Vitamin D for men has been sold as a fix for everything from low energy to weak muscles. Large trials have since tested many of those claims, and the results are more sobering than the marketing.
Here is who is actually at risk, what a blood test can and cannot tell you, how much you need, and what the evidence says about muscle and bone after 35.
Key takeaways
- The RDA for adult men up to age 70 is 600 IU (15 mcg) per day; the upper limit is 4,000 IU (100 mcg) per day, per the NIH Office of Dietary Supplements.
- Deficiency is common even in sunny countries such as India, mainly because of indoor lifestyles, darker skin and low dietary intake.
- The large VITAL trial found that 2,000 IU a day did not reduce cancer, heart attacks, strokes or fractures in mostly non-deficient adults.
- Vitamin D appears to give a small strength benefit, mainly in older or clearly deficient people, and no clear effect on muscle mass.
- Experts disagree on what blood level counts as “enough,” and routine testing for healthy adults is not recommended by the Endocrine Society.
Why vitamin D matters
Vitamin D helps your body absorb calcium and keep bones mineralised. Receptors for it are found in muscle and many other tissues, which is why researchers have explored links to strength, immunity and chronic disease.
Your skin makes vitamin D when exposed to UVB sunlight. Few foods contain much of it naturally, so sun exposure, fortified foods and supplements are the main sources for most people.
Who is at risk of low vitamin D?
The NIH Office of Dietary Supplements lists these groups as more likely to have inadequate vitamin D:
- Older adults, whose skin makes less vitamin D
- People with limited sun exposure, such as office workers and people who cover most of their skin
- People with darker skin, which needs more sun to make the same amount
- People with obesity or who have had gastric bypass surgery
- People with conditions that limit fat absorption, such as Crohn’s or coeliac disease
For a typical man over 35 who commutes by car, works indoors and trains in a gym, several of these boxes may apply.
The sun exposure paradox in India and Latin America
You might assume plenty of sun means plenty of vitamin D. The data says otherwise.
A 2017 systematic review in the Indian Journal of Endocrinology and Metabolism looked at 40 studies of apparently healthy Indians. The pooled average blood level was about 14 ng/mL, and only 35% of studies reported average levels above 20 ng/mL. The authors linked this to darker skin, indoor and urban lifestyles, sunscreen use and low intake of vitamin D-rich foods. Rural residents, who spent more time outdoors, tended to have higher levels.
The same pattern applies to many urban professionals in Latin America: a sunny climate does not help much if you spend daylight hours inside. In cities at high altitude, such as Bogotá, UV can be strong, which is a reason to be careful about burning, not to stay indoors.
Some expert bodies suggest that roughly 5 to 30 minutes of midday sun on uncovered skin a few times a week usually produces enough vitamin D. The right amount varies with skin tone, season and location, and UV exposure is also the leading preventable cause of skin cancer. Short, regular exposure without burning is the sensible middle ground.
Testing: what 25(OH)D tells you and the debated cut-offs
The standard blood test measures 25-hydroxyvitamin D, written as 25(OH)D. It reflects vitamin D from sun, food and supplements over the past few weeks.
The problem is that experts disagree on what level is “enough.”
| 25(OH)D level | NIH ODS / National Academies interpretation |
|---|---|
| Below 12 ng/mL (30 nmol/L) | Associated with deficiency |
| 12 to below 20 ng/mL (30–50 nmol/L) | Generally considered inadequate for bone and overall health |
| 20 ng/mL (50 nmol/L) or more | Generally considered adequate for most people |
| Above 50 ng/mL (125 nmol/L) | Linked to potential adverse effects, especially above 60 ng/mL |
In 2011, the Endocrine Society argued that levels above 30 ng/mL were needed for the best effect on bone and muscle. That higher target is why many labs flag 20 to 29 ng/mL as “insufficient.”
In 2024, the Endocrine Society updated its guidance for healthy people. It did not recommend routine 25(OH)D testing for healthy adults and said the evidence was not strong enough to set specific blood-level targets for disease prevention. For healthy adults aged 19 to 74, it suggested not taking more than the standard recommended intake.
Testing still makes sense when there is a medical reason, such as osteoporosis, malabsorption, kidney or liver disease, or symptoms your doctor wants to investigate. If you have several risk factors, it is reasonable to ask your doctor whether a test is worthwhile.
How much vitamin D do you need?
| Age | RDA | Upper limit (UL) |
|---|---|---|
| 19–70 years | 600 IU (15 mcg)/day | 4,000 IU (100 mcg)/day |
| Over 70 years | 800 IU (20 mcg)/day | 4,000 IU (100 mcg)/day |
The RDA assumes minimal sun exposure. The upper limit is the highest daily intake unlikely to cause harm for most people, not a target. Doctors sometimes prescribe higher doses for a limited period to correct a confirmed deficiency, which should be done under medical supervision.
Food sources, including vegetarian options
- Salmon or trout (3 oz, cooked): roughly 570 to 645 IU
- UV-exposed mushrooms (½ cup): about 366 IU. Regular mushrooms contain very little.
- Fortified milk (1 cup): about 120 IU. Some plant milks are fortified too; check the label.
