Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

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highest percentage of water and the lowest level

of food energy of these fruits. An intake of 100 g of

strawberries would provide the US Department of

Agriculture adult daily requirement for ascorbic acid

(vitamin C). The ascorbic acid content of strawberries

is slightly higher than that of oranges, and much

higher than that of apples. Although not a rich source

of potassium, a 100-g portion would provide about

10% of the suggested minimum estimated safe daily

intake. This is more than apples, less than oranges,

and about 42% of that provided by bananas.

0014 Strawberries contain several vitamins and minerals

(Table 3) in concentrations that would provide less

than 5% of the minimum daily requirement. There

are also 18 amino acids in strawberries, but all occur

in extremely low concentrations. (Refer to individual

nutrients.)

Handling and Storage

0015 Strawberries are sold by volume or by weight. The

volume containers hold approximately 0.25, 0.5 or

1 l. A small container would hold approximately 225

g; some of the larger containers may hold up to 3 kg.

Fruit for the fresh market is generally harvested

directly into the retail container. These are placed in

fiberboard or corrugated trays, or masters, each hold-

ing a convenient multiple of the smaller harvesting

containers.

0016 Fresh-market strawberries must be harvested in a

manner which eliminates, or keeps to a minimum,

bruising, skin disruptions, and the bleeding of fruit

juices. Berries should be harvested by pinching off

the stem at the cap, as clasping the fruit between the

fingers and then pulling causes excessive bruising.

Good commercial practice is to hold harvested fruit

out of the sun and protected from warm winds and

blowing dirt. Growers following recommended prac-

tices move their fruit to cold storage within 1 or 2 h of

harvest. Warm fruit bruises easily and must be trans-

ported gently.

0017 Field heat must be removed rapidly to reduce losses

from rot, caused by fungi such as Botrytis cinerea

(grey mold), Phytophthora cactorum (leather rot),

and Rhizopus nigricans (black whisker rot). These

fungi either grow very slowly, or not at all, at fruit

temperatures of 0–2



C. Changes in the fruit associ-

ated with senescence, e.g., skin darkening, softening

of the flesh, and loss of flavor, occur more slowly at

lower temperatures. (See Ripening of Fruit.)

0018 Forced-air cooling is the preferred method of

removing field heat in many strawberry-producing

areas. In these coolers, the fruit can be cooled from

25–35



Cto2–4



C within 1–2 h. In these coolers,

trays of fruit are placed so as to form the side walls of

a plenum, open to a wall with an exhaust fan. With

the open top and end covered with fabric, chilled air

is drawn from the cold room through the trays of

fruit. To retain the best quality, the chilled fruit is

held at 0–2



C and 90–95% relative humidity. Fruit

treated in this manner can be stored for 5–7 days and

retains its quality during 3–5 days of marketing after

storage. (See Controlled-atmosphere Storage: Appli-

cations for Bulk Storage of Foodstuffs.) In some

growing areas, fruit is forced-air-cooled on pallets

and then covered with an airtight plastic bag. Carbon

dioxide is added to an approximate level of 15% to

help maintain quality during shipping to market.

Some varieties of strawberries become 25–40%

firmer when they are exposed to 10–20% carbon

dioxide; with others, the carbon dioxide serves only

to maintain firmness. There are fewer losses from

decay among these berries, and their respiration

rates are reduced.

0019Although the vast majority of strawberries are har-

vested by hand for the fresh market, a small number

are mechanically harvested (predominantly in Eur-

ope). Mechanically harvested berries are not suitable

for the fresh-market trade because of extensive bruis-

ing during the harvesting process. However, mechan-

ically harvested fruit is suitable for processing. The

berries from the harvester are collected in large totes,

or bulk bins, for transporting to the processing facil-

ity. This fruit is processed within a few hours of

harvest and thus may not be cooled before processing.

Recovery of finished product is generally higher when

the fruit is cooled before processing. The quality of

mechanically harvested berries does not deteriorate

excessively for 2–3 days, possibly longer when they

are cooled to 0–2



C immediately after harvesting.

Mechanically harvested fruit does contain a moderate

quantity of green berries. Some of this green fruit is

incorporated into the end product without affecting

quality.

