The troubled U.S. economy may be taking a toll on the growth of organic product sales, according to new data from Nielsen.

After several years of 20% to 30% sales growth, U.S. sales of organic products are showing the first signs of slowing.

While 52-week dollar sales of UPC-coded organics are up 21% vs. last year, the most recent four-week period ending October 4, 2008, shows growth of only 11.2%.  Last year, organics saw 27.1% sales growth during the comparable four-week period ending October 6, 2007.

Meanwhile, in Great Britain, organics sales growth has also slowed -- to just 4%, year over year, for the most recent year, ending September 6, 2008.  In comparison, during the year ending September 8, 2007, organic products saw 18% sales growth in Britain.

Organic products are clearly here to stay, but the days of boundless growth may be over.

Read coverage of Nielsen's findings in The New York Times.