Transcript Being Fit with Phytochemicals

Fruits and Vegetables – The Real Thing Matters!
Being Fit with Phytochemicals
Mollie Smith, MS, RD
California State University, Fresno
Department of Food Science and
Nutrition
Objectives
• What are phytochemicals?
• Where are they found?
• What are the health benefits?
• Are there any risks?
• What are functional foods and how are
they regulated?
• What do we tell consumers?
Definition of Phytochemicals
• Biologically active chemical compounds
found in plants
• Not nutrients like vitamins or minerals
• Believed to have health benefits especially
related to heart disease and cancer
• Consumers often read exciting headlines
about potential health benefits from eating
foods that contain phytochemicals
– Store shelves are overflowing with such
supplements alongside functional foods
whose labels often make fantastic claims for
their health-promoting powers
How Scientists View
Phytochemicals in Foods
– Some phytochemicals have profound effects
on the body through actions such as
• Acting as antioxidants
• Mimicking hormones
• Altering blood constituents in ways that may
protect against some diseases
Phytochemicals And Functional
Foods
• Some Cautions
– Foods consist of thousands of different
chemicals
• Each has the potential of being beneficial, neutral,
or harmful to the body
• Some may be beneficial in some ways and harmful
in others
• Some chemicals may exert different effects on
different people or when taken at differing doses
or at different life stages
Is More Better?
Choose Food First
Avoid Overdosing
Avoid Self Prescribing
Phytochemicals And Functional
Foods
• Research on phytochemicals is in its
infancy
– What is current today will likely be challenged
a year from now by further studies
• In most cases, the health benefits
observed with intakes of certain foods
cannot be ascribed to individual
phytochemicals
• Much less to purified supplements of them
Phytochemicals And Functional
Foods
• Currently, the evidence is insufficient to
say with any degree of certainty whether
any phytochemical is effective in fighting
diseases or if it is safe to consume in
concentrated doses
Whole Foods, Wine, and Tea
– Epidemiological evidence spanning many
countries indicates that deaths from cancer,
heart disease, and heart attacks are less
common where these foods are plentiful in
the diet, where tea is a beverage, or where
red wine is consumed in moderation
Phytochemicals
• Whole Foods, Wine, and Tea
– Historically, diets containing whole grains,
fruits, vegetables, herbs, spices, teas, and red
wines have been reputed to possess healthpromoting qualities
– These foods and beverages all have
something in common
• Phytochemicals of the flavonoid family
Flavonoids
• Many flavonoids act as antioxidants
– May protect against cancers and heart disease
by this mechanism
– More evidence is needed before any claims
can be made for flavonoids themselves as the
protective factor in foods
• Particularly when they are extracted from foods or
herbs and sold as supplements
Why are antoxidants important?
• free radicals are molecules missing
electrons: unstable
• formation of 1 free radical causes a chain
reaction with many free radicals formed
• antioxidants prevent formation of free
radicals or break the chain reaction by
becoming oxidized
Antioxidants, con’t
• Harmful effects from uncontrolled free
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radicals
oxidation of lipids in cell membrane
oxidation of DNA in cell nucleus
? cause of cancer
? cause of heart disease
? inflammatory diseases
? part of aging process
Antioxidants
• Because flavonoids often impart a bitter
taste to food, food producers may refine
away natural flavonoids to please
consumers who generally prefer milder
flavors
– To produce white grape juice or white wine,
makers remove the red, flavonoid-rich grape
skins to lighten the flavor and color of the
product
• While greatly reducing its flavonoid content
Antioxidants
• Whether or not research confirms the
cancer-fighting and heart-defending
nature of flavonoids, consumers should
seek out a variety of whole fruits,
vegetables, and other plant-derived foods
with their flavonoids intact in place of their
more refined counterparts
– Such diets are consistently associated with
low rates of disease
Antioxidants
• Flavonoid supplements have not been proved
•
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effective or safe
As for red wine, the potential health benefits
may not be worth alcohol’s immediate and
substantial risk
Other sources:
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Blueberries
Tea
Grapes
Vegetables
Tea
• Black- most often sold, fermented and
