Researching and Ending Disparities by Understanding and Creating Equity Act of 2020 or the REDUCE Act of 2020 This bill requires the Centers for Disease Control and Prevention to implement a Health in All Policies demonstration project. States, territories, tribes, and local government entities may apply for grants through the project to establish or enhance collaborative approaches to improve the health of individuals and communities. The grant funds must be used to (1) integrate health considerations in policymaking across sectors; (2) address health, equity, and sustainability; and (3) target a significant proportion of Medicare beneficiaries, Medicare-Medicaid dual eligibles, or long-term care Medicaid recipients. The bill also directs the National Academies of Sciences, Engineering, and Medicine or another appropriate entity to produce a report on eliminating health disparities to improve health equity.