Industrial Uses

0020Although most strawberries are destined for the fresh

market, there are certain production areas that con-

centrate on processed fruit. Inferior fruit from the

fresh market, and a small quantity of mechanically

harvested fruit with green berries included, are used

for making pure

e, juice, and concentrate. The pure

and the juice are preserved by freezing or by adding

sulfur dioxide. Hand-harvested fruit is processed

as frozen whole pack with or without sugar, individu-

ally quick-frozen (IQF), brined in sulfur dioxide,

or heat-processed in lacquered cans. Since fruit is

needed throughout the year, products for further pro-

cessing are usually stored in bulk containers. During

STRAWBERRIES 5627

processing, calcium salts are often added to the fruit

to minimize structural changes. (See Freezing: Oper-

ations.)

0021 Brined fruit, used in the manufacture of some

strawberry jams, can be preserved in more than

2000 p.p.m. sulfur dioxide. Much of the sulfur

dioxide dissipates during the cooking process. Fast

freezing of strawberries is essential for retention of

firmness and quality. Fast freezing is either accom-

plished in an air-blast freezer where jets of cold air

blow up through berries on a mesh belt, or the berries

are frozen in liquid nitrogen; both methods provide

IQF fruit. Berries can also be fast-frozen in small

packages in a blast freezer or more slowly in larger

containers on pallets in a freezing room. When berries

are frozen in a sugar pack, the ratio of sugar to fruit,

by weight, can range from 1:3 to 1:27, depending

on the secondary manufacturer’s specifications. (See

Freezing: Blast and Plate Freezing.)

0022 Strawberries or strawberry-based products are

present as the main fruit ingredients or as a mixture

with other fruit in many consumer products. Large

volumes are used in the production of jams, jellies,

icecream and fruit yogurts. Strawberries in moderate

quantities are used in spreads, preserves, icecream

toppings, strawberry syrups, juices, juice blends,

nectars, drinks, milkshakes, and various bakery prod-

ucts, such as pies, pastries, turnovers, doughnuts, and

cheesecakes. Lesser quantities of fruit are used in the

production of fruit beverage mixes, alcoholic bever-

ages, flakes, glazes, powders, and freeze-dried whole

fruit used in cereals and other products.

Seealso: Controlled-atmosphere Storage:Applications

forBulkStorageofFoodstuffs; Freezing:Operations;

BlastandPlateFreezing; Ripening of Fruit

Further Reading

Chandler CK (1991) North American strawberry cultivars.

In: Dale A and Luby JJ (eds) The Strawberry into the

21st Century, pp. 60–65. Portland, Oregon: Timber

Press.

Committee on Dietary Allowances (1989) Recommended

Dietary Allowances. Washington, DC: National Acad-

emy of Sciences.

Darrow GM (1966) The Strawberry. New York: Holt,

Rinehart and Winston.

Food and Agriculture Organization (1998) Production

Statistics. FAOSTAT. Available at http://apps.fao.org

(February 2000).

Galletta GH and Himelrick DG (1990) Small Fruit Crop

Management. New Jersey: Prentice Hall.

Hancock JF (1999) Strawberries. Wallingford, UK: CABI

Publishing.

Hancock JF and Scott DH (1988) Strawberry cultivars and

worldwide patterns of strawberry production. Fruit

Varieties Journal 42: 102–108.

Janick J and Moore JN (1996) Fruit Breeding, vol. 3. Vine

and Small Fruits. New York: Wiley.

Rosati P (1991) The strawberry in Europe. In: Dale A

and Luby JJ (eds) The Strawberry into the 21st Century,

pp. 27–35. Portland, Oregon: Timber Press.

USDA (1982) Composition of Foods: Fruits and Fruit

Juices, Raw, Processed, Prepared. US Department of

Agriculture, Human Nutrition Information Services,

Agriculture Hand-book, pp. 8–9. Washington, DC: US

Government Printing Office.

STRESS AND NUTRITION

A C Brown and C I Waslien, University of Hawaii at

Manoa, Honolulu, HI, USA

Introduction

0001 Hans Selye first described the stress phenomenon as

the body’s response to a wide range of stressors.

Others have defined stress as anything interfering

with a person’s optimal mental and physical health.

Sources of stress can be exogenous (external) or

endogenous (internal) and include anything that is

‘perceived,’ psychologically or physiologically, to

be a threat to the organism. Examples of physical

stressors include trauma, injury, or violence, illness

(heart attack, cancer, infection, hemorrhage), surgery,

climate (cold, heat), muscular exercise, fasting,

weather changes, chemical exposure, drugs, and bio-

chemical changes (postnatal depression, schizophre-

nia). Some psychological stressors include driving to

work, phone calls, having lunch with a client, giving a

speech, unstable relationships, work conflicts, pur-

pose-in-life conflicts, and significant life events, as

shown in Table 1.

