A comfortable retirement is not as certain as you may think. And not merely because of the market's recent downturns or the problems facing our country's Social Security system.

No, dear Fool, it is inflation -- inflation much higher than you expect -- that will, quite likely, ruin your work-free days.

Unless, that is, you're prepared to, well, prepare.

Let me explain ...
Inflation destroys the value of your wealth, bit by bit, year after year. As prices rise (which they're sure to do!), the money you have is able to buy you less and less. Averaged out over the last hundred years or so, inflation has accounted for an annual 3% deterioration of your wealth.

Or so you've been told.

According to a recent market commentary by PIMCO bond guru Bill Gross, the official barometer of domestic inflation -- the Consumer Price Index (CPI) -- actually deflates the reality of inflation's impact. He argues that our government takes significant liberty in calculating this figure, as evidenced by the fact that no other country agrees with our methods, and by the fact that the Foreign CIP Composite, which tracks inflation in more than 20 countries, is much higher.

And this is why you should be worried.

Gross argues that the real level of inflation in the United States is darn close to the 7% the rest of the world is experiencing.

So what?
So if you've been taking refuge in bonds to avoid the market turmoil -- even Treasury Inflation-Protected Securities (TIPS) -- you're losing money at a drastic pace each year.

And if you were planning to transfer your current investments into these "safe" income-bringing securities when you retire, odds are you'll run out of money much more quickly than the "worst-case scenario" for which you've likely planned.

What's a Fool to do in order to ensure that his diligent, well-orchestrated years of retirement planning haven't been for naught?

Don't go broke!
Gross argues that investors should flock to stocks that are tapping the momentum of the developing economies of Brazil, Russia, India, and China (BRIC). This might include dabbling in foreign commodities-based companies like Petroleo Brasileiro (NYSE:PBR) and PetroChina (NYSE:PTR), and foreign banks like HDFC Bank (NYSE:HDB).

Or you could opt for more diversity through a focused index like iShares MSCI BRIC Index (BKF), which in addition to some of the companies mentioned above owns China Mobile (NYSE:CHL) and Banco Bradesco (NYSE:BBD). Another more conservative option is to own U.S.-based stocks that are poised to profit from international expansion, such as Wynn Resorts (NASDAQ:WYNN) and Starbucks (NASDAQ:SBUX).

This certainly makes sense, and wise investors have to be ready to surf the wave of international growth. Which is why, in a recent Rule Your Retirement issue, Robert Brokamp reminded readers that it was not America that had the best annualized returns from 1900 to 2000, but rather ... wait for it ... Sweden.

Which goes to show: To have a chance at beating the effects of 7% inflation -- building your nest egg in the process -- U.S.-based investors must own foreign stocks. There's a diversification benefit, but, even more importantly, the returns available in some overseas markets (BRIC included) are too promising to ignore.

For more information on the benefits of owning international stocks, or for tips on how to build a well-diversified portfolio in preparation for -- or sustenance during -- retirement, or just to learn more about how to plan for those carefree days, click here to try out Rule Your Retirement free for 30 days.

Adam J. Wiederman plans to battle the ravages of inflation by investing in strong companies, which is why he owns shares of Starbucks. The Motley Fool also owns shares of Starbucks, which is an Inside Value and Stock Advisor recommendation. Petroleo Brasileiro is an Income Investor selection. HDFC is a Global Gains choice. The Fool has an inflation-beating disclosure policy.