Doctor and broadcaster Xand van Tulleken has written a book investigating the modern health and wellness industry, prompted by his own experience as a physician who found himself unable to answer confidently when patients and viewers asked about trends such as continuous glucose monitors, NAD supplements, red-light therapy and biological age tests. His inquiry matters because it challenges the assumption that emerging wellness products, often endorsed by confident, highly qualified podcast hosts, are backed by solid evidence, when his research suggests otherwise.

Van Tulleken focuses first on vitamins, noting there are only 13 essential human vitamins and that deficiency-related conditions such as scurvy and rickets are now rare, yet diet-related illness remains a leading cause of death in the UK and US. He cites a 2007 study led by Professor Christian Gluud of Copenhagen University Hospital, which analysed 68 randomised trials involving almost 250,000 people and found that multivitamin supplements, including vitamin C, do not prevent chronic diseases such as cancer or cardiovascular disease, do not reduce premature death, and may even increase mortality risk.