Of the vitamins we include in Vitamin Coffee, vitamin C is the only one that has been found to break down under heating. This breakdown tends not to occur unless it is placed in boiling water for an extended period of time, but to safeguard we've added additional vitamin C in every blend. We've put together the following reading list if you're still concered, but do remember coffee is generally brewed off the boil and not kept at a high temperature for an extended period of time:
Barros, Ana I.R.N.A. et al. "Effect Of Cooking On Total Vitamin C Contents And Antioxidant Activity Of Sweet Chestnuts (Castanea Sativa Mill.)". Food Chemistry 128.1 (2011): 165-172. Web.
Bernhardt, Simone and Elmar Schlich. "Impact Of Different Cooking Methods On Food Quality: Retention Of Lipophilic Vitamins In Fresh And Frozen Vegetables". Journal of Food Engineering 77.2 (2006): 327-333. Web.
Hanson, A.L. and L.E. Metzger. "Evaluation Of Increased Vitamin D Fortification In High-Temperature, Short-Time–Processed 2% Milk, UHT-Processed 2% Fat Chocolate Milk, And Low-Fat Strawberry Yogurt". Journal of Dairy Science 93.2 (2010): 801-807. Web.
Kaur, S. and M. P. Bansal. "Protective Role Of Dietary-Supplemented Selenium And Vitamin E In Heat-Induced Apoptosis And Oxidative Stress In Mice Testes". Andrologia 47.10 (2014): 1109-1119. Web.
Lafuente, María T. et al. "Effect Of High-Temperature-Conditioning Treatments On Quality, Flavonoid Composition And Vitamin C Of Cold Stored ‘Fortune’ Mandarins". Food Chemistry 128.4 (2011): 1080-1086. Web.
Lešková, Emília et al. "Vitamin Losses: Retention During Heat Treatment And Continual Changes Expressed By Mathematical Models". Journal of Food Composition and Analysis 19.4 (2006): 252-276. Web.
Somsub, Weenanan et al. "Effects Of Three Conventional Cooking Methods On Vitamin C, Tannin, Myo-Inositol Phosphates Contents In Selected Thai Vegetables". Journal of Food Composition and Analysis 21.2 (2008): 187-197. Web.