New research links vitamin D to cancer prevention, slower aging, and heart health. Here's what to know.
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| | | | | Nearly 42% of U.S. adults are deficient in vitamin D, a hormone that's essential for immune function, inflammation control, and more. As winter brings shorter days and less sun exposure, three recent studies offer compelling reasons to get your levels checked. Here's what the science shows and why getting tested matters. | | | | | | | Let's look into it,
Tim Snaith
Newsletter Editor, Healthline |  | | Written by Tim Snaith
December 19, 2025 • 3.5 min read | | | | | | | |
| |  | | | | 3 ways vitamin D may boost longevity | | Vitamin D plays a key role in supporting bone health, immune function, and managing inflammation. Darker skin pigmentation, sunscreen use, and reduced UV radiation from sunlight during winter months all contribute to insufficient levels. Older adults, people with obesity, and those with chronic kidney or liver disease face an even higher risk. | | Growing evidence links vitamin D deficiency to increased risk of certain cancers, immune diseases, and cardiovascular conditions, with three recent studies showing just how significant this connection may be. | | Reduced colorectal cancer risk | | A recent review of 50 studies involving over 1 million participants found that higher vitamin D levels were associated with a lower risk of colorectal cancer. Among people with colorectal cancer, higher vitamin D levels are linked to improved survival and lower mortality. | | Researchers suggest it may be useful alongside other cancer treatments, though more research is needed to understand how genetics, lifestyle, and other treatments affect vitamin D's role in cancer prevention. | | Slower biological aging | | Telomeres are DNA sequences that protect the ends of chromosomes from damage. They shorten with age, and shorter telomeres are associated with age-related diseases. One study found that vitamin D3 supplementation may preserve telomere length in white blood cells among older adults, potentially slowing biological aging. | | Protection against repeat heart attacks | | Low vitamin D levels have been linked to poor cardiovascular health. A new study found that targeted vitamin D3 supplementation may drastically reduce the risk of a second heart attack. | | Though there was no significant difference in the total number of cardiac events between groups, repeat heart attacks occurred in 3.8% of the vitamin D3 group compared to 7.9% in the control group — less than half the risk. | | Why getting tested matters | | The 25-hydroxy vitamin D test measures how much vitamin D your body has. Doctors use it to monitor levels and determine if you need more sun exposure, dietary changes, or supplements. | - Deficiency: less than 12 ng/mL
- Potential deficiency: 12 to 20 ng/mL
- Normal levels: 20 to 50 ng/mL
- High levels: higher than 50 ng/mL
| | A low level may mean you're not eating a balanced diet, your intestines aren't absorbing the vitamin properly, or you're not getting enough sun exposure. High levels usually result from taking too many supplements and can lead to liver or kidney problems. | | Vitamin D is found in fish, eggs, fortified dairy products, and dietary supplements. Your skin also produces it when exposed to UV rays. During the winter months with less sunlight, monitoring your levels becomes especially important. | | Though the recommended daily amount for most people is around 600 to 800 IU for adults, the Endocrine Society recommends an intake of 1,500 to 2,000 IU. Your doctor can help determine if you need supplements based on your test results. | | | | Over to you: Do you regularly check your vitamin D levels? Have you ever? Email wellnesswire@healthline.com and let us know. | | | | |   | | | | | | | | Until next time, |  | Take care of yourself, and we'll see
you again soon! | | |  | | |  | | This edition was powered by | | egg nog. | | | | | | | | View in browser
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