Vitamin D3 (incl. HMB + vitamin D)
Sunlight-made hormone that regulates immunity and muscle; linked to slower telomere shortening and preserved function in trials.
Summary
Vitamin D is made in skin from UVB light, and its active form turns on genes in immune and muscle cells, nudging T cells toward a regulatory, less inflammatory phenotype. In the VITAL RCT, 2,000 IU/day D3 slowed telomere shortening over 4 years, but 2,000 IU/day alone did not slow epigenetic clocks in older Swiss adults. For muscle, trials show vitamin D helps deficient older people gain muscle mass, and a 12-month trial of HMB (a leucine metabolite) plus vitamin D improved function in over-60s. An unpublished draft covers a meta-analysis showing daily or weekly vitamin D reduces respiratory infections, most in deficient people; a mouse study pairs it with resveratrol for Parkinson's.
Takes a coconut-oil D3 (Sports Research) in winter, more than 2,000 IU but not every day.From Research Roundup: Telomeres and Vitamin D3
The evidence
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Human trial
In the VITAL randomized trial (1,000+ participants, 4 years), vitamin D3 at 2,000 IU/day significantly reduced telomere attrition, while 1 g/day omega-3 had no effect.
Read the study Discussed in Research Roundup: Telomeres and Vitamin D3 -
Human trial
In a 12-month double-blind trial in people over 60, HMB plus vitamin D without exercise improved a functional index (body composition, lean mass, strength, function) vs control; adding exercise gave no extra gain over exercise alone.
Read the study Discussed in HMB and Vitamin D for Muscle in Aging -
Human trial
A 2019 meta-analysis of 25 RCTs found daily or weekly vitamin D cut respiratory infection risk by about 20% overall and 70% in deficient people; large bolus shots had no significant effect.
Read the study Discussed in Vitamin D for Preventing Respiratory Infections (draft) -
Human trial
In a placebo-controlled trial in vitamin D-deficient older people, 10,000 IU three times per week improved skeletal muscle mass but not handgrip strength.
Read the study Discussed in Preventing Muscle Loss in Aging -
Human trial
In an RCT in older people with low muscle mass, vitamin D plus leucine-enriched whey improved chair-stand time and appendicular muscle mass.
Read the study Discussed in Preventing Muscle Loss in Aging -
Human trial
In a post hoc analysis of 777 older Swiss adults over 3 years, vitamin D (2,000 IU/day) alone did not slow epigenetic aging; combined with omega-3 and exercise it added benefit on one clock (PhenoAge).
Doses used in studies
Amounts reported in the research, not dosing recommendations.
| Dose | Context |
|---|---|
| 2,000 IU/day D3 | VITAL RCT, 4 years, telomere length |
| 3.0 g/day HMB (split into two doses) + 2,000 IU/day D3 | 12-month trial in adults over 60 |
| 10,000 IU three times per week | Placebo-controlled trial in vitamin D-deficient older people |
| 2,000 IU/day | Epigenetic clock study; she suggests this may have been too low since 30% were deficient at baseline |
| 280,000 IU injection | Hospitalized COVID-19 patients; 87% less likely to die (unpublished draft) |
| 1,000 IU with magnesium and B12 | Small trial in hospitalized COVID patients (unpublished draft) |
Cautions
- HMB can cause nausea and diarrhea; stop if these occur and talk with your doctor if you have health conditions.
- Many vitamin D supplements use soybean or cottonseed oil; she prefers coconut or olive oil versions.
- Large single bolus shots did not significantly reduce respiratory infections in the meta-analysis; daily or weekly dosing did.