Nutrition & aging

definition changed with the years due to extended life-span

proportion of elderly people increases (increased number of centenarians)

active healthy seniors

institutionalized people (retirement home, long-stay services)

specificity of old-old

environmental & psychological factors: poverty, isolation/loneliness, depression (loss of spouse/close family), dementia, intestinal disorders (diarrhea, constipation), incontinence

physical factors: dependency (physical abilities/visual acuity), alteration of the dental apparatus, swallowing disorders (false path), non-recovery syndrome

—>loss of metabolic flexibility, can’t recover from malnutrition, no adaptation

physiological factors: altered eating behavior (unsuitability to the restriction/for overfeeding), taste alteration (loss of sensitivity, prefer sugared food), perception threshold, impaired sense of smell, alteration of amino acid metabolism

iatrogenic factor: harmful role of poly-medication

—>environmental, psychic, physiological & iatrogenic factors contribute to a decrease in food intake & therefore to the establishment of undernutrition

immune cells are normaly highly capable to adapt

due to malnutrition decreased immune function

continuous loss of function if starvation for longer than 12 h

when fridge empty the owner hospitalized 3x faster / more frequently on the next visit

in elderly maintained weight loss

in adults recovery due to increased food intake

biological marker of nutritional state

the lower the higher death percentage

life-span correlates with malnutrition

synthesized in the sun by the skin but not in sufficient amounts

the whole population has vitamin D deficiency

nutrition rich in vitamin D: fish oil liver, mushroom, egg, fish

supplementation of vitamin D & calcium reduced falls in elderly (weaker muscles)—>interfere with muscle function

contribution below recommendations

potentiator of insulin: increase in the number of insulin receptors, change insulin/receptor binding, increased insulin internalization

improved glucose tolerance &lipid metabolism (increase HDL & decrease LDL)

if weight loss > 5 kg high increased in mortality

food preferences

user-friendliness, comfort

ergonomic cutlery

help with eating a meal

respect the needed time to eat the meal

avoid prolonged periods of fasting

avoid anorectic drugs

after-meal medication

no effect on the risk of infectious diseases /infectious rate

arguments for multivitamin administration in the elderly weak & contradictory but the placebo effect

Progressive decline in muscle mass due to aging

decreased muscle mass and strength

—>decreased protein synthesis, anabolic hormones, protein intake, innervation & physical activity

leads to sedentarity, falls & dependence

imbalance in protein synthesis & protein breakdown

continuous decrease in muscle mass —>replaced by fat mass

few ways to preserve muscle mass

not modified between elderly and young subjects

does not explain the loss of muscle mass

defect of anabolic stimulation in the elderly

—>decreased performance, muscle strength (12-15% per decade)

—>increased fatigability, acceleration of sarcopenia during stress

—>artifical ventilation required, cardiac failure, inability to recover during long-term

excess of AA neurotoxic—>limit level of AA to proteic requirement

90-95% of AA absorbed in intestine

regulator of AA homeostasis: kidney via ureagenesis

Arg transformed into citrulline —> in the kidney released as Arg—> excreted in the urea

come from a meal —>absorbed in the intestine—>kidney delivers only required AA into the plasma to stimulate protein synthesis

in elderly plasma decreased in AA—>lack of stimulation of protein synthesis

significantly increased in the elderly

too low in periphery —>decreased AA levels

by leucine

elderly react delayed to increased levels of leucine —>delay in protein synthesis

for same level of stimulation of protein synthesis higher level of AA needed

regulates muscle protein synthesis

activated by AA

S6 kinase has lost sensitivity to phosphorylation in the elderly

—> Not only decreased amount of systemic AAs in post-prandial situations but also the ability of AA to stimulate protein synthesis is blunted —>improve sensitivity or higher AA concentration

(mTOR inhibited in anti-cancer therapy —>increases malnutrition

no effect on muscle mass neither muscle strength

protein pulse

improves protein retention in elderly

efficient in elderly undernourished subjects but difficult to prepare meals low/high in proteins—>not translated in real life

leucine bioavailability decreased in elderly & stimulates synthesis via mTOR

in short term increased muscle protein synthesis post-prandial but long term no effect on muscle mass & function

leucine side effects: promotion of prostate cancer, BCAAs mTOR AKT depression, cell transformation, renal load—>more side effects than use

high protein diets (compliance, satiety)

pulsed diet; concept validated scientifically but difficult to transpose to a population

fast proteins, use of leucien ineffective

vitamin D already supplemented

AA only produced by the intestine

not metabolized by the intestine

no hepatic captation —>escapes splanchnic sequestration

—>itrogen intake escaping splanchnic sequestration could improve effectiveness of renutrition in elderly

significant increase in muscle protein content & protein synthesis

weight gain correlated with muscle gain (electrophysiology)

—>oral citrulline supplement increases muscle protein & stimulates muscle protein sy

nthesis & muscle strength

—>good candidate for possible nutritional strategy in malnurished elderly

2-fold increase with citrulline in malnurished rats—>pharmacological effect

inhibitor of mTOR (Rapamycin) blocks effect of citrulline in vivo & in vitro

thermodynamic action of citrulline—>reallocates ATP consumption —> works in malnutriton but not normal state —> inefficient during musculation

citrulline administration improves nitrogen balance in healthy volunteers but need for muscle protein synthesis

volunteers with protein restriction during 3 days then consumption of citrulline or non assential AA

—>citrulline concentration reaches plateau

—>citrulline increases muscle protein synthesis by 25%

—>oral administration of 10g citrulline stimulates muscle protein synthesis in human

evaluation of long term effects of citrulline supplementation in healthy aged rats

—>statistical significant decrease in mortality with Cit (but low number of rats)

—>body weight equal to control group but different composition —> decrease in fat & increase in lean mass (muscles)

—>increased muscle proteins & muscle content

bigger size of fibers

after 21 days increased muscle mass & decreased fat mass

rats: restores muscle mass during aging, increases muscle strength, chronic administration corrects the effects of aging on body composition

humans: oral administration of citrulline is very well tolerated, increases muscle protein synthesis, restores muscle mass in malnurished elderly, improves muscle function