Does Vitamin D Affect Muscle Strength?

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.

 

Do Older Adults Eat Enough Protein?

The Impact Of Inadequate Protein Intake On Healthy Aging

Author: Dr. Stephen Chaney

 

Do older adults eat enough protein?

older adults signMost Americans lose lean muscle mass as they age, a physiological process called sarcopenia. There are three factors that influence the rate at which we lose muscle mass as we age:

  • Our physiology changes. Our bodies break down our protein stores more rapidly and we have a harder time utilizing the protein in our diet to replenish those protein stores.
  • We become less active. In some cases this reflects physical disabilities, but all too often it is because we are not giving weight-bearing exercises the proper priority in our busy lives.
  • Our diets become inadequate. The major driver of this phenomenon is loss of appetite which results in decreased caloric intake. However, physical disability, isolation, and insufficient income also contribute.

Sarcopenia in turn results in:

  • Loss of muscle strength. Even the simple act of picking up a grandchild or a bag of groceries can become problematic.
  • Increased risk of falls and fractures.
  • Lower quality of life.

Obviously, sarcopenia is a major health issue for those of us in our golden years. If you are younger, it is a concern for your parents or grandparents. Sarcopenia is a health issue that affects everyone.

But what can be done to prevent sarcopenia? We can’t change our physiology, but we can change our activity level and our diet. Weight-bearing exercise tugs on our muscle fibers. That stimulates those fibers to incorporate protein into new muscle cells. It is no wonder that weight-bearing exercise is recommended for preventing sarcopenia.

What about diet? Are older adults getting enough protein in their diet? The conventional wisdom is that protein intake is not a problem. We’ve been told that Americans get enough protein in our diet. In fact, we’ve been told that most of us get more protein than we need.

Is that true for older Americans? In fact, very few studies have specifically looked at protein intake in older Americans. This study (JL Krok-Schoen et al, The Journal of Nutrition, Health & Aging, 23: 338-347, 2019 ) was designed to fill that void.

 

How Was The Study Done?

older adults eat enough protein studyThis study used data on 11,680 Americans who participated in NHANES surveys between 2005 and 2014. (NHANES or National Health and Nutrition Examination Surveys is a program run by the CDC that is designed to assess the health and nutritional status of adults and children living in the United States).

Participants in the study were grouped into three groups: 51-60 years (4,016 participants), 61-70 years (3,854 participants), and 71 years and older (3,810 participants).

Protein intake and diet quality were based on the average of two 24-hour dietary recall interviews. Trained dietary interviewers collected detailed information on all foods and beverages consumed during the past 24 hours.

Participants also filled out a questionnaire designed to assess health outcomes that might be affected by loss of muscle mass.

Note: The NHANES database is used for many studies on the association between diet and health outcomes. However, it is important to remember that a 24-hour diet recall is a single snapshot in time. This is a weakness of this and all similar studies. For example, in this study a participant’s average protein intake may be more or may be less than the amount reflected in the 24-hour diet recall.

 

Are Older Adults Eat Enough Protein?

older adults eat enough protein puzzleTo determine whether American older adults eat enough protein in their diet, the investigators compared protein intake in each age group with the DRI (Dietary Reference Intake) for protein of 0.8 grams of protein per kilogram of body weight (0.36 grams per pound). This is the standard set by the Food & Nutrition Board of the National Academy of Sciences for all adults over the age of 19.

The results were:

  • Up to 46% of older adults were not getting the recommended 0.8 g/kg/day of protein. When broken down by age groups, the percentages were:
    • 38% of the 51-60 age group.
    • 42% of the 61-70 age group.
    • 46% of those over 70.
  • Women were more likely to be consuming inadequate protein than men.
  • Blacks were more likely to be consuming inadequate protein than other demographic groups.

When the investigators looked at the correlation between diet quality and protein intake, those consuming inadequate protein:

  • Had significantly lower calorie intake.
  • Skipped meals more frequently.
  • Had lower HEI (Healthy Eating Index) scores. Specifically:
  • They scored low on intake of greens, beans, dairy, total protein foods, seafood protein foods, and plant protein foods.
  • They scored high on intake of refined grains and added sugars.
  • Had inadequate intakes of fiber, zinc, selenium, vitamin C, vitamin E, and vitamin D.

