luni, 10 octombrie 2011

Impact of caloric and dietary restriction regimens on markers of health and longevity in humans and animals: A summary of available findings

Impact of caloric and dietary restriction regimens on markers of health and
longevity in humans and animals: A summary of available findings
Nutrition Journal 2011, 10:107 doi:10.1186/1475-2891-10-107
John F Trepanowski (jtrepa2@uic.edu)
Robert E Canale (rcanale@memphis.edu)
Kate E Marshall (kmarsh14@uthsc.edu)
Mohammad M Kabir (mkabir@memphis.edu)
Richard J Bloomer (rbloomer@memphis.edu)
ISSN 1475-2891
Article type Review
Submission date 23 June 2011
Acceptance date 7 October 2011
Publication date 7 October 2011
Article URL http://www.nutritionj.com/content/10/1/107


OVERALL SUMMARY AND CONCLUSIONS

CR has been demonstrated to extend the maximal lifespan of a diverse group of species. 24
This extension of life is maximized when: 1) the magnitude of CR is elevated to the highest
possible value before inducing malnutrition and 2) the duration of CR is maximized. Animals on
CR regimens exhibit a variety of improvements in overall health in general and cardiovascular
health in particular. Unfortunately, the likelihood of discovering whether or not CR extends
human life is rather remote due to the ethical and logistical limitations of research design. The
optimal magnitude and duration of CR for humans will also likely never be known for the same
reason. Nonetheless, many human CR studies have noted favorable changes in biomarkers
related to cardiovascular and glucoregulatory function, which likely relate to quality of life and
may relate to longevity.

Due to the austerity of following a CR regimen of sufficient magnitude and duration,
alternatives such as CE, ADF, and DR may prove to be more appealing. The most pertinent
consideration to make when evaluating these alternatives is whether or not they elicit benefits
that are comparable to CR. ADF has been demonstrated to extend life and improve both
cardiovascular and glucoregulatory funnction in animals. Human trials have noted heterogeneous
findings and sex-specific differences regarding ADF’s effects on glucoregulatory function.
Unfortunately, it is difficult to compare the effects of ADF and CR regimens across different
studies due to an enormous number of confounding variables. Future studies should feature an
ADF group and a CR group so that direct comparisons can be made. Regarding DR, neither
carbohydrate restriction nor lipid restriction extend life. However, protein restriction appears to
extend maximum lifespan by 20%. Recent findings suggest that methionine restriction may be
the single cause of life extension observed in protein restriction studies. Future studies should
examine the effects of different magnitudes of methionine restriction on life extension.
As noted above, considerable research has recently focused on whether CE augments any 25
of the health-promoting benefits caused by CR alone. Very few conclusions can currently be
made due to the mixed results of the studies. CE does not appear to extend life beyond any
extension observed to be caused by CR. However, CE may be more manageable for many
individuals due to the smaller reduction in dietary calorie consumption. Future work in this area
should examine different exercise intensities, volumes, frequencies, and modalities.

Also, future work should compare different amounts of exercise-induced caloric expenditure.
Islamic Ramadan, the three principal fasting periods of Greek Orthodox Christianity, and
the Daniel Fast each provide a unique and interesting vantage point for evaluating the effects of
food restriction/modification. The majority of findings related to Ramadan fasting are mixed,
and these discrepancies are most likely due to the differences in cultural norms – particularly
dietary norms – of the groups studied. The three Greek Orthodox Christian fasts appear to
decrease body mass and lower both total and LDL cholesterol levels, although these fasts
minimally affect the intake of most vitamins and minerals. Finally, the Daniel Fast is associated
with profound and favorable effects on a variety of markers related to human health, including
blood pressure, blood lipids, insulin sensitivity, and biomarkers of oxidative stress.

This paper has touched on some of the numerous methods of restricting dietary intake.

Whether one chooses to restrict energy intake daily, fast every other day, restrict intake of a
particular macronutrient, or fast for religious purposes, the authors hope that this paper can serve as a valuable tool to understanding the ability of dietary modification to improve overall health and the quality of life. Furthermore, we hope that this information will fuel the development of new ideas and research studies focused on investigating the health benefits of caloric and dietary
restriction.


Abbreviations: ADF, alternate-day fasting; ASUI, Asthma Symptom Utility Index; BDNF,
brain-derived neurotrophic factor; CALERIE, Comprehensive Assessment of Long Term Effects
of Reducing Caloric Intake; CE, caloric restriction combined with exercise; CR, caloric
restriction; DR, dietary restriction; FEV1, forced expiratory volume; HDL, high density
lipoprotein; LDL, low density lipoprotein; MDA, malondialdehyde; MI, myocardial infarction;
mini-AQLQ, mini-Asthma Quality of Life Questionnaire; PEF, Peak Expiratory Flow

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