more processed
• Oolong- semi-fermented, heated and dried
more than green tea but less than black,
served in Chinese restaurants
• Green- unfermented, very little processing
• White- unfermented, very little processing,
harvested before leaves are fully open
Tea
• Calorie Free
• 87% of dietary
flavonoids consumed
• Antioxident
polyphenols including
flavonoids
– Catechin
– EGCG
– Proanthocyanidins
Tea’s effect on Heart Disease
• Lower blood pressure
• Lower cholesterol
• Black tea may lower LDL cholesterol
• Improved blood flow and blood vessel
function
Cancer
• Protects against free radical damage
• Decrease growth of abnormal cells
• Associated with decreased risk of rectal,
colon and skin cancer
Other Benefits
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Memory
Immune function
Oral health
Decreased risk of kidney stones
Obesity
• Mostly epidemiological research and research on
tea consumption, concentrated tea extracts may
not be safe
Antioxidants
• Chocolate
– Research subjects were instructed to eat
three ounces of dark (bittersweet) chocolate
chips
• Flavonoid antioxidants from chocolate accumulate
in the blood
– The level of certain harmful oxidizing compounds
dropped 40%
• The antioxidant effects of dark chocolate may turn
out to be as powerful as those of tea or red wine
Chocolate
• In theory, chocolate may also “thin the
blood” by reducing the tendency of blood
to clot
– Blood clots are a major cause of heart attacks
and strokes
– No evidence exists to indicate that people
who eat chocolate suffer fewer heart attacks
or strokes than people who do not
Chocolate
• Chocolate consumption promotes weight
gain
– Three ounces of sweetened chocolate candy
contain over 400 calories
• A significant portion of most people’s daily calorie
allowance
– Chocolate contributes few nutrients save fat
and sugar
Antioxidants
• For most people,
antioxidant
phytochemicals are
best obtained from
nutrient-dense lowcalorie fruits and
vegetables and calorie
-free green or black
tea
– With chocolate
enjoyed as an
Soybeans
– Compared with people living in the West,
Asians living in Asia suffer less frequently
from:
• osteoporosis
• cancers, especially of the breast, colon, and
prostate
• heart disease
• Asian women also suffer less from symptoms
related to menopause
Soybeans
• When Asians migrate to the U.S. and
adopt Western diets and habits they
experience these disease and problems at
the same rates as native Westerners
• Among many differences between the
diets of the two regions
– Asians consume far more soybeans and soy
products such as miso, soy drink, and tofu
than do Westerners
Soybeans
• Soybeans contain phytochemicals known
as phytoestrogens
– Researchers suspect that the phytoestrogens
of soy foods, their protein content, or a
combination of these factors may be
responsible for the health effect in soy-eating
peoples
– Research, though ongoing, is limited and
inconsistent
Soybeans
• We know with certainty that
phytoestrogens are plant-derived chemical
relatives of the human hormone estrogen
– They weakly mimic or modulate the
hormone’s effects on some body tissues
– They act as antioxidants
Soybeans
• We know that breast cancer, colon cancer,
and prostate cancer are estrogen-sensitive
– They grow when exposed to estrogen
– It is unknown if actions of phytoestrogens
may alter the course of estrogen-sensitive
cancers
• Results from recent breast cancer studies do not
support the idea unless soy is consumed beginning
in childhood
Soybeans: genistein
• Symptoms of menopause
– Phytoestrogens may reduce risk of adult bone
loss and the sensation of elevated body
temperature known as “hot flashes”
– A diet high in soy may offer bone protection
rivaling that of hormone replacement therapy
(HRT)
– May not reverse bone loss but may prevent it
Soybeans
– Because HRT involves some serious health
risks, supplements of soy are often sold to
menopausal women as a “natural” alternative
– Research does not support taking
phytoestrogen supplements for bone mineral
retention or hot flashes
Soybeans
• Phytoestrogen supplement use may
involve some risk
– While studying one soy phytoestrogen,
genistein, researchers found that instead of
suppressing cancer growth, high doses
appeared to speed division of breast cancer
cells in laboratory cultures and in mice
Heart Disease
• 1999: FDA approved claim that 25 gm of
soy protein per day may reduce your risk
of heart disease
• 2000: AHA endorsed soy as a heart
healthy food
• Research supports LDL lowering effect of
soy, better effect in divided doses
• 2006: AHA reevaluating endorsement due
to conflicting research
Soybeans
• Findings on the health effects of phytoestrogens
should raise a red warning flag against taking
