| Finding | Result |
|---|---|
| Telomere shortening | The vitamin D group showed less than half the telomere shortening compared to the placebo group |
| Autoimmune diseases | The vitamin D group had fewer autoimmune diseases |
| Inflammation markers | The vitamin D group had reduced inflammation markers |
| Safety | 2,000 IU per day was “very safe,” without side effects or adverse events |
Lead Researcher’s Comments
Lead study author JoAnn Manson, professor of medicine at Harvard Medical School, said the findings “suggest a promising role for vitamin D in slowing a pathway for biological aging and age-related chronic disease.”
While the researchers were surprised that vitamin D was linked to such substantial protection against telomere shortening, Manson said the findings are consistent with previous evidence.
“Vitamin D tamps down inflammation, a major cause of telomere shortening and chronic diseases of aging.”
— Dr. JoAnn Manson, Harvard Medical School
What This Means for You: Vitamin D Recommendations
The question of what constitutes an “adequate” blood level of vitamin D is a “controversial topic,” according to Manson.
Current Guidelines
| Organization | Recommendation |
|---|---|
| National Academy of Medicine | 600 IU/day for adults up to age 70; 800 IU/day above age 70 |
| Endocrine Society (recent guidelines) | May be helpful for adults aged 75+, infants/children, pregnant women, and those with prediabetes |
| U.S. Preventive Services Task Force | Does not recommend universal screening or routine use of vitamin D supplements |
Dr. Manson’s Practical Advice
For anyone who has concerns about getting adequate vitamin D from their diet and/or time outdoors, Manson said that supplementation with 1000 to 2000 IU/day of vitamin D would be “very reasonable.”
“More is not necessarily better, and very high doses—such as more than 10,000 IU/day—may be associated with high blood or urine calcium levels and toxicity.”
— Dr. JoAnn Man
