muscle strength

Does Low Vitamin D Make You Weak?

by

Why Is Vitamin D Research So Controversial?

Author: Dr. Stephen Chaney

vitamin dMillions of Americans lose muscle strength as they age, something called sarcopenia. This is not a trivial matter. Loss of muscle mass:

  • Leads to loss of mobility. It can also make it difficult to do simple things like lifting your grandchild or carrying a bag of groceries.
  • Increases your risk of falling. This often leads to serious fracture which increases your of dying prematurely. In fact, bone fractures increase your risk of dying by 3-fold or more. Even in those who recover their mobility and quality of life may never be the same.
  • Lowers your metabolic rate. This increases your risk of obesity and all the diseases that are associated with obesity.

Loss of muscle strength as we age is preventable. There are several things we can do to preserve muscle strength as we age, but in today’s article I will focus on the effect of vitamin D on muscle strength.

What if something as simple as preventing vitamin D deficiency could improve muscle strength as we age? That idea has been around for a decade or more. But, for reasons I will detail below, it has proven controversial. Let me start by sharing a recent study on vitamin D and muscle strength (N Aspell et al, Clinical Investigations in Ageing, volume 2019:14, pages 1751-1761).

How Was The Study Done?

Clinical StudyThe data for this study came from 4157 adults who were enrolled in the English Longitudinal Study On Aging. Participants in this study were all over the age of 60 and were still living in their own homes. The general characteristics of the study population were:

  • Their average age was 69.8 with 45% male and 55% female.
  • While 76% of the participants rated their health as “good” or above
    • 73% were overweight or obese.
    • 54% had a longstanding disease that limited mobility.
    • 29% were taking multiple medications.

Serum 25-hydroxy vitamin D levels were determined as a measure of vitamin D status.

  • 22% of the participants were vitamin D deficient (<30 nmol/L 25-hydroxy vitamin D).
  • 34% of the participants were vitamin D insufficient (between 30 and 50 nmol/L 25-hydroxy vitamin D).
  • 46% of the participants had adequate vitamin D status (>50 nmol/L 25-hydroxy vitamin D).

Muscle strength was assessed by a handgrip strength test with the dominant hand. Muscle performance was assessed with something called the short physical performance battery (SPPB), consisting of a walking speed test, a repeated chair raise test, and a balance test.

Does Low Vitamin D Make You Weak?

When the data on handgrip strength were analyzed:

  • Only 22% of the participants who had adequate vitamin D status had low handgrip strength.
  • 40% of participants who were vitamin D deficient had low handgrip strength. That’s almost a 2-fold difference.
  • Handgrip strength increased linearly with vitamin D status.
    • The relationship between vitamin D status and handgrip strength was highly significant (p<001).
    • The beneficial effect of vitamin D status on handgrip strength plateaued at around 55-69 nmol/L 25-hydroxy vitamin D. In other words, you need adequate vitamin D status to support muscle strength, but higher levels provide no additional benefit.

When the data on muscle performance (the SPPB test) were analyzed:

  • Only 8% of the participants who had adequate vitamin D status scored low on this test.
  • 25% of participants who were vitamin D deficient scored low on this test. That’s a 3-fold difference.
  • Muscle performance also increased linearly with vitamin D status.
    • The relationship between vitamin D status and muscle performance was also highly significant (p<001).
    • The beneficial effect of vitamin D status on muscle performance also plateaued at around 55-69 nmol/L 25-hydroxy vitamin D.

The authors concluded: “Vitamin D deficiency was associated with impaired muscle strength and performance in a large study of community-dwelling older people. It is generally accepted that vitamin D deficiency should be reversed to prevent bone disease. This strategy may also protect skeletal muscle function in aging.”

Why Is Vitamin D Research So Controversial?

ArgumentYou can be forgiven if you are saying to yourself: “I’ve heard this sort of thing before. I see a blog or headline claiming that vitamin D has a certain benefit, but it’s usually followed by later headlines saying those claims are false. Why can’t the experts agree? Is all vitamin D research bogus?”

The relationship between vitamin D status and muscle strength is no different.

  • Many, but not all, studies looking at the association between vitamin D status and muscle strength find that vitamin D status affects muscle strength.
  • However, many randomized, placebo-controlled clinical trials looking at the effect of vitamin D supplementation on muscle strength have come up empty.

