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Vitamin D: Vital to Your Health

A vitamin that has a significant affect on the health of your cells.

Key points

  • Vitamin D is a potent cancer inhibitor due to its immune-modulating effect.
  • This super-vitamin helps regulate calcium metabolism and is also involved in immune function.
  • Low levels of vitamin D are linked to depression.
  • The primary way to obtain vitamin D is through sun exposure, but sunscreen has limited this option.

There is no shortage of ads for vitamins and supplements. Just try to have dinner while watching the news, and you will be bombarded with commercials for them. The vitamin and supplement industry is worth $35.6 billion, and 77% of Americans take at least one supplement.

Vitamin D deficiency is prevalent globally, affecting close to one billion people. In the 1930s, the decision to fortify milk with vitamin D was effective in eliminating rickets, a bone deficiency in children. However, digestive illnesses such as malabsorption, celiac disease, and the sequelae of weight reduction surgeries are some of the reasons for our continued deficiency.

What’s So Important About Vitamin D?

Vitamin D is a fat-soluble vitamin found naturally in some foods and has a significant impact on the health of cells. It reduces cellular growth (which promotes cancer) and improves cell differentiation (which puts cells into an anti-cancer state). That makes vitamin D one of the most potent cancer inhibitors and explains why vitamin D deficiency has been linked to colon, prostate, breast, and ovarian cancer.

This super-vitamin helps regulate calcium metabolism, which is necessary for bone development. But did you know it is also involved in immune function? In addition to cancer, it helps prevent cardiovascular disease, diabetes, depression, autoimmune disorders, and some forms of dementia. Vitamin D helps fight inflammation in your body. It modulates the immune system by regulating cell signaling pathways through vitamin D receptors (VDR) found in bone, muscle, kidneys, skin, and the digestive tract.

Inflammation is our body’s defense mechanism against phenomena it recognizes as foreign. However, as with any complicated defense system, an error may occur. Inflammation helps our body fight off bacteria, viruses, and other toxins. However, if our immune response continues after the threat has passed, it can damage our healthy tissue, as is the case with autoimmune disorders. Interestingly, in countries where sun exposure leads to high levels of vitamin D in their population, autoimmune disorders are rare.

Impact of Vitamin D on Inflammatory Bowel Disease

Vitamin D inhibits the production of inflammatory mediators involved in the development of Crohn’s disease and ulcerative colitis. As discussed in a previous post, inflammation in the gut leads to increased permeability of the gut protective barrier. This may lead to what is known as the “leaky gut syndrome,” in which harmful bacteria can leak into the bloodstream and travel to distant sites to cause tissue damage. Vitamin D can help maintain the integrity of the gut by keeping inflammatory mediators at bay. Research has shown that higher levels of vitamin D deficiency are found among patients with irritable bowel disease.

Vitamin D and Cancer

Although the precise mechanism by which vitamin D may influence cancer outcomes is still unknown, recent evidence suggests it may be involved in modulating your body’s inflammatory response. Markers of inflammation are associated with cancerous growths, higher tumor grades, and increased mortality. Therefore, it seems reasonable that vitamin D3 supplementation could be a potential means to improve cancer outcomes.

In a study published in Clinical Nutrition, researchers reviewed clinical trials in which cancer patients were given vitamin D3 supplementation along with chemotherapy or standard chemotherapy alone. They found that patients supplemented with vitamin D showed a significant reduction in some of the inflammatory markers associated with cancer and precancerous lesions.

Vitamin D and Depression

Vitamin D receptors have been discovered in the central nervous system and play a role in brain functions. The receptors are particularly prevalent in an area of the brain involved in memory and emotion. Vitamin D deficiency can make it challenging for your body to manufacture a neurochemical known as serotonin, which is involved in numerous human behaviors and mental health disorders. In the elderly population who have co-existing cardiovascular disease, vitamin D deficiency is significantly associated with depression.

Low levels of vitamin D in pregnant patients are associated with an increased risk of depression. In one study, vitamin D supplementation during pregnancy was associated with decreased perinatal depression. In another study, patients with depression were assigned to two treatment groups. One group was treated with antidepressants alone, the other with antidepressants and 1,500 units of vitamin D. The subjects in the group that had the additional vitamin D had lower depression scores at the end of the trial than those who were treated with antidepressants alone.

How to Make Sure You Are Getting Enough Vitamin D

The best way to obtain vitamin D naturally is through sun exposure. During exposure to sunlight, a substance in our skin called 7-dehydrocholesterol absorbs ultraviolet B radiation, which turns into the precursor to vitamin D3 and then converts to the active form. The effective campaign to prevent skin cancer has contributed to the prevalence of vitamin D deficiency. People who avoid the sun are three times more likely to be vitamin D deficient than those who enjoy being outdoors during sunny days.

“There is a chance that we are inadvertently putting some of our patients at risk for vitamin-D deficiency because they’re avoiding sunlight, they’re putting on sunscreen, they’re staying in the shade,” says Jean Tang, a dermatology professor at Stanford Medical School and the principal investigator of the study published in The Archives of Dermatology. Basal cell skin cancers, the most common type of cancer in the United States, are generally not lethal. Patients must look after their overall health. Thus, getting outside in the sunshine is a good idea. Just remember to take precautions, especially if you are prone to or have been diagnosed with skin cancer.

Ask your medical provider to test your vitamin D level at your annual physical. If you are deficient, take the right amount of vitamin D—5,000 to 10,000 IU daily. Monitor your vitamin D status until you are in the optimal range. Restoring your vitamin D stores can take six to 10 months.

Some people may need higher doses over the long run to maintain optimal levels because of differences in vitamin D receptors, older age, living in areas with less sunlight, skin pigment, and ethnic background. Aging skin produces less vitamin D. The average 70-year-old creates only 25 percent of the vitamin D a 20-year-old does. Skin color makes a difference as well. People with dark skin produce less vitamin D. In populations where traditional clothing is worn to limit skin exposure (some Muslim groups and Orthodox Jews), there is a higher incidence of vitamin D deficiency.

Finally, try and incorporate vitamin D-rich foods into your diet. These include:

  • Fish liver oils, such as cod liver oil.
  • Cooked wild salmon.
  • Cooked mackerel.
  • Sardines.
  • Eggs.
  • Canned tuna.
  • Mushrooms (wild are best)


Gwenzi, Tafirenyika, et al. “Effects of Vitamin D Supplementation on Inflammatory Response in Patients with Cancer and Precancerous Lesions: Systematic Review and Meta-Analysis of Randomized Trials.” Clinical Nutrition, no. 7, Elsevier BV, July 2023, pp. 1142–50.

Laird, Eamon, et al. “Vitamin D Status and Associations with Inflammation in Older Adults.” PLOS ONE, 2023.

Li, Chengxi, et al. “Link between Depression and Bone Mineral Density in Cooper Center Longitudinal Study: Indirect Effects of Vitamin D, Inflammation, and Physical Activity.” Journal of Affective Disorders, Elsevier BV, Jan. 2024, pp. 277–83.

Topalova-Dimitrova, Antonia, et al. “Lower Vitamin D Levels Are Associated with the Pathogenesis of Inflammatory Bowel Diseases.” Medicine, no. 41, Ovid Technologies (Wolters Kluwer Health), Oct. 2023, p. e35505.

Zhang, Chi, et al. “Combined Effects of Vitamin D Deficiency and Systemic Inflammation on All-Cause Mortality and Cause-Specific Mortality in Older Adults.” BMC Geriatrics, no. 1, Springer Science and Business Media LLC, Feb. 2024.

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