Nutrition and Ageing
Remaining physically active and optimising nutrition
intake as we age has enormous health benefits - physiological
functioning is improved and the risk of chronic disease
is reduced.
It is therefore very important to encourage older
adults to remain active. There are similarities between
the ageing process and the deterioration associated
with physical inactivity. Physical exercise has important
benefits for the cardiovascular system, musculoskeletal
system, psychological wellbeing, bowel function and
glucose tolerance as well as fat and carbohydrate
metabolism.
Clinical trials have shown that high-intensity strength
training can improve muscle mass, preserve bone density
and improve strength and balance as we age.
Nutritional considerations
When considering nutrition for the physically active
ageing individual, recommendations should be based
on requirements of the ageing process as well as the
nutritional requirements for exercise.
Why is optimal nutrition important in the older
age group?
Nutrition interacts with the ageing process. 13%
of the population of developing countries is over
65 years. This represents a large group of individuals
who may require specialised nutritional advice. One
of the great challenges of nutrition in this older
age group is the vast heterogeneity.
Heterogeneity
Of all the age groups, older adults have the greatest
heterogeneity. As people age the more dissimilar they
become from their contemporaries meaning that there
are a wide range of physiological and nutritional
requirements within the older age group. This is because
individuals age at different rates due to genetic,
environmental, lifestyle, and cultural differences.
Therefore the nutritional requirements for older individuals
can vary substantially.
Factors to consider
A large proportion of the older adult population
may suffer from some type of chronic disease and so
can often be taking various medications. Nutrient
interactions with medications can occur.
The ageing process can also be associated with a
decrease in muscle mass, impaired immune function,
gastric atrophy, deteriorating dental health, reduced
bone mineral density and a loss of the thirst sensation.
These factors should be considered when offering nutritional
advice to the older age group.
Changes in digestion
Ageing itself does not seem to have a drastic effect
on the digestive system. It appears that impaired
digestion and absorption seen in older adults is more
reflective of medication use and various disease states.
One of the important changes with ageing is the reduction
in gastric acid output in those with gastric atrophy.
Atrophy of the stomach becomes more common with ageing
and can affect about one third of those over 60 years
of age. It results in a lowered secretion of acid,
intrinsic factor and pepsin, all of which are important
for the digestion and absorption of nutrients such
as vitamin B12, calcium, iron, and folate.
Physiological changes with ageing
Physiological changes as we age can affect both training
and competition potential. Many of these changes can
affect nutrition.
The following are some nutritional consequences that
occur because of the physiological changes that occur
during ageing.
Decreased energy requirements: Decreased muscle
mass, decreased aerobic capacity, and decreased glycogen
storage capacity can all decrease energy requirements
Increased requirement for calcium and/or vitamin
D: Decreased bone density, decreased capacity
of the skin to synthesise cholecalciferol (for vitamin
synthesis), decreased calcium bioavailability, decreased
gastric acid
Increased requirements for certain micronutrients:
Impaired immune function, decreased gastric acid,
decreased efficiency in the use of some vitamins (e.g.
vitamin B6).
Increased fluid requirements: This results
from the combination of decreased thirst perception
and impaired kidney function.
Drug-nutrient interactions
Some prescription medicines can affect nutrition,
usually by increasing the requirement of a nutrient.
Some drugs can reduce appetite, the sense of taste
and smell, or cause nausea or gastrointestinal disturbances.
These factors will reduce food and therefore nutrient
intake.
Energy
The most important factor determining energy requirements
as with other age groups is energy expenditure. It
has been suggested that daily energy requirements
of the ageing population decreases in general because
of decreased physical activity as well as reduced
resting metabolic rate. Therefore the reduction in
energy requirements as we age is due to the combination
of a reduction in physical activity and the age-related
reduction in fat free mass.
Research in sedentary individuals suggest body composition
changes dramatically with ageing with approximately
a doubling of body fat between 20 and 50-60 years
of age, followed by a fall in body fat after 70 years.
Athletes require energy to maintain normal metabolic
function and to provide energy for the exercising
muscle during training and competition. Physical exercise,
aerobic and/or resistance training has been shown
to effectively increase energy requirements and maintain
metabolically active muscle mass in healthy individuals.