A meta-analysis (L Rejnmark, Therapeutic Advances in Chronic Disease, 2: 25-37, 2011) of randomized, placebo-controlled clinical trials of vitamin D supplementation and muscle strength provides insight as to why so many of them come up empty.

The meta-analysis combined data from 16 clinical trials. The conclusions were similar to what other meta-analyses have found:

  • Seven of the studies showed a benefit of vitamin D supplementation on muscle strength. Nine did not.
  • When the data from all 16 studies were combined, there was only a slight beneficial effect of vitamin D supplementation on muscle strength.

However, it was in the discussion that the reason for these discrepancies became apparent. There were three major deficiencies in study design that were responsible for the discrepancies.

1) There was a huge difference in study design.

  • The subjects were of different ages, genders, and ethnicity.
  • The dose of vitamin D supplementation varied.
  • Different measures of muscle strength and performance were used.

Until the scientific and medical community agree on a standardized study design it will be difficult to obtain consistent results.Garbage In Garbage Out

While this deficiency explains the variation in outcomes from study to study, there are two other deficiencies in study design that explain why many of the studies failed to find an effect of vitamin D on muscle strength. I call this “Garbage In, Garbage Out”. Simply put, if the study has design flaws, it may be incapable of detecting a positive effect of vitamin D on muscle strength.

2) Many of the studies did not measure vitamin D status of the participants at the beginning of the study.

  • The results of the study described above show that additional vitamin D will be of little benefit for anyone who starts the study with an adequate vitamin D status.
  • In the study above 46% of the participants had adequate vitamin D status. This is typical for the elderly community. When almost 50% of the participants in a study have adequate vitamin D status at the beginning of a study it becomes almost impossible to demonstrate a beneficial effect of vitamin D supplementation on any outcome.

It is essential that future studies of vitamin D supplementation focus on participants who have low vitamin D status. Otherwise, you are almost guaranteeing a negative outcome.

3) Most of the studies ignored the fact that vitamin D status is only one of three factors that are essential for muscle strength.

  • In the case of muscle strength, especially in the elderly, the three essentials are vitamin D, protein, and exercise. All three are needed to maintain or increase muscle strength. Simply put, if one is missing, the other two will have little or no effect on muscle strength. Unfortunately, you cannot assume that exercise and protein intake are adequate in older Americans:
  • Many older adults don’t get enough exercise because of physical limitations.

Unfortunately, many clinical studies on the effect of vitamin D supplementation and muscle strength fail to include exercise and adequate protein intake in the study. Such clinical trials are doomed to failure.

Now you know why vitamin D research is so controversial. Until the scientific and medical community get their act together and perform better designed experiments, vitamin D research will continue to be controversial and confusing.

What Does This Mean For You?

Old Man Lifting WeightsLoss of muscle mass as we age is not a trivial matter. As described above, it:

  • Leads to loss of mobility.
  • Increases your risk of falling. This often leads to serious fractures which increase your risk of disability and death.
  • Lowers your metabolic rate, which increases your risk of obesity and obesity-related diseases.

So, what can you do prevent loss of muscle mass as you age? The answer is simple:

  • Aim for 25-30 grams of high-quality protein in each meal.
    • That protein can come from meat, fish, eggs, or vegetable sources such as beans, nuts, and seeds.
    • That doesn’t mean you need to consume an 8-ounce steak or a half chicken. 3-4 ounces is plenty.
    • However, it does mean you can’t subsist on green salads and leafy greens alone. They are healthy, but you need to include a good protein source if you are going to meet your protein needs.
  • Aim for 150 minutes of moderate intensity exercise per week.
    • At least half of that exercise should be resistance exercise (lifting weights, for example).
    • If you have physical limitations, consult your doctor and work with a physical therapist or personal trainer to design resistance exercises you can do.
    • Aim for a variety of resistance exercises. You will only strengthen the muscles you exercise.
  • Aim for an adequate vitamin D status.
    • Start with a multivitamin containing at least 800 IU of vitamin D3.
    • Because there is large variation in the efficiency with which we convert vitamin D to 25-hydroxy vitamin D, you should get your serum 25-hydroxyvitamin D tested on a yearly basis. Your health professional can tell you if you need to take larger amounts of vitamin D3.
    • This study suggests that a serum 25-hydroxy vitamin D level of 55-69 nmol/L is optimal, and higher levels provide no additional benefit. That means there is no need to take mega-doses of vitamin D3 unless directed by your health professional.

