Regular and Long-Term Effects of a Commercial Diet on Bone Mineral Density

Round 1

Reviewer 1 Report

The manuscript is interesting and fits in the scope of the Dietetics journal. The Authors described the impact of the commercial Fitlap diet on the human organism. I believe that this is a valuable study for those dealing with unconventional ways of nutrition and dietetics. However, major revisions should be made in the text. I believe that it cannot be suggested that a commercial diet is the only rational nutrition; therefore, these phrases should be changed throughout the manuscript. After all, it is known that rational nutrition is varied nutrition covering human energy and nutrient requirements, and no nutritional program is needed for this.

General comment:

1. Title: it should inform that this is a commercial diet, as the wording “Balanced Diet” is misleading; it suggests that a standard way of rational nutrition is analyzed in the study.
2. The Fitlap feeding plan should be introduced, as it is not known by many readers. As highlighted by the Authors, the diet is popular in Estonia. Without this information, the reader cannot recognize the source of the differences in Ca and Mg content.
3. Section 2. Materials and Methods: the consecutive sections have wrong numbering, please change to "2.1", "2.2" etc.

1.4. Blood analysis – what analyses were performed?

4. Results: clearly described
5. Discussion:

The Authors should explain why the blood of Fitlap users has the same amount of Ca and Mg as in the control group although the Fitlap diet contains significantly higher levels of of these elements - can any component of the diet interfere with the absorption of minerals?

Tab. 1. The authors showed that the BMI in the females from both groups is not statistically significantly different – then why did they devote so much space to discussing the relationship between excess body weight and bone mineralization?

Line 300-306: “It can be assumed that the representatives of the FDF group were more physically active at school age, but we did not examine these data” – what were the grounds for formulation of such a thesis? only because the FDF females had less fat?

6. Conclusions: The uthors cannot suggest that a commercial diet is the only wholesome diet; it should be made clear in the conclusions that Fitlap is an example of a commercial nutrition program and that the diet had no negative effects on bones.

Author Response

Comments and Suggestions for Authors

The manuscript is interesting and fits in the scope of the Dietetics journal. The Authors described the impact of the commercial Fitlap diet on the human organism. I believe that this is a valuable study for those dealing with unconventional ways of nutrition and dietetics. However, major revisions should be made in the text. I believe that it cannot be suggested that a commercial diet is the only rational nutrition; therefore, these phrases should be changed throughout the manuscript. After all, it is known that rational nutrition is varied nutrition covering human energy and nutrient requirements, and no nutritional program is needed for this. Thank you for your excellent remark! We fully agree with you and have adapted the manuscript accordingly.

General comment:

Title: it should inform that this is a commercial diet, as the wording “Balanced Diet” is misleading; it suggests that a standard way of rational nutrition is analyzed in the study. Thank you for your excellent remark, the title is changed as follows: “Regular and Long-Term Effects of a Commercial Diet on Bone Mineral Density”

The Fitlap feeding plan should be introduced, as it is not known by many readers. As highlighted by the Authors, the diet is popular in Estonia. Without this information, the reader cannot recognize the source of the differences in Ca and Mg content. Thanks for the comment! According to the information available to us, the text has been supplemented as follows: According to the commercial Fitlap program manual, each recipe (1000+ recipes) is suita-ble for every meal due to the similar energy value and nutrient ratio. Vegetables with a ca-loric content of less than 20 kcal per 100 g are covered by the so-called free reserve and can be eaten indefinitely during a meal. These include, but are not limited to, spinach, pump-kin, tomato, cucumber, bell pepper, kohlrabi. It is recommended to eat at least 400 g per day of the mentioned vegetables. There are no consumption restrictions on water, un-sweetened coffee and tea. In addition, it is recommended that high-fiber foods (such as ce-reals and fruits or berries) be eaten at least once a day and that red fish be consumed at least twice a week.

Section 2. Materials and Methods: the consecutive sections have wrong numbering, please change to "2.1", "2.2" etc. Thank you, these corrections are done.

1.4. Blood analysis – what analyses were performed? - Thank you, the corrected information is: Blood for analysis (2 x 3.5 mL with clot activator and gel) was taken by a registered nurse. The serum was separated by centrifugation for clinical chemistry analyses and stored at –20° C until analysis. Assays were performed in the THCC laboratory with a fully automated clinical chemistry analyzer Cobas e411 (Roche Diagnostics International AG, Rotkreuz, Switzerland) for the determination of serum vitamins D and B12 and Cobas c111 (Roche Diagnostics International AG, Rotkreuz, Switzerland) for serum magnesium and calcium concentrations. It is the equipment of recognized companies and accuracy is guaranteed by calibration and quality control.

Results: clearly described. Thank you!

