How to get enough Vitamin D during winter.

As the days grow shorter and temperatures drop, our exposure to sunlight diminishes, which can significantly impact our vitamin D levels. Known as the "sunshine vitamin," vitamin D is crucial for maintaining healthy bones and a strong immune system. Ensuring adequate vitamin D intake becomes even more important during the winter months due to limited sunlight exposure.

Sources of Vitamin D

Vitamin D exists in two forms: D3 (from sunlight) and D2 (from some foods). However, it's difficult to get enough Vitamin D from diet alone.

1. Sunlight (Vitamin D3): The most natural way to get vitamin D is through exposure to sunlight. However, during winter, especially in higher latitudes, the sun’s rays are not strong enough to produce adequate vitamin D in the skin.

2. Diet (Vitamin D2): Incorporating vitamin D-rich foods into your diet can help maintain your levels. These include fatty fish, such as salmon, mackerel, and sardines; fortified foods, such as margarine, milk, orange juice, cereals, and sun-exposed mushrooms, egg yolks, and cheese.

3. Supplements: For many, dietary intake and sunlight exposure may not be sufficient, especially in the winter. Vitamin D supplements can be an effective way to ensure you’re meeting your daily requirements.

Role of Vitamin D in our body

Image: Pathway of Vitamin D production (DOI 10.1007/s00223-012-9693-3)

Vitamin D is mainly obtained from sunlight (Vitamin D3) and diet (Vitamin D2). When UVB rays from the sun hit the skin, they convert a substance called 7-DHC into Vitamin D3. Too much sun can destroy Vitamin D3, turning it into inactive substances. Dietary Vitamin D2 is absorbed into the bloodstream and both forms of Vitamin D are carried by a protein to the liver.

In the liver, Vitamin D is converted to 25(OH)D, which is used to measure vitamin D levels in the body. 25(OH)D then travels to the kidneys, where it is converted into its active form, 1,25(OH)2D. The production of active Vitamin D in the kidneys can be influenced by levels of calcium and phosphorus.

Active Vitamin D plays several vital roles in the body:

• Bone Health: The main role of Vitamin D is to help our body absorb calcium, which is necessary for building and maintaining strong bones. Bones can become thin, brittle, and misshapen without sufficient vitamin D. Vitamin D deficiency can cause rickets in children and osteoporosis (porous bones) or osteomalacia (soft bones) in adults. 

• Immune Support: Vitamin D supports the immune system, helping to protect against infections and diseases.

• Mood Regulation: Some studies suggest that vitamin D can influence mood and may help reduce the risk of depression, particularly seasonal affective disorder (SAD), which is common in winter.

The recommended amount of Vitamin D

A recent study reported that 6% of Australians have a moderate Vitamin D deficiency. 

Individual needs vary based on factors, such as skin colour, age, geographical location, and existing health conditions. 

For infants to get enough vitamin D from sunlight alone, they would need about 2 hours of sun exposure per week if only their face is exposed, or 30 minutes per week if they are wearing just a nappy. However, it is recommended that infants are not exposed to direct sunlight exposure. Therefore, infant Vitamin D drops are recommended for both breastfed and bottle-fed babies for their first twelve months of life. 

For the rest of us, regular sun exposure typically negates the need for dietary vitamin D. 

Those most at risk of Vitamin D deficiency include those who:

• Have darker skin

• Spend most of their time indoors

• Are obese

• The elderly and people who are housebound or institutionalised

• Cover up for cultural or religious reasons

• Live in the southern areas of Australia, (during winter)

• Train or compete predominantly indoors

• Have diets that are very low in fat

• Babies and infants of Vitamin D deficient mothers, especially if the babies are exclusively or partially breastfed 

• Patients with osteoporosis

Tips for maintaining Vitamin D levels in winter

1. Maximise sunlight exposure: Spend time outdoors during midday when the sun is at its peak, even on cloudy days. Aim for 15-30 minutes of exposure on the face, arms, and hands several times a week when the UV index in below 3. 

2. Eat a balanced diet: Include vitamin D-rich foods in your meals. Consider fortified options if natural sources are limited.

3. Consider supplements: If you’re unable to get enough vitamin D from sunlight and diet, talk to your healthcare provider about taking a supplement. They can recommend the appropriate dosage based on your specific needs.

4. Check your levels: If you’re concerned about your vitamin D status, especially if you have risk factors for deficiency, ask your doctor for a blood test to measure your levels.

Conclusion

Winter poses unique challenges to maintaining adequate vitamin D levels due to reduced sunlight exposure. By being mindful of your diet, taking advantage of available sunlight, and considering supplements if necessary, you can ensure you’re getting enough of this crucial nutrient to support your overall health. Stay proactive about your vitamin D intake to keep your bones strong, your immune system robust, and your mood balanced throughout the winter months.