The old story has been walked back
The idea that a daily glass of red is good for you has not held up. When researchers account for who actually abstains and why, the apparent benefit largely disappears.
What the global reviews now say
The Global Burden of Disease study concluded that the level of drinking that minimises overall health harm is zero. For cancer specifically, the World Cancer Research Fund and the International Agency for Research on Cancer both state there is no safe level, and that risk for breast and oesophageal cancer begins below one drink a day.
Even light drinking shows up
A comprehensive 2015 meta-analysis found small but real increases even at about one drink a day: breast cancer around 1.04 times, mouth and throat around 1.13 times, oesophagus around 1.26 times. It is strongly dose-dependent, so heavy drinking is far worse, but there is no threshold under which the risk is zero.
Keeping it in proportion
This is about "no safe level," not "one drink will get you." The absolute risk from the occasional drink is small. But less is genuinely better, all the way down to zero, and that is what the evidence supports.