- Egg (1 large): about 44 IU
For vegetarians, fortified dairy or plant milks, UV-exposed mushrooms, eggs if you eat them, and sensible sun exposure are the main options. Food alone rarely reaches 600 IU a day without fortified products.
What large trials did and did not show
Observational studies long linked low vitamin D with many diseases. But people with low levels are often less active, heavier or unwell, so cause and effect are hard to separate. Large randomised trials were designed to answer the question properly.
The VITAL trial
VITAL gave 25,871 US adults (men 50 and over, women 55 and over) either 2,000 IU of vitamin D3 a day or a placebo, for a median of 5.3 years.
- Cancer: no significant reduction in overall cancer incidence. A secondary analysis suggested a possible benefit for cancer deaths, and people of normal weight seemed to respond better.
- Heart disease and stroke: no significant reduction in heart attacks, strokes or cardiovascular deaths.
- Fractures: a 2022 analysis found no reduction in total, hip or non-spine fractures, regardless of baseline vitamin D level.
An important caveat: most VITAL participants were not deficient at the start. The results tell you that extra vitamin D does not add much for people who already have enough. They do not tell you that fixing a real deficiency is pointless.
Vitamin D, muscle and bone after 35
This is where most active men are curious. Can vitamin D help you get stronger?
A 2014 meta-analysis in the Journal of Clinical Endocrinology and Metabolism pooled 30 randomised trials with more than 5,600 people. Vitamin D had a small positive effect on muscle strength, but no significant effect on muscle mass or power. The strength benefit was larger in people aged 65 and over and in those who started with very low levels (below 30 nmol/L, or 12 ng/mL).
For falls, the US Preventive Services Task Force concluded with moderate certainty that vitamin D does not reduce falls in community-dwelling adults aged 65 and over.
The practical message: if you are deficient, correcting it is sensible for bone and possibly for strength. If your levels are already adequate, more vitamin D is unlikely to add muscle. Lifting, protein and sleep will do far more. Start with our guides to strength training after 35 and protein after 35.
Low vitamin D is also often mentioned alongside fatigue and low testosterone. The evidence for supplementation fixing either in non-deficient men is weak. For a broader look, see why you are always tired after 35.
A practical plan for men over 35
- Get regular, short sun exposure without burning, especially if you work indoors.
- Include fortified foods and, if you eat them, oily fish and eggs.
- If you have risk factors, such as darker skin, obesity, very little sun or a malabsorption condition, ask your doctor whether a test or supplement makes sense.
- If you supplement, stay at or near the RDA unless your doctor prescribes more, and never exceed 4,000 IU a day on your own.
- Do not expect miracles. Vitamin D supports bone health, but training and nutrition drive strength and body composition.
Safety note: Too much vitamin D can raise blood calcium, causing nausea, vomiting, weakness, kidney stones and, in severe cases, kidney damage or heart rhythm problems. Vitamin D can interact with some medicines, including thiazide diuretics (risk of high calcium), corticosteroids, orlistat and some statins. If you have kidney disease, sarcoidosis, hyperparathyroidism or a history of kidney stones, check with your doctor before supplementing.
FAQ
Should every man over 35 take vitamin D?
Not necessarily. The 2024 Endocrine Society guidance suggests healthy adults under 75 do not need more than the standard recommended intake. People with risk factors or a confirmed deficiency should follow their doctor’s advice.
What vitamin D level should I aim for?
The NIH Office of Dietary Supplements considers 20 ng/mL (50 nmol/L) or more adequate for most people. Some groups prefer above 30 ng/mL. Levels above 50 ng/mL bring no clear benefit and may raise risk.
Will vitamin D boost my muscle growth?
Only modestly, and mainly if you are older or clearly deficient. Trials show a small effect on strength and no significant effect on muscle mass.
Is vitamin D3 better than D2?
Both raise blood levels. D3 tends to raise and maintain 25(OH)D levels somewhat more effectively, which is why it is used more often. Some D3 is animal-derived, so vegetarians should check the source.
Can I get enough vitamin D from the sun in India or Colombia?
Many people can, but surveys in India show widespread low levels despite strong sun, mostly due to indoor lifestyles. Regular short outdoor exposure helps, while avoiding sunburn.
Free tool: see which daily habits to fix first with the 2-minute Fit After 35 score.
Sources
- NIH Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals.
- Manson JE, et al. Vitamin D supplements and prevention of cancer and cardiovascular disease (VITAL). N Engl J Med. 2019.
- Mass General Brigham. VITAL fracture analysis (LeBoff MS, et al. N Engl J Med. 2022).
- Endocrine Society. 2024 clinical practice guideline on vitamin D for the prevention of disease.
- Beaudart C, et al. The effects of vitamin D on skeletal muscle strength, muscle mass and muscle power. J Clin Endocrinol Metab. 2014.
- Selvarajan S, et al. Systematic review on vitamin D level in apparently healthy Indian population. Indian J Endocrinol Metab. 2017.
This article is for general education and is not medical advice. Check with your doctor before starting a new training or nutrition plan, especially if you have a health condition.
