GHM summative practice

Main claim of the study:

• fruit and vegetable intake significantly lowers risk of CVD, cancer, and premature death

• Recommended intake is around 800 g per day

CVD and diet:

• Diet containing increased fruit and vegetable intake reduces the risk of CVD

  • Only increasing fruit intake decreases RR of CVD more than only increasing vegetable intake

  • Fruits decrease the risk of CVD more than vegetables do

• Not exercising may lead to CVD

• Eating food high in sodium increases blood pressure, having a negative affect on the cardiovascular system

• Food high in saturated fats, trans fats, and cholestrol contribute to heart diseases and may result in conditions such as atherosclerosis

Cancer and diet:

• Diet containing fruits, vegetables, whole grains, and lean protein reduces the risk of cancer

  • Only increasing vegetable intake decreases RR of cancer more than only increasing fruit intake

  • Vegetables decrease the risk of cancer more than fruit

• High fat, low carb diet contribute to the risk of many types of cancer, such as bowel or lung cancer.

• Reducing alcohol intake reduces the risk of cancer

• Maintaining a healthy body weight reduces the risk of cancer

Fruit or vegetables to reduce risk of stroke:

• 33% risk reduction when fruit and vegetable are combined together

• 20% risk reduction for only fruit intake 200-350 g per day

• 28% risk reduction for only vegetable intake 500 g per day

• Answer: vegetables

All-cause mortality and longevity:

• Fraction of all causes of mortality globally = 11.3%

• Factors enhancing life expectancy:

  • Gender

  • Genetics

  • Access to health care

  • Exercise

  • Hygiene

  • Nutrition

  • Diet

    • More fruits and vegetables are proven to enhance life expectancy due to the vitamins and minerals in these whole food

Reliability of these claims in regards to scientifically:

• These claims are trusted and reliable because many studies and resources were brought together to create this systemic review

• These resources also included many different graphs and tables providing detailed analysis of statistics regarding life health and expectancy.

Key messages

• provide short statements which explain what the study is about overall

• include main points for the audience to follow throughout the article without complex or technical terms

Type of study:

• Systematic review and meta analysis

• Advantages:

  • Comprehensive evaluation providing existing evidence through and researching to create a relevant study.

  • Reduces bias

  • Increases statistical power by using many different studies.

  • Generalized study in which it was conducted in diverse population

• Disadvantages:

  • Time consuming

  • Resource consuming

  • Variability within populations, study approaches, and outcomes; may possibly draw meaningless conclusions.

  • May be susceptible to publication bias, in which studies with significant result are more likely to be shown compared to studies with nonsignificant results.

  • Poor quality studies are included, therefore the quality of studies cannot be controlled -> increase bias.

Authors mentioned sampling biases:

• yes they did

Recommended portions of fruit and vegetables (daily)

• WHO recommends 400 g per day

• The systematic review concluded that 800 g per day is the most optimal, because:

  • Vegetable and fruit intake below 800 g per day contributed to;

  • 1.25-2.26 million CVD deaths

  • 1.34 million coronary heart disease

  • 2.68 million stroke deaths

  • 660 thousands cancer deaths

  • 7.8 million premature death

  • The lowest RR risk for coronary disease, stroke, CVD was identified at 800 g per day

Number of cohort studies conducted: 95 studies

i-2:

• Percentage variation across studies due to heterogeneity rather than chance

  • The higher i2, the higher the difference between studies

  • The higher i-2, the higher heterogeneity gets

  • As i-2 increases, less number of correct analysis can be drawn from the study.

• For the study:

  • I-2 was moderate to high, indicating some variability among studies

  • Overall, results were shown to be consistent and statistically significant regardless of the variability.

Systematic review:

• A review that is done by a comprehensive plan and strategic research with the goal of reducing bias and increasing statistical power to create a relevant study on a particular topic

What is relative risk (RR)?

• It is a risk ratio which compares the probability of disease risk if exposed with the probability of diseases risk if not exposed.

  • In other words, ratio of the risks for an event for the exposed group to the risks for the non-exposed group.

• RR value interpretation:

  • If RR>1, the event (disease) is more likely to occur with the exposure.

