(S (S (BASENP (DT The) (NNS researchers)) (VP (VBP say) (SBAR (IN that) (S (NP (EX there)) (VP (VBZ is) (NP (NP (NP (DT an) (NP (JJ emerging) (QT (DQL ``) (BASENP (JJ widespread) (NN consensus)) (DQR '')))) (PP (IN among) (BASENP (NNS experts)))) (SBAR (IN that) (S (NP (BASENP (DT a) (JJ large) (NN part)) (PP (IN of) (BASENP (DT the) (NN population)))) (VP (VBZ has) (NP (NP (NP (BASENP (NNS levels)) (PP (IN of) (BASENP (NN Vitamin) (NN D)))) (PP (IN in) (BASENP (PRPD their) (NNS bodies)))) (SBAR (WHNP (WDT that)) (S (VP (VP (VP (VBZ is) (PP (ADVP (RB well)) (PP (IN below) (NP (BASENP (JJ optimal) (NNS concentrations)) (PP (IN for) (BASENP (NN health))))))) (COMMA ,) (PP (ADVP (RB particularly)) (PP (IN in) (BASENP (JJ temperate) (NNS regions))))) (COMMA ,) (PP (PP (IN due) (PP (TO to) (NP (BASENP (JJ decreased) (NN sunlight)) (CONJP (CC and) (CC or)) (NP (BASENP (JJR less) (NN time)) (ADVP (RB outdoors)))))) (CONJP (COMMA ,) (CC and)) (PP (PP (PP (IN during)) (CC or) (PP (ADVP (RB just)) (IN after))) (BASENP (DT the) (NN winter) (NNS months))))))))))))))))) (PERIOD .))