Unit 15
PHYTO-CHEMICALS
Biologically-active Components in Food
Objectives
 To recognise that these substances profoundly affect our health
 To identify their role in disease prevention
 To understand the role that soy foods play in providing a variety of
nutrients and compounds
 To recognise that soy is a team player
INTRODUCTION
Phyto-chemicals (pronounced ‘fight-o-chemicals’) are components of foods that are
not nutrients but do affect our health3.
Phyto-chemicals what are they? Phyto means plant; so the term phyto-chemicals
means natural chemicals found in plants5. (Not present in any animal foods or
products.)
In 1983, Dr Lee Wattenberg, one of the pioneers in the phyto-chemical field, detailed
the many ways in which the phyto-chemicals in cruciferous vegetables and other
plant foods may prevent cancer3.
Over the past decade, study after study has shown how potent the phyto-chemicals
are against cancer and other diseases. A great deal of attention has been focused
on plant pigments in particular. These are the food components that give fruits and
vegetables their colour3.
The best-known plant pigment is beta-carotene, one of a class of compounds called
carotenoids. There are over five hundred different carotenoids in nature, and many
may be as powerful as, or more powerful than, beta-carotene in fighting disease3.
The carotenoids are just one group among many important phyto-chemicals.
Researchers at the University of Minnesota highlighted fifteen different classes of
phyto-chemicals in fruits and vegetables that show anti-cancer activity3.
About 200 dietary studies have revealed that a regular consumption of fruits and
vegetables provides significant protection against cancer at many sites. They are
most effective against those cancers that involve epithelial cells such as cancer of
lung, cervix, stomach, colon and pancreas. Higher intakes of fruit provided reduced
risk of epithelial cancers, although the protection was generally of a lesser magnitude
than that provided by vegetables2.
COLOUR ME HEALTHY - WITH FRUITS AND VEGETABLES6
Many people in Australia and New Zealand struggle to eat the recommended
amounts of fruits and vegetables each day.
Why are fruits and vegetables so good?
Not only do fruits and vegetables contain plenty of vitamins, minerals and fibre, there
is something else about fruits and vegetables that makes them special.
Fruits and vegetables contain Phytochemicals. They are nature’s chemicals or
nutrients found in plant foods, responsible to a large degree for the protective
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properties of fruits and vegetables. In addition, it is the phytochemicals that give
fruits and vegetables their distinctive colours and smells.
We generally classify fruits and vegetables into five colour groups according to the
phytochemicals they contain - Green, yellow/orange, red, blue/purple and
white/brown. There are many different phytochemicals that work together to protect
your health. You will probably find that some have quite unusual names but don’t let
this deter you from finding out about their unique health benefits. To ensure you
receive a great variety of phytochemicals in your diet, choose fruits and vegetables
from each of the colour groups every day.
Red foods
The phytochemicals lycopene, ellagic acid and a flavonoid called kaempferol
contribute to the special features of red fruit and vegetables. Red foods include:
These phytochemicals act as antioxidants, can be cancer protective and can also
help reduce the risk of heart disease. Lycopene is a powerful antioxidant belonging to
the group of carotenoids. A high intake of lycopene in particular has been linked with
a reduced risk of prostate cancer.
Purple/blue foods
The colour in purple/blue fruits and vegetables is mainly due to the flavonoids,
anthocyanins, which are powerful antioxidants and have a mild anti-bacterial effect.
Another phytochemical discovered in this group of fruits and vegetables includes
resveratrol, which is most commonly found in grapes and may have a cancer
protective effect. Purple/blue foods include:
Orange/yellow foods
There are abundant antioxidants in yellow and orange fruit and vegetables, including
the carotenoids (beta-carotene, lutein, zeaxanthin), which give this group their bright
colour. A wide range of other phytochemicals including terpenes and flavonoids
(quercetin) also occur in this group. Orange/yellow foods include:
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Carotenoids, terpenes and flavonoids act as antioxidants to protect against cancer
and heart disease. Of interest is lutein (pronounced ‘loo-teen’), which is a carotenoid
that gets stored in the eye. This is important to help prevent two of the most common
causes of blindness: cataracts and age-related macular degeneration.
Green Foods
Like orange/yellow foods, green fruits and vegetables are particularly rich in
antioxidants. They include varying amounts of many phytochemicals including
flavonoids and carotenoids (lutein, beta-carotene and zeaxanthin). The Brassica
group (broccoli, cabbage, Brussels sprouts) also contains indoles, which can trigger
enzymes to act against certain cancer causing substances. Saponins, another
phytochemical found in green plant foods, also have anti-cancer properties. They
interfere with the process whereby cancer cells multiply. Green foods include:
pinach
White/brown foods
While these colours are not as vibrant as the other colour groups, we should not
underestimate the nutritional contribution these vegetables can make to our diet.
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Fruits and vegetables from this group contain phytochemicals including allicin,
indoles and isothiocyanates, to name just a few! Many of the phytochemicals found in
this group of foods have effects ranging from antibacterial, antiviral and anti-cancer,
to the prevention of heart disease. This knowledge goes some way to understanding
the long held belief that garlic is good for you!
WHAT IS AN ANTIOXIDANT?Antioxidants are chemicals, often found naturally in
plant foods, that can help protect our body cells from being damaged by ‘free
radicals’. Antioxidants can therefore guard against cancer and heart disease, as well
as diseases of the eye, all of which can be influenced by damaged body cells. The
role of antioxidants in the prevention and treatment of a number of other conditions is
also being investigated.
PROMOTING FRUIT AND VEGETABLE CONSUMPTION AROUND THE WORLD
