ml) was associated with an increased risk of prostate cancer diagnosis at time of biopsy.
  • In both European American and African American men severe vitamin D deficiency (<12 ng/ml) was associated with increased risk of aggressive prostate cancer diagnosis at time of biopsy.

The authors concluded: “Our work supports the hypothesis that 25-hydroxy vitamin D is a potential biomarker that plays a clinically significant role in prostate cancer, and it may be a useful modifiable risk factor in the disease”.

That’s “science speak” for “adequate vitamin D status may help prevent prostate cancer” or “low vitamin D may indeed be one of the risk factors of prostate cancer.”

VitaminD-smashes-cancer

Why Have Some Studies Failed To Find A Correlation Between Vitamin D Deficiency and Prostate Cancer?

The authors of the current study had an interesting hypothesis for why some previous studies have not seen an association between vitamin D status and prostate cancer risk. When you compare all of the previous studies, the strongest correlations between vitamin D deficiency and prostate cancer were the studies conducted at northern latitudes, in African American men, or focusing on aggressive prostate cancer as an end point.

That offers a few clues as to why other studies may have failed to find a link between vitamin D status and prostate cancer risk. For example:

  • The clue that the correlation between vitamin D deficiency and prostate cancer risk was strongest at northern latitudes and with African American men suggests that you need to have a significant percentage of subjects with deficient or very deficient levels of 25-hydroxy vitamin D before you can see a correlation. Other studies may have failed to show a correlation simply because most of the men in the study had normal vitamin D status.
  • The clue that the correlation is strongest for aggressive prostate cancer is more subtle. The authors hypothesized that prostate cancer develops over a lifetime. If that is the case, measuring vitamin D deficiency at the time of diagnosis may not represent the lifetime vitamin D status. The vitamin D status could have decreased because the men were older or had become overweight, or the vitamin D status could have changed simply because they moved from one geographical location to another.

In contrast, the progression from benign to aggressive prostate cancer is generally short term, so it would be affected by the most recent vitamin D status. If that is the case, then the vitamin D status measured at the time of diagnosis may more accurately reflect the vitamin D deficiency that affected the aggressiveness of the cancer.

 

The Bottom Line

1)     The latest study suggests that vitamin D deficiency (<20 ng/ml serum 25-hydroxy vitamin D) may significantly increase the risk of prostate cancer. The correlation between low vitamin D status and prostate cancer risk is strongest for African American men.

2)     The study also suggests that severe vitamin D deficiency (<12 ng/ml serum 25-hydroxyvitamin D) may significantly increase the risk of aggressive prostate cancer in both African American and European American men.

3)     This is a very well done study, and it is consistent with many, but not all, of the previous studies. Clearly more research needs to be done. Future research should be focused on high risk subjects and subjects with low vitamin D status so that the correlation between vitamin D status and prostate cancer risk can be adequately tested.

4)     This is another example of why I recommend that you have your serum 25-hydroxy vitamin D level measured on a regular basis and that you aim to keep it in the normal range (20-80 ng/ml). Some experts believe that 30-80 ng/ml is optimal.

5)     If you are African American, overweight, live in northern latitudes or it is winter, you may need supplemental vitamin D3. 1,000 – 4,000 IU/day of vitamin D3 is generally considered to be safe. If higher amounts are needed to normalize your 25-hydroxy vitamin D levels I recommend that you consult your physician for the appropriate dose.

 

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)

  • Theresa Bankert

    |

    Is there a version #1 of the Myths e-books? The one I downloaded says #2. Just curious.
    Thank you,
    Theresa

    Reply

    • Dr. Steve Chaney

      |

      Dear Theresa,

      Book #1 of the “Myths” eBook series is still in preparation. I’m following the Star Wars model 🙂

      Dr. Chaney

      Reply

  • support prostate health

    |

    Everything is very open with a precise explanation of the challenges.

    It was truly informative. Your site is very helpful.
    Many thanks for sharing!

    Reply

  • omega 3 fatty acids prostate cancer risk

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    Cancer cann often be detected through a rectal examination conducted byy a doctor and through a prostate-specific antigen (PSA)
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Latest Article

A Low Carb Diet and Weight Loss

Posted January 15, 2019 by Dr. Steve Chaney

Do Low-Carb Diets Help Maintain Weight Loss?

Author: Dr. Stephen Chaney

 

low carb dietTraditional diets have been based on counting calories, but are all calories equal? Low-carb enthusiasts have long claimed that diets high in sugar and refined carbs cause obesity. Their hypothesis is based on the fact that high blood sugar levels cause a spike in insulin levels, and insulin promotes fat storage.