The Bottom Line 

A recent study looked at the effect of vitamin D status on muscle strength and performance in a healthy population with an average age of 69.

When they looked at handgrip strength:

  • Only 22% of the participants with an adequate vitamin D status had low handgrip strength.
  • 40% of participants who were vitamin D deficient had low handgrip strength. That’s almost a 2-fold difference.
  • Handgrip strength increased linearly with vitamin D status.

When they looked at muscle performance:

  • Only 8% of the participants with an adequate vitamin D status scored low on this test.
  • 25% of participants who were vitamin D deficient scored low on this test. That’s a 3-fold difference.
  • Muscle performance also increased linearly with vitamin D status.

The authors concluded: “Vitamin D deficiency was associated with impaired muscle strength and performance in a large study of community-dwelling older people. It is generally accepted that vitamin D deficiency should be reversed to prevent bone disease. This strategy may also protect skeletal muscle function in aging.”

If we look at the research more broadly, there are three factors that are essential for maintaining muscle mass as we age: exercise, protein, and vitamin D. Therefore, my recommendations are to:

1)  Aim for 25-30 grams of high-quality protein in each meal.

2) Aim for 150 minutes of moderate intensity exercise per week. At least half of that exercise should be resistance exercise.

3) Aim for an adequate vitamin D status (>50 nmol/L of serum 25-hydroxy vitamin D). A good place to start is with a multivitamin providing at least 800 IU of vitamin D3.

For more details on my recommendations and a discussion of why studies on vitamin D supplementation are often confusing, 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

 

Do Collagen Supplements Build Muscle?

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Could Collagen Supplements Make You Leaner? 

Author: Dr. Stephen Chaney

Sports SupplementsCollagen supplements have been considered “vanity products”. Their largest market is people who want to have younger, more beautiful skin. And for many people, collagen delivers on this promise.

However, collagen plays many other roles in the body. It also helps rebuild tendons and ligaments. Many people take collagen supplements to reduce joint pain.

But could collagen supplements coupled with resistance training also build muscle and reduce fat? If so, that would be huge.

A recent study (D Zdzieblik et at, British Journal of Nutrition, 114: 1237-1245, 2015) suggested collagen supplements may do just that. This study showed that a collagen supplement plus resistance training increased lean muscle mass and decreased fat mass in elderly men (average age = 72).

If this finding is duplicated in future studies, it has significant health implications. Both men and women in their 70s lose muscle mass at a rapid rate (a process called sarcopenia). Anything that slows or reverses this process has the potential to extend high quality life and prolong their golden years.

But what about younger adults? Could a collagen supplement plus resistance training also help them build muscle and lose fat? This study (D Zdzieblik et at, International Journal of Environmental Research and Public Health, 18: 4837-4855, 2021) was designed to answer that question.

It was a randomized, placebo-controlled study comparing 15 g of collagen peptides with 15 g of whey protein, and a placebo (silicon dioxide).

How Was This Study Done?

couch potatoThe study recruited 120 middle-aged (average age = 50), overweight (average BMI = 30) men who were untrained (<60 minutes of exercise per week over the previous year). [In other words, the study recruited middle-aged couch-potatoes.]

The participants were asked to fill out a three-day diet analysis at the beginning and end of the 12-week study with the assistance of a nutritionist.

  • Average caloric intake was 2,600 calories/day.
  • Average protein intake was 104 grams/day. That is 30% higher than the recommended protein intake for men of that age and weight.
  • The macronutrient content of the diet was 16% protein, 37% fat, and 43% carbohydrate.
  • These values were not significantly different between groups and did not change during the study.

All participants participated in a one-hour training program three times per week. The training began with a 10-minute cardio exercise to warm up. That was followed by a three-set program consisting of horizontal leg presses (both legs), reverse crunches, lat-pull exercise, sit-ups, and chest presses with 1 to 2 min rest periods between sets. The intensity of exercise was gradually increased over the 12-week study.

The participants were randomly divided into three groups. After each workout they were given sachets containing 15 g of collagen peptides, 15 g of whey isolate, or 15 g of silicon dioxide (placebo). They were instructed to dissolve the powder in 8 ounces of water and drink it within one hour of the workout. They were also given the same sachets and instructed to take them at the same time of day for the days they were not working out.