supplements
– Especially in women whose close relatives have
developed breast cancer
• Until more is known, a safer route to obtaining
soy phytoestrogens is to include moderate
amounts of soy-based foods in the diet
– As generations of Asian people have safely done
through the ages
Make meat and poultry choices that
are low fat or lean
• Choose a variety of types of protein foods
•
including fish, dry beans and peas, nuts and
seeds
Consider dry beans and peas as an alternative to
meat or poultry
• To provide a variety of nutrients in the diet
including vitamin E while keeping saturated fat
and cholesterol low
Flaxseed
Historically, people have used flaxseed
for relieving constipation or digestive
distress
– Currently, flaxseed and its oil are under study
for potential health benefits
– Contains lignans, compounds converted into
biologically active phytoestrogens by bacteria
that normally reside in the human intestine
Flaxseed
– Studies of populations suggest that women
who excrete more phytoestrogens in the urine
(an indicator of phytoestrogen intake from
flaxseed and other sources) have lower rates
of breast cancer
– Animal studies show a decrease in tumors of
the breast and lung when fed flaxseed
Flaxseed
• Studies of the direct effects of giving
flaxseed to people are lacking
• Some risks are possible with its use
– Flaxseed contains compounds that may
interfere with vitamin or mineral absorption
• Thus high daily doses could cause nutrient
deficiency diseases
– Large quantities can cause digestive distress
Flaxseed
• Although no clear role has been
established for flaxseed in the prevention
of human cancer
– Including a spoonful or two of flaxseed in the
diet may not be a bad idea
– Flaxseed richly supplies linolenic acid
• A needed nutrient often lacking in the U.S. diet
Choose most fats from sources of
monounsaturated and
polyunsaturated fatty acids
• Keep the amount within calorie needs
• Choose more fish, nuts and vegetable oils
• Use lean meats and low fat dairy products
• Limit saturated and trans fats
• To provide essential fatty acids and
vitamin E while keeping calories controlled
and cholesterol and saturated fat low
Tomatoes
– People around the
world who eat the
most tomatoes, about
5 tomato-containing
meals per week, are
less likely to suffer
from cancers of the
esophagus, prostate,
or stomach than those
who avoid tomatoes
Tomatoes
• Among the phytochemical candidates for
promoting this effect is lycopene
– A red pigment with antioxidant activity
– Found in guava, papaya, pink grapefruit,
tomatoes (especially cooked tomatoes and
tomato products), and watermelon
Tomatoes
• Lycopene may inhibit the reproduction of
cancer cells
– Some research suggests that low blood levels
of lycopene and related compounds correlate
with
• increased risk of breast cancer
• elevated incidence of heart disease, heart attack,
and stroke
– May also protect against the damaging sun
rays that cause skin cancer
Tomatoes
• In one study, women who consumed a diet rich
•
in fruits and vegetables had high lycopene
concentrations and a greatly reduced
concentration of an indicator of cervical cancer
Do scientists conclude that lycopene prevents
cervical cancer? No.
– The suggestion is that a diet rich in fruits and
vegetables with their host of nutrients and
phytochemicals reduces women’s risk of cervical
cancer and many other diseases
Tomatoes
• A lesson about supplements can be
learned from experience with lycopene’s
chemical cousin
– The normally beneficial vitamin A relative
beta-carotene
• Diets high in fruits and vegetables that
contain beta-carotene often correlate with
low rates of lung cancer
– When beta-carotene supplements were given
to smokers lung cancer rates increased
Garlic
– Descriptions of its uses for headaches, heart
disease, and tumors are recorded in early
Egyptian medical writings
– In modern medical research, over 3,000
publications have investigated the potential health
benefits of garlic
• Many have reported positive findings
Garlic
• Among garlic’s active compounds are
organosulfur compounds
– Reported to inhibit cancer development in
laboratory animals
– suppress the formation of certain harmful
oxidizing compounds that damage DNA and
trigger cancerous changes
• This evidence hints that eating garlic may be
beneficial against some forms of cancer in human
beings
Garlic
• More potential roles for garlic
– allergies
– heart disease
– bacterial cause of ulcers
– fungal infections
– reduce the clotting of the blood
– improve levels of blood cholesterol in people
whose cholesterol is too high for heart health
Garlic
• Volatile sulfur compounds are not present as
•
such in intact cells.
