When the going gets tough, the tough go shopping. Apparently, that's NBTY's (NYSE:NTY) credo these days. The giant maker of supplements and vitamins announced the acquisition of Wyeth's (NYSE:WYE) Solgar Vitamin and Herb business.

For $115 million, NBTY is getting a business with $104 million in sales last year and about $64 million in net assets.

This is an interesting time for NBTY to expand. The market for supplements and vitamins has shrunken of late, and NBTY's performance has suffered. Look no further than the lowered analyst earnings expectations or the building inventory on the balance sheet, and you'll see what I mean.

But that's pretty much the way the nutritionals business has always worked. While there is a steady segment of the population that buys vitamins, supplements, and other nutritional items, sales are often tied to fads.

A study or two will suggest that some vitamin, mineral, or other substance is the "key" to good health, and people will buy it up by the armful. Then, a few years later, another study completely refutes the original theories, and the buyers go away. Luckily for NBTY, though, there is a steady and reliable stream of customers for things like Vitamin C, weight-loss products, and exercise supplements to keep things afloat between fads.

Judging by NBTY's current valuation and the price that it just paid for Solgar, we seem to be on the lower end of the peak-to-trough cycle. If the pattern holds to form, we've probably seen the bottom on a price-to-sales basis. A bottom in the P/E (likely in the high single digits or low teens) should come within the next year or so.

I can't say I love NBTY's business -- it largely relies upon pseudoscience and the public's general lack of scientific literacy -- but there's no denying that it serves up what the buying public wants. And let's be honest, if we turned up our noses at every company that played upon humanity's less glorious traits, we would cut out a wide swath indeed.

I doubt I'll ever be a major fan of the company or its products, but if the nutritionals business is in fact seeing its cyclical lows, opportunistic investors might want to bone up on NBTY and competitors like Nature's Sunshine (NASDAQ:NATR), USANA (NASDAQ:USNA), and Perrigo (NASDAQ:PRGO) as possible turnaround plays.

Fool contributor Stephen Simpson has no financial interest in any stocks mentioned (that means he's neither long nor short the shares).