What does the scientific evidence say about this popular fruity beverage?
Well-known for its vitamin C content, a refreshing serving of pure fruit juice is often part of our breakfast ritual, but there’s also plenty of science inside the glass.
According to a survey commissioned by the Fruit Juice Science Centre, more than six in 10 adults drink fruit juice to get their vitamins – and this is justified given that one small glass of orange juice provides more than 80% of the vitamin C recommendation.
This e-news – written by health experts Dr Carrie Ruxton and Dr Gill Jenkins – explores what’s in fruit juice and how a daily serving can support several aspects of our health – from blood pressure to optimal immunity.
A nutrient feast
As well as vitamin C – an important antioxidant and immunity nutrient, fruit juice also contains potassium, a mineral that supports normal blood pressure, and folate, a B vitamin that has several roles in the body including fighting tiredness and fatigue.
What it doesn’t contain – by law – is added sugars, colours, flavours, or preservatives.
Depending on the fruits used to make the juice, whether these are oranges, apples, berries, tomatoes, or pineapples, you will also find plant bio-actives such as carotenoids, pectin, and polyphenols, including hesperidin from citrus juice.
What’s in your orange juice?
A new review, published in Nutrition Bulletin, found that people who drink fruit juice regularly tend to have higher intakes of vitamin C, vitamin A, folate, and potassium.
They also eat more fruit, showing that fruit juice is not replacing whole fruits in the diet.
Dietitian Dr Carrie Ruxton, says: “We are all advised to eat five servings of fruit and vegetables a day, but many people struggle to do this.
It’s good to know that, by having a morning glass of juice (150ml), you’re already one portion closer to this goal.
Snack on a handful of dried fruit, enjoy a bowl of soup at lunchtime and take double veg serving with your evening meal and 5-a-day is a done deal!
A research review, published in Frontiers in Immunology, found that a simple glass of orange or grapefruit juice contains nutrients and bioactive substances that help our immune system to work efficiently.
The authors gathered evidence from nearly 200 different studies and reports and concluded that vitamin C, folate and polyphenol compounds in citrus have the capacity to impact on immune health, fight inflammation and improve our defence against bacteria and viruses.
Co-author Philip Calder, professor of nutritional immunology at Southampton University, said: “Citrus fruit juices are particularly good sources of vitamin C and folate, which have roles in strengthening the gut and skin barriers which are the first line of defence against viruses and bacteria.
“In addition, these nutrients – which are absorbed well from fruit juices –support the function of many types of immune cells including phagocytes, natural killer cells, T-cells, and B-cells.
“Another area of research is the bioactive polyphenols found in citrus fruit juices which include hesperidin, narirutin and naringin.
“These not only have anti-inflammatory effects but could also have direct anti-viral effects according to emerging data from modelling studies.”
Dr Ruxton says: “Having enough vitamin C and folate in the diet – from fruits, vegetables and fortified cereals – ensures that our immune system functions within the optimal range.
“A glass of fruit juice provides more than 15% of the daily recommendation for folate.”
C is for collagen
Vitamin C is probably best known for its role in the maintenance of normal skin, bones, and teeth. This is because the vitamin is used in the body to make collagen, a vital structural protein.
GP Dr Gill Jenkins says: “In former centuries, sailors often suffered from scurvy – a disease characterised by bleeding of the skin and gums caused by vitamin C deficiency.
“Long before vitamins were discovered, a British doctor in the 1700s found that giving citrus fruits to sailors cured scurvy which is why British sailors were known as ‘limeys’!
“Nowadays, few people suffer scurvy but there are still vulnerable groups in the population with inadequate vitamin C intakes, particularly during this pandemic.
“Experts have suggested that we may need 200mg of vitamin C to fight infections rather than the 40mg recommended for healthy adults in the UK”.
Vitamin C and folate are known to contribute to the reduction of tiredness and fatigue.
This may be because folate, like other B vitamins, is involved in the release of energy from foods, while vitamin C helps protect body cells from oxidative damage (e.g., damage from free radicals).
As neither nutrient can be made in the body, we need a regular dietary supply.
Dr Ruxton says: “The UK National Diet and Nutrition Survey reveals that nine out of 10 women of child-bearing age have inadequate blood folate levels.