0002Some people are more susceptible to stress by their

exaggerated perception of the stressor, lack of neces-

sary skills to handle minimum daily life stressors, and/

or lack of an ability to adapt or cope in such a way to

restore homeostasis. A person’s reaction to stress,

whether psychological or physical, orchestrates a

neuroendocrine response that can in turn cause

5628 STRESS AND NUTRITION

more stress by resulting in illness or diminished psy-

chological or physical health (Table 2). The question

arises, however, as to why the response to stress

becomes so severe and prolonged in some individuals

that it develops into an incapacitating clinical

disorder. This individual susceptibility may be attrib-

utable to factors in the person’s genetic background,

personality, and environment. (See Atherosclerosis;

Colon: Diseases and Disorders; Coronary Heart

Disease: Intervention Studies; Inflammatory Bowel

Disease; Migraine and Diet.)

Stress Reaction

0003The stress reaction is defined by Hans Selye in his

general adaptation syndrome model (Figure 1). Each

of the stages in this model – alarm, resistance, and

exhaustion – involves the body’s neuroendocrine

system, which is influenced by psychological and

physical stimuli.

0004Alarm, fight or flight, is the immediate response of

the body to ‘perceived’ stress. Physiologically, this

starts at the brain’s hypothalamus, which acts as the

central computer chip of the body regulating such

functions as heart rate, blood pressure, respiration,

body temperature, digestion, hunger, thirst, and

libido. Surrounding the hypothalamus is the limbic

system, one of the oldest parts of the brain, which

houses the emotions. Powerful feelings such as fear

and rage trigger the hypothalamus, which sends

messages to the autonomic nervous system by the

hypothalamic–pituitary–adrenal (HPA) axis and sep-

arately through the autonomic nervous system. The

nerves of the autonomic nervous system are split into

either parasympathetic or sympathetic branches, the

latter of which causes an immediate stress reaction by

releasing catecholamines (adrenaline-like chemicals).

These chemicals released from the adrenal gland

increase heart rate, respiration, and blood pressure.

0005The activated hypothalamus also secretes its own

hormones and stimulates the pituitary gland to

secrete hormones, which produce some of the same

effects as those of the catecholamines but which last

some 10 times longer and have a far wider reach. One

of these hormones, corticotropin-releasing hormone

(CRH), is sent to the pituitary to trigger the release

of adrenocorticotropin hormone (ACTH). ACTH

travels through the bloodstream to the adrenal

glands, on top of the kidneys, to produce glucocorti-

coids (such as cortisol), which start a cascade of

events, including increased blood glucose concentra-

tions, elevated blood pressure, and slowed digestion

(Figure 2). Specifically, insulin’s ability to facilitate

glucose uptake by the cells is reduced, while gluco-

neogenesis, the synthesis of new glucose (from gly-

cerol and amino acids) is increased. Blood pressure

rises as the kidneys are signaled to retain more

sodium, which raises water volume in the blood

vessels. Also, digestion slows as hormonal changes

cause muscles to become engorged with oxygen and

glucose-rich blood that is shunted away from the

digestive tract. The body in this conditional response

tbl0001 Table 1 Part of the Holmes–Rahe Social Adjustment Scale that

assigns values to various stressful events (good or bad) (the

higher the score, the greater the risk of a stress-related health

condition)

Events Value

Death of a spouse 100

Divorce 73

Marital separation 65

Personal injury or illness 53

Marriage 50

Retirement 45

Pregnancy 40

Change in work responsibilities 29

Outstanding personal achievement 28

Trouble with boss 23

Change in residence or schools 20

Change in working hours or conditions 20

Change in social activity 18

Vacation 13

Christmas 12

tbl0002 Table 2 Partial list of conditions related to stress

Physical Psychological

Gastrointestinal: Anxiety disorder

Indigestion Phobic states

Gastrointestinal reflux disease Depression

Peptic ulcers Post traumatic stress disorder

Ulcerative colitis Chronic fatigue syndrome

Constipation/diarrhea Eating disorders:

Irritable bowl syndrome Binge eating

Diverticulosis Bulimia

Cardiovascular: Anorexia nervosa

Heart disease Alcoholism

Hypertension Drug addiction

Palpitations Panic disorders

Arrhythmias Chronic pain

Cancer Family dysfunction

Diabetes mellitus Sleep disorders

Osteoporosis

Reproductive:

Amenorrhea

Infertility

Immune function (suppressed):

Common cold

Autoimmune diseases

Rheumatoid arthritis

Systemic lupus erythematosus

Neurological:

Migraine headaches

STRESS AND NUTRITION 5629

to stressors is ready for fight or flight. (See Hormones:

Pituitary Hormones.)

