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.

 

Are There Anti-Aging Vitamins?

Could You Live To Be 120 And Beyond?

Author: Dr. Stephen Chaney

anti-aging viataminsRecent headlines suggest that we can slow biological aging just by increasing our consumption of certain vitamins. That sounds wonderful.  After all, everyone is still hoping for that mythical “Fountain of Youth” and anti-aging vitamins could be just the ticket.

But, what did the paper behind the headlines actually show? The paper (J-Y Lee et al, Journal of Human Nutrition and Dietetics, DOI: 10.1111/jhn.12403, 2016) reported that people who consumed the most vitamin C and folic acid had the longest telomeres.

You might be wondering how journalists extrapolated from that study to headlines proclaiming that those vitamins could slow biological aging. To understand the answer to that question you need to know two things:

  • What is biological aging?
  • What are telomeres and why are they important?

What Is Biological Aging?

biological agingIn simplest terms, biological aging refers to the aging process on a cellular level. This concept is based on the “Hayflick Limit” first proposed by Leonard Hayflick in 1962. He showed that normal human cells have a maximum lifespan of 40-60 cell divisions. As they approach that upper limit, DNA damage accumulates and cell division slows and eventually stops.

The “Hayflick Limit” is important because our tissues depend on constant cell division to remain young and vital. Our organs are made up of various tissues and depend on those tissues performing at an optimal level. Thus, as more and more cells lose the ability to divide, our tissues and our organs begin to age. This is thought to be associated with disease and eventually death.

Thus, even though biological aging refers to aging at a cellular level, its significance is thought to extend far beyond the cellular level. It is thought to influence aging, disease, and death at a whole-body level. It reminds me of the famous quote “For want of a nail…the kingdom was lost.” If you’ve forgotten that quote, look it up. It is a perfect analogy for how something that seems so inconsequential can have such a profound effect on our health and mortality.

What Are Telomeres And Why Are They Important?

anti-aging vitamins telomeresTelomeres are sequences of repetitive DNA at the ends of our chromosomes that protect their integrity. Telomeres become progressively shorter as we age. As a very simple analogy we can think of telomeres as being similar to the tips of our shoelaces. If you have ever lost the tip of your shoelace, you know that the shoelace is worthless once the tip is gone.

That analogy holds perfectly with respect to our telomeres. As the telomers become progressively shorter, DNA division slows and eventually stops. DNA division is essential for cell division. Telomere shortening is postulated to be responsible for the Hayflick Limit. Thus, it is no surprise that telomere shortening is associated with aging, age-related diseases such as hypertension, diabetes, heart disease and dementia, and death.

Telomere shortening is a bad news, good news phenomenon. On the “bad” side, telomere shortening is inevitable. I hate to be the bearer of bad news, but we will all die at some point.

On the “good” side, there is tremendous heterogeneity in telomere length between individuals at any given age. Some of these differences in telomere length may be genetic, but many appear to be lifestyle related (MA Shammas, Current Opinion in Clinical Nutrition & Metabolic Care, 14: 28-34, 2011). For example, short telomers appear to be associated with things like smoking, environmental pollution, stress, meat consumption, and fat consumption. Long telomeres are associated with the lack of those things and with positive lifestyle characteristics such as exercise and consumption of fresh fruits and vegetables.

Are Some Vitamins Anti-Aging Vitamins?

slow agingMore recent studies have begun to look at the influence of individual nutrients on telomere length. The study featured this week (J-Y Lee et al, Journal of Human Nutrition and Dietetics, DOI: 10.1111/jhn.12403, 2016) is just the latest example.

This study used food frequency questionnaires to assess nutrient intake of 1958 middle-aged and older Koreans between June 2001 and January 2003. They measured intake of vitamins A, B1, B2, B3, B6, B9 (folate), C and E plus calcium, phosphorous, potassium iron and zinc.

