Tuesday, August 28, 2012

Protein Restriction And Longevity

Read this post first: Dietary Restriction: Impact On Health And Longevity.  This is a continuation of that post which summarized the benefits of caloric restriction (CR). This post will deal with an alternative to CR, restriction of dietary components.

Dietary Restriction (DR): Reducing Carbs, Fat, Or Protein Instead Of Calories1
"Neither carbohydrate restriction nor lipid restriction appear to be effective alternatives to CR. Lipid restriction has been shown to have no effect on longevity. Regarding carbohydrate, several studies have found that increasing intake either increases or has no effect on longevity, suggesting that restriction would not extend life. Moreover, both forms of macronutrient restriction fail to decrease reactive oxygen species production or oxidative DNA damage."

"Protein restriction appears to be a viable candidate for an alternative to CR. Sixteen out of 18 reviewed experiments found that protein restriction increased maximum lifespan in rodents). The average increase in maximum lifespan in the 16 positive studies was approximately 20%. When this is compared to the ~40% increase in lifespan found in many CR investigations, it suggests that protein restriction accounts for approximately half of this effect. Moreover, several of the reviewed studies compensated for the reduction in protein by increasing carbohydrate intake; this balanced total caloric intake and ensured that the prolongation of life was due to restriction of protein and not calories."

A wealth of evidence indicates that methionine restriction might account for most or all of the life-extending benefits of protein restriction:
  • Methionine content has an inverse relationship with maximum life span in mammals.
  • Of the amino acids, methionine is one of the most vulnerable to oxidation by reactive oxygen species.
  • Methionine supplementation increases LDL cholesterol oxidation.
  • Raising methionine intake increases plasma homocysteine concentrations, which in turn elevates the risk of cardiovascular disease and mortality.
So, low-carb and low-fat won't rival the insane benefits of caloric restriction. But low-protein will, specifically, low-methionine. What foods are good sources of methionine? A quick search in NutritionData says animal foods.

Next up, periodic fasting.

This was one in a series of 4 posts:
1 Impact Of Caloric And Dietary Restriction Regimens On Markers Of Health And Longevity In Humans And Animals: A Summary Of Available Findings, Nutrition Journal, October 2011


Reijo Laatikainen said...

Thanks for a great review (and reference). Very interesting that in animals protein restriction would increase longevity. This is in line with prospective cohort studies: animal protein based low carbohydrate diet seems to increase mortality and morbidity in humans.

Claudia said...

Right so what are the low-carb people saying about this? Can you live to 100 on a caveman diet? How do they know what cavemen ate anyway.

Tristan Trefoil said...

The original cavemen (big apes) ate fruit and veggies = low methionine and low protein diet.