In a four-part article and video series, Michael Greger, MD—the voice behind nutritionfacts.org, a non-commercial, science-based public service site—explains how a vegan diet leads to significantly reduced asthma symptoms in long-time sufferers by improving lung capacity and protecting the respiratory system from oxidative damage. Furthermore, the physician cites a Swedish study wherein severe asthmatics were placed on a vegan diet for one year. After four months, 71 percent of patients reported improvement, which increased to 92 percent by the end of that year. Patients reporting lowered drug usage, improved breathing, and decreased asthmatic triggers. The annual cost of asthma in the United States is an estimated $56 billion, and the disease affects more than 25 million Americans.