The problem is that there has been scant evidence to support that hypothesis. In fact, a recent meta-analysis of 32 published clinical studies (KD Hall and J Guo, Gastroenterology, 152: 1718-1727, 2017 ) concluded that low-fat diets resulted in a higher metabolic rate and greater fat loss than isocaloric low-carbohydrate diets.

However, low-carb enthusiasts persisted. They argued that the studies included in the meta-analysis were too short to adequately measure the metabolic effects of a low-carb diet. Recently, a study has been published in the British Medical Journal (CB Ebbeling et al, BMJ 2018, 363:k4583 ) that appears to vindicate their position.

Are low carb diets best for long term weight loss?

Low-carb enthusiasts claim the study conclusively shows that low-carb diets are best for losing weight and for keeping it off once you have lost it. They are saying that it is time to shift away from counting calories and from promoting low-fat diets and focus on low-carb diets instead if we wish to solve the obesity epidemic. In this article I will focus on three issues:

  • How good was the study?
  • What were its limitations?
  • Are the claims justified?

 

How Was The Study Designed?

low carb diet studyThe investigators started with 234 overweight adults (30% male, 78% white, average age 40, BMI 32) recruited from the campus of Framingham State University in Massachusetts. All participants were put on a diet that restricted calories to 60% of estimated needs for 10 weeks. The diet consisted of 45% of calories from carbohydrate, 30% from fat, and 25% from protein. [So much for the claim that the study showed low-carb diets were more effective for weight loss. The diet used for the weight loss portion of the diet was not low-carb.]

During the initial phase of the study 161 of the participants achieved 10% weight loss. These participants were randomly divided into 3 groups for the weight maintenance phase of the study.

  • The diet composition of the high-carb group was 60% carbohydrate, 20% fat, and 20% protein.
  • The diet composition of the moderate-carb group was 40% carbohydrate, 40% fat, and 20% protein.
  • The diet composition of the low-carb group was 20% carbohydrate, 60% fat, and 20% protein.

Other important characteristics of the study were:

  • The weight maintenance portion of the study lasted 5 months – much longer than any previous study.
  • All meals were designed by dietitians and prepared by a commercial food service. The meals were either served in a cafeteria or packaged to be taken home by the participants.
  • The caloric content of the meals was individually adjusted on a weekly basis so that weight was kept within a ± 4-pound range during the 5-month maintenance phase.
  • Sugar, saturated fat, and sodium were limited and kept relatively constant among the 3 diets.

120 participants made it through the 5-month maintenance phase.

 

Do Low-Carb Diets Help Maintain Weight Loss?

low carb diet maintain weight lossThe results were striking:

  • The low-carb group burned an additional 278 calories/day compared to the high-carb group and 131 calories/day more than the moderate-carbohydrate group.
  • These differences were even higher for those individuals with higher insulin secretion at the beginning of the maintenance phase of the study.
  • These differences lead the authors to hypothesize that low-carb diets might be more effective for weight maintenance than other diets.

 

What Are The Pros And Cons Of This Study?

low carb diet pros and consThis was a very well-done study. In fact, it is the most ambitious and well-controlled study of its kind. However, like any other clinical study, it has its limitations. It also needs to be repeated.

The pros of the study are obvious. It was a long study and the dietary intake of the participants was tightly controlled.

As for cons, here are the three limitations of the study listed by the authors:

#1: Potential Measurement Error: This section of the paper was a highly technical consideration of the method used to measure energy expenditure. Suffice it to say that the method they used to measure calories burned per day may overestimate calories burned in the low-carb group. That, of course, would invalidate the major findings of the study. It is unlikely, but it is why the study needs to be repeated using a different measure of energy expenditure.

#2: Compliance: Although the participants were provided with all their meals, there was no way of being sure they ate them. There was also no way of knowing whether they may have eaten other foods in addition to the food they were provided. Again, this is unlikely, but cannot be eliminated from consideration.

#3: Generalizability: This is simply an acknowledgement that the greatest strength of this study is also its greatest weakness. The authors acknowledged that their study was conducted in such a tightly controlled manner it is difficult to translate their findings to the real world. For example:

  • Sugar and saturated fat were restricted and were at very similar levels in all 3 diets. In the real world, people consuming a high-carb diet are likely to consume more sugar than people in the other diet groups. Similarly, people consuming the low-carb diet are likely to consume more saturated fat than people in the other diet groups.
  • Weight was kept constant in the weight maintenance phase by constantly adjusting caloric intake. Unfortunately, this seldom happens in the real world. Most people gain weight once they go off their diet – and this is just as true with low-carb diets as with other diets.
  • The participants had access to dietitian-designed prepared meals 3 times a day for 5 months. This almost never happens in the real world. The authors said “…these results [their data] must be reconciled with the long-term weight loss trials relying on nutrition education and behavioral counseling that find only a small advantage for low carbohydrate compared with low fat diets according to several recent meta-analyses.” [I would add that in the real world, people do not even have access to nutritional education and behavioral modification.]

 

low carb diet and youWhat Does This Study Mean For You?

  • This study shows that under very tightly controlled conditions (dietitian-prepared meals, sugar and saturated fat limited to healthy levels, calories continually adjusted so that weight remains constant) a low-carb diet burns more calories per day than a moderate-carb or high-carb diet. These findings show that it is theoretically possible to increase your metabolic weight and successfully maintain a healthy weight on a low-carb diet. These are the headlines you probably saw. However, a careful reading of the study provides a much more nuanced viewpoint. For example, the fact that the study conditions were so tightly controlled makes it difficult to translate these findings to the real world.
  • In fact, the authors of the study acknowledged that multiple clinical studies show this almost never happens in the real world. These studies show that most people regain the weight they have lost on low-carb diets. More importantly, the rate of weight regain is virtually identical on low-carb and low-fat diets. Consequently, the authors of the current study concluded “…translation [of their results to the real world] requires exploration in future mechanistic oriented research.” Simply put, the authors are saying that more research is needed to provide a mechanistic explanation for this discrepancy before one can make recommendations that are relevant to weight loss and weight maintenance in the real world.
  • The authors also discussed the results of their study in light of a recent, well-designed 12-month study (CD Gardener et al, JAMA, 319: 667-669, 2018 ) that showed no difference in weight change between a healthy low-fat versus a healthy low-carbohydrate diet. That study also reported that the results were unaffected by insulin secretion at baseline. The authors of the current study noted that “…[in the previous study] participants were instructed to minimize or eliminate refined grains and added sugars and maximize intake of vegetables. Probably for this reason, the reported glycemic load [effect of the diet on blood sugar levels] of the low-fat diet was very low…and similar to [the low-carb diet].” In short, the authors of the current study were acknowledging that diets which focus on healthy, plant-based carbohydrates and eliminate sugar, refined grains, and processed foods may be as effective as low-carb diets for helping maintain a healthy weight.
  • This would also be consistent with previous studies showing that primarily plant-based, low-carb diets are more effective at maintaining a healthy weight and better health outcomes long-term than the typical American version of the low-fat diet, which is high in sugar and refined grains. In contrast, meat-based, low-carb diets are no more effective than the American version of the low-fat diet at preventing weight gain and poor health outcomes. I have covered these studies in detail in my book “Slaying The Food Myths.”

Consequently, the lead author of the most recent study has said: “The findings [of this study] do not impugn whole fruits, beans and other unprocessed carbohydrates. Rather, the study suggests that reducing foods with added sugar, flour, and other refined carbohydrates could help people maintain weight loss….” This is something we all can agree on, but strangely this is not reflected in the headlines you may have seen in the media.

The Bottom Line

 

  • A recent study compared the calories burned per day on a low-carb, moderate-carb, and high-carb diet. The study concluded that the low-carb diet burned significantly more calories per day than the other two diets and might be suitable for long-term weight control. If confirmed by subsequent studies, this would be the first real evidence that low-carb diets are superior for maintaining a healthy weight.
  • However, the study has some major limitations. For example, it used a methodology that may overestimate the benefits of a low-carb diet, and it was performed under tightly controlled conditions that can never be duplicated in the real world. As acknowledged by the authors, this study is also contradicted by multiple previous studies. Further studies will be required to confirm the results of this study and show how it can be applied in the real world.
  • In addition, the kind of carbohydrate in the diet is every bit as important as the amount of carbohydrate. The authors acknowledge that the differences seen in their study apply mainly to carbohydrates from sugar, refined grains, and processed foods. They advocate diets with low glycemic load (small effects on blood sugar and insulin levels) and acknowledge this can also be achieved by incorporating low-glycemic load, plant-based carbohydrates into your diet. This is something we all can agree on, but strangely this is not reflected in the headlines you may have seen in the media.
  • Finally, clinical studies report averages, but none of us are average. When you examine the data from the current study, it is evident that some participants burned more calories per hour on the high-carb diet than other participants did on the low carb diet. That reinforces the observation that some people lose weight more effectively on low-carb diets while others lose weight more effectively on low-fat diets. If you are someone who does better on a low-carb diet, the best available evidence suggests you will have better long-term health outcomes on a primarily plant-based, low-carb diet such as the low-carb version of the Mediterranean diet.

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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