1. **Calcium Absorption:** One of the most well-known functions of vitamin D3 is its role in promoting the absorption of calcium and phosphorus from the intestines. This is essential for maintaining strong bones and teeth. Without sufficient vitamin D, your body may have difficulty absorbing these minerals, which can lead to conditions like osteoporosis.

2. **Bone Health:** Vitamin D3 is crucial for bone health. It helps in the mineralisation of the bones, ensuring that they remain strong and healthy.

3. **Immune System Support:** Vitamin D3 also has immunomodulatory properties, which means it can help regulate the immune system. Some research suggests that it may play a role in supporting the body's defence against infections and autoimmune diseases.

4. **Cell Growth and Function:** Vitamin D3 is involved in the regulation of cell growth, differentiation, and other cellular processes. It may play a role in preventing the development of certain cancers.

5. **Mood and Mental Health:** Some studies have suggested a link between vitamin D3 deficiency and mood disorders like depression. Adequate vitamin D levels may have a positive impact on mental health.

6. **Cardiovascular Health:** There is ongoing research into the potential connection between vitamin D and heart health. Some studies suggest that sufficient vitamin D levels may reduce the risk of cardiovascular disease.

7. **Hormonal Regulation:** Vitamin D3 is involved in the regulation of various hormones, including insulin and parathyroid hormone, which helps maintain calcium balance in the body.

Whether it's healthy to take vitamin D3 every day depends on your individual circumstances, including your current vitamin D levels, diet, exposure to sunlight, and any underlying health conditions.

1. **Get Your Vitamin D Levels Checked:** If you are considering vitamin D3 supplementation, it's a good idea to have your vitamin D levels tested first. This can help determine if you have a deficiency and, if so, how much supplementation is necessary to bring your levels to a healthy range.

2. **Diet and Sunlight:** Vitamin D can also be obtained from dietary sources and sunlight. If you can meet your daily vitamin D requirements through a balanced diet and reasonable sun exposure, you may not need a daily supplement. In many cases, a varied diet and spending time outdoors in the sun can provide sufficient vitamin D.

3. **Age and Risk Factors:** Certain groups of people, such as older adults, individuals with limited sun exposure, those with dark skin, and people with malabsorption issues, may be at a higher risk of vitamin D deficiency and may benefit from daily supplementation.