The Science of Fruits and Vegetables

  • A healthy diet includes fruits and vegetables, rich in vitamins, minerals, fiber and phytochemicals that may have many health benefits. Choose colorful and dark green fruits and vegetables for the most antioxidants.
  • A daily consumption of 400–500 g of fruits and vegetables (that’s about 5 cups per day) is known to play an important role in prevention of chronic diseases.
  • Most studies have shown an approximately 10%–25% lower chance of dying (all-cause mortality) when comparing people with high and low fruit and vegetable consumption.

The AHA categorizes vegetables as: dark green vegetables: raw baby spinach 
broccoli romaine lettuce; orange vegetables: 
baby carrots, 
baked sweet potato; dry beans
 and peas: 
cooked black beans cooked kidney beans 
cooked pinto beans, starchy vegetables: 
cooked corn, 
baked potato and other vegetables: raw cauliflower, 
cooked green beans, 
iceberg lettuce, 
raw mushrooms, 
red onion, 
raw tomato, 
tomato juice, and 
raw zucchini.

More is better

Eating more fruits and veggies have benefits on cardiovascular risk factors as well as significant decreased risk for first heart attack. More than 3 servings per week of blueberries and strawberries (highest intake) compared to those at the lowest level was associated with a stunning 32% lower risk of a new heart attack in middle-aged women (Nurses’ Health Study 2, Circulation 2013). Habitual intake of colorful red and blue fruits and vegetables are a recurring theme with many large observational studies showing associations with important health benefits including clinically important lower blood pressure readings. In over 130,000 participants in the Nurses’ Health Study and the Health Professionals Follow-up Study a significant 8 mm Hg drop in blood pressure in those at highest intake compared to lowest intake of colorful fruits and vegetables was found after controlling for multiple variables (American Journal of clinical Nutrition, 2010).

Beetroot: superfood?

Beetroot seems to be the “vegetable de jour” and the “new” superfood. Some small studies report mild improvement in exercise performance and clinically important blood pressure lowering effect with drinking about 500 cc (about 2 cups) of beetroot juice. Consumption of beets and/or beetroot may have side-effects -especially if you are dehydrated or if taken in combination with some medicines -especially nitrates with dangerous drops in BP and dizziness or even passing-out. Red beetroot as well as celery, cress, chervil, lettuce and spinach, rocket (rugola) all have very high nitrate levels (converted in the body to the blood vessel dilator called nitric oxide).

Also, beware that beetroot can cause urine to become red or pink in color -a condition“called beeturia” but this is not considered harmful (and might otherwise be a sign of blood). About 5-15% of U.S. adults are estimated to experience beeturia following consumption of beets in everyday amounts according to the British Medical Journal. Beetroot and other vegetables high in oxalic acids and may occasionally need to be avoided or eaten sparingly in some with calcium oxalate kidney stones. Other high oxalate containing vegetables include: rhubarb, spinach, chard (silverbeet), watercress, leeks, okra, purslane, parsley, cacao, nuts such as almonds and cashews, buckwheat, some fruits such as starfruit, rhubarb, plums, and figs.

A variety of colorful fruits and vegetables is recommended by most authorities and is a major component of a healthy food pattern (and makes up half of the healthy plate) -stay clear of claims of “superfoods” and moderation in just about all things makes some common sense.


Any health benefits with fruit cannot be assumed to be there with  juicing. Juicing should not be confused with a “health drink” since much of the benefit of fruits and vegetables is related to its fiber content -the pulp and many of the phytonutrients in the fruit skin that remains in the juicer. What we don’t digest with fruits and vegetables (insoluble and soluble fiber) is believed to have considerable health benefits. Studies show that greater consumption of fruit juices was associated with a higher risk of type 2 diabetes. Eating more whole fruits, particularly blueberries, grapes, and apples, was significantly associated with a lower risk of type 2 diabetes, according to a study led by Harvard School of Public Health (HSPH) researchers. (Isao Muraki, Qi Sun et al British Medical Journal 2013). Data gathered between 1984 and 2008 from 187,382 participants in the Nurses’ Health Study, Nurses’ Health Study II, and Health Professionals Follow-Up Study reported that for those consuming at least two servings each week of certain whole fruits — particularly blueberries, grapes, and apples their risk for type 2 diabetes was cut by as much as 23 percent in comparison to those who ate less than one serving per month. For those who consumed one or more servings of fruit juice each day increased their risk of developing type 2 diabetes by as much as 21 percent. The researchers found that swapping three servings of juice per week for whole fruits would result in a 7 percent reduction in diabetes risk. The high glycemic index of fruit juice compared to that of fiber-rich whole fruit is believed to be a major factor linking juice consumption and increased diabetes risk. So skip higher glycemic juice and go for whole fruit. See more about glycemic index and glycemic load -and the science behind carbohydrates and blood sugar.

Fruits and veggies for life!

Most prospective studies have consistently shown an approximately 10%–25% lower chance of dying (the medical term: lower all-cause mortality) in people with high compared to low fruit and vegetable consumption. The benefits of increased consumption of fruits and vegetables extend to decreased rates of heart attack and cancer: the two major causes of death so it is not surprising fruits and vegetables are the foundation of a healthy nutrition pattern.

According to the 2007 expert report of the World Cancer Research Fund and the American Institute for Cancer Research, some types of vegetables and fruits may protect against certain types of cancer. Limited studies have estimated an increase in cancer-free life expectancy by 1 year or more for those consuming 400 g/day or more fruits and vegetables (5-cups) when compared with only 250 g/day (about 3 cups).

  • Phytochemicals (plant-made chemicals) with biological activity, fiber, vitamins, antioxidants, plant hormones (isoflavones), and essential minerals are all present in fruits and vegetables and are considered among the important micronutrients. A major source in the US diet of anti-oxidant and anti-inflammatory phytochemicals called: anthocyanins are found in blueberries and strawberries. Other sources of anthocyanins were: eggplants, blackberries, and black currants. Previous studies have suggested a preliminary association with anthocyanins found in berries and grapes to lowered heart attack risk.

The European Prospective Investigation Into Cancer and Nutrition (EPIC) study was designed to investigate the relationships between diet, nutritional status, lifestyle and environmental factors and the incidence of cancer and other chronic diseases. This study of over half a million (520,000) people in ten European countries: Denmark, France, Germany, Greece, Italy, The Netherlands, Norway, Spain, Sweden and the United Kingdom showed again the relation between more fruit and vegetable consumption and lowered all-cause mortality. An interesting additional finding was that  the survival relationships were even stronger for raw than for cooked vegetable consumption.

Serving size

The United States Department of Agriculture (USDA) sets a serving size for vegetables to be equal to about one-half cup, except for greens like spinach and lettuce, which have a serving size equal to one full cup. One serving of sliced fruit or berries is equal to one-half cup; however a single piece of fruit, such as an apple or an orange counts as one serving. The USDA chose one-half cup as a serving size based on the portion sizes that people typically eat, ease of use, and the nutritional content of fruits and vegetables. “More is better”. Five daily “portions” is about right amount of fruits and vegetables a person needs to eat per day to reduce the risk of an early death due to heart disease.


The science shows more fruits and vegetables are important for good health -and should make up about half of your plate. There is  also good evidence for what is called a dose-response relationship, that is, the more fruits and veggies the greater the health benefits. Yes, mom was correct “eat more fruit and vegetable portions” and be healthy.

Wang X, et al. Fruit and vegetable consumption and mortality from all causes, cardiovascular disease, and cancer: Systematic review and dose-response meta-analysis of prospective cohort studies. BMJ 2014