While Fools should generally take the opinion of Wall Street with a grain of salt, it's not a bad idea to take a closer look at particularly stock-shaking analyst upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of Unilever plc (NYSE:UL) slipped about 1% in pre-market trading Wednesday after Nomura Securities downgraded the consumer-products giant from neutral to reduce.

So what: Along with the downgrade, analyst David Hayes lowered his price target to 29.7 euros from 30.9 euros, representing about a 10% downside to yesterday's close. While momentum traders might be attracted to Unilever's year-to-date price strength, Hayes' call could reflect a sense on Wall Street that the risks surrounding its growth trajectory are being largely overlooked.

Now what: Nomura cut its 2015 EPS estimate for Unilever by 6%.  According to Hayes:

The food division continues to struggle more than we hoped, and emerging market growth seems stalled at a lower level than the recent past. We see a growing risk to the current valuation. We see slowing consumer trends across emerging markets, notably, key markets like India, Indonesia and China. US also looks increasingly subdued, as disposable income (and federal subsidies) provide less support for spending.

When you couple that downbeat outlook with Unilever's near-20 forward P/E, it's easy to understand Nomura's cautious stance.