BOSTON ( TheStreet) -- Some Americans are using their Individual Retirement Accounts to invest in cattle, sports teams and restaurants, betting they can make more money than in the stock and bond markets. Self-Directed Individual Retirement Accounts, accounting for less than 4% of the 47 million IRAs in the U.S., put the responsibility for investments in the hands of account holders. Contribution limits are the same as on a traditional IRA or a Roth IRA. Plan holders retain a trustee or custodian to file Internal Revenue Service paperwork, issue statements, and navigate rules and restrictions. "There isn't any limit to what can be done," says Tom Anderson, founder of Pensco Trust Co., an administrator and custodian of self-directed IRAs. "Not to say we are getting 400 people buying alpacas or something with their IRA. But a lot of people invest in what they know." Popular options include real estate investments and small-business loans. A bankruptcy expert buys nothing but bankruptcy claims, cherry picking the best deals that return a good yield, Anderson says. Another client bought fishing rights from the state of Alaska. "Because she is a fisherwoman, out on a boat 10 hours a day, she understands fishing," Anderson says. "So she has exclusive rights to a part of the ocean to fish for black cod, and she subleases to other day fishermen. We have a guy who has 40 heads of cattle in his IRA. He has been in the cattle business all his life and he knows how to make a profit with cattle."