Source: p 185 , ETFs for Canadians for Dummies (2013; by Russell Wild and Bryan Borzykowski).
In a recent interview with the Journal of Indexes, famed investment guru Burton G. Malkiel, professor of economics at Princeton and author of A Random Walk Down Wall Street, had this to say about commodity investing: “I think [commodities] should be in every portfolio, but for individuals, my sense is that the way they should get them is through ensuring that they have in their portfolios companies that mine or manufacture the commodities.”
He is not alone. Frustrated with the problems of commodity investing I’ve outlined in this chapter, and doubtful that commodity investing in the very long run will provide returns commensurate with the risk, many investment advisors of late have turned to Malkiel’s solution. The drawback is that stocks in commodity-producing companies are not going to show the same lack of correlation, or offer the same diversification power, as pure commodities do. Investing in commodities this way is a trade-off.
However, a Google search revealed this which rebuts Prof Malkiel's recommendation above.