Introduction
Aging is a physiological process. Aging in Iran has an increasing trend. The elderly need to follow a healthy lifestyle to have a good life. Healthy lifestyle includes proper nutrition, adequate sleep, physical activity, and not smoking. Nutrition is one of the important factors affecting the health of the elderly. To have a proper nutrition, in addition to having a diet plan suitable for the physical and mental condition, educational programs are needed. Since education can be effective in maintaining healthy behavior, this study aims to determine the effectiveness of three educational methods (speech, question & answer, presentation of pamphlets) on nutrition status and sustainability of nutritional knowledge in older people in Bandar Abbas, Iran.

Methods
In this semi-experimental study, the study population consists of all older adults (≥60 years) in Bandar Abbas city. Of these, 120 (30 in the control group and 30 in each of three intervention groups) were selected using a two-stage sampling method. To determine the sustainability of nutritional knowledge, the standard questionnaire of nutritional knowledge sustainability for the elderly was used. This questionnaire was designed by Iran’s Ministry of Health and Medical Education. It has 20 items answered by I agree (1 point), I don’t know (0 point), and I disagree (0 point). The scores are summed up and then the total score is divided into three categories in percentage: 0-50% (0-10 agreed answers) indicating the elderly with poor lasting knowledge who need re-education, 50-70% (10-14 agreed answers) indicating the elderly with moderate lasting knowledge who need educational interventions, and 70-100 (15-20 agreed answers) indicating the elderly with good lasting knowledge who do not need re-education or educational interventions. Based on this, those in the first and second categories entered the study and completed the 18-item mini-nutritional assessment (MNA). The data were analyzed in SPSS software, version 23 using one-way analysis of variance and repeated measures analysis of variance.

Results
The age range of participants was 60-70 years. Majority of them were male (53.3%). The mean age of those in the intervention groups was 64.99±3.39 years and in the control group it was 63±4.31 years. In all groups, most of older people had primary education (50% control group, 46.3% lecture group, 43.3% Q&A group, 43.3% pamphlet group). The results of analysis of variance showed that the mean nutritional status (P=0.281) and sustainability of nutritional knowledge (P=0.392) were not significantly different among the intervention and control groups at baseline. The results of two-factor analysis of variance showed that the effect of lecture method on nutrition status and sustainability of nutritional knowledge was not significant. Therefore, it can be said that lecturing method was not effective in improving the nutrition status and sustainability of nutritional knowledge of the elderly. The effect of Q&A method on nutrition status and sustainability of nutritional knowledge was significant. It seems that Q&A sessions played an important role in changing the attitude of the participants by having group discussions and clearing ambiguities. The results of analysis of variance showed a significant difference between the intervention groups and the control group in posttest and follow-up phases. The results of repeated measures analysis of variance showed that only the Q&A method had a significant effect on nutrition status (F=4.397, P=0.031) and sustainability of nutritional knowledge (F=10.108, P=0.002) over time. The methods of education by lecture method and pamphlet presentation had no significant effect on nutrition status and sustainability of nutritional knowledge in the elderly.

Conclusion
The Q&A method can improve nutrition and sustainability of nutritional knowledge of the elderly compared to education by lecture method and pamphlet presentation which had no significant effect. It seems that the development of educational programs regarding healthy nutrition for the elderly, in the form of Q&A sessions and group discussions can help in the promotion of nutrition status and the sustainability of nutritional education effect. If the design of educational methods is based on educational needs assessment and health literacy level of the elderly, the education can be more effective.

Ethical Considerations
Compliance with ethical guidelines
This research was approved by the Ethics Committee of Hormozgan University of Medical Sciences (Code: HUMS.REC.1395.90)

Funding
The financial support of this study was carried out by the Research Deputy of Hormozgan University of Medical Sciences.

Authors' contributions
All the authors participated in the design, execution and writing of all parts of this research.

Conflicts of interest
The authors declared no conflict of interest 

Acknowledgements
We express our gratitude and appreciation to all dear seniors and respected personnel who helped us in conducting this study, especially who patiently answered the questions of the questionnaire. In addition, we are very grateful for the efforts and cooperation of the relevant officials at Hormozgan University of Medical Sciences, without doubt, this study would not have been possible without their support.

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