The reaction between
– The enzyme allinase and
– The volatile precursors
• S-alk(en)yl cysteine sulfoxide and
• Sulfonic acid
takes place when cells are ruptured
– Results in the formation of
• Different thiosulfonates and
• Related sulfonic acid derivatives
Garlic
• Studies of garlic supplements, such as
powders and oils, have been disappointing
– Positive results seem to be associated with an
aged preparation of garlic that lack garlic’s
characteristic odor
• But is rich in antioxidants and other compounds
– From the scientist’s point of view, no evidence
that large doses of concentrated chemicals
from garlic may improve a person’s health or
injure it
Phytochemicals And Functional
Foods
• Supporters and Detractors of
Phytochemical Supplements
– Phytochemcials can alter body functions
• Sometimes powerfully, in ways that are only partly
understood
– Evidence for the safety of isolated
phytochemicals in human beings is lacking
Regulation of Phytochemicals
And Functional Foods
– No regulatory body oversees the safety of
phytochemicals sold to consumers
• No studies are required to prove that they are safe or
effective before marketing them
– Phytochemical labels may make claims about
contributing to the body’s structure or functioning
• Research to support such claims may be weak
– Researchers who study phytochemicals conclude that
the best-known, most effective, and safest sources
for phytochemicals are foods, not supplements
Functional Foods
• The Concept of Functional Foods
– Manufacturers have taken this concept a step
further by adding phytochemicals and other
substances perceived to be beneficial to foods
– Not long ago, most of us could agree on what
was a food and what was a drug
• As these new foods come to market, this
distinction is becoming less clear
Functional Foods
• Cholesterol-Reducing Margarine,
Juice, and Candies
– Cholesterol is an indicator of an
increased risk of heart disease
– Replacing butter with ordinary liquid
margarine in the diet may gradually
lower blood cholesterol by a few
percentage points over several
months
• Cholesterol-lowering medication
takes just weeks to dramatically
lower cholesterol by as much as
40%
Functional Foods
• Regular daily uses of foods enhanced with
sterol esters or stanol esters may
reduce blood cholesterol 10%-15% over a
relatively short time
Functional Foods
• The sterol esters added to foods act like a
drug in the body
– Reports link high blood levels of these
compounds with early signs of heart disease
in people who have an inherited disability to
clear them from the blood
– May lower the blood concentration of some
beneficial carotenes
• Such as lycopene
Functional Foods
• No one yet knows how these substances
may affect children and teenagers
– Yet children and teens may encounter them in
the diet in the form of margarine, juice, and
candies
Who regulates what in
the United States?
• FDA
• Regulates safety and claims
• FTC
• Enforces consumer protection laws on
advertising
• USDA
• Regulates label claims containing over a
certain % of meat or poultry
NLEA of 1990
• Mandates FDA to establish uniform
nutrition labels
• Establish when claims can be made
• Allowed FDA-approved claims
• FDA considers new health claims
through rule-making
DSHEA of 1994
• Amended labeling laws
• Exempts dietary supplements
• Permits use of structure-function claims
– Without prior FDA approval
– Must notify FDA 30 days after marketing
• Must include the following disclaimer:
– "This statement has not been evaluated by
the Food and Drug Administration. This
product is not intended to diagnose, treat,
mitigate, cure or prevent any disease"
DSHEA of 1994
• Defines supplements
• Sets criteria for regulating labeling
• Defines dietary ingredient
– Component of supplement
– Not subject to previous additive laws
– Distinct category of food material
Dietary Ingredient Definition
Dietary Ingredient
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Vitamin
Mineral
Herb or other botanical
Amino acid
Any other ingredient used to supplement the
diet
• Metabolite, constituent, extract, concentrate of
combination of these
Structure-Function Claim vs.
Health Claim
Functional Food
To modulate relevant target functions
Improvement of Metabolic
or Physiologic Process
Structured-Function Claim
Reduction of Risk of
Pathologic Process
Health Claim
What is a Health Claim?
• Characterizes the relationship of any substance
to a disease or a health related condition
• Uses terms “may” or “might”
• Does not quantify the degree of risk reduction
• Indicates disease depends on many factors
• Framed within the context of the whole diet.
How are Health Claims
Approved?
• Approved by FDA through NLEA
• Need extensive research
• Are subject to a lengthy & costly review
by FDA
• Once authorized, ANY company can use
it
• Cannot be based solely on fortification
Some Health Claims Permitted
• Calcium and decreased risk of osteoporosis
• Sodium and increased risk of hypertension
• Dietary saturated fats, cholesterol and increase
risk of CHD
• Dietary fat and increase risk of cancer
• Fiber-containing grain products, fruits,
vegetables and decrease risk of cancer
• Fruits, vegetables, grain products containing
fiber (soluble fiber) and decrease risk of CHD
• Fruits, vegetables and decrease risk cancer
Structure-Function Claims
• Include statements explaining how a substance
affects the structure or function of the body (i.e.
Calcium helps build strong bones)
• According to DSHEA, must tell FDA within 30
days after first marketing
• Permitted without prior approval
• Cannot claim to decrease risk of disease
• Disclaimer: “ This statement has not been
evaluated by the FDA. This product is not
intended to diagnose, treat, cure or prevent
disease.”