0006 Resistance (adaptation), the second stage of the

stress response, is to achieve optimal adaptation in

resisting the stressor. Everyday stressors (eustressors)

are beneficial in maintaining the psychophysiological

balance that results when the stressor is successfully

removed, adapted, or coped with by the person. Stress

is actually a necessary component in life because it

contributes to survival and, ultimately, growth. Opti-

mal stress fuels maximum performance, but excess

stress results when the demands on a person exceed

or fall far below their capabilities. Hans Selye said the

only time an individual is free from stress is death –

the ultimate flight. However, too much stress, and

failure to adapt and reach a healthy homeostasis,

can also result in illness or death.

0007 Exhaustion, the last stage of the stress response, a

continued, chronic response to stress, can be a risk

factor for many multifactorial disorders. These in

turn may lead to a downward spiral of more stress,

exhaustion, and possibly extinction. Eustress becomes

distress if not adequately handled by the body and

mind (Table 3). Physical and psychological well-being

become ‘ill,’ decreasing the quality of life, if not its

very presence.

0008 While the changes produced by stress-initiated hor-

mones are beneficial in the short term, they can be

detrimental when prolonged. It is now generally be-

lieved that most signs and symptoms of stress-related

disease are the result of stress hormones marshaled by

the hypothalamus in response to an alarm for which

their particular actions are no longer appropriate.

Stress and Nutritional Needs

0009 The hormonal concert of changes occurring in the

stress response creates a cascade of biochemical and

physiological events that require energy and nutri-

ents. The main physical stressors to the body requir-

ing an increase in energy and nutrients are injuries,

surgeries, burns, illnesses, and infections. These con-

ditions inflict greater requirements than emotional

stressors whose exact nutrient needs have not yet

been clearly documented. However, it is well estab-

lished that physical stressors do increase requirements

for energy and protein. Less information is available

for the vitamins, minerals, and electrolytes. The

degree to which these physical stressors foster a

need for more nutrients is based on the severity/

duration of the condition, the person’s age and

nutritional status, and individual ability to overcome

stressors in life. If not corrected, malnutrition during

these states can result in an increased recovery time,

length of hospitalization time, and/or morbidity and

mortality.

Energy

0010With acute stress, such as surgery, energy require-

ments rise only about 10%; severe infections raise

requirements by 20–40%, bone fractures by 10–

30%, and burns by 40–125%. The extra energy

requirements caused by psychological stresses such

as fear, anger, or rage are difficult to determine but

presumably fall within the range error and are not

given a special allocation. Acute stress of short dur-

ation is usually self-corrected by an increase in appe-

tite after the stress has abated, but special enteral

or parental formulae may be needed for treating

severe stress. (See Burns Patients – Nutritional Man-

agement.)

Protein

0011Additional energy intake not only supplies necessary

energy, but spares the body’s protein reserves – pri-

marily the muscle. If glycogen reserves from the liver

Alarm

Resistance (adaptation)

Exhaustion

Medical therapy

Death

Continuous stress

High

Normal

Low

Shock

Countershock

Resistance level to stress

fig0001 Figure 1 General adaption syndrome, consisting of three stages: (1) alarm, (2) resistance, and (3) exhaustion.

5630 STRESS AND NUTRITION

and muscles are depleted and additional energy is not

provided during the catabolic state of acute stress, the

body turns toward its fat and protein resources. Al-

though the loss of fat is usually not a problem ini-

tially, it is detrimental to the skeletal muscles if they

are broken down to serve as a source of amino acids

to make glucose (gluconeogenesis). Physical stressors

also stimulate glucocorticoid secretion, which in-

duces protein breakdown. If prolonged, this leads to

massive tissue wasting. Adequate protein of a high

biological value is necessary to avoid a negative nitro-

gen balance and to prevent the following: diminution

in immunocompetence, hypoalbuminemia, decreased

wound healing, decreased synthesis of enzymes

and plasma proteins, infection, and pressure sores

associated with poor protein status.