Discussion:

The Authors should explain why the blood of Fitlap users has the same amount of Ca and Mg as in the control group although the Fitlap diet contains significantly higher levels of of these elements - can any component of the diet interfere with the absorption of minerals?

Actually, the intake and level in blood are certainly influenced by several mechanisms. Although the Fitlap diet contains significantly higher levels of calcium and magnesium in the diet than control group, the differences of these microelements in in blood was not emerged. It is anticipated, that organism without durative pathology catch several time after eating balance the blood values. Previously have considered, that calcium absorption decreases with age and important independent positive predictors are dietary fat, serum estradiol and 1,25-dihydroxyvitamin D3 (Sharpses et al. 2012). Intestinal calcium absorption increases during high-protein diet (Kerstetter 2005) and dietary protein influences positively calcium metabolism that influence on bone health and is associated with molecular, cellular, and endocrine bases of the interactions (Conigrave 2008). Also, the multiple factors additionally to dietary intake affecting magnesium status, such as high pH (<7.4) in ileum, gender (young women have better magnesium retention than young men), and weight (obese, BMI ≥ 30) have been shown to have lower magnesium consumption and reduced magnesium status. Serum changes can also be influenced by albumin levels (Workinger 2018), but the results of our study showed the high serum value negative effect to bone density. Increased dietary fiber intake does not affect magnesium status but can increase magnesium excretion in faeces (Workinger 2018).

Sharpses, S.A.; Sukumar, D.; Schneider, S.H.; Schlussel, Y.; Brolin, R.E.; Taich, L. Hormonal and dietary influences on true fractional calcium absorption in women: role of obesity. Osteoporos. Int. 2012, 23(11), 2607–2614.

Conigrave, A.D.; Brown, E.M.; Rizzoli, R. Dietary Protein and Bone Health: Roles of Amino Acid–Sensing Receptors in the Control of Calcium Metabolism and Bone Homeostasis. Annu. Rev. Nutr., 2008, 28(1), 131–155.

Kerstetter, J.E.; O'Brien, K.O.; Insogna, K.L. Dietary protein, calcium metabolism, and skeletal homeostasis revisited. Am. J. Clin. Nutr., 2003, 78(3), 584S–592S.

Workinger, J.L.; Doyle, R.P.; Bortz, J. Challenges in the Diagnosis of Magnesium Status. Nutrients, 2018, 10(9), 1202.

Tab. 1. The authors showed that the BMI in the females from both groups is not statistically significantly different – then why did they devote so much space to discussing the relationship between excess body weight and bone mineralization?

Thank you for this observation. We did it by the reason, as this was interesting for us (we hoped, that also for the others). We were inclined to think, that better bone density is associated with fat-free-mass, as higher physical activity. Actually, we have shown previously, that for bones the better result is associated with greater physical activity in school years. We have read, that little women are threatened by osteoporosis, but however it was interesting result.

Line 300-306: “It can be assumed that the representatives of the FDF group were more physically active at school age, but we did not examine these data” – what were the grounds for formulation of such a thesis? only because the FDF females had less fat? The discussion was based on the statement that perhaps the members of the FL study group were more physically active during school hours and thus had better bone density. However, we agree that this is not a good wording, so we tried to add an idea that we think is better suited to the context: “Although it has been found that PA can play an important role in reducing fractures even in postmenopausal age [41], our study results did not show the effects of different PA levels on bone. However, since our results did show that fat-free mass is the major factor influencing BMD, as was found by other authors [42], and due to PA, we cannot claim that PA does not affect BMD. The assessment of physical activity on the basis of the IPAQ questionnaire is rather subjective and thus we cannot be completely sure of the actual level of physical activity of the subjects.”

Conclusions: The uthors cannot suggest that a commercial diet is the only wholesome diet; it should be made clear in the conclusions that Fitlap is an example of a commercial nutrition program and that the diet had no negative effects on bones. “Regular adherence to a balanced commercial diet benefits micro-nutrient intake (calcium and magnesium) and BMD. However, micro-nutrients that affect bone density, such as calcium, magnesium, and vitamin D, should be obtained as food and not as a food supplement. However, it must be remembered that a rational diet is a varied diet that meets a person's need for energy and nutrients. Fitlap is an example of a commercial diet plan that has no negative effects on bones. Thus, it is necessary to teach a balanced diet and develop eating and exercise habits from early school age, because according to Movassagh [55], healthy dietary habits established during childhood and adolescence may continue into adulthood.”

Reviewer 2 Report

This manuscript evaluated the effect of a balanced diet on bone mineral density in Estonian women

The paper is generally well written but I have some concerns about methodology.

In details:

- to demonstrate an effect of a specific diet on bone mineral density (BMD) a longitudinal study design should be preferable instead of a cross sectional study to better define the effect of this diet on BMD.

- sample size is reduced and should be implemented.

