This isnt true. If i had pushed my body a bit harder, i am quite certain i would have had a stroke or heart attack. Just because something is 'safe', doesnt mean that if the right circumstances occur, it will not be able to harm you. Mescaline increases your heart rate quite a bit, so does marijuana. I combined both, then exerted huge amounts of energy riding up a hill in the hardest gear of my bike. If the hill had been double the length, and i didnt notice my heart doing what it was.. im pretty sure i would have ended up in the ER.