Programs are being conducted around the world to encourage people to enjoy fresh
fruits and vegetables. Several of us at the Sanitarium Nutrition Service recently
attended the 4th International 5 A DAY Symposium in Christchurch, New Zealand to
hear more about how other countries are promoting the consumption of fruits and
vegetables.
The World Health Organisation partially sponsored this symposium in an effort to
globalise the ‘5 A DAY’ initiative to increase fruit and vegetable consumption around
the world.
The team learned that although specific recommendations for fruit and vegetable
consumption may vary in different countries, the message is still the same. We need
to eat MORE fruits and vegetables.
Australian’s are encouraged to eat 7 serves of fruit and vegetables. Specifically, 2
serves of fruit and 5 serves of vegetables each day. The department of Health in
Western Australia run an excellent program to promote fruit and vegetable
consumption in their State. Visit www.gofor2and5.com.au for more information.
Kids can also learn more about fruits and vegetables at the following interactive
website: www.freshforkids.com.au
How many serves did you have yesterday?
Here is a guide to define a serve of fruit and vegetables:
s
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*Based on the Dietary Guidelines for Australian Adults- A guide to healthy eating.
NHMRC, 2003. 6
We certainly do not know everything there is to know about phyto-chemicals. That
will take many years of intense research. But we do know that it is no longer
appropriate to judge foods solely according to their nutrient contents, e.g. fat, protein,
carbohydrate, vitamins and minerals3.
SOYBEANS
If soybeans did nothing but lower your risk of cancer or heart disease, they would
quite obviously still be worth including in your daily diet. If they were nothing more
than a rich source of phyto-chemicals, they would be a wonderful menu item. But
soy offers a lot more for health. Soybeans, and the foods made from them, also
provide excellent nutrition in general3.
Soybeans are one of the few plant sources of the omega-3 essential fatty acid, alphalinolenic acid4.
The Chinese believe that soy can cure a number of diseases and medical conditions.
In Chinese, the word for soybean is ta-tou, which means “greater bean” 2.
PLANT FOODS AND DISEASE PREVENTION
SOY PROTEIN AND HEALTH
Soybeans are also an excellent source of protein. They have almost twice as much
protein as any other legume. It has been known for some time that soy protein is a
high quality protein, equivalent to the protein quality of milk, egg or meat. Now,
scientists are taking a very careful look at the health-promoting properties of
soybeans. Research shows that soy may be useful for lowering the risk of heart
disease, cancer, kidney disease, osteoporosis and other problems2.
Soybeans and soy protein contain a range of phyto-chemicals. To date, the most
widely studied phyto-chemicals in soy foods, which have been associated with
positive health benefits, are phyto-estrogens4.
WHAT ARE PHYTO-ESTROGENS?
Phyto-estrogens are plant-based dietary estrogens. They have a similar structure to
the body’s hormone - estrogen, but are much weaker in their actions. The specific
types of phyto-estrogens found in soy foods are called isoflavones. Soybeans and
most soy foods are a particularly rich source of isoflavones4.
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LESS CANCER WITH SOY
Consumption of soybeans is suggested as a contributing factor in the low incidence
of breast and prostate cancer in Japanese women and men respectively2.
Isoflavones in soy can inhibit the action of key enzymes required for cancer cells to
grow. They may also halt the growth of cancer cells, by restricting their blood supply,
which would otherwise provide nutrients to nourish the cells4.
It is believed that a high level of the body’s own estrogen increases the risk of
developing breast cancer. When soy protein, rich in isoflavones was eaten by premenopausal women, it extended the length of their menstrual cycle by a few days, as
is normally seen in Asian women, who have a low incidence of breast cancer. This
effect is considered to be highly beneficial, as over a lifetime, it means the female
body is less exposed to estrogen, possibly protecting from the development of breast
cancer4.
Although isoflavones have been studied extensively, researchers have identified
further components of soy that could also act as anticarcinogens. These include
phytic acid, trypsin inhibitors and saponins4.
HEART PROTECTION
Heart disease is the leading cause of death in Australia and New Zealand, and
elevated blood cholesterol levels are a significant risk factor for this disease 4.
Isoflavones are also thought to be heart protective in other ways. They act like
antioxidants to protect cholesterol from being oxidized or changed into the form,
which clogs up arteries. They also help to keep blood thin and prevent it from
clogging and help to maintain the elasticity of the blood vessels to promote blood
flow4.
MANAGING THE MENOPAUSE
Asian women (who traditionally consume large amounts of soy foods) report a lower
incidence of various menopausal symptoms such as hot flushes, compared to
Western Women4.
During the menopause, estrogen levels drop, which is the reason for the symptoms
women experience. Because of their similarity in chemical structure to estrogen, soy
phyto-estrogens (isoflavones) may act as a substitute to top up low estrogen levels,
and potentially assist with managing menopause symptoms4.
Further research is needed to investigate the potential role of soy protein and
isoflavones in reducing menopause symptoms4.
HEALTHY BONES
Isoflavones can protect against bone loss in animal studies. Early studies with postmenopausal women are indicating a similar benefit in promoting bone health 4.
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The type and amount of protein eaten, also seems to be important in preserving the
structure of the bones. Generally, a high protein intake increases the loss of calcium
from the body via the urine. However, not all proteins have the same effect. When
animal protein is replaced with soy protein, much less calcium is lost from the body4.
SOY IS A ‘TEAM PLAYER’ NOT A MIRACLE FOOD!
It is not enough to wash your ‘Big Mac’ and fries down with a glass of soymilk. The
best approach to a healthy diet is to have a diet based on a variety of plant foods 3.
Soy in perspective
Is there a negative side to the bean story? Are they too good to be true?

