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Muscle Weakness Linked to Lack of Vitamin D
Sunshine-seafood vitamin sustains aging muscles, but shortages abound

11/04/2019 By Craig Weatherby

Muscle strength matters at any time, but becomes more critical as we age.

Among people over 60, muscle weakness can crimp confidence, impair independence, and foster crippling falls.

Resistance exercise is key to preserving and building muscle, but there’s growing evidence that vitamin D helps enable and sustain  strength: for example, see Vitamin D Aids Muscle Strength, Resiliency, and Recovery and its links to related articles.

But, as we reported in Many Americans are Likely to Lack Vitamin D, one in four middle-aged folks in northern latitudes need more of the “sunshine-and-seafood” nutrient — which supplements can also supply.

Now, a new study from Ireland adds more evidence that vitamin D is critical to muscle strength, especially in middle age and later.

Irish study links vitamin D lack to muscle weakness
New research from Trinity College Dublin suggests that vitamin D deficiency undermines muscle function as we age (Aspell N et al. 2019).

The findings are based on the Dublin-based team’s analysis of data from 4,157 community-dwelling people aged 60 years or older (average 69.8 years) who’d participated in the English Longitudinal Study of Aging (ELSA).

The Trinity College scientists measured the participants' strength using two validated tests of muscle function: hand grip strength and the Short Physical Performance Battery (SPPB).

During the original ELSA study, the participants’ blood vitamin D levels were measured, and — in accordance with official guidelines — the Dublin team defined vitamin D deficiency as a blood level lower than 30 nmol/L (equivalent to 12 ng/mL).

Unsurprisingly, the Dublin-based team found that the study participants who regularly engaged in moderate physical activity were significantly less likely to suffer from poor muscle strength and physical performance.

But they also found that maintaining an "adequate" vitamin D blood level (i.e., above 30 nmol/L) seems to help preserve muscle strength and performance:

  • Vitamin D deficiency significantly raised the likelihood of impaired muscle strength and performance.
  • The risk of muscle weakness was twice as high among study participants with vitamin D deficiency (40.4%) compared to those with adequate vitamin D levels (21.6%).
  • The risk of impaired muscle performance was three times higher in the participants with vitamin D deficiency (25.2%) compared to those with adequate vitamin D levels (7.9%).

We should note that while a blood level of 30 nmol/L (12 ng/mL) — the usually recommended minimum — reduces the risk for osteoporosis and muscle weakness, it is probably too low for optimal health.

The U.S. Institute of Medicine recommends maintaining a blood level of 50 to 100 nmol/L (20 to 50 ng/mL), while leading researchers defined vitamin D “sufficiency” as having a minimum blood level of 75 to 250 nmol/L (30 to 100 ng/mL).

Raise blood levels with supplements, sun, and seafood 
Fortunately, vitamin D deficiency and insufficiency are relatively easy to remedy.

You can either get more sun (within safe limits), eat more fatty fish, and/or take supplemental vitamin D3 — the form in fatty fish and many supplements. Vitamin D3 is a more potent, beneficial form than the vitamin D2 found in mushrooms and some supplements.

The fish highest in vitamin D3 — such as wild salmon, sablefish, halibut, and albacore tuna (fresh/frozen or canned) — provide per-serving “doses” comparable to those found in supplements.

Compared with wild salmon, farmed salmon have much less vitamin D: see Wild Salmon Beats Farmed for Vitamin D (Again).

Among common species of fish, wild sockeye salmon rank as the richest source of vitamin D, with a single 3.5 ounce serving surpassing the US RDA of 600 IU by about 15 percent:

Vitamin D3 per 3.5 oz serving

  • Sockeye salmon 687 IU
  • Albacore tuna 544 IU
  • Silver salmon 430 IU
  • King salmon 236 IU
  • Sardines 222 IU
  • Sablefish 169 IU
  • Halibut 162 IU

Note: There aren't big differences between the vitamin D levels in fresh/frozen or canned versions of these fish.


Sources

  • Aspell N, Laird E, Healy M, Lawlor B, O'Sullivan M. Vitamin D Deficiency Is Associated With Impaired Muscle Strength And Physical Performance In Community-Dwelling Older Adults: Findings From The English Longitudinal Study Of Ageing. Clinical Interventions in Aging. 15 October 2019; Volume 2019:14 Pages 1751—1761. DOI https://doi.org/10.2147/CIA.S222143
  • Aspell N, Laird E, Healy M, Shannon T, Lawlor B, O'Sullivan M. The Prevalence and Determinants of Vitamin D Status in Community-Dwelling Older Adults: Results from the English Longitudinal Study of Ageing (ELSA). Nutrients. 2019 Jun 1;11(6). pii: E1253. doi: 10.3390/nu11061253.
  • Herrick KA, Storandt RJ, Afful J, Pfeiffer CM, Schleicher RL, Gahche JJ, Potischman N. Vitamin D status in the United States, 2011-2014. Am J Clin Nutr. 2019 May 10. pii: nqz037. doi: 10.1093/ajcn/nqz037. [Epub ahead of print].
  • O'Sullivan F, Raftery T, van Weele M, van Geffen J, McNamara D, O'Morain C, Mahmud N, Kelly D, Healy M, O'Sullivan M, Zgaga L. Sunshine is an Important Determinant of Vitamin D Status Even Among High-dose Supplement Users: Secondary Analysis of a Randomized Controlled Trial in Crohn's Disease Patients. Photochem Photobiol. 2019 Jul;95(4):1060-1067. doi: 10.1111/php.13086. Epub 2019 Mar 12.