0012Moderate stress requires 1.0–1.5 g of protein per

kilogram or bodyweight, whereas severe stress

requires 1.5–2.0 g protein per kilogram. This is only

slightly higher than the 0.8 g of protein per kilogram

required in most healthy adults. During severe stress,

the body may be unable to convert essential amino

acids to nonessential amino acids, so they must be

obtained from the diet. Research shows promising

results for the use of branched-chain amino acids,

glutamine, and arginine during periods of hyper-

metabolic states. Blood levels of branched-chain

amino acids (BCAA), leucine, isoleucine, and valine,

are low during stress. Mixed results have been

reported with BCAA formulas for improving morbid-

ity or mortality, reducing the length of hospital stay,

or maintaining tissue protein reserves of hospital

patients. As a precaution, a 35–50% BCAA formula

is recommended for highly stressed patients who

cannot achieve nitrogen balance within a reasonable

amount of time after receiving a standard formula. A

similar recommendation exists for glutamine, the

principal free amino acid in muscle. Catabolic pa-

tients receiving a glutamine-peptide-supplemented

solution were in a more positive nitrogen balance

than control patients given isonitrogenous, isoener-

getic, or conventional total parenteral nutrition

amino acid mixtures. Another amino acid, arginine,

is beneficial during critical illness. Supplementation

during this time with arginine may increase nitrogen

retention, accelerate wound healing, and enhance the

immune system by increasing lymphocyte response.

(See Glucose: Function and Metabolism; Glycogen;

Protein: Requirements.)

tbl0003Table 3 Factors and feelings associated with eustress and

distress

Eustress Distress

Increased mental acuity Forgetfulness

Diminished attention to detail

Poor work performance

Pleasure/happiness Sadness

Emotional outbursts

Euphoria Lethargy, apathy

Modified from Clancy J and McVicar A (1993) British Journal of Nursing 2(8):

410–417.

Cortisol

ACTH

Adrenal gland

Kidney

Pituitary gland

Hypothalamus

CRH

Stress triggers cells in the brain (hypothalamus) to release

corticotropin-releasing hormone (CRH).

CRH signals the brain's pituitary gland to release

adrenocorticotropin hormone (ACTH).

ACTH travels through the bloodstream to the adrenal

glands − just above the kidneys − where they produce

glucocorticoids such as cortisol.

Excess cortisol levels are prevented by feedback to the

hypothalamus that occurs when elevated cortisol levels

nal the brain to sto

releasin

CRH.

fig0002 Figure 2 Hypothalamic–pituitary–adrenal (HPA) axis that sets

in motion a myriad of stress-related psychophysiological events.

STRESS AND NUTRITION 5631

Fatty Acids

0013 o-3 fatty acids appear to improve survival rates of

burn patients, and reduce infections and wound

complications of postoperative patients. Perhaps this

is related to the fact that certain polyunsaturated

fatty acids are used in the biosynthesis of eicosanoid

mediators influencing the systemic inflammatory

response. o-3 fatty acids lessen inflammation,

whereas o-6 fatty acids increase the inflammatory

response. Sources of o-3 fatty acids include canola

oil, fish oils, and green vegetables, whereas o-6 fatty

acids are derived from corn, safflower, soybean,

and sunflower oils. It has been postulated that pa-

tients with inflammatory conditions (systemic lupus

erythematosus, rheumatoid arthritis, and multiple

sclerosis) on hospital tube feedings (enteral and par-

enteral formulas, intravenous emulsions) would fare

better if the lipid source were o-3 instead of o-6 fatty

acids.

Vitamins, Minerals, and Electrolytes

0014 The adrenal glands have the highest concentrations of

vitamin C of any organ in the body, and because this

vitamin is needed for the synthesis of catecholamines,

massive doses of the vitamin have been advocated to

help cope with modern-day stress. However, clinical

evidence at this time does not support this suppos-

ition. Other nutrients that are lost in the urine with

stress, such as zinc, copper, magnesium, and calcium,

do not present problems for people with good dietary

intakes. Potassium, which is lost along with protein

catabolism of muscle and organ tissue, may be an

exception but can be replaced with increased

consumption of fruits and vegetables.

0015 In severe stress, the requirements for vitamins A,

, C, D, E, K, nicotinic acid, folate, and

pantothenic acid, as well as for the minerals iron,

zinc, copper, selenium, and magnesium are probably

increased, although actual requirements are un-

known. Vitamin C is known to be required for

wound healing and collagen formation, and urinary

losses are increased during stress; thus, supplements

may be prescribed to promote extensive tissue regen-

eration. Studies have shown that 1000 mg of vitamin

C per day appears to speed the healing of bone

fractures. Tissue regeneration is also dependent on

vitamin A; low levels of plasma retinol have been

observed in fracture patients after surgery. Pyridox-

ine, potassium, magnesium, phosphate requirements,

and, to a lesser extent, calcium requirements seem to

parallel the level of protein consumption; hence, sup-

plements of these nutrients may be needed when

protein and carbohydrate intakes are greatly in-

creased. (Refer to individual nutrients.)

