US STOCKS-Wall St loses gains as health stocks, oil prices slide
* Oil prices fall for sixth day in a row
* McKesson, Celgene slump on weak profit forecasts
* Under Armour hit by Morgan Stanley rating cut
* Alcoa to kick off earnings season after close
* Indexes down: Dow 0.16 pct, S&P 0.32 pct, Nasdaq 0.52 pct (Adds details, changes comment, updates prices)
By Abhiram Nandakumar
Jan 11 (Reuters) - Wall Street gave up early gains and were lower late on Monday morning, dragged down by health stocks and as crude prices slid further ahead of the start of the corporate earnings season.
The S&P materials and energy sectors were both off more than 1 percent, under pressure as oil prices fell for the sixth day in a row. U.S. crude fell to $31.93, its lowest since 2003.
The health sector fell the most, declining 1.38 percent, dragged down by Celgene and McKesson. Continuación...