Property and alternatives: these high-yielding investment trusts offer attractive income. : Retirement investors looking to generate sustainable income should consider investing in a diversified portfolio of different types of investments. This is because combining various asset classes that have low correlations with each other provides downside protection during tough times, helping you to generate superior risk-adjusted returns. Beyond equities and bonds, investors should also consider investing in property and alternatives, such as private equity, infrastructure and credit investments, to further broaden a retirement portfolio.