Ellie Matthews, a 20-something HR manager, had been struggling with bloating and digestive issues when she spoke to me for my book “Bad Influence: How the Internet Hijacked our Health.” Her primary care physician had just 15 minutes to see her. He’d ordered a battery of scans, stool samples and blood work that all came back normal. At the end of the appointment, he asked her if she was vegan — she was, but didn’t see the relevance — and he told her there was nothing wrong.