  • If RR<1, the event (disease) is less likely to occur with the exposure.

  • If RR=1, the exposure does not make a difference.

Prospective cohort study:

• A type of study which focuses on following a cohort (group of people) over a period of time and collect their data on a certain exposure to a factor the researchers are interested in.

Components of fruits and vegetables that decrease premature mortality:

• Nutrients:

  • Fibre

  • Vitamin C

  • Carotenoids

  • Antioxidants

  • Potassium

  • Flavonoids

Strawberry findings:

• Not the best choice of fruit, since the analysis shows low number of studies and high relative risk as long as high i-2 value

• Mostly taken with sugar content as preferred by most people, such as chocolate or cream.

Fruit with the least beneficial effect on stroke:

• Berries, due to:

  • High relative risk compared to other types of fruit

  • high heterogeneity

Benefits of dried fruit:

• Concentrated with essential nutrients, which are vitamins, fibres, minerals, antioxidants which protect cell from oxidative damage, potassium and polyphenols also contribute to low blood pressure

Figure 2:

• Graph B: fruit and vegetable intake affecting coronary heart diseae

  • Fruit and vegetable reduced RR significantly

• Graph D: fruit intake affecting CHD:

  • RR slightly reduced

• Graph F: vegetable intake affect on CHD:

  • RR reduced with a bigger impact

• Conclusion: Fruit and vegetable intake is proven to have a significant effect on CHD, vegetable have a bigger impact than fruit on reducing risk of CHD

Figure 4:

• Graph B: fruit and vegetable intake affecting CVD

  • RR is decreased

• Graph D: Fruit intake affecting CVD

  • RR is decreased with a steeper slope thus bigger impact

• Graph F: vegetable intake affecting CVD

  • RR is decreased with a shallower slope thus less impact.

• Conclusion: Fruit and vegetable intake reduce relative risk of CVD, but fruits have bigger impact than vegetable on reducing risk of CVD.

Figure 5:

• Graph B: fruit and vegetable intake affecting cancer

  • Fruit and vegetable reduced RR but more towards slightly rather than significantly.

• Graph D: fruit intake affecting cancer:

  • RR slightly reduced

• Graph F: vegetable intake affect on cancer:

  • RR reduced with a bigger impact

• Conclusion: Fruit and vegetable intake is not proven have a significant effect on cancer, vegetable have a bigger impact than fruit on reducing risk of cancer

How a diet works:

• Fruit and vegetable are rich in antioxidants, fiber, vitamins, and minerals

• These nutrients are proven to:

  • reduce risk of common chronic diseases

  • lower inflammation

  • enhance heart health.

  • improve cholestrol levels

  • lower blood pressure

  • support immune system.

Alternative explanations for the positive effects of fruit and vegetables:

• People consuming more fruit and vegetable end up having healthier lifestyle, such as doing more physical activity by exercise.

Feasibility of the proposed diet (doable or not)

• Feasible enough but may be complicated to follow in low income regions where it is hard to find fresh product or prices are expensive.

Reasonable claims or not:

• Claims from this study are reasonable, since they come from large and long term comprehensive studies with strong and increased statistical power.

Implications or actions to take if the claims are true:

• Promotion of higher fruits and vegetable intake by public health organizations.

• Reduction of healthcare costs related to CVD and cancer

Differences that the study contribute to individual and population:

• Individual:

  • Higher fruits and vegetables intake reduces risk by 20 to 30%

• Population:

  • Prevention of premature deaths worldwide as 7.8 million deaths are contributed to fruit and vegetable intake lower than 800 g per day.

Alternative inclusion or exclusion criteria:

• include studies only with validated food intake measurements

• Exclude studies with short follow up period that produce insignificant results

Design of animal study after looking at this study:

• Separate two groups of animals with similar exposure

  • First group:

    • High fruit and vegetable intake

  • Second group:

    • Low fruit and vegetable intake

• Measure their cardiovascular health and lifespan between groups

Advise for a patient based on this study:

• Aim for higher fruit and vegetable intake around 800 g per day

• Focus on eating whole food rather than processed food, increase physical activity by exercising at least twice a week.