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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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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