0016Actually, the immediate major concern following a

physical stress is correcting fluid and electrolyte

losses. Intravenous infusions may be needed, but

even hydration may be restricted if stress leads to

renal shutdown. A diet high in protein and energy

can be initiated within approximately 5 days. Excess

delay in realimentation is also not warranted as it is

critical to prevent weight loss that may approach 20–

30% of body weight if nutritional support is not

promptly implemented. A weight loss of 40–50% is

generally fatal.

Stress and Appetite

0017Stress, depending on the individual, can either

increase or decrease appetite. Some people under

pressure eat less, whereas others overeat in an effort

to relieve stress. According to one study, snacking

behavior in 212 college students exposed to stress

increased by 73%. However, the total daily food

intake decreased in 42% of the students, whereas

38% reported an increase. This study, along with

other research, revealed that dieters are much more

likely to overeat during stress than nondieters. The

increased food consumption in dieters is especially

pronounced when the stress source is a threat to the

ego or self-image. Results from a study revealed that

psychosocial stress induces a large cortisol response

in glucose-treated subjects, compared with fasting

subjects subjected to the same stressor but without

the resulting cortisol peak. The researchers concluded

that low glucose levels appear to inhibit the HPA axis

response resulting in the secretion of cortisol and

its influence on appetite. Another appetite theory is

that stress-prone subjects are prone to serotonin

deficiency, which may be related to ‘carbohydrate

craving’ and subsequent binging and/or obesity. It is

interesting to note that the weight gains of genetically

obese rats are abolished by adrenalectomy, while

cortisol (corticosterone) treatment restores their

diminished food intake to normal levels.

Stress-inducing Foods

Refined Carbohydrates

0018Refined cereals and sugars have been made scape-

goats, responsible for the stress of Western diets.

Claims are made that these foods, low in B vitamins,

rob the body of vitamins. Some authors go on to

advocate up to 100 times the recommended intake

of vitamins as compensation. Certainly, when chronic

stress increases nutrient requirements, ‘empty

calories’ are inappropriate, but there is no rationale

for labeling moderate amounts of refined cereals and

5632 STRESS AND NUTRITION

sugars as ‘stress producing.’ Sugar has come under

particular fire because of its supposed role in hypo-

glycemia. Although it is true that hypoglycemia can

affect behavior in a number or ways, e.g., alternating

‘highs’ and ‘lows,’ there are two major misunder-

standings. Contrary to popular opinion, diagnosable

hypoglycemia is quite rare; the Mayo Clinic finds a

rate of approximately one case per 2500 persons.

Although a person with hypoglycemia should avoid

sugar in any form, sugar does not cause the disease.

Both the low blood sugar reaction and the hormonal

response described as the alarm reaction are symp-

toms of hypoglycemia. (See Glucose: Maintenance

of Blood Glucose Level.)

Fasting

0019 Researchers report that a good portion of the psycho-

logical syndrome of anorexia nervosa is in response to

starvation. Emotional instability is a classic sign of

the ketosis that accompanies fasting. One does not

have to endure long-term starvation to feel less than

able to cope with stress. Just skipping a meal or two

can have this effect. Steady eating of moderate, bal-

anced meals is likely to be more beneficial to stress-

prone individuals than a lifetime supply of various

supplements. (See Anorexia Nervosa.)

Caffeine

0020 Certain commercial advertisements insist that stress

can be reduced by drinking decaffeinated coffee or

caffeine-free soft drinks. While some research reports

indicate that caffeine induces stress, others show that

caffeine reduces it. A recent study clarified the situ-

ation by demonstrating that persons habituated to the

use of caffeine had increased anxiety when deprived of

it but were calmed by a dose of caffeine. In contrast,

low-caffeine users showed a slight increase in tension

when given caffeine. Apparently, the kind of response

depends on previous use and individual differences.

Sodium

0021 For many people, excessive fluid retention, and other

premenstrual changes in women, may be related to

emotional stability and resistance to stress. Stress

itself induces sodium retention and water accumula-

tion. Any dietary factors that further contribute to

fluid retention, in particular excessive intake of

sodium, may therefore increase the stress effect. (See

Premenstrual Syndrome : Nutritional Aspects.)

