With all the talk of deflation in the news, it's easy to forget that there's a real risk of inflation in coming years. And if your retirement portfolio is mostly invested in stocks, that means --

Oh geez, you're doing it again.

Doing what?

You're going on about something boring! Here, watch -- I can do your whole article in three words: Diversify your 401(k). There. All done.

Actually, that's not really what I was planning to --

Forget that stuff. Tell me about health care instead. What's this Obama plan going to do to my holdings in UnitedHealth Group (NYSE:UNH) and WellPoint (NYSE:WLP)? Your Fool buddy Brian Orelli was talking about Congress starting a witch hunt to bust their chops. Should I hang onto them or what?

Y'know, I don't follow that sector, but CAPS players seem to like UnitedHealth quite a bit right now. But that's not what I want to talk about. Listen up, because I think you need to hear this. I think that inflation is something that long-term investors need to keep in mind and plan for.

Yeah, yeah. Save more because your holdings will be worth less when you're old. There, I finished your article for you again. Now c'mon, let's talk about my oil stocks. Do you think BP (NYSE:BP) will be able to keep paying that big dividend? Some Fool said that their payout ratio is kind of high, which might mean trouble.

I think it depends on where oil prices go. But even if they trim it in the near term, I think it'll be fine in the long run -- I own some BP stock too, and I think it's a well-run company. But I'm glad you brought up oil, because that's what I wanted to talk about: I think there's a strong case for adding commodities exposure to your long-term portfolio right now.

Commodities? Sorry, I don't think my 401(k) has a pork belly fund.

There's a lot more to commodities than pork bellies, smart guy. And more than oil, too. For instance, copper has been on a run in recent months, and as demand picks up going in to the recovery, that run could continue, which should be great for miners like Vale (NYSE:VALE) and Freeport-McMoran (NYSE:FCX).

But stocks aren't the only way to get exposure to commodities -- you can also buy ETFs that are linked to particular commodities. You can also buy stocks that aren't directly linked to the commodity, but that will typically rise if that commodity gets expensive.

Like what?

Well, if you think energy prices are going to rise in the near future, you could buy solar-energy companies like MEMC Electronic Materials (NYSE:WFR) or ReneSola (NYSE:SOL). Depending on the commodity you're interested in, you might be able to find several different ways to take a position on its movements.

Yeah, okay. But why should I do this?

Well, commodities prices tend to rise with inflation, which is a real risk right now. And it's a good diversification move -- you own small caps and large caps and bonds because they move in different ways in different times and help spread your risk around, right?

Yeah, see, I knew you were going to go on about diversification again. I'm diversified. So what?

So, commodities are another corner of the investing world that isn't strongly correlated to either stocks or bonds. Adding them to your portfolio is another way to get more overall stability and upside over the long term.

Okay, fine. But commodities are complicated. And I know there are some funky risks. Like, I don't know anything about the global demand for copper. How do I research that?

I'm running out of space here because you kept distracting me. But I can point you to a great resource. In the August issue of the Fool's Rule Your Retirement --

Oh, geez, a pay service.

Naah, you can grab a free trial and see everything for 30 days. And this is worth looking at -- Robert Brokamp put together a big section in the August issue called "Resources for the Commodity Curious." It's got a bunch of links to good articles that will get you up to speed on all of this in a hurry.

Fine. So what do I do?

Just claim that free trial. It only takes a few seconds -- click here to get started.

Fool contributor John Rosevear owns shares of BP. The Fool owns shares of UnitedHealth Group, which is a Motley Fool Stock Advisor pick. UnitedHealth Group and WellPoint are Motley Fool Inside Value picks. Try any of our Foolish newsletters today, free for 30 days. The Motley Fool has a disclosure policy.