Finally, the participants were instructed not to change their diet or physical activity apart from the intake of the powder in the sachets they were given and the one-hour training sessions.

Do Collagen Supplements Build Muscle?

Collagen Supplement & Muscle MassAll three groups had statistically significant:

  • Increases in percent lean muscle mass.
  • Decreases in percent fat mass.
  • Increases in leg muscle strength.

No surprises here. If you take a group of middle-aged couch-potatoes and put them in a strength training program, you will see increases in lean muscle mass, decreases in fat mass, and increases in muscle strength.

The real question was what was the effect of the collagen and whey protein supplements? This is where the results got really interesting.

  • The collagen peptide supplement gave a significantly greater increase in lean muscle mass and decrease in fat mass than the placebo. The increase in leg muscle strength was also greater than the placebo, but this difference was not statistically significant.
  • The whey protein supplement also increased lean muscle mass and decreased fat mass compared to the placebo, but these differences were not statistically different.

In other words, at the doses used in this study (see next section for discussion), the collagen supplement worked better than the whey protein supplement. Here is the actual data from the study:

  • Increase in percent lean muscle mass: collagen supplement = 7.4%, whey protein supplement = 5.8%. placebo = 5.0%.
  • Decrease in percent fat mass: collagen supplement = 15%, whey protein supplement = 11.5%, placebo = 10%.

In the words of the authors, “In conclusion, collagen peptide supplementation combined with resistance training was associated with a significantly greater increase in fat free mass and a decrease in fat mass compared with placebo. Resistance training combined with whey protein also had a positive impact on body composition, but the respective effects were more pronounced following the collagen peptide administration.”

Could Collagen Supplements Make You Leaner?

strengths-weaknessesThis study leaves lots of questions. Let me handle the main ones here.

What Are The Strengths and Weaknesses Of The Study?

The strengths are obvious. This was a well-design, randomized, placebo-controlled clinical trial, which is the gold standard for determining the efficacy of a treatment.

The weaknesses are also obvious. This was a very small clinical study. There is one previous study that showed the same benefit of collagen in an older age group. However, both studies were published by the same group of scientists. And these scientists were funded by the manufacturer of the collagen product used in the study. More and larger studies performed by other laboratories are needed to confirm this finding.

How Do Resistance Exercise, Whey Protein, And Collagen Stimulate Muscle Growth?

Muscle growth is stimulated by a regulatory pathway called mTOR that (among other things) regulates protein Weight Trainingsynthesis in muscle cells. For the purposes of this article, I will discuss 3 mechanisms for activating mTOR and increasing muscle protein synthesis.

#1: Resistance exercise (weight training) activates mTOR. That should come as no surprise. The main reason people do weight training is to increase strength and muscle mass. mTOR is the pathway that makes this possible.

#2: Whey protein is rich in the essential amino acid leucine, and leucine also stimulates the mTOR pathway.

  • Leucine is one of three branched chain amino acids. While all three branched chain amino acids have been traditionally credited with stimulating muscle protein synthesis, recent research has shown that only leucine is needed. The other two branched chain amino acids just play a supportive role. You only need enough of the them to make a complete protein.
  • While whey protein gets all the attention in the sports world, any complete protein with high levels of leucine has the same effect.
  • The effect of leucine and resistance training on the mTOR pathway are additive. That is why whey and other leucine-rich proteins enhance the effect of resistance exercise on both muscle mass and strength.

#3: Collagen does not contain enough leucine to activate the mTOR pathway. However, the authors have proposed another mechanism to account for collagen activation of the mTOR pathway.

  • Most proteins we eat are digested to their individual amino acids before they are absorbed. However, collagen is rich in an unusual amino acid called hydroxyproline that makes collagen resistant to our digestive enzymes.
  • Thus, collagen is not digested to individual amino acids, but to small peptides that are absorbed from our intestine.
  • One of these breakdown products, a dipeptide composed of glycine and hydroxyproline, has been shown to stimulate the mTOR pathway.

While this mechanism has not been proven, collagen does appear to enhance the effect of resistance exercise on both muscle mass and strength.

Collagen Only Has 8 Essential Amino Acids. How Could It Stimulate The Synthesis Of Muscle Protein, Which Requires 9 Essential Amino Acids?