Protein
Because protein is continually degraded and synthesised,
a dietary supply of protein is needed to offset protein
losses.
The current recommended intake of protein is 0.75-0.80
grams of protein per kilogram of body weight per day.
However, some recent research has suggested that 0.80g/kg/day
may be inadequate to maintain protein balance in the
older age group.
It is suggested that for those who are physically
active, the requirement of protein may be even higher
because of increased use of protein during exercise.
Protein requirement may depend upon exercise intensity,
carbohydrate availability, exercise mode, energy balance,
gender, training, timing of macronutrient intake and
age. There is an important association between energy
intake and protein balance. Insufficient energy intake
is associated with negative nitrogen balance and therefore
protein loss. It is therefore important to consume
sufficient energy along with adequate protein.
The protein requirements for active older adults are
likely to be less than their physically active counterparts.
This is because of an age-related decrease in protein
turnover and protein synthesis and the fact that older
adults do not appear to train at the same intensity
as younger adults.
Suggestions of protein intake for older adults range
from 1.0-1.25g/kg/day in order to maintain or promote
a positive nitrogen balance.
It is important to keep in mind that in terms of
protein recommendations, adjustments may be needed
due to illness, chronic disease or suboptimal energy
intake.
Carbohydrate
For the exercising older adult carbohydrate is an
important fuel source during high intensity or prolonged
endurance exercise.
In older adults, glycogen storage per unit of muscle
is lower than in similarly trained younger athletes
whilst glycogen utilisation per unit of energy expenditure
is higher during exercise. However regular endurance
training can increase glycogen storage.
Recommendations for carbohydrate intakes are similar
to that of younger adults. The absorption and utilisation
of carbohydrate appears to remain intact with ageing.
It is recommended that the older athlete should consume
at least 55% of calories from carbohydrate, and should
be largely comprised of high fibre, low GI carbohydrate
sources.
Fat
Fat is an important energy source during prolonged
exercise. It also provides important nutrients such
as the fat-soluble vitamins. During ageing the ability
to digest, absorb and utilise fat is maintained.
It is recommended that a fat intake comprising 25-30%
of total energy be consumed by older adults. Fat intake
should not be overly restricted because of the subsequent
risk of inadequate intake of fat-soluble vitamins
(A, D, E, K). As with other age groups, for cardiovascular
health, saturated fat should be minimised with monounsaturated
and polyunsaturated fats being favoured.
Micronutrients
Vitamins and minerals are important for maintaining
body function and for optimising sporting performance.
Nutrient intakes of physically active older adults
that may be of concern include calcium, iron, zinc,
magnesium and vitamin D, folate and vitamin B12.
Athletes may have greater losses of some micronutrients
from sweat and urine. The risk of suboptimal intake
of micronutrients is higher in athletes who have low
energy intakes. Also some medical conditions may impair
the absorption and utilisation of some micronutrients.
Older adults may be at greater risk of sub-optimal
intake due to age-related gut impairment which is
associated with reduced nutrient absorption.
Vitamin A
Vitamin A is important for vision, immune function,
growth, and skin.
In an ageing population the clearance of vitamin
A is decreased by about 50% compared to younger adults.
Therefore requirements are likely to be less in the
older age group. Vitamin A supplementation in this
age group is not recommended due to risk of vitamin
A toxicity. Vitamin A toxicity can result in peeling
skin, headaches, vomiting, impaired immune response.
Older adults should focus on obtaining their vitamin
A from dietary sources, including the carotenoids.
Riboflavin
This B vitamin is important for energy metabolism
and therefore important when considering the physically
active older adult. Some evidence suggests that older
adults who are physically active may require more
riboflavin than younger counterparts. Ensuring that
older adults consume plenty of dairy products should
encourage an adequate riboflavin intake.
Vitamin B6
Vitamin B6 is involved in protein and glycogen metabolism.
As it aids the formation of myoglobin and haemoglobin
(oxygen carriers in the muscle and blood respectively)
vitamin B6 is important for active individuals. It
has been suggested that for ageing athletes the recommended
intake of vitamin B6 be increased to 2mg/day.
Vitamin B12
Vitamin B12 is important for new cell synthesis,
maintaining nerve cells, and the metabolism of some
fatty acids and amino acids. It is also used to convert
folate to its active form.