 

The Impact Of Inadequate Protein Intake On Healthy Aging

crying iconWhen the investigators compared older adults with inadequate protein intake to adults in the same age groups with adequate protein intake, those with inadequate protein intake:

  • Had a higher prevalence of physical, mental, and social limitations.
  • Were more likely to be limited when stooping, crouching, or kneeling, standing or sitting for long periods, walking up 10 steps, preparing meals, and walking for a quarter mile.
  • They had trouble lifting more than 10 or 15 pounds.

Limitations on everyday activities like these have a significant impact on the quality of life experienced by these individuals.

 

What Does This Study Mean For You?

  • older adults eat enough protein questionIf you are over 50 or have a family member over 50, this study should serve as a wake-up call. You or your loved ones may not be getting enough protein.

In the words of the authors: “A considerable portion of older adults (31%-50%) did not meet their protein recommendation (0.8 g/kg/d)…This contradicts the common perception that Americans are usually meeting or exceeding the 0.8 g/kg/d protein recommendation.”

  • The situation may be even worse than this study indicates. This study used the DRI standard for adequate protein intake of 0.8 g/kg/d. Many recent studies suggest that significantly higher protein intakes (1-1.2 g/kg/d) are needed for older adults to prevent loss of muscle mass (sarcopenia). If so, the likelihood that you or your loved ones are not getting enough protein is even higher.

In the words of the authors: “There is a general consensus recommending dietary protein intakes of 1-1.2 g/kg/d…for older adults…If over one third of older adults are not meeting the recommendation of 0.8 g/kg/d, these data suggest that far fewer older adults would be meeting the proposed higher levels (1-1.2 g/kg/d) needed to meet the demands to promote healthy aging.”

  • supplement shakeThe consequences of inadequate protein intake in the older adults may have a significant effect on their quality of life.

In the words of the authors: “This analysis found a positive association between achieving the recommended protein intake and self-reported physical functioning. The functional limitations associated with not meeting the protein requirement were all related to activities of daily living…”

  • Because of decreased appetite in many older adults, it is difficult to meet protein intakes of 1-1.2 g/kg/d with food alone. Protein supplementation can play a valuable role.

In the words of the authors: “When food alone is insufficient to meet a patient’s needs, oral nutritional supplementation may provide a means to meet protein intake recommendations.

“To some extent, sarcopenia can be managed with protein supplementation, considering all the factors that are working to reduce food intake in aging.” [The authors used the phrase “To some extent” because weight-bearing exercise is also required to manage sarcopenia].

  • While this study focused on protein intake, weight-bearing exercise is also essential to prevent sarcopenia. Exercise and adequate protein intake work together to build and maintain lean muscle mass.
  • Finally, we should not ignore the fact that those adults who were not getting enough protein were also getting insufficient levels of many micronutrients that affect the aging process. A good diet and supplementation are also important for healthy aging.

Specifically, the authors noted:

  • “Dietary fiber is associated with many benefits, especially in reducing the risk of heart disease.”
  • “Vitamin D inadequacy is associated with reduced mobility and an increase in risk for falls and fracture.”
  • “Zinc deficiencies…may cause dysfunctions in immunity and reduced healing time.”

The Bottom Line

 

A recent study analyzed protein intake in older American adults. The conclusions of the study were:

  • If you are over 50 or have a family member over 50, this study should serve as a wake-up call. You or your loved ones may not be getting enough protein.
  • The situation may be even worse than this study indicates. This study used the DRI standard for adequate protein intake of 0.8 g/kg/d. Many recent studies suggest that significantly higher protein intakes are needed for older adults to prevent loss of muscle mass (sarcopenia). If so, the likelihood that you or your loved ones are not getting enough protein is even higher.
  • The consequences of inadequate protein intake in the older adults may have a significant effect on their quality of life.
  • Because of decreased appetite in many older adults, it is difficult to meet protein intakes of 1-1.2 g/kg/d with food alone. Protein supplementation can play a valuable role.
  • While this study focused on protein intake, weight-bearing exercise is also essential to prevent sarcopenia. Exercise and adequate protein intake work together to build and maintain lean muscle mass.
  • Finally, we should not ignore the fact that those adults who were not getting enough protein were also getting insufficient levels of many micronutrients that affect the aging process. A good diet and supplementation are also important for healthy aging.

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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