Vitamin D is often called the “sunshine-and-seafood” vitamin.
This hormone-like substance is normally made in the skin using energy from sunlight.
Vitamin D is found in a few foods – including fish, fish-liver oils, egg yolks, mushrooms, and fortified cereals.
Fatty fish like tuna and sardines are the richest food sources by far, but wild Pacific salmon – especially sockeye – top the list.
Many Americans are deemed vitamin D deficient … with the highest risk found among darker-skinned people, the elderly, and people living in northern states.
Vitamin D plays key roles in bone formation, and its role in critical organs, systems, and health conditions is just now becoming clearer.
Blood levels are boosted most effectively and swiftly by taking vitamin D supplements (and/or receiving vitamin D injections).
Fish fit the vitamin D bill;
Sockeye salmon stand out
In addition to getting vitamin D from supplements, certain fish rank among the very few substantial food sources of vitamin D, far outranking milk and other D-fortified foods.
Among fish, wild sockeye salmon rank as the richest source, with a single 3.5 ounce serving surpassing the US RDA of 600 IU by about 15 percent.
Vitamin D 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
Like the omega-3s in seafood (DHA and EPA), vitamin D is essential to health and survival, and plays broad roles in the body.
And growing evidence shows that vitamin D is equally or more important to muscle health, strength and recovery.
Vitamin D helps regulate various processes within our muscles – such as calcium and phosphorous metabolism, and protein synthesis – that help them move, repair, and grow.
Now, the results of three separate studies combine to strengthen the idea that our muscles benefit from higher blood levels of vitamin D.
Vitamin D seen to speed recovery from muscle injuries
Recently, a Utah-based scientific team reported that vitamin D can speed muscle recovery after intense exercise … and may deter exercise-induced muscle damage (Barker T et al. 2013).
Invisible muscle damage is one inevitable effect of any intense exercise, and is caused by a variety of factors, such as micro-tears, muscle strains, and local inflammation.
For example, after a long steep hike, bike ride, or fast run, the affected muscles typically become sore and a bit weaker than normal.
How much “D” do we need?
Recently, the U.S. Institute of Medicine (IOM) revised the recommended vitamin D intakes upward, to 600 IU/day for adults and 800 IU/day for people older than 70.
The Endocrine Society currently recommends the following vitamin D intakes, preferable vitamin D3 (Holick MF et al. 2011):
Age 0 to 1 year: 400 to 1,000 IU/day
Age 1 to 18 years: 600 to 1,000 IU/day
All adults over age 18: 1,500 to 2,000 IU/day
Pregnant or nursing women under age 18: 600 to 1,000 IU/day
Pregnant or nursing women over age 18: 1,500 to 2,000 IU/day
There's also general agreement among expert researchers that vitamin D intakes of up to 4,000 IU/day are safe. However, when it raised the vitamin D RDAs, the IOM only raised the upper intake limit to 2,000 IU.
Likewise, a recent report by the Institute of Medicine recommended maintaining a blood level of 20 to 50 ng/mL.
But many experts recommend 30 to 100 ng/mL to achieve true vitamin D “sufficiency” (Holick MF et al. 2011; Heaney RP et al. 2011).
After a few days, exercise-injured muscles recover, regain their full strength, and will gain a bit of size and strength.
The study was led by Tyler Barker, Ph.D., of The Orthopedic Specialty Hospital, and included researchers from the University of Utah, the Intermountain Medical Center, USANA Health Sciences, the LDS Hospital, and ARUP Laboratories.
Barker and his colleagues wanted to see what effect vitamin D levels had in the muscle-recovery process.
And, affirming earlier indications, the Utah team found that higher vitamin D blood levels aided muscle recovery.
“We wanted to study the relationship between vitamin levels and recovery following intense exercise,” said Barker. “And we found that those who had higher vitamin D levels had a faster rate recovery from muscle damage.”
“This research sheds new light on the importance of vitamin D in our bodies,” said co-author Dr. Brian Dixon, of USANA Health Sciences. “I see the potential benefits of this study being far reaching,” he added. “This study is especially appealing on a personal level. For those of us who consider ourselves ‘weekend warriors', [it] looks like we can play a little harder and maybe not suffer as much on Monday.”
The Utah team recruited 14 physically active adults for the study.
Before and after intense exercise, the scientists measured the volunteer's vitamin D levels and the amount of leg force they could exert.
Each participant performed intense exercise with one leg while the other leg acted as a control.
Then their leg strength was tested at day one, two, three, and seven following the initial intense exercise, by pushing against a special force-measuring plate.
By assessing leg strength, researchers could assess the initial muscle damage, and then the recovery time.
It became clear that the volunteers with higher blood levels of vitamin D regained their strength more quickly.
The researchers concluded that higher vitamin D levels appear to protect against muscular weakness caused by muscle damage.