“Folate intakes have been declining over the past decade, probably because women have reduced their intakes of good sources like fruit juice, liver and fortified breakfast cereals.”
Iron is an essential nutrient with many functions in the body, not least immune support, and cognitive function.
Although fruit juice is not a source of iron, its vitamin C helps the body to absorb iron from our diet, particularly from non-animal sources.
Dr Jenkins says: “Given the rise in plant-based diets and with women shunning red meat, it will become more challenging to get enough iron from the diet.
“Drinking a glass of orange juice with a meal – especially dinner – is a good way of improving iron absorption from beans, pulses and green vegetables.”
The potassium found in all fruits and juices is important for maintaining healthy blood pressure.
Blood Pressure UK estimates that half of all heart attacks and strokes are caused by high blood pressure. A recent US study suggested that the pandemic has led to an increase in blood pressure in adults.
A meta-analysis (super study) published in the European Journal of Nutrition examined 21 observational studies and 35 randomised controlled trials looking at fruit juice and health impacts.
The results showed a clear link between drinking 100% fruit juice and reduced risk of stroke and heart attack with the greatest benefit seen at 150-200 ml a day.
Yet, average daily intakes in Europe are 50 ml – equating to just one-third of a serving.
Dr Jenkins says: “A good intake of potassium from fruit, fruit juices, vegetables and seafood can help maintain healthy blood pressure, and this is recommended by several international medical associations.
“The blood pressure reductions from drinking fruit juice are in a similar range to what you would see from cutting 4g a day of salt from your diet – which is clinically significant.”
A recent research review, published in Frontiers in Neuroscience, has found that eating citrus fruits and drinking their juices can have a positive impact on brain health, particularly in our later years.
Scientists believe the secret lies in the citrus polyphenols – called flavonoids – which occur naturally in oranges, lemons, limes, and grapefruit.
Scientists based at the University of East Anglia in Norwich collated hundreds of laboratory studies that looked at the impact of citrus flavonoids on brain cells and nerves, as well as 10 clinical studies in humans.
The results showed that citrus polyphenols have clear anti-inflammatory and anti-oxidative properties –important for protecting brain tissues from damage, for example, due to ageing or underlying health conditions.
Damage to brain and nerve cells is one of the earliest signs of degenerative conditions, such as Alzheimer’s and age-related cognitive decline.
Author Dr David Vauzour, senior research fellow at the Norwich Medical School, says: “The human studies carried out so far suggest that eating citrus fruits improves cognitive performance and reduces the risk of degenerative brain diseases.
“We see similar effects for whole fruits and 100% juices, and effectiveness in both healthy people and those with existing neurological conditions”.
Our antioxidant defence system is a complex network involving nutrients from the diet, as well as substances made in the body.
If we had no antioxidants, our body cells and DNA would come under constant attack from free radicals – chemicals that are made during normal metabolism or stimulated by stress, smoking, inflammation, or disease.
Vitamin C functions as a water-soluble antioxidant and plays a major role in neutralising free radicals. This activity protects our cells and DNA from oxidative damage.
Helpful, not harmful
Some commentators have claimed that fruit juices push up blood sugar levels and cause type 2 diabetes. But this isn’t backed by published meta-analyses.
Dr Gill Jenkins, who has type 2 diabetes herself, says: “Both fruit and fruit juices are classed as low GI (glycaemic index) and neither contains added sugars.
“Studies show that drinking fruit juice has no impact on proper blood glucose control, insulin levels, insulin resistance or risk of type 2 diabetes.
“Like the general public, people with existing type 2 diabetes can enjoy a small daily glass of fruit juice with a meal.”
Dr Ruxton adds: “Neither does fruit juice cause obesity according to a 2020 meta-analysis which found that drinking fruit juice daily for several weeks had no impact on adult body weight.
“This is probably because a small glass of orange juice contains just 62 calories.”
Fruit juice is an important and convenient source of vitamin C, folate, and potassium.
Studies show that fruit juice is a helpful part of our diet and has been linked with vascular and cognitive health.
The nutrients in fruit juice can provide important immunity support.
A daily glass of orange juice contains the nutrient equivalent of 1-2 oranges and is a healthy drink to accompany breakfast or other meals.