- It is not very clear if BMD of lumbar spine and hip was performed directly or derived from the whole body DXA analysis. This point should be clarified.

-There are no data about the time of blood sample storage; fasting state? Which period of the year? This could interfere with serum levels especially when we evaluate vitamin D status. Timing of collection should be add in the analysis to better investigate the effect of the different diet on vitamin D status-

-There no data about exclusion criteria or possible comorbidities or concomitant medications which could influence bone metabolism and BMD variation. Moreover no data are provided about history of fragility fracture in the study population or other risk factors of bone fragility.

- I have some concerns about the possible effect of physical activity in the different groups. There is a significant increased percentage of very active subjects in the Fitlap group probably related to the increased prevalence of overweight and obese subjects in the Fitlap group who need a specific and increased energy expenditure to obtain the desired weight. However this different proportion of physical exercise could represent a  bias. Please clarify.

- Information about bone turnover markers should be added, if available or discussed as study limitation

 

Minor comments:

In the legend of table 2 “PA-physical activity” does not appear in the table and could be eliminated

Author Response

The paper is generally well written but I have some concerns about methodology.

In details:

- to demonstrate an effect of a specific diet on bone mineral density (BMD) a longitudinal study design should be preferable instead of a cross sectional study to better define the effect of this diet on BMD. Thank you for your excellent remark. We fully agree with your statement and we definitely plan to investigate the matter further longitudinally. These are the primary cross-sectional results and the corresponding information is now included in the work limits.

- sample size is reduced and should be implemented. Thank you for the comment. This is part of a larger study involving different study groups (gluten intolerant, physically overactive, elderly, etc.). Therefore, only 68 subjects in the present manuscript follow the FITLAP diet, and the control group is chronic disease-free peers. The size of the study group is really small, but a number of different time-consuming methods have been used. Based on these initial results, a larger and longer-term study must be planned in the near future.

- It is not very clear if BMD of lumbar spine and hip was performed directly or derived from the whole body DXA analysis. This point should be clarified. Areal bone mineral density were determined directly, not from the whole body analysis. Information is added to the manuscript.

-There are no data about the time of blood sample storage; fasting state? Which period of the year? This could interfere with serum levels especially when we evaluate vitamin D status. Timing of collection should be add in the analysis to better investigate the effect of the different diet on vitamin D status- Thank you for these comments. Serum was separated by centrifugation for clinical chemistry assays and stored at -20 ° C for one month until analysis (information added also to the manuscript). The remaining biological material was destroyed by autoclaving. This is part of a larger study and therefore the requirement was not to eat for 2 hours before the blood test, but fasting does not affect the parameters reported in this article. We added also to chapter 2: “It is known that June is usually one of the sunniest in Estonia and thus it can affect the value of vitamin D.” There is also a discussion on the topic in the discussion chapter.

-There no data about exclusion criteria or possible comorbidities or concomitant medications which could influence bone metabolism and BMD variation. Moreover no data are provided about history of fragility fracture in the study population or other risk factors of bone fragility. Thank you for the comment. Exclusion criteria were menopause, diagnosis of chronic diseases affecting the bones, and absence recurrent fractures. Unfortunately, we did not study the number of pregnancies, the use of hormonal contraceptives, and smoking. Corresponding additions have been added to the methodology chapter and also to the limitations.

- I have some concerns about the possible effect of physical activity in the different groups. There is a significant increased percentage of very active subjects in the Fitlap group probably related to the increased prevalence of overweight and obese subjects in the Fitlap group who need a specific and increased energy expenditure to obtain the desired weight. However this different proportion of physical exercise could represent a bias. Please clarify. We agree with the statement that the assessment of physical activity on the basis of the IPAQ questionnaire is rather subjective and thus we cannot really be sure of the actual level of physical activity of the subjects. This idea is added to the discussion.

- Information about bone turnover markers should be added, if available or discussed as study limitation.  Thank you for a good comment! This is definitely a shortcoming of our work and the relevant information is included in the manuscript. “The shortcoming of our research are the relatively small sample and the cross-sectional research method. In order to ensure the homogeneity of the study group, smokers and long-term users of hormonal drugs (including contraceptives) should also be excluded. An examination of bone turnover markers would certainly be necessary in the following study.”

 

Minor comments:

In the legend of table 2 “PA-physical activity” does not appear in the table and could be eliminated – The PA is deleted in Table 1.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

 

The manuscript is very interesting and fits in the scope of the Dietetics journal. The Authors described the impact of the commercial Fitlap diet on the human organism. I believe that this is a valuable study for those dealing with unconventional ways of nutrition and dietetics.

I have thoroughly reviewed the manuscript. I believe the authors addressed all the issues raised by the reviewer satisfactorily. I do not have any comments or suggestions.

 

Reviewer 2 Report

Authors had sufficiently answered to reviewer comments