Stress-relieving Foods

0022 Can specific foods be used to reduce stress? When

under stress, most people instinctively turn to certain

foods – foods that create a feeling of security. The

most common security food is milk, perhaps as a

symbol of the more protected days of childhood and

a desire to return to them. In fact, it has been specu-

lated that the use of milk to treat ulcers may be

successful partly because it stimulates this ‘return to

the womb’ association. Our choice of security foods

seems to be based on our childhood experiences, and

those that trigger comfort in one person may trigger

anxiety in another.

0023Among women, chocolate is the most craved food.

Researchers believe that this may be due to a combin-

ation of chocolate’s sensory characteristics, nutrient

composition, and psychoactive ingredients. It has

been suggested that chocolate may be used by some

women as a form of self-medication to balance low

levels of neurotransmitters involved in mood regula-

tion. The desire for chocolate by women fluctuates

with hormonal changes and is higher just before and

during their menses. This hormonal link in turn might

be related to endogenous opiates (endorphins) that

influence appetite. Women tend to eat when they feel

emotionally low, and the affinity to chocolate may be

due to its ‘drug-like’ constituents that remain elusive.

Dietary Supplements

0024Alternative/complementary treatments are used by

20–30% of the general North American population.

Among these are plants that have been used medicin-

ally throughout history for thousands of years. About

25% of pharmaceutical drugs used today are derived

from botanical sources. Among psychotropic herbs,

two of the earliest were the opium poppy and the coca

plant, producing two of the most notorious street

drugs, heroin and cocaine. Drugs are often taken to

treat the symptoms rather than the cause, and many

people opt to select dietary supplements rather than

prescriptions to reduce the side-effects of stress such

as anxiety, depression, and insomnia. A few of the

more popular, but not necessarily proven effective,

psychotropic herbs are discussed below.

California Poppy (

Eschscholtzia californica

)

0025This flowering plant has a long history of treating

insomnia. It does not contain the narcotic morphine

found in its cousin, the opium poppy.

Chamomile (

Matricaria recutita

)

0026This flower, usually in the form of a tea, has been used

medicinally for thousands of years. Its primary use is

for anxiety and mild insomnia as well as an anti-

spasmodic and antiinflammatory agent, especially

for ulcers. The active ingredient is attributed to chry-

sin, a flavonoid component. Potential rare side-effects

include allergies and contact dermatitis.

STRESS AND NUTRITION 5633

Kava (

Piper methysticum

)

0027 The roots of this plant have long been used by people

in the South Pacific, where it is grown, for ceremonial

purposes in much the same way that some cultures use

wine. Kava differs from wine in that it is nonaddictive.

Its sedative-like quality may be due to kavalactones

(kavapyrones), which appear to act as monoamine

oxidase inhibitors. Side-effects include dizziness, a

drunk-like state, and gastrointestinal upset. Excessive

use is associated with Kava dermopathy (scaly, shiny

skin), seizures, impaired vision and hearing, yellow

discoloration of skin/nails, and liver dysfunction.

Reports linking Kava to hepatitis have resulted in

some European countries banning this supplement.

Kava has also been known to potentiate the effects of

alcohol, barbiturates, and Xanax.

Hops (

Humulus lupulus L.

)

0028 Although hops are traditionally used by the brewing

industry, the flowers of this plant have long been

utilized as a mild sedative. Side-effects include allergy

and disrupted menstrual cycles.

Passion Flower (

Passiflora incarnata L.

)

0029 Native to the Americas, its vine leaves are used as a

sedative, which is supported by some animal studies.

Skullcap (

Scutellaria laterifolia

)

0030 Rooted in traditional Chinese medicine, this herb has

a long history of being used as a sedative and anticon-

vulsant. Scutellarin is the plant flavonoid glycoside

thought to be responsible for the sedative effects of

skullcap. Reported adverse reactions include giddi-

ness, confusion, sedation, and seizures. The most

serious possible side-effect is hepatitis, which was

reported in a some people taking herbal stress remed-

ies that contained skullcap and valerian. It is import-

ant to read the label of such products to determine

whether skullcap is an ingredient.

St. John’s Wort (

Hypericum perforatum

)

0031 Long-term stress is occasionally a risk-factor for mild

depression, which has been reported in some cases to

respond to St. John’s Wort. An analysis of 23 con-

trolled studies concluded that it is significantly more

effective than a placebo in treating mild to moderate

depression. The effective dose in clinical trials is

300 mg three times a day from an extract standard-

ized at 0.3% hypericin. This active ingredient in

St. John’s Wort appears to act as a weak monoamine

oxidase inhibitor. The main side-effect associated

with this herbal antidepressant is photosensitivity to

the sun, resulting in rashes. Other less commonly

reported side-effects include gastrointestinal upset,

dizziness, dry mouth, sedation, and constipation.