Safety of Functional Foods
• Unsafe products may reach the consumer
• Products do not have safety information
on labels
• May not know extent of health problems
Removal of “NEW” Dietary
Ingredient
• Burden of Proof on FDA
• Done in the courts
• Inadequate information
Functional Foods
• Is Every Food Functional?
– Many functional foods occur in nature
• A serving of broccoli sprouts provides a
concentrated source of phytochemicals associated
with cancer prevention
• Drinking a half-cup of cranberry juice may reduce
the incidence of urinary tract infections in women
Phytochemicals And Functional
Foods
• Cooked tomatoes provide lycopene along with
lutein (an antioxidant associated with healthy
eye function), vitamin C (an antioxidant
vitamin), and may other healthful attributes
• All vegetables, fruits, and whole foods of every
kind possess characteristic arrays of thousands
of potentially healthful constituents
Phytochemicals And Functional
Foods
• Even butter and cheese, foods known to contain
fats damaging to the heart and arteries when
eaten in excess, may qualify as “functional
foods” by virtue of their content of conjugated
linoleic acid (CLA)
– In some animal studies
• inhibits cancer
• lowers cholesterol
• improves diabetes
• improves immune function
• nudges body composition towards leanness
Phytochemicals And Functional
Foods
• Virtually all foods have some special value
in supporting health
Phytochemicals And Functional
Foods
• Functional Food and Phytochemical
Concerns
– Large doses of purified phytochemicals added
to foods may produce effects vastly different
from those of phytochemicals in whole foods
Phytochemicals And Functional
Foods
• Foods sold as functional foods often
contain untested medicinal herbs
– Such herbs have in recent years caused
serious damage to health and even some
deaths among consumers
– Research has not matured enough to identify
which isolated phytochemicals, medicinal
herbs, or other constituents may appropriately
be added to foods
• Consuming these foods can be risky in
unimaginable ways
Phytochemicals And Functional
Foods
• One might also question the wisdom of
dousing foods of low nutrient density with
phytochemicals and then calling them
“functional”
– Implying that they will enhance health
• Until research determines more about
functional foods, consumers are on their
own to make sure that the products they
use are safe and effective
Questions to Ask
• Does it work?
– Well-controlled, peer-reviewed research is
generally lacking or inconclusive for
manufactured functional foods
• Is it safe?
– Check the research for well-controlled safety
studies
– The active ingredients of functional foods may
cause allergies, drug interactions, dizziness, or
other side effects
Questions to Ask
• Has the FDA issued warnings about any of
the ingredients?
– Check the FDA’s MEDWATCH web site or call
the FDA to find out
• How much of what does it contain?
– Manufacturers are required to list the names
of added herbs and phytochemicals on labels
• But not the quantities added
– Beware, especially, of combinations of
“functional” ingredients
Questions to Ask
• Is the foods in keeping with the Dietary
Guidelines for Americans?
– A candy or brownie or “smoothie” shake may
be fortified with herbs and phytochemicals
– But is is still made mostly of sugar and fat
Phytochemicals And Functional
Foods
• When considering concentrated
supplements of phytochemicals
• Be aware that any normally beneficial
substance, even water, can be toxic when
taken in too high a dose
• Though most naturally occurring substances
are safe for most healthy people when
consumed in foods
• Virtually no safety studies exist to support the
taking of any purified phytochemical
• Nor have safe dosages been established
• The Final Word
– In light of all of the evidence for and against
phytochemcials and functional foods
• It seems clear that a moderate approach is
warranted
• People who eat the recommended amounts of a
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variety of fruits and vegetables may cut their
risk of many diseases by as much as half
Replacing some meat with soy foods or other
legumes may lower heart disease and cancer
risks
In the context of a healthy diet, foods are timetested for safety, posing virtually no risk of toxic
levels of nutrients or phytochemicals
Phytochemicals And Functional
Foods
• Beneficial constituents are widespread
among foods
– Don’t try to single out one phytochemical for
its magical health effect
– Take a no-nonsense approach where your
health is concerned
– Choose a wide variety of whole grains,
legumes, fruits, and vegetables in the context
of an adequate, balanced, and varied diet
Dietary Guideline and Food Guide
Pyramid Messages
• Plant based diet containing plenty of
whole grains, whole fruits and vegetables
• Color
• Variety
• Moderation
What do we tell consumers?
• Eat more fruit
• Increase vegetable portions
• Use herbs and spices
• Replace some meat
• Add grated vegetables
• Try new foods