[1] Univ Calif Riverside, Sch Med, Palo Alto, CA USA
[2] Stanford Univ, Dept Pediat, Sch Med, Palo Alto, CA USA
[3] Univ Calif San Francisco, Inst Hlth Policy Studies, San Francisco, CA USA
[4] Univ Calif San Francisco, Dept Humanities & Social Sci, San Francisco, CA USA
[5] Univ Calif Oakland, Nutr Policy Inst, Div Agr & Nat Resources, Oakland, CA USA
[6] Univ Calif San Francisco, Div Biostat, San Francisco, CA USA
[7] Stanford Univ, Dept Pediat, Sch Med, 3145 Porter Dr,F110, Palo Alto, CA 94304 USA