10 Low Vitamin D Side Effects That Are Scary and Surprising

Depression is one of the telltale signs of a vitamin D deficiency. People with low vitamin D levels are more likely to experience depression and anxiety, per a 2022 review. One study even found that people deficient in vitamin D were 75% more likely to develop depression than those who weren’t. What’s more? The lower your vitamin D levels, the more severe your depression and anxiety symptoms, a 2020 review suggests.

Research suggests people with low vitamin D are more likely to get prostate cancer—and die of it. A 2025 study found that many prostate cancer patients were low on vitamin D, and levels were especially low among those with metastatic prostate cancer (cancer that had spread to other parts of the body). A 2018 meta analysis also found that people with high vitamin D were significantly less likely to die of prostate cancer than those who were low on the nutrient.

Research suggests a pretty direct relationship between vitamin D and dementia. In one 2014 study, people with vitamin D deficiency were 51% more likely to develop dementia—and people with severe vitamin D deficiency were 122% more likely to. More recent research has backed up these results. A 2023 study also found that people with high vitamin D levels were 40% less likely to develop dementia, and that was especially true for women.

Psoriasis is an autoimmune condition that causes your skin to become itchy, scaly, and irritated. And about 30% of people with it also develop psoriatic arthritis, which causes joint pain, swelling, and stiffness, per the National Psoriasis Foundation. Both conditions—psoriasis and psoriatic arthritis—have been linked to low vitamin D levels. And the lower your vitamin D levels, the more severe your symptoms, per a 2022 study.

Heart disease is the leading cause of death for American adults, and it’s been closely linked to vitamin D levels. A 2021 review found that people with low vitamin D were 1.4 times more likely to experience heart failure—and people with very low vitamin D were twice as likely to. A 2025 review found the same, adding that the people with the lowest vitamin D levels were the most likely to die of the condition.

If you’re deficient in vitamin D, you’re 1.64 times more likely to develop pneumonia, per a 2019 meta analysis. You’re also more likely to experience severe pneumonia. In one 2021 study, pneumonia patients with the highest levels of vitamin D had the fewest complications. Meanwhile, patients with the lowest levels were more likely to experience complications and die of the infection. A 2019 study found the same: The lower your vitamin D levels, the worse your pneumonia and the longer your hospital stay.

About 37% of the population is deficient in vitamin D—but about 70% of people with schizophrenia are, per a 2021 meta analysis. This link is complicated, because people with schizophrenia also tend to have worse diets, get less exercise, and have poorer health outcomes than the general population. But other research suggests that people who are vitamin-D-deficient in early childhood are more likely to develop neurological conditions, like schizophrenia, later in life.

People with vitamin D deficiency are 54% more likely to develop multiple sclerosis (MS) than people who get enough of the nutrient, per a 2024 meta analysis. And your vitamin D levels may impact your experience with the condition. People with high vitamin D levels are less likely to experience MS relapses, and their MS tends to progress more slowly, per a 2019 review. Other research has found the same pattern with Parkinson’s disease: Low vitamin D tends to mean more severe symptoms and a faster-progressing disease.

People with low vitamin D may not live as long as people who get enough of the nutrient, research suggests. And that’s true, even if you consider yourself healthy. A 2019 review linked vitamin D deficiency with higher all-cause mortality—even in people who reported being in good, very good, or excellent health. And a 2020 review found that severe vitamin D deficiency dramatically increases your risk of death, disease, and infection.