Can You Eat Spinach For Muscle Growth

Written by Dr. Steve Chaney on . Posted in Exercise, muscle growth

Was Popeye Right?

Author: Dr. Stephen Chaney

can eat spinach for muscle growthYou may have seen the recent headlines proclaiming that eating spinach will make you stronger. The more “mature” adults among my readers may remember the Popeye cartoons of our youth. Every time Popeye was on the brink of disaster he would down a can of spinach and become superhuman. Was Popeye right? Can spinach actually improve strength and endurance?  Can you eat spinach for muscle growth?  To answer those questions, I analyzed the study behind the headlines.

The short answer is that there may be some truth to the headlines, but you would never be able to prove it from the study they quoted.

Even worse, this study and the headlines it generated are typical of the sports nutrition marketplace. There are far too many headlines and sports nutrition products based on weak and inconclusive studies.

Spinach for Muscle Growth?

spinachLet’s start at the beginning. In the first place the study behind the headlines (De Smet et al., Frontiers In Physiology, 7: 233-244, 2016) did not actually use spinach. In fact, participants were advised to avoid nitrate-rich foods like spinach and beets during the study.

The study enrolled moderately-trained male students from the University of Leuven in Belgium. All the participants completed 5 weeks of sprint interval training (SIT) consisting of 30 second sprints followed by 4.5-minute recovery intervals on an exercise cycle. This was repeated 4-6 times per session 3 times per week.

One group took a sodium nitrate supplement containing 400 mg of nitrate 30 minutes before each workout. The other group received a placebo. There were only 9 students in each group. [I have simplified the study design for the purposes of this discussion. There were other aspects of the study, but they are not relevant to our discussion.]

The investigators measured maximum oxygen consumption (a measure of exercise efficiency and endurance), maximum power output during a 30-second sprint, and composition of quadriceps muscle fibers both before the 5-week training started and again when it was completed.

The results were disappointing:

  • thumbs downNitrate supplementation caused a modest increase in fast twitch (type IIa) muscle fibers compared to placebo. That is a physiological response that may (or may not, depending on who you believe) allow high intensity exercise to be sustained for longer without fatigue.
  • Nitrate supplementation failed to show any significant benefit for any other measure of exercise capacity. In particular, no effect of nitrate supplementation was observed on:
    • Maximum oxygen consumption
    • Maximum power output
    • Peak heart rate
    • Time to exhaustion.
    • Various metabolic markers of exercise efficiency

In spite of these largely negative results, the authors concluded: “The current experiment demonstrated that oral nitrate supplementation during short-term sprint-interval training increased the proportion of type IIa muscle fibers, which may contribute to enhanced performance in short maximal exercise events…”

“May” is the operative word here. Their data did not provide any evidence that nitrate supplementation actually improved performance.

Online headlines (the kind of nutrition information most people read) took it a step further. For example, one headline claimed “Spinach Can Boost Your Physical Fitness and Muscle Strength.” That headline came out of thin air.

Sports Nutrition Myths

mythsUnfortunately, this study is typical of many of the sports nutrition studies I have reviewed over the years. Most of them are very small studies. In many of them only one or two measure exercise performance change, while other measures show no effect of supplementation.

That doesn’t stop bloggers from hyping the studies and creating sports nutrition myths. It also doesn’t stop companies from offering sports products with those ingredients and making outrageous claims about how their product will make you bigger, faster, and stronger.  For example, a claim that you can eat spinach for muscle growth.

It is only when dozens of studies have been published, and a meta-analysis combines the data from all the studies that we are in a position to see whether any particular nutrient has a statistically significant effect on performance.

Must You Eat Spinach for Muscle Growth or Could Nitrates Provide Exercise Benefits?

nitrates and exerciseDespite the weakness of this particular study, there is reason to believe that nitrates might improve exercise performance.

  • There is a plausible mechanism. In the body nitrates are converted to nitric oxide, which improves arterial health, lowers blood pressure, and enhances blood flow. Increased blood flow to the muscles could enhance exercise efficiency.
  • Other studies have come to a similar conclusion. There are several other exercise studies Health Benefits of Beetroot Juice involving supplements containing either nitrates or beetroot juice (which is rich in nitrates) that have suggested that supplementation improves exercise efficiency. Each of the studies are small and inconclusive by themselves, but in the aggregate they suggest that nitrate may have some benefits.
  • Arginine, which also enhances nitric oxide production, is well established in the sports nutrition world. There are dozens of published exercise studies involving arginine and meta-analyses of these studies suggest that arginine provides modest benefits. However, there is an important caveat, which I shall explain below.

In short, the idea that nitrate supplementation might improve exercise performance is plausible. However, plausible is a long way from proven.

The Ultimate Irony

When you analyze the meta-analyses of arginine supplementation and exercise performance studies, the ultimate irony is that arginine supplementation is most effective for untrained individuals who are just beginning an exercise program. It provides little benefit for trained athletes (R. Bescos et al, Sports Medicine, 42: 99‐117,2012).

There is a logical explanation for this observation. Intense exercise also enhances nitric oxide production and blood flow to the muscle. Most highly trained athletes have already maxed their nitric oxide levels and have excellent blood flow to their muscles. Arginine (or nitrate) supplementation provides little additional benefit for them.

Why do I call this the ultimate irony? Think about it for a minute.

The people most likely to use sports supplements with arginine or nitrate are gym rats and highly trained athletes – the people who get the least benefit from those supplements.

The people least likely to use special sports supplements with arginine or nitrate are the weekend warriors and the busy professionals who are just trying to stay fit – the people who are most likely to benefit from those supplements.

 

The Bottom Line

 

  • Recent headlines have suggested that you can eat spinach for muscle growth and exercise performance.
  • When you look at the study behind the headlines, the study was done with nitrate, not with spinach. Spinach is a nitrate-rich food (as are beet roots), but the headlines were clearly misleading.
  • The study was also inconclusive. It was a small study, and most parameters of exercise performance were not affected by nitrate supplementation.
  • Unfortunately, this kind of small, inconclusive study is all too common in the sports nutrition literature. That doesn’t stop bloggers from hyping the studies and creating sports nutrition myths. It also doesn’t stop companies from offering sports nutrition products with those ingredients and making outrageous claims about how their product will make you bigger, faster, and stronger.
  • However, other studies suggest the idea that nitrate in food or supplements could improve exercise performance is plausible.
  • In our bodies, nitrate is converted to nitric oxide, which enhances blood flow to the muscles.
  • Other studies with nitrate and with beetroot juice (an excellent source of nitrate) have shown some exercise benefits.
  • Arginine, which is also converted to nitric oxide, is a fairly well established sports supplement.

Of course, plausible is a long way from proven.

  • The ultimate irony is that the people most likely to use sports supplements with arginine or nitrates are gym rats and highly trained athletes. They already have excellent blood flow to their muscles. They are the people who get the least benefit from those supplements.
  • In contrast, the people least likely to use special sports supplements with arginine or nitrates are the weekend warriors and the busy professionals who are just trying to stay fit. Those are the people who are most likely to benefit from those supplements.

 

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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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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