Soy foods are not ‘quick fixes’ or ‘miracle foods’.

Eating them will not make you instantly healthy.

While eating them will reduce your risk of some disorders, they must
always be viewed as one part of a well-balanced, healthy eating plan.

Best advice: start with an eating plan based on a variety of plant foods.

Plant foods are a good contributor of vitamins and minerals, fibre and
other important nutrients our bodies need.

Adding soy foods to this basic plan will ensure a good supply of
isoflavones - a good way to prevent disease.
Too much of a good thing?

There is no scientific evidence to suggest that soy foods have any
adverse effects of human health, especially when eaten as part of a
balanced diet that includes a variety of foods.

Consuming more than 3 serves of soy foods a day will probably not
provide extra advantages. Up to 3 serves of a soy food each day, could
provide positive health benefits1,5. This is easily incorporated into menu
planning with a wide variety of soy foods available including soy
beverages, tofu, tempeh, miso, soy cheese, soy flour, soy nuts,
textured vegetable protein and soy beans themselves.
Any side effects?

Soy foods have the potential to cause flatulence (wind).

Soybeans and soy flour are more likely to cause wind than tofu which
has most of the indigestible carbohydrate removed.

Discard water after soaking beans.

Introduce beans gradually into the diet; allow your body to adjust.
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
Food allergies are a much rarer reaction when eating soy foods.

These only occur in people who are extremely sensitive to food protein.

Allergic reactions to soy are rare in adults, although they occasionally
affect children who have a family history of allergic diseases.
WHAT IS THE VERDICT?
Overall, it seems that for most people, the benefits of soy foods in a balanced, varied
diet would far outweigh any negatives and harmonise with our health needs.
REFERENCES:
1. Anderson J, et al;
META-ANALYSIS OF THE EFFECTS OF SOY PROTEIN INTAKE ON
SERUM LIPIDS
New England Journal of Medicine 1995; 333(5): 276-282
2. Craig W;
NUTRITION AND WELLNESS
Golden Harvest Books Berrien Springs Michigan 1999:
117, 135, 138
3. Messina M, Messina V, Setchell K;
THE SIMPLE SOY BEAN AND YOUR HEALTH
Avery Publishing Group Garden City Park New York
1994: 2,16-19,133
4. Sanitarium Nutrition Service;
ENJOYING SOY FOR GOOD HEALTH
Sanitarium Health Food Company April 2000
5. Sanitarium Nutrition Service;
SOYA BEANS, GOOD HEALTH AND YOU
Sanitarium Health Food Company 1997
6. Sanitarium Nutrition Service; COLOUR ME HEALTHY
www.sanitarium.com.au 2006
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