Fruit and Vegetable consumption linked with cancer risk - L16

Question 1

What is the consistent evidence for fruit and veg consumption and mortality ?

Answer 1

diets rich in fruit and veg and other plant foods are associated with moderately lower overall mortality rates and lower death rates from cardiovascular disease and some types of cancer

Question 2

What consumption of fruit and veg is advised per day and why ?

Answer 2

5 portions of fruit and veg per day - increasing consumption by 80g per day ( 1 serving) would reduce risk of cancer by 20% the WCRF stated in 1997

Question 3

Why is the consumption of fruit and veg reduction in risk not quite the same anymore?

Answer 3

the 20% reduction in risk associated with consumption of 5 portions of fruit per day may not strictly be true nowadays due to changes in obesity

Question 4

Why do plant foods protect against cancer and heart disease?

Answer 4

contain nutrients - important for normal cell functioning
contain fibre- good for intestine and binds carcinogens
generally low in fat
not meat
contain protective factors

Question 5

What does it mean by plant protective factors ?

Answer 5

these are beneficial compounds that are not nutrients

Question 6

Why nowadays do we not have as good an understanding of why plants are good for us ?

Answer 6

thought that we would know more nowadays but we dont and it is thought that this is due to obesity problems

Question 7

What % of cancers are caused by tobacco ?

Answer 7

30%

Question 8

What % of all cancers are related to diet, exercise and weight?

Answer 8

30-40%

• 20%= related to low intake of fruit and veg
• 4-14% related to obesity in men
• 14-19% related to obesity in women

Question 9

What is a protective factor ?

Answer 9

it is a food plant secondary metabolite which is NOT a nutrient but it has biological activity that may protect against disease in humans
activity may be dependent upon- dose, duration of dose, timing of dose, age, gender and health of the individual

Question 10

What happens if you remove a nutrient from your diet ?

Answer 10

you will get unwell but once you replace it you get better

Question 11

What are some examples of protective factors ?

Answer 11

FLAVENOIDS
- flavon-3-ol= kaempferol in tea, onions, apples, broccoli, french beans
- flaven-3-ol= tannins in tea, apples, wine, fruit
- isoflavones- daidzein in soybean, chickpeas
-glucosinolates - brassicas
- alkenyl cysteine sulfoxides
ellagitanins - pomegranetes

Question 12

What are the 2 types of preventative mechanisms?

Answer 12

BLOCKING AGENTS= prevent the genotoxic reagent from reaching the critical target sites e.g. inhibit metabolic activation reactions, activation/induction of detoxifying reactions and trapping genetoxic species
SUPPRESSING AGENTS= prevent the evolution of the neoplastic process in cells previously exposed to doses of carcinogenic agents that would otherwise cause cancer

Question 13

Where can protective factors act?

Answer 13

There are plenty of different places where protective factors can act

• reduce activation of phase 1 enzymes to reduce production of ultimate carcinogens
• enhance phase 2 enzymes to increase metabolic detoxification
• act to enhance DNA repair
• enhance replication and cell cycle control, help induce apoptosis when necessary

Question 14

What experiments are needed to prove that protective factors are beneficial ?

Answer 14

• epidemiology/in vitro/animal studies
• knowledge of food composition- what are the levels of compounds within food
• understanding of the absorption and metabolism of the compound
• human studies
• hypothesis of mechanism
• dose-response curves

Question 15

What are the alternatives to the direct antioxidant action ?

Answer 15

The low molecular weight compounds in fruit and veg may…
- induce protective enzymes - phase 2 enzymes
- inhibit phase 1 enzymes
- induce apoptosis
altogether leading to protection of cellular DNA, proteins and lipids against toxins and free radical oxygen species

Question 16

What are cruciferous vegetables ?

Answer 16

family of plants that include various familiar members of the species brassica oleracea
e.g. broccoli, cabbage, cauliflower, kale, brussel sprouts, oriental cabbage, arugula, watercress and radish etc

brassicas are part of cruciferae veg and there are any different types

Question 17

What are glucosinolates?

Answer 17

secondary metabolites produced in plants, containing a sugar and phosphate group
many different types: sinigrin, gluconapin, progoitrin, glucobrassicin- they dont have the same activites and their levels vary in foods

Question 18

How many glucosinolates have been identified?

Answer 18

at least 120, majority from crucifers, but other plant families also contain them

Question 19

What are the functions of glucosinolates in plants ?

Answer 19

they are the precursors of isothiocyantes (mustard oils)
play a protective and evolutionarily important role in plants
- ALLELOPATHY= suppression of growth of neighbouring plants, more nutrients, space and light
- SPECIFIC POSITIVE AND NEGATIVE FEEDING CUES= for some insects
- BROAD ANTIBIOTIC PROPERTIES= including nematodes, anti-microbial, anti-fungal, anti-protozoal and insecticidal activities

Question 20

Why do the levels of glucosinolates vary ?

Answer 20

levels vary according to genetics and growing condition
composition of individual glucosinolates varies from variety to variety
processing/cooking will affect their levels
consumption of different types will vary in different countries

Question 21

What happens when food is prepared or chewed ?

Answer 21

the enzyme tyrosinase is released an it hydrolyses glucosinolates to isothiocyanates

Question 22

What happens when food is cooked?

Answer 22

the tyrosinase is inactivated and therefore not present

we have the ability to convert glusinolates efficiently to isothiocyanates through the action of microflora in the GIT

Question 23

What does the enzyme myrosinase do to glucosinolates?

Answer 23

it removes the sugar and phosphate group to produce isothiocyanates

Question 24

What is sulforaphane ?

Answer 24

it is an isothiocyanate isolated from SAGA broccoli as the principal and very potent phase 2 enzyme inducer
- stimulates the biosynthesis of enzymes that will help remove toxic compounds more quickly

Question 25

What have sulforaphanes been able to do in animal models ?

Answer 25

inhibit tumour development when administered with or after carcinogens or both and is effective against a variety of carcinogens

Question 26

What has been shown between glucosinolates and bladder cancer ?

Answer 26

there was no significant association found between total fruit and veg consumption, fruits only or veg only for reduced risk of bladder cancer
BUT
the multivariate risk reduction ratio for cruciferous veg was highly significant- associated with a statistically significant 51% decrease in bladder cancer

Question 27

What has been shown between glucosinolates and prostate cancer?

Answer 27

high fruit consumption didn’t reduce risk in >65 year old men but high veg consumption in particular cruciferous veg consumption did demonstrate protective effects
3 or more servings of cruciferous veg a week, compared to 1 serving reduces the risk of prostate cancer by 41%

Question 28

What is the link between cruciferous veg consumption and breast cancer?

Answer 28

increased consumption reduces risk with the highest quartile having only 50% of the risk of the lowest intake group

Question 29

What was shown about cruciferous veg consumption and non-hodgkin lymphoma?

Answer 29

nurses’ health study showed that a high intake (5 or more servings a week) vs less than 2 was associated with a 33% lower risk of non-hodgkins lymphoma