The news just keeps getting better about vitamin D. Earlier this year, studies linked proper levels of the "sunshine vitamin" to a decreased risk of diabetes, heart attacks, and cancer; that's in addition to the previously understood role that vitamin D plays in keeping bones strong. Building on all these findings, a new study suggests that maintaining proper levels of the nutrient can even stave off death from heart attacks and other causes. Researchers point out that they haven't yet demonstrated a causal relationship, just a connection.