Vitamin D levels decline in autumn as sunlight decreases

As autumn approaches, health experts warn of declining vitamin D levels due to reduced sunlight and shorter days. In Italy, the Istituto Superiore di Sanità notes that healthy individuals can typically produce sufficient vitamin D through sun exposure only from late March to late September. From October onward, the body begins to deplete summer reserves as UVB radiation decreases.

Vitamin D plays a critical role in bone health by fixing calcium, supporting the immune system, and aiding muscle function. Low levels are associated with increased risks of fractures, respiratory infections, fatigue, and mood disturbances, including Seasonal Affective Disorder (SAD). While 80-90% of vitamin D is synthesized through the skin via sunlight, only 10-20% is obtained through diet.

For those engaging in outdoor activities like mountain trekking during the colder months, additional nutritional support may be necessary. Experts suggest monitoring intake of magnesium, iron, potassium, and B vitamins to maintain energy, muscle function, and oxygen transport during increased physical exertion in low temperatures.