The incidence of the anaemia associated with the
malabsorption of vitamin B12 increases in the older
age group. This results from the age-related decrease
in stomach acid and intrinsic factor which are needed
to absorb vitamin B12.It is recommended that older
adults should consume foods that are fortified with
vitamin B12.
There is a suggestion that the recommended intake
of vitamin B12 be increased to 2.4m g per day, especially
if they are partaking in regular exercise.
Vitamin D
Vitamin D has several important functions including
a role in bone metabolism and immune function in physically
active individuals taking part in heavy training.
In the older age group there is an impaired capacity
of the skin to synthesize pre-vitamin D3, impaired
hydroxylation of vitamin D3 in the kidneys, and reduced
sun exposure. These factors can contribute to a reduced
vitamin D status seen in older adults.
For older adults who have limited sun exposure, a
low dose (10-15m g per day) vitamin D supplement may
be recommended.
Folate
Folate is important for amino acid metabolism and
red blood cell formation. Folate may be a problem
in older adults with gastric atrophy where there is
a decrease in folate absorption.
Some investigators have suggested that supplemental
folic acid may improve memory and cognitive function
in older adults.
Calcium
It is important at all ages to consume and absorb
sufficient calcium for physiological requirements.
If insufficient dietary calcium is consumed some bone
calcium will be mobilised to maintain blood calcium
levels.
Calcium needs are higher for the oestrogen-deprived
post-menopausal female.
Iron
Iron is an important component of haemoglobin and
myoglobin which carry oxygen in the blood and muscle
respectively. Iron is also important for enzymes involved
in aerobic metabolism.
Iron deficiency and iron deficiency anaemia can reduce
exercise capacity and/or maximal aerobic power.
Iron losses have not been studied in older adults.
Iron stores generally increase with ageing and therefore
older people need less iron. Iron deficiency is rarely
seen in the older population, with anaemia being the
result of an underlying chronic disease. It has been
suggested that older adults consume around 10mg of
iron per day.
Zinc
Zinc has an important role in tissue repair and immune
function. Zinc is also involved in a large number
of enzymes involved in fat, protein and carbohydrate
metabolism.
Zinc is lost through the skin, and intestinal cells,
sweat, urine and faeces. Although there seems to be
a reduction in zinc absorption in the elderly it also
seems that zinc excretion is reduced, meaning that
zinc balance is maintained.
Fluids
The ageing process is related to a number of changes
that may make the older adults more susceptible to
dehydration than their younger counterparts. The age-related
decrease in total body protein leads to a reduction
in total body water. It also appears the ADH receptors
in the kidney lose their effect which leads to increased
water excretion by the kidney.
Age-related reductions in thirst sensation due to
a reduction in osmoreceptors that are sensitive to
blood concentration of fluid-regulatory hormone and
electrolytes are apparent in the older age group.
These changes can make older adults more susceptible
to dehydration. It is therefore crucial to stress
the importance of fluid intake to this age group.
Also during exercise in the heat there appears to
be decreased blood flow to aged skin as a result of
reduced availability of vasodilate. There also appears
to be an age-related decrease in sweat production.
This means that older adults may have more problems
with over-heating and fluid balance.
It is recommended that athletes should consume 500ml
of fluid prior to exercise, 400-1000ml per hour during
exercise, and drink to cover losses at the completion
of exercise.
Supplements
There are certain circumstances where supplementation
appears to be beneficial for older adults. Examples
of this are supplementation of vitamin B12 (2.4m g/day),
nutritional doses of vitamin D (10-15m g/day) for
those who may get inadequate sunlight exposure, and
calcium. A general multivitamin/mineral supplement
with a supply of nutrients at the recommended level
may benefit those with very low food intakes. Otherwise
a well-balanced diet should provide most healthy older
adults with the nutrients they need.
Hints for ensuring an adequate nutrient intake
As we age our sense of smell decreases, which affects
the way we enjoy food. This can lead to a reduction
in food intake for some individuals. The following
are some strategies to minimise the effect of a reduction
in the sense of smell:
- Have a variety of food on the plate so that individuals
can swap from food to food so that taste buds do
not become desensitised
- Chew foods as much as possible to release as much
taste as possible
- Use spices and herbs to flavour foods
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