Question MarkThe answer is simple. The people in this study were consuming 30% more than the recommended amount of protein in their diet in addition to the collagen supplement. They already had all the essential amino acids needed to synthesize muscle protein. The collagen supplement simply stimulated the rate of muscle protein synthesis by activating the mTOR pathway.

However, there are situations in which the 9th essential amino acid could become important for muscle protein synthesis. Here are two examples

  • Vegans and strict vegetarians might not be getting enough protein in their diet. As I pointed out in a previous article vegan “experts” know how to get enough protein from their diet, but many vegan “novices” do not.
  • Older Americans are also at risk. They need extra protein in their diet to prevent sarcopenia (muscle loss) as they age. And some of them are on restrictive diets, either because of the latest fad or because of loss of income and/or mobility.

Why Did The Collagen Supplement Work Better Than Whey Protein In This Experiment? 

Again, the answer is simple. Both collagen and leucine-rich proteins like whey enhance muscle protein synthesis by activating the mTOR pathway (see above). This study used the same amount of protein (15 g/day) for both collagen supplement and the whey protein supplement.

While 15 g/day appears to be optimal for the collagen supplement, the authors pointed out that previous studies suggest that the optimal dose for whey protein is closer to 20 g/day for middle-aged men.

So, I would ignore the apparent difference in effectiveness of the collagen and whey protein supplements.

The important conclusion is that both collagen and leucine-rich proteins like whey enhance the effect of resistance exercise on lean muscle mass to a similar extent. But they appear to do so by slightly different mechanisms.

What Does This Mean For You?

This study is intriguing. It suggests that collagen may have some tricks up its sleeve we didn’t know about.

  • It may do more than give you a healthy, youthful looking skin.
  • It may do more than help with achy joints.
  • Coupled with resistance exercise it may also help you increase muscle mass and reduce fat mass. It may make you leaner.

The Bottom Line

Collagen supplements have been considered “vanity products”. Their largest market is people who want to have younger, more beautiful skin. And for many people, collagen delivers on this promise.

However, collagen plays many other roles in the body. It also helps rebuild tendons and ligaments. Many people take collagen supplements to reduce joint pain.

But collagen may have other tricks up its sleeve. A recent study suggests that collagen supplements may enhance the effect of resistance exercise on increased muscle mass and reduced fat mass. It may make you leaner.

The study also concluded that both collagen and whey protein enhance the effect of resistance exercise on lean muscle mass to a similar extent. But they appear to do so by slightly different mechanisms.

Let me be clear. I am not recommending you take a collagen supplement to help you build muscle mass. I consider these results as preliminary, and we have good evidence that leucine-rich proteins plus resistance exercise helps build muscle mass. 

However, if you are taking a collagen supplement for another reason and are working out, this could be an unexpected benefit.

For more details about this study and how collagen supplements may increase muscle mass, 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.

Does Vitamin D Affect Muscle Strength?

by

Why Is Vitamin D Research So Controversial?

vitamin dMost people lose muscle strength as they age, something called sarcopenia. This is not a trivial matter. Loss of muscle mass:

  • Leads to loss of mobility. It can also make it difficult to do simple things like lifting your grandchild or carrying a bag of groceries.
  • Increases your risk of falling. This often leads to serious fracture which increases your of dying prematurely. In fact, bone fractures increase your risk of dying by 3-fold or more. Even in those who recover their mobility and quality of life may never be the same.
  • Lowers your metabolic rate. This increases your risk of obesity and all the diseases that are associated with obesity.

Loss of muscle strength as we age is preventable. There are several things we can do to preserve muscle strength as we age, but in today’s article I will focus on the effect of vitamin D on muscle strength.

What if something as simple as preventing vitamin D deficiency could improve muscle strength as we age? That idea has been around for a decade or more. But, for reasons I will detail below, it has proven controversial. Let me start by sharing the latest study on vitamin D and muscle strength (N Aspell et al, Clinical Investigations in Ageing, volume 2019:14, pages 1751-1761).

How Was The Study Done?

Clinical StudyThe data for this study came from 4157 adults who were enrolled in the English Longitudinal Study On Aging. Participants in this study were all over the age of 60 and were still living in their own homes. The general characteristics of the study population were:

  • Their average age was 69.8 with 45% male and 55% female.
  • While 76% of the participants rated their health as “good” or above
    • 73% were overweight or obese.
    • 54% had a longstanding disease that limited mobility.
    • 29% were taking multiple medications.

