( Often ( , ( ( a ( secondary ( food source ) ) ) ( ( was ( ( ( ( issued , ) ( such ( as ( ( ( ( a ( D-ration bar ) ) , ) or ) ( fresh oranges ) ) ) ) ) , ) ( in ( an ( attempt ( to ( ( bring up ) ( the ( calorie ( and ( vitamin content ) ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB Often)) (, ,) (NP (DT a) (JJ secondary) (NN food) (NN source)) (VP (VBD was) (VP (VBN issued) (, ,) (PP (JJ such) (IN as) (NP (NP (DT a) (JJ D-ration) (NN bar)) (, ,) (CC or) (NP (JJ fresh) (NNS oranges)))) (, ,) (PP (IN in) (NP (DT an) (NN attempt) (S (VP (TO to) (VP (VB bring) (PRT (RP up)) (NP (DT the) (NN calorie) (CC and) (NN vitamin) (NN content))))))))) (. .)))
Often, a secondary food source was issued, such as a D-ration bar, or fresh oranges, in an attempt to bring up the calorie and vitamin content.
(ROOT (S (NP (NP (DT The) (NN energy) (NN content)) (PP (IN of) (NP (NNS foods)))) (VP (VBZ is) (ADVP (RB often)) (VP (VBN expressed) (PP (IN in) (NP (NNS calories))))) (. .)))
The energy content of foods is often expressed in calories.