* Nike down after flagging weakness in N. America sales
* Health stocks drag, energy top gainers on S&P
* Celgene falls after follicular lymphoma regimen fails trial
* Indexes down: Dow 0.14 pct, S&P 0.13 pct, Nasdaq 0.21 pct (Updates to early afternoon)
Dec 22 (Reuters) - Wall Street's major indexes slipped in thin pre-holiday trading on Friday, pressured by losses in Nike and UnitedHealth.
Nike shares fell as much as 7 percent to hit a 4-month low of $60.14 after the company forecast muted growth in current-quarter revenue.
UnitedHealth was down 1.2 percent after the health insurer agreed to buy Chilean healthcare company Banmedica SA for $2.8 billion.
Investors are winding down ahead of the Christmas holiday on Monday, when the market will be closed.
"Volumes in the stock market are down 28 percent," said Michael Antonelli, managing director, institutional sales trading at Robert W. Baird in Milwaukee.
Still, major Wall Street indexes were on track to end the week higher, buoyed by a historic overhaul of the U.S. tax code.
President Donald Trump signed Republicans' massive $1.5 trillion tax overhaul into law on Friday and also approved a short-term spending bill that averts a possible government shutdown.
At 12:26 p.m. ET (1726 GMT), the Dow Jones Industrial Average was down 35.85 points, or 0.14 percent, at 24,746.44 and the S&P 500 was down 3.45 points, or 0.13 percent, at 2,681.12.
Data on Friday showed U.S. consumer spending accelerated in November and shipments of key capital goods orders increased for the 10th straight month, the latest sign of strong momentum in the economy as the year winds down.
"The data is relatively mixed but biased to the upside, and consumer sentiment continues to be strong and that bodes well for economic strength in 2018," said Matthew Miskin, market strategist at John Hancock Investments in Boston, Massachusetts.
The benchmark S&P has climbed about 20 percent this year and is on track for its best performance since 2013 on solid corporate earnings, strong economic fundamentals and hopes of tax cuts and looser regulations.
On Friday, six of the 11 major S&P sectors were higher, led by energy index's 0.54 percent rise. Health stocks were the biggest decliners, falling 0.43 percent.
Celgene shares fell more than 2 percent after the company's follicular lymphoma regimen failed in a clinical trial.
The Nasdaq Composite dipped 0.21 percent to 6,950.49 as losses in Amazon and Intel dragged.
Wildly volatile bitcoin plunged below $13,000, losing around a third of its market value in five days. Companies that have been trying to ride the bitcoin wave were hit hard by the cryptocurrency's slump.
Long Blockchain, Overstock.com, Xunlei , Riot Blockchain and Marathon Patent Group tumbled between 2 percent and 15 percent.
Advancing issues outnumbered decliners on the NYSE by 1,426 to 1,389. On the Nasdaq, 1,661 issues fell and 1,159 advanced. (Reporting by Sruthi Shankar in Bengaluru; Editing by Anil D'Silva)