Serum 25-hydroxy vitamin D levels were determined as a measure of vitamin D status.

  • 22% of the participants were vitamin D deficient (<30 nmol/L 25-hydroxy vitamin D).
  • 34% of the participants were vitamin D insufficient (between 30 and 50 nmol/L 25-hydroxy vitamin D).
  • 46% of the participants had adequate vitamin D status (>50 nmol/L 25-hydroxy vitamin D).

Muscle strength was assessed by a handgrip strength test with the dominant hand. Muscle performance was assessed with something called the short physical performance battery (SPPB), consisting of a walking speed test, a repeated chair raise test, and a balance test.

Does Vitamin D Affect Muscle Strength?

When the data on handgrip strength were analyzed:

  • Only 22% of the participants who had adequate vitamin D status had low handgrip strength.
  • 40% of participants who were vitamin D deficient had low handgrip strength. That’s almost a 2-fold difference.
  • Handgrip strength increased linearly with vitamin D status.
    • The relationship between vitamin D status and handgrip strength was highly significant (p<001).
    • The beneficial effect of vitamin D status on handgrip strength plateaued at around 55-69 nmol/L 25-hydroxy vitamin D. In other words, you need adequate vitamin D status to support muscle strength, but higher levels provide no additional benefit.

When the data on muscle performance (the SPPB test) were analyzed:

  • Only 8% of the participants who had adequate vitamin D status scored low on this test.
  • 25% of participants who were vitamin D deficient scored low on this test. That’s a 3-fold difference.
  • Muscle performance also increased linearly with vitamin D status.
    • The relationship between vitamin D status and muscle performance was also highly significant (p<001).
    • The beneficial effect of vitamin D status on muscle performance also plateaued at around 55-69 nmol/L 25-hydroxy vitamin D.

The authors concluded: “Vitamin D deficiency was associated with impaired muscle strength and performance in a large study of community-dwelling older people. It is generally accepted that vitamin D deficiency should be reversed to prevent bone disease. This strategy may also protect skeletal muscle function in aging.”

Why Is Vitamin D Research So Controversial?

ArgumentYou can be forgiven if you are saying to yourself: “I’ve heard this sort of thing before. I see a blog or headline claiming that vitamin D has a certain benefit, but it’s usually followed by later headlines saying those claims are false. Why can’t the experts agree? Is all vitamin D research bogus?”

The relationship between vitamin D status and muscle strength is no different.

  • Most, but not all, studies looking at the association between vitamin D status and muscle strength find that vitamin D status affects muscle strength.
  • However, many randomized, placebo-controlled clinical trials looking at the effect of vitamin D supplementation on muscle strength have come up empty.

A meta-analysis (L Rejnmark, Therapeutic Advances in Chronic Disease, 2: 25-37, 2011) of randomized, placebo-controlled clinical trials of vitamin D supplementation and muscle strength provides insight as to why so many of them come up empty.

The meta-analysis combined data from 16 clinical trials. The conclusions were similar to what other meta-analyses have found:

  • Seven of the studies showed a benefit of vitamin D supplementation on muscle strength. Nine did not.
  • When the data from all 16 studies were combined, there was only a slight beneficial effect of vitamin D supplementation on muscle strength.

However, it was in the discussion that the reason for these discrepancies became apparent. There were three major deficiencies in study design that were responsible for the discrepancies.

1) There was a huge difference in study design.

    • The subjects were of different ages, genders, and ethnicities.
    • The dose of vitamin D supplementation varied.
    • Different measures of muscle strength and performance were used.

Until the scientific and medical community agree on a standardized study design it will be difficult to obtain consistent results.

While this deficiency explains the variation in outcomes from study to study, there are two other deficiencies in Garbage In Garbage Outstudy design that explain why many of the studies failed to find an effect of vitamin D on muscle strength. I call this “Garbage In, Garbage Out”. Simply put, if the study has design flaws, it may be incapable of detecting a positive effect of vitamin D on muscle strength.

2) Many of the studies did not measure vitamin D status of the participants at the beginning of the study.

    • The results of the study described above show that additional vitamin D will be of little benefit for anyone who starts the study with an adequate vitamin D status.
    • In the study above 46% of the participants had adequate vitamin D status. This is typical for the elderly community. When almost 50% of the participants in a study have adequate vitamin D status at the beginning of a study it becomes almost impossible to demonstrate a beneficial effect of vitamin D supplementation on any outcome.