Ten years later they measured telomere length in the same population and reported that:

  • Telomere length was positively associated with intake of vitamin C, folate, and potassium.
  • No association with telomere length was seen for the other nutrients.

So, are these anti-aging vitamins?  Let’s look at the strengths and weaknesses of this study.

This study has some notable strengths:

  • It is a fairly large study, so the results are statistically significant.
  • There is a good biochemical rationale for vitamin C and folate being protective for telomeres.
  • Antioxidants such as vitamin C, vitamin E, carotenoids, and polyphenols protect the DNA from oxidative damage.
  • Folic acid, vitamin B6, and vitamin B12 are involved in pathways that stabilize and repair DNA.
  • It is consistent with previous studies (See below)

However, this study also has some glaring weaknesses:

  • It only measures associations, not cause and effect.
  • The diet analysis was not repeated at the end of the study. The authors assumed that dietary habits did not change, but we don’t know that.
  • The use of dietary supplements was not assessed, so we don’t know how that might have influenced the outcome.

What Does This Study Mean For You?

If we look at the totality of published studies(MA Shammas, Current Opinion in Clinical Nutrition & Metabolic Care, 14: 28-34, 2011) :

  • There is good evidence that optimal intake of the antioxidants C and E is positively associated with telomere length.
  • There is good evidence that optimal intake of folic acid and vitamin B12 is positively associated with telomere length.
  • There is preliminary evidence that optimal intake of carotenoids, polyphenols, and omega-3 fatty acids is positively associated with telomere length.

However, there is a lot we don’t know about telomeres. We know that short telomeres are associated with aging, age-related diseases and death. What we do not know is whether telomere shortening is the cause of the aging process or merely a marker of aging. Let me rephrase those two possibilities in a more understandable manner.

  • If telomere shortening is the cause of the aging process, anything we can do to decrease the rate of telomere shortening would slow the aging process and delay the onset of age-related diseases.  If the vitamins mentioned above then caused this decrease, they could indeed be considered anti-aging vitamins.
  • If telomere length is simply a marker of aging, we can consider it like the “canary in the coal mine”. That analogy might be particularly apt. The value of the canary is that it can detect toxic gases when they are still undetectable to humans. It turns out that it is virtually impossible to detect the effect of nutrient intake on longevity (We simply live too long), and it has proven very difficult to determine the effect of nutrient intake on age-related diseases. Having a simple marker of the aging process may well give us valuable insight into how we can best delay the aging process.

Either way longer telomeres are probably a good thing. Based on a limit of 40-60 cell divisions for normal human cells, Leonard Hayflick estimated a maximum human lifespan of 120 years. If we could truly decrease the rate of telomere shortening, would that potentially increase maximum human lifespan or would it mean that more of us reach 120 in good health? Most of us would probably be happy with either outcome.

 

The Bottom Line

 

  • Telomeres are the tips at the end of our chromosomes that protect the chromosomes from unraveling.
  • Our telomeres get progressively shorter as we get older. Short telomeres are associated with aging, age-related diseases, and death.
  • Recent studies have shown that our lifestyle can influence the rate of telomere shortening. For example:
  • Short telomers are associated with things like smoking, environmental pollution, stress, meat consumption, and fat consumption.
  • Long telomeres are associated with the lack of those things and with positive lifestyle characteristics such as exercise and consumption of fresh fruits and vegetables.
  • Recent studies have also shown that optimal intake of certain nutrients can influence the rate of telomere shortening. For example:
  • There is good evidence that optimal intake of the vitamins C, E, folic acid, and B12 is positively associated with telomere length.
  • There is preliminary evidence that optimal intake of carotenoids, polyphenols, and omega-3 fatty acids is positively associated with telomere length.
  • There is a lot that we do not know about telomere length. In particular,
  • We do not know whether telomere shortening is the cause of the aging process or merely a marker of aging, like the canary in the coal mine.
  • In either case, anything we can do to reduce the rate of telomere shortening is probably a good thing.

 

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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