Final answer:
The nurse should advise the new mother who is breastfeeding to increase her daily caloric intake by approximately 500 calories to support lactation.
Step-by-step explanation:
The nurse should instruct the client who is breast-feeding that her calorie needs should increase by approximately 500 calories a day. For the production of milk having an energy value of 80 Kcal, the mother must expend 100 Kcal. Considering the efficiency of milk production and the amount of milk a healthy baby may need, which is 850 ml daily with an energy value of 68 Kcal/100 ml, it equates to providing an extra diet of approximately 720 Kcal/day to meet the demands of lactation. Although this is an average estimate, it is important to note that every individual's needs can vary and additional factors such as the mother's pre-pregnancy weight, activity level, and the baby's demands can influence the exact number of additional calories needed.