1. “An apple a day keeps the doctor away.”: The science behind the saying.
Why do we need “5-a-day”? (1)
In 2014, newspapers and other media sources were filled with claims that eating seven
portions of fruit and vegetables a day would be more beneficial to health than consuming
just five (1). These claims brought to light a far more pressing issue: many people, including
highly qualified nutritionists and dieticians, were confused as to the meaning of five a day,
let alone seven. Did it mean five different fruits and vegetables each day? What were the
portion sizes? What counts towards five a day? Why five? To begin to dissipate the
confusion, it is important to understand the meanings of the terms “fruit” and vegetables”:
Fruit: a part of a plant which carries, protects, and disperses the fertilised seeds. This
includes foods like apples, bananas and tomatoes. Although tomatoes are traditionally
found on the vegetable aisle in a supermarket, they are actually a fruit by the above
definition. They are found alongside the vegetables due to their flavour complementing the
flavour of vegetables used in traditional meals and salads.
Vegetables: a part of the plant not involved in reproduction, such as the roots, leaves, and
stems. This includes carrots, beetroots, and potatoes (2).
It is also important to remember that it’s not just the type of food eaten that counts, but the
quantity consumed too. One portion of fruit or vegetables is roughly 80 g for an adult (3),
but a more applicable way of measuring a portion size is to see how much will fit
comfortably in a cupped hand. This accounts for differences in size, even for children, as
larger people tend to have bigger hands, so will receive the larger portion they need.
The reasoning as to why five portions of fruit and vegetables should be consumed each day
is based upon the antioxidant content of these foods. Antioxidants are compounds that will
be subjected to oxidation reactions in preference to other molecules in the body, protecting
them from damage via oxidation. For example, studies have shown that consuming
antioxidants reduces the risk of developing cancer; if DNA is oxidised, the gene for cell
replication may be damaged, causing the uncontrolled and rapid mitosis (cell replication) of
the effected cells, which are said to be cancerous (4). Separate studies have also shown a
correlation between antioxidant consumption and the reduced risk of atherosclerosis,
where fats are oxidised, accumulating as plaques in arteries and inhibiting blood flow (5).
2. While antioxidant content appears to be a good reason to eat five portions of fruit and
vegetables per day, further research shows that this conclusion is illogical. Antioxidants
belong to a group known as the phytonutrients (a.k.a phytochemicals), which are not
essential for survival, but are simply beneficial to health (6). Therefore, the basis of the five
a day thesis would be the consumption of beneficial compounds over essential ones. It has
also been recognised that other non-fruit and vegetable foods such as wheat, chocolate,
coffee and tea would contribute towards the five portions needed a day, as they are rich in
antioxidants (4). On the other hand, despite being a vegetable, potatoes would not count, as
they lack antioxidants. It is now apparent as to why there is so much confusion concerning
fruit and vegetable consumption.
However, this does not mean that we should stop or reduce the consumption of fruit and
vegetables. There are many other health benefits in connection with their role in the diet.
They are often rich in vitamins, which are essential compounds for survival. This includes
vitamin C, ascorbic acid, which plays a significant role in collagen synthesis; collagen is found
in bones, ligaments, tendons, and other connective tissue, and allows the body to function
as it should. The B-vitamins are often found in fruit and vegetables too; these often have a
role in respiration and other metabolic processes that sustain life. Vitamin A, in the form of
carotenoids in plants, plays a vital role in the maintenance of bones and the immune
system, as well as forming a pigment in the eye which allows light to be detected.
Carotenoids are usually red or orange in colour, and are actually antioxidants themselves,
although this may not be their primary function in the human body (7).
Fruit and vegetables also contain fibre, which maintains the health of the intestines, and
reduces the risk of colon cancer with increased age. Alongside this, they are a good source
of carbohydrate, specifically sucrose, which is broken down to form fructose and glucose,
providing energy for the body.
It is vital to recognise that while fruit or vegetable juices appear to be healthy, they lack
fibre, and are highly calorific. When the fibrous material of the plant tissue is removed to
leave the juice, the volume is greatly reduced. Therefore, multiple portions of the same food
may be required to create one glass of juice. This raises the calories consumed, but the main
reason for the increase in calories is that the sucrose, which is a form of sugar, is
concentrated in the fruit juice. Removing the fibre removes very few calories, leaving a high
calorie drink that lacks the health benefits provided by actual pieces of fruit and vegetables.
All fruits and vegetables have slightly different vitamin, fibre and carbohydrate content, and
it is therefore recommended that a variety of five different fruits and vegetables are
consumed each day to obtain the health benefits that arise from following the five a day
thesis. Although the reasoning behind eating five fruits and vegetables a day may seem
irrational, it is still worth consuming this amount, or maybe even more. They provide lower
calorie snacks for those struggling with weight gain or diabetes, and sustain supplies of
essential compounds in the bodies of all individuals, as well as reducing the risk of a wide
variety of diseases.
