Don’t give vitamin D supplements for longevity to people who are not deficient

People who were not deficient and then supplemented for 5 years had the same numbers of cancers, cardiovascular disease, and deaths as those who did not. Adults who rarely go out and get little sun may take 400 IU a day and should not exceed 2000 IU a day. At high doses, bone density falls more and falls increase. Fatigue alone does not mean vitamin D deficiency; if you have been tired for weeks with no clear reason, see a doctor.

Cost

About 0.2 to 0.5 yuan a day, or 100 to 200 yuan a year. The money is not much; the real cost is thinking you have already done prevention.

Benefit

The VITAL trial enrolled 25871 people who took 2000 IU daily and followed them for a median of 5.3 years. Cancer, cardiovascular disease, and death showed no difference. For cancers that spread, HR was 0.96 (HR is a hazard ratio; 1 means the two sides match; 95% CI 0.88–1.06 is the credible range). For major cardiovascular events, HR was 0.97 (0.85–1.12). For all-cause death, HR was 0.99 (0.87–1.12). The D-Health trial enrolled 21315 Australians aged 60 and above who took 60000 IU monthly and followed them for 5 years. That trial also showed no difference: all-cause death HR 1.04 (0.93–1.18). Death rates were 5.3% versus 5.1%. It looks worthwhile because some studies only record and never intervene, find that people with low vitamin D die more often, and that is misread as “supplementing works.” People who rarely go out have a separate recommendation. The UK Department of Health advises adults who rarely go out, live in care homes, or cover most of their skin when outdoors to take 10 micrograms of vitamin D daily year-round. The NHS states that 1 microgram equals 40 IU, so 10 micrograms is 400 IU. China’s health industry standard recommends 10 micrograms a day for adults aged 18 to 64 and 15 micrograms for those 65 and above. The same standard sets the tolerable upper intake at 50 micrograms a day (2000 IU), because too much raises blood calcium. The NHS adult upper limit is wider: 100 micrograms (4000 IU). Fatigue has many causes; the NHS lists insufficient sleep, stress and depression, iron-deficiency anemia, diabetes, hyperthyroidism, and sleep apnea. It advises seeing a doctor if fatigue lasts several weeks without a clear reason, or if it interferes with daily life. More is not better. VITAL also counted fractures: people on 2000 IU daily matched those who did not supplement (HR 0.98, 0.89–1.08). VITAL also looked at depression among 18353 of the participants aged 50 and above who were not depressed at the time. Those who supplemented had 12.9 cases of depression or relapse per 1000 person-years; those who did not had 13.3; no difference (HR 0.97, 0.87–1.09). Mood scores also did not differ. The authors state that the results do not support adults using vitamin D to prevent depression. A Canadian trial enrolled 311 healthy people aged 55 to 70 without osteoporosis, in three groups taking 400, 4000, or 10000 IU daily for 3 years. The higher the dose, the more bone density fell at the wrist radius: 1.2%, 2.4%, and 3.5% respectively. Bone compressive strength showed no difference. The authors conclude that this does not support high-dose vitamin D helping bone. A Swiss trial enrolled 200 people aged 70 and above who had fallen; they took 24000 IU or 60000 IU monthly for a year. The 60000 IU group’s leg function did not improve, and more of them fell within the year (66.9% versus 47.9%). An Australian trial enrolled 2256 women aged 70 and above who took 500000 IU once each autumn–winter. Their falls were about 15% higher (RR 1.15, 1.02–1.30) and fractures about 26% higher (RR 1.26, 1.00–1.59).

Notes

Controversy: Neither VITAL nor D-Health specially recruited people who were truly vitamin D deficient, so the conclusions cover only “people who were not already deficient.” People confirmed deficient, people with osteoporosis, and infants and young children should still supplement as their doctor says. Severe deficiency does not have to mean an injection. The 2016 global consensus on rickets recommends oral dosing because oral raises levels faster than intramuscular injection. One trial enrolled 61 children with rickets: one group got a single injection of 600000 IU; the other took 60000 IU orally each week for 10 weeks. At 12 weeks, labs and imaging did not differ between groups. After finishing the dose the doctor prescribed, recheck; if levels still do not rise, have the doctor look for an absorption problem. People who get little sun taking 400 IU daily are preventing deficiency. The health industry standard states that vitamin D deficiency causes rickets, osteomalacia, and osteoporosis. That does not mean it prevents cancer or heart disease, or that it treats fatigue. If a doctor has prescribed a different dose, follow the doctor. Whether supplementing helps people who already have depression is mixed. A 2023 analysis pooling 41 trials saw a small drop in depression scores, but results varied widely across trials and the authors rated the evidence quality in the lowest tier. A 2024 analysis split by duration found that trials followed for a year or more showed no effect. If you have depression, go to psychiatry or clinical psychology first; do not replace treatment with vitamin D. This item looked at all-cause death, cancer, cardiovascular disease, bone, falls, and depression; nothing else. How infants should supplement is in Section 20, Item 16 (400 international units of vitamin D daily).

Sources · 14

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