There's a catch-22 in world food supply and demand. The demand for food from developing nations is putting pressure on supplies across the globe. But governments are getting increasingly nervous and worried about unrest. To try and preempt civil disturbances, governments have stepped in and are buying food staples. This government buying is driving prices still higher.

Algeria and Saudi Arabia have announced extraordinary purchases of wheat, driving prices to a two and a half year high. Last week Algeria bought 600,000 tons of wheat, much more than usual. Saudi Arabia announced plans to double the size of its wheat stockpile.

Gold exchange-traded funds (ETFs) and exchange-traded notes (ETNs) have become the new fad for 401k plans and individual investors. Folks have been flocking to the key gold ETFs via SPDR Gold Trust (GLD), Market Vectors Gold Miners ETF (GDX), iShares COMEX Gold Trust (IAU) and even the ETFS Physical Swiss Gold Shares (SGOL). In fact, the SPDR Gold Trust would be one of the top five or six central government banks in the world if measured solely in gold holdings.

Anytime you get a hot market, as we can see now with gold, you can bet more investment vehicles pop up to capitalize on the fad. Enter leveraged gold ETFs and ETNs, which add another layer to playing the gold market right now.

If I were to choose one word to describe the stock market for the past few weeks, it would be volatile.

Sometimes, a volatile stock market can be a bullish thing, but most of the time -- like during the past few weeks as we've seen 10% drops in the Dow -- volatility equals bearishness.

But investors can make money when volatility increases by trading one of the iPath exchange-traded notes (ETNs) that track the CBOE Volatility Index (VIX). The trick is choosing the right one.

In the past, Richard Lehmann has recommended positions in both energy and agriculture in his Forbes/Lehmann ETF Investor. His latest recommendation is a single fund that invests in both.

The advisor explains, "We've felt that oil prices would likely continue to remain high, mostly because OPEC has control of supply and has become accustomed to $60 plus oil rather than the old $35 target price."

He adds, "We've also recommended positions in agriculture Fund because distortions caused by increased ethanol production has caused an increase in corn prices, which translated to higher wheat and soybean prices as farmers switched production to corn."

Now, he says, there is a fund that tracks not only agricultural commodities but also energy prices at the same time -- the iPath Dow Jones-AIG Commodity Index Total Return ETN (ASE: DJP).

Actually, this "fund" is not an ETF; rather, it is an ETN, or Exchange-Traded Note. Lehmann explains, "ETN's have an advantage over ETF's in that they don't have to pay out distributions and are treated like a zero coupon debt instrument or a promissory note backed by Barclays."

This ETN, he notes, tracks several commodity sectors. According to Lehmann, the fund has 35% invested in the energy sector, 28% in the agricultural sector, 19% in industrial metals and 9% each in precious metals and livestock.

He suggests, "This ETF will tend to be uncorrelated with the broader equity market. Barclays invests in the respective futures contracts and keeps any remaining cash in Treasuries."

Each day, Steven Halpern's TheStockAdvisors.com features the latest investment ideas and market commentary from the financial newsletter community.