Valerian (

Valeriana officialis

)

0032The root of the valerian plant has been used as a

calming and sleep-promoter for centuries. German

health officials have approved it as a mild sedative

and sleep-aid. Two double-blind, placebo-controlled

cross-over studies (400–450 mg before bedtime)

resulted in significantly improved sleep quality. There

was also no reported residual sedation in the morning

or addiction associated with valerian use. Valerian

appears to work by inhibiting the enzyme-induced

breakdown of g-aminobutyric acid (GABA) in the

brain. Symptoms are rare, but may include headaches,

palpitations, insomnia, and possibly hepatitis.

Amino Acids

0033High intakes of tryptophan – the amino acid precur-

sor of the neurotransmitter serotonin – have been

popularized as a treatment for stress. Although

taken off the market because of a contaminant that

elicited neurological side-effects, tryptophan still has

many proponents. A high-carbohydrate meal can

have some of the same benefits by causing insulin

secretion and favoring the uptake of amino acids

other than tryptophan into muscle. This increases

the concentration of tryptophan present in the blood

and increases its uptake by the brain and its subse-

quent conversion to serotonin. Supplementation with

tyrosine, the precursor for the catecholamine neuro-

transmitters, has also been shown to reduce psycho-

logical and physiological effects of stress. Tyrosine

has also been recently demonstrated to ameliorate

stress-induced increases in ventricular vulnerability

to arrhythmias in conscious animals.

0034Limited research suggests that subclinical deficien-

cies of other nutrients involved in the synthesis of

neurotransmitters (e.g., nicotinic acid, riboflavin,

folic acid, vitamin C, and copper) may contribute to

the ability to withstand stress, and that others (e.g.,

o-3 fatty acids) may alter the stress response, making

it less hazardous for the arteries. In most cases, the

alteration in the level of these nutrients needed to

make a detectable difference in stress response is

of such a magnitude as to preclude normal diets.

However, differences in an individual’s stress-related

illness may in part reflect lifelong differences in

intakes of some of these nutrients.

Melatonin

0035This hormone secreted by the pineal gland is used by

some people as a sleep-aid taken 30 min to 2 h before

bedtime. Melatonin acts as a mild sedative, but its

affect on insomnia remains controversial. It is known

that melatonin released nightly by the pineal gland to

signal the body to sleep does subside as people age.

5634 STRESS AND NUTRITION

However, supplements often contain 10 times the

amount secreted by the body (3 mg or more), and it

is recommended that less than one-third of that

be taken. Melatonin is also not appropriate in

children younger than 12. Side-effects include fatigue,

headache, confusion, and depression.

0036 Dietary supplements are categorized as neither a

food nor a drug, so they are exempt from FDA regu-

lation. As a result, no proof of efficacy or warnings

about side-effects (known or testing for the unknown)

are required. There are also currently no standardiza-

tion or quality assurance methods for herbal formu-

lations. Even if there were, it would be very difficult

to identify the active ingredient(s) of a herbal product

for the often more than one ailment it is claimed to

benefit. Added to this is the possibility of contamin-

ation, mislabeling, and misidentification of herbs.

Assuming that herbs are ‘natural,’ and therefore

safe, can be a wrong assumption. The long-term

hepatotoxic effect and other side-effects of many

herbs are unknown and may not be elucidated for a

long time. As with many compounds, herbal supple-

mentation is not recommended during pregnancy or

lactation.

Summary

0037 A moderate, well-balanced diet with emphasis on the

stress-related nutrients and regular but not exces-

sively large meals is probably one approach that can

be recommended. There is no evidence that any one

special dietary preparation or plan is more effective

than any other in coping with stress, but specific

recommendations concerning energy and nutrients

exist in the literature that may benefit certain

conditions.

See also: Anorexia Nervosa; Atherosclerosis; Burns

Patients – Nutritional Management; Colon: Diseases

and Disorders; Coronary Heart Disease: Intervention

Studies; Glucose: Function and Metabolism;

Maintenance of Blood Glucose Level; Glycogen;

Hormones: Pituitary Hormones; Inflammatory Bowel

Disease; Migraine and Diet; Premenstrual Syndrome:

Nutritional Aspects; Protein: Requirements