Ballet dancers benefited from supplemental D
Earlier this year, researchers in Britain decided to test the muscle-health effects of vitamin D in ballet cancers, who, like athletes, suffer muscle injury routinely.
The team included researchers from the University of Wolverhampton, the Jerwood Centre for the Prevention and Treatment of Dance Injuries, and the National Institute of Dance Medicine and Science.
They recruited 24 elite classical ballet dancers, and divided them into two groups for a placebo-controlled, four-month clinical trial (Wyon MA et al. 2013).
Each group was assigned to a different daily regimen:
Before and after the trial, the scientists assessed the dancers' muscle strength by testing isometric muscular strength and vertical jump height.
They also recorded the rate of injuries among the dancers during the trial period.
After four months, the vitamin D group showed key benefits:
The vitamin D group also sustained significantly fewer, milder injuries than the controls.
As the British team concluded, “Oral supplementation of vitamin D3 during the winter months has beneficial effects on muscular performance and injury occurrence in elite ballet dancers.” (Wyon MA et al. 2013)
Vitamin D found to support strength from within muscle cells
Findings from the UK's Newcastle University reveal that Vitamin D is vital for optimal human efficiency and energy (Sinha A et al. 2013).
Vitamin D is thought to boost activity and efficiency of our mitochondria … the biological “power plants” of human and animal cells.
A group led by Dr. Akash Sinha found that muscle function improved after subjects took vitamin D supplements.
The researchers recruited 12 patients with severe vitamin D deficiency.
The UK team used non-invasive magnetic resonance (MRI) scans to measure the subjects' response to exercise, before and after taking supplemental vitamin D.
As Dr. Sinha said, “Examining this small group of patients … we found that those with very low vitamin D levels improved their muscle efficiency significantly when their vitamin D levels were improved.”
Alongside poor bone health, muscle fatigue is a common symptom in vitamin D deficient patients.
This fatigue could be due to reduced efficiency of the mitochondria found in every cell of the body.
Mitochondria use glucose and oxygen to make energy in a form that can be used to run the cell … an energy-rich molecule called ATP.
Muscle cells need large amounts of ATP for movement and they store phosphocreatine as a ready and available energy source to make ATP.
The mitochondria also replenish this phosphocreatine store after muscle contraction, and measuring the time taken to replenish these stores is a good gauge of mitochondrial efficiency.
The UK team found that phosphocreatine recovery rates significantly improved after the patients took vitamin D for 10 to 12 weeks, from 34.4sec to 27.8sec.
And all 12 patients reported feeling less fatigued after taking vitamin D supplements.
In a parallel study, the UK group also linked low vitamin D levels with reduced mitochondrial function: “We have proved for the first time a link between vitamin D and mitochondria function,” said Dr. Sinha.
He added a note of urgency regarding low vitamin D levels: “Of the patients I see, around 60 percent are vitamin D deficient and most people living north of Manchester will struggle to process enough vitamin D from sunlight alone, particularly during winter and spring. So a simple vitamin D tablet could help boost your energy levels – from within the cells.”
In terms of latitude, Manchester lies about midway between Seattle, Washington and Anchorage, Alaska.
- Barker T, Henriksen VT, Martins TB, Hill HR, Kjeldsberg CR, Schneider ED, Dixon BM, Weaver LK. Higher serum 25-hydroxyvitamin d concentrations associate with a faster recovery of skeletal muscle strength after muscular injury. Nutrients. 2013 Apr 17;5(4):1253-75. doi: 10.3390/nu5041253
- Gomez J, The Orthopedic Specialty Hospital (TOSH). Vitamin D Can Help in Muscle Recovery: TOSH Study Finds Vitamin D May Prevent Muscle Damage. May 13, 2013. Accessed at http://intermountainhealthcare.org/hospitals/tosh/about/news/Pages/home.aspx?NewsID=1459
- Newcastle University (NU). Vitamin D proven to boost energy – from within the cells. April 6, 2013. Accessed at http://www.ncl.ac.uk/press.office/press.release/item/vitamin-d-proven-to-boost-energy-from-within-the-cells
- Sinha A et al. Improving the vitamin D status of vitamin D deficient adults is associated with improved mitochondrial oxidative function in skeletal muscle. Endocrine Abstracts (2013) 31 OC1.6 | DOI:10.1530/endoabs.31.OC1.6. Accessed at http://www.endocrine-abstracts.org/ea/0031/ea0031OC1.6.htm
- Wyon MA, Koutedakis Y, Wolman R, Nevill AM, Allen N. The influence of winter vitamin D supplementation on muscle function and injury occurrence in elite ballet dancers: A controlled study. J Sci Med Sport. 2013 Apr 22. doi:pii: S1440-2440(13)00055-8. 10.1016/j.jsams.2013.03.007. [Epub ahead of print]