It is essential that future studies of vitamin D supplementation start with participants who have low vitamin D status. Otherwise, you are almost guaranteeing a negative outcome.

3) Most of the studies ignored the fact that vitamin D status is only one of three factors that are essential for muscle strength.

    • In the case of muscle strength, especially in the elderly, the three essentials are vitamin D, protein, and exercise. All three are needed to maintain or increase muscle strength. Simply put, if one is missing, the other two will have little or no effect on muscle strength. Unfortunately, you cannot assume that exercise and protein intake are adequate in older Americans:
      • Many older adults don’t get enough exercise because of physical limitations.

Unfortunately, many clinical studies on the effect of vitamin D supplementation and muscle strength fail to include exercise and adequate protein intake in the study. Such clinical trials are doomed to failure.

Now you know why vitamin D research is so controversial. Until the scientific and medical community get their act together and perform better designed experiments, vitamin D research will continue to be controversial and confusing.

What Does This Mean For You?

Old Man Lifting WeightsLoss of muscle mass as we age is not a trivial matter. As described above, it:

  • Leads to loss of mobility.
  • Increases your risk of falling. This often leads to serious fracture which increase your risk of disability and death.
  • Lowers your metabolic rate, which increases your risk of obesity and obesity-related diseases.

So, what can you do prevent loss of muscle mass as you age? The answer is simple:

1) Aim for 25-30 grams of high-quality protein in each meal.

    • That protein can come from meat, fish, eggs, or legumes.
    • That doesn’t mean you need to consume an 8-ounce steak or a half chicken. 3-4 ounces is plenty.
    • However, it does mean you can’t subsist on green salads and leafy greens alone. They are healthy, but you need to include a good protein source if you are going to meet your protein needs.

2) Aim for 150 minutes of moderate intensity exercise per week.

    • At least half of that exercise should be resistance exercise (lifting weights, for example).
    • If you have physical limitations, consult your doctor and a physical therapist or personal trainer to design resistance exercises you can do.
    • Aim for a variety of resistance exercises. You will only strengthen the muscles you exercise.

3) Aim for an adequate vitamin D status.

    • Start with a multivitamin containing at least 800 IU of vitamin D3.
    • Because there is large variation in the efficiency with which we convert vitamin D to 25-hydroxy vitamin D, you should get your serum 25-hydroxyvitamin D tested on a yearly basis. Your health professional can tell you if you need to take larger amounts of vitamin D3.
    • This study suggests that a serum 25-hydroxy vitamin D level of 55-69 nmol/L is optimal, and higher levels provide no additional benefit. That means there is no need to take mega-doses of vitamin D3 unless directed by your health professional.

The Bottom Line

A recent study looked at the effect of vitamin D status on muscle strength and performance in a healthy population with an average age of 69.

When they looked at handgrip strength:

  • Only 22% of the participants with an adequate vitamin D status had low handgrip strength.
  • 40% of participants who were vitamin D deficient had low handgrip strength. That’s almost a 2-fold difference.
  • Handgrip strength increased linearly with vitamin D status.

When they looked at muscle performance:

  • Only 8% of the participants with an adequate vitamin D status scored low on this test.
  • 25% of participants who were vitamin D deficient scored low on this test. That’s a 3-fold difference.
  • Muscle performance also increased linearly with vitamin D status.

The authors concluded: “Vitamin D deficiency was associated with impaired muscle strength and performance in a large study of community-dwelling older people. It is generally accepted that vitamin D deficiency should be reversed to prevent bone disease. This strategy may also protect skeletal muscle function in aging.”

If we look at the research more broadly, there are three factors that are essential for maintaining muscle mass as we age: exercise, protein, and vitamin D. Therefore, my recommendations are to:

1)  Aim for 25-30 grams of high-quality protein in each meal.

2) Aim for 150 minutes of moderate intensity exercise per week. At least half of that exercise should be resistance exercise.

3) Aim for an adequate vitamin D status (>50 nmol/L of serum 25-hydroxy vitamin D). A good place to start is with a multivitamin providing at least 800 IU of vitamin D3.

For more details on my recommendations and a discussion of why studies on vitamin D supplementation are often confusing, 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.

 

Health Tips From The Professor