Section 1: Unlocking the source code of vitamin D<br>Chapter 1: Environmental factors and vitamin D<br>Ambreen Surti, Haseeb Waheed and Rehana Rehman<br>Chapter 2: Sources of vitamin D<br>Faiza Alam, Mussarat Ashraf and Maah Amir<br>Chapter 3: Biochemistry of vitamin D<br>Mohammad Perwaiz Iqbal<br>Section 2: The power of D: health, performance, and global impact<br>Chapter 4: Vitamin D and bone health<br>Saira Perwaiz Iqbal and Mohammad Perwaiz Iqbal<br>Chapter 5: Vitamin D and sports performance<br>Mirza Mohammad Feisal Subhan<br>Chapter 6: Vitamin D and the immune system<br>Ihsan Nazurah Zulkipli and Liyana Ahmad<br>Chapter 7: The interplay of epigenetics and vitamin D: regulation, mechanisms, and implications for health and disease<br>Sofia Amjad and Rehana Rehman<br>Chapter 8: Genetic variability in vitamin D metabolism: implications for health<br>Farzana Abubakar and Khalid Ahmed<br>Chapter 9: Vitamin D disorders: proteomic and metabolomic perspectives<br>Munazza Raza Mirza, Soma Vankwani and Rabia Sultan<br>Chapter 10: Global perspectives on vitamin D<br>Tarek Arabi, Belal Nedal Sabbah and Dileep Kumar Rohra<br>Chapter 11: Vitamin D deficiency<br>Faiza Alam, Samar Zaki and Maah Amir<br>Section 3: The health matrix: vitamin D and the many systems it touches<br>Chapter 12: Vitamin D and chronic respiratory diseases: a complex relationship<br>Muhammad Irfan, Midrar Ullah, Amna Ansari and Nousheen Iqbal<br>Chapter 13: Vitamin D and cardiovascular health: a vital connection<br>Rabiya Ali, Nazra Remtulla and Faiza Alam<br>Chapter 14: Vitamin D: illuminating the shadows of pancreatic dysfunction<br>Faiza Alam, Fasiha Fatima and Ihsan Nazurah Zulkipli<br>Chapter 15: Vitamin D and metabolic syndrome-associated diseases: interconnections and implications<br>Salaar Ahmed and Syeda Sadia Fatima<br>Chapter 16: Vitamin D and reproductive health: a critical link of vitamin D deficiency with subfertility<br>Arfa Azhar, Rehana Rehman and Chaman Nasrullah<br>Chapter 17: Vitamin D and male reproductive health: complex interplay in male fertility e-only chapter<br>Rashida Sultana and Sofia Amjad<br>Chapter 18: Vitamin D and cancer<br>Ya Chee Lim, Khalid Ahmed and Siti Rohaiza Ahmad<br>Chapter 19: Vitamin D, parathyroid and renal bone diseases, vitamin D, and FGF23<br>Lena Jafri<br>Chapter 20: Vitamin D and fragility fractures<br>Saira Perwaiz Iqbal<br>Chapter 21: Rare disorders of vitamin D metabolism<br>Aysha Habib Khan and Manju Chandran<br>Chapter 22: Vitamin D, pregnancy, and child health<br>Rehana Rehman and Shaheen Basheer<br>Chapter 23: Vitamin D and mental health<br>Aisha Noorullah, Nargis Asad and Shahina Pirani<br>Chapter 24: Vitamin D and aging<br>Rabia Mahmood Khan and Mahwish Nida<br>Chapter 25: Vitamin D and infectious diseases<br>Nosheen Nasir, Kiren Habib and Iffat Khanum<br>Chapter 26: Vitamin D in physiotherapy: unlocking new frontiers in recovery and rehabilitation<br>Fatima Syed, Bushra Madad Ali Malik and Rehana Rehman<br>Section 4: Optimising health with vitamin D: Clinical tools, public solutions, and future possibilities<br>Chapter 27: Vitamin D testing and measurement<br>Lena Jafri, Ya Chee Lim and Sibtain Ahmed<br>Chapter 28: Practical tips for maintaining optimal vitamin D levels<br>Lena Jafri, Hafsa Majid and Nayab Afzal<br>Chapter 29: Vitamin D supplementation protocols<br>Lena Jafri, Hafsa Majid and Afzal Nayab<br>Chapter 30: Vitamin D therapy: a promising appraoch for subfertility<br>Chaman Nasrullah, Fatima Syed and Rehana Rehman<br>Chapter 31: Public health initiatives in promoting awareness and vitamin D supplement use in low- and middle-income countries<br>Kiran Fatima, Shiza Batool, Irum Fatima and Nighat Nisar Khan<br>Chapter 32: Future directions in vitamin D research<br>Rehana Rehman and Faiza Alam