For such a small fruit the humble cranberry seems to have an awful lot to offer. In just the past four months alone studies have suggested that cranberries in various forms can improve our memory, lower levels of harmful cholesterol and potentially reduce the risk of heart disease.
If that wasn’t enough, another study, published in April in the journal Microbiology Spectrum, suggested that cranberry with manuka honey — also prized for its health-boosting properties — may have the potential to prevent tooth decay.
That adds to a long back