VTE

Written by Dr. Steve Chaney on . Posted in Food and Health, Health Current Events, Supplements and Health

Benefits of Omega-3

Author: Dr. Stephen Chaney

venous-thomboembolism

 When a blood clot ends up in your lungs, it can be deadly. But that blood clot didn’t start out in your lungs. It initially formed in your veins where it is referred to as a thrombus. Then it broke off and migrated to your lungs – a process called venous thromboembolism or VTE. Venous thromboembolism is the third most common form of cardiovascular disease, killing around 100,000 Americans each year.

What if something as simple as adding more omega-3 fatty acids to your diet could dramatically decrease your risk of VTE? That’s exactly what a recent study (Hansen-Krone et al, J. Nutr., 144: 861-867, 2014) has suggested. It claims that one of the benefits of omega-3 in your diet may be to help prevent venous thromboembolism.

What Is Venous Thromboembolism or VTE?

As described above, venous thromboembolism starts when a blood clot (also called a thrombis) forms in a vein. About 2/3 of the time, the blood clot forms in the deep veins in the leg (called deep vein thrombosis or DVT) and stays there before eventually dissolving. The symptoms of deep vein thrombosis or DVT are generally leg pain and swelling.

About 1/3 of the time, the clot breaks loose and travels to the lung where it blocks blood flow to a portion of the lung (a process called pulmonary embolism). The symptoms of pulmonary embolism are severe shortness of breath, chest pain when breathing or coughing, and death! While the first two symptoms are pretty frightening, it’s the last symptom (death) that we’d really like to avoid.

Why Might Omega-3s Prevent Venous Thromboembolism or VTE?

One of the benefits of Omega-3s is they have been shown to reduce inflammation and platelet aggregation, two of the most important risk factors for venous thromboembolism. So it is logical to think that omega-3s might help reduce the risk. However, good scientists don’t rely on logic alone. They test their hypotheses by doing clinical studies.

Unfortunately, the results of previous clinical studies have been mixed. One study showed a protective effect of omega-3s, but two other studies found no correlation between omega-3 fatty acid intake and VTE. However, these studies had some significant limitations:

benefits-of-fish-oil-pills

  • They were all performed with populations in the United States where fish consumption is relatively low and many of the fish have low omega-3 content. As a consequence omega-3 fatty acid intake was low and there wasn’t much of a range in intake.
  • Some of the studies did not ask about the use of omega-3 supplements. In a country where 37% of the population takes fish oil supplements, that is a huge omission.
  • They did not measure omega-3 fatty acid levels in the blood to verify that their dietary surveys were accurate.

 

Do Omega-3s Prevent Venous Blood Clots or DVT?

pulmonary-embolism

The current study (Hansen-Krone et al, J. Nutr., 144: 861-867, 2014) followed 23,631 people aged 25-97 from Tromso, Norway for 16 years.

  • The participants filled out a comprehensive dietary survey at the time of enrollment where they indicated the number of times per week they ate fish and how often they used fish oil supplements.
  • The scientists in charge of the study verified the estimated omega-3 intake from the dietary analysis in a subgroup of the population by measuring omega-3 fatty acid levels in their blood.
  • Finally, they utilized Norway’s excellent health records to determine how many of the people in their trial experienced a venous thromboembolism – either fatal or non-fatal.

The results were pretty impressive:

  • Blood level measurements of omega-3 fatty acids verified the omega-3 intake estimates from the dietary survey. There was a direct correlation between estimated intake and blood levels of the omega-3 fatty acids.
  • Those participants who ate fish most often (≥3 times/week) were 22% less likely to experience a VTE than those who ate fish least often (1-2 times/week). That difference was borderline significant.
  • Those participants who ate fish most often and took fish oil supplements were 48% less likely to experience a venous thromboembolism than those who ate fish least often and took no fish oil supplements. That difference was highly significant.

 

Strengths & Weaknesses of the Study

Since not all of the previous clinical studies have reached the same conclusion, it is important to look at the strengths and weaknesses of the study compared to the previous studies.

Strengths of the Study:

  • Tromso is located on the northeast coast of Norway, so fish consumption is high and most of the local fish are excellent sources of omega-3 fatty acids. Consequently, omega-3 intake was relatively high, which significantly increases the chance of seeing an effect if one exists. Fish consumption in the US is generally lower and not all of the fish consumed are good sources of omega-3s.
  • The study also took into account the use of omega-3 supplements. Some of the US studies did not.
  • The estimates of omega-3 intake from the dietary survey were verified by blood analysis of omega-3 fatty acids.

Weaknesses of the Study:

  • The amount of omega-3 fatty acids in the supplements was not recorded, so it is unclear what level of omega-3 fatty acid intake was required to see a significant decrease in VTE risk. This will make it difficult for future investigators to repeat the study.
  • They did not measure other nutrients that might affect the venous thromboembolism risk.

 

The Bottom Line

1)     VTE is a serious condition with a high rate of mortality.

2)     A recent study suggests that a combination of high fish consumption and fish oil supplement use may significantly decrease the risk of venous thromboembolism.

3)     It is interesting to note that even three servings/week of omega-3 rich fish was not enough to cause a significant decrease in venous thromboembolism risk. It required additional omega-3s from fish oil supplements before the decreased risk was significant.

4)     Not all previous studies have come to the same conclusion. So while the most recent study had several improvements in design compared to previous studies, the case can’t be considered closed. More studies are clearly needed.

5)     This study suggests that omega-3 fatty acids may help prevent VTE from occurring. You should not consider them to be a treatment for the condition. If you are experiencing symptoms of venous thromboembolism (leg pain and swelling for deep vein thrombosis (DVT) or shortness of breath and pain when breathing for pulmonary embolism), don’t reach for your fish oil capsules. Call your doctor right away.

 

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)

  • Joanne M. Cottrell

    |

    I enjoy reading Dr Cheney’s newsletters and appreciate his reference to the particular studies. There is just so much hype out there and the information that is being presented to the masses has no scientific basis. I like fish, however I don’t consume it three times a week. Walleye, whitefish, Cod, and many of the types that are mild in taste do not contain the Ogema 3’s. This article is making me realize that I do need to be consistent in finding and taking a high quality Omega 3 supplement. Thank You Dr. Chaney!

    Reply

  • Muriel Donaldson

    |

    Very interesting. Looking forward to your newsletters.
    Muriel

    Reply

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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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