guest post by susan macfarlane, registered dietitian nutritionist
As hard as we might try to fight it, aging is an inevitable part of life. And yet, scientists are still puzzling over what drives aging in humans. In this post, I’m taking a closer look at some of more common theories on aging and exploring the idea that dietary changes may influence the aging process.
What Causes Aging?
Aging, which is characterized by a progressive loss of function, is an outlier to natural selection’s “survival of the fittest”. However, this paradox is explained by the suggestion that a decline in the force of natural selection allows aging to endure (1). When considering theories of aging, we have two camps: those that believe that aging is genetic or programmed and those that support damage theories of aging. Genetic theories of aging propose that an internal biological clock regulates aging by systematically turning genes on and off (2). However, there is no one gene responsible for aging and results from twin studies estimate that genes are responsible for only 20-30% of aging (3), which gives scientists room to explore the role of damage theories. Such theories, which include the free-radical theory of aging, propose that accumulated damage over time drives aging (1). However, critics have challenged this theory since humans can repair damage and animals kept in safe environments will continue to age without an increase in lifespan (1).
The simple truth is that aging is likely a complex combination of both of these theories and may have the evolutionary intention of allowing for the survival of our species at an individual cost.
Are There Any Diet Changes That Can Slow Aging?
Thanks to the advancement of medicine, the average lifespan in developed countries has increased from a short-lived 45 years in the early 1900s to 75 and 80 years for men and women, respectively (4). Nowadays, the scientific community is interested in finding novel ways to extend both the quantity and quality of life.
When it comes to diet and aging, there are no shortage of theories.
Calorie Restriction
One popular theory is that of calorie restriction, which posits that reducing daily calories below usual intake (without inducing malnutrition) may extend lifespan.
This theory has been proven effective in rats and mice (where a 30-60% reduction in calorie intake beginning shortly after weaning resulted in a 30-60% increase in life span; 5).
When it comes to humans, however, the effects of calorie restriction are not so clear. Based on the findings of a 2007 meta-analysis in the Journal of the American Medical Association (4), calorie restriction that maintains a lower (but not malnourished) weight, results in improved insulin sensitivity and a lower body fat percentage, blood pressure, lipid level, and inflammatory status.
However, it is not possible to determine a safe calorie restriction target for everyone given the variation that exists in body composition and energy expenditure. Plus, it is possible that calorie restriction may improve the health of some body systems (cardiovascular) at the detriment of others (bone), given that weight loss has been associated with lower bone and muscle mass (6, 7).
The Mediterranean Diet
A more favourable dietary trend associated with longevity is the Mediterranean diet, which is characterized by a diet rich in fruits, vegetables, cereals, fish, whole grains, legumes, olive oil, and red wine, with limited amounts of meat and dairy. Several of these dietary components, specifically fruits and vegetables, possess anti-oxidant and anti-inflammatory properties that are helpful for reducing the risk of chronic disease and extending longevity (8).
But to truly understand the types of diets (and lifestyles) that favour longevity, we need look no further than the Blue Zones.
The Blue Zones represent five distinct geographic regions that house the world’s healthiest and oldest residents. Included in the Blue Zones are: Sardinia, Italy; Okinawa, Japan; Nicoya, Costa Rica; Loma Linda, California, U.S.A.; and Ikaria, Greece (9).
What Can The Blue Zones Teach Us?
Probably one of the most important takeaways from Blue Zone populations is that longevity is more than diet alone. According to the Blue Zone’s website, there are 9 important lifestyle factors shared among these distinct regions directly related to cultivating physical, mental, and social well-being. There are also many similarities that exist among these groups with regards to diet, which have been summarized into 10 nutrition guidelines (10):
- 95/5 rule – make at least 95% of your diet plants
- Limit meat (and avoid processed meats, such as bacon)
- Add fish (up to 3x per week; limit each portion to the size of a deck of cards)
- Avoid dairy
- Include 1 cup of legumes (beans, lentils, tofu) per day
- Reduce sugar
- Include a daily serving (1/4 cup) of nuts
- Choose whole grains
- Avoid processed foods
- Satisfy your thirst with water (tea and coffee are fine)
To find out more about the Blue Zones, check out their website. You can also take their True Vitality TestTM to find out what your estimated life expectancy is (I’m at 84.7 years but could live up to 97.3 with a few simple changes!).
And to learn more about plant-based eating, check out my previous blogs and videos:
Everything You Need to Know About Plant-based Eating – Part 1 and Part 2
Fundamentals of a Whole Food, Plant Based Diet with Susan Macfarlane RD
References:
- Lipsky MS, King M. Biological theories of aging. Dis Mon. 2015 Nov;61(11):460-6.
- Weinert BT, Timiras PS. Invited review: theories of aging. J Appl Physiol (1985). 2003;95(4):1706–1716.
- Barzilai N, Guarented L, Kirkhope TB, et al. The place of genetics in ageing research. Genetics. 2012;13:589–592.
- Fontana L, Klein S. Aging, adiposity, and calorie restriction. JAMA. 2007 Mar 7;297(9):986-94.
- Weindruch R, Sohal RS. Caloric intake and aging. N Engl J Med. 1997;337:986-994.
- Villareal DT, Fontana L,Weiss EP, et al. Bone mineral density response to caloric restriction-induced weight loss or exercise-induced weight loss: a randomized controlled trial. Arch Intern Med. 2006;166:2502-2510.
- Weiss EP, Racette SB, Villareal DT, et al. Lower extremity muscle size and strength and aerobic capacity decrease with caloric restriction but not with exercise-induced weight loss. J Appl Physiol (1985). 2007 Feb;102(2):634-40. Epub 2006 Nov 9.
- Di Daniele N, Noce A, Vidiri MF, et al. Impact of Mediterranean diet on metabolic syndrome, cancer and longevity. Oncotarget. 2017 Jan 31;8(5):8947-8979.
- Dan Buettner: Blue Zones. History of Blue Zones. n.d. Retrieved from: https://www.bluezones.com/about/history/
- Dan Buettner: Blue Zones Project by HealthWays. 10 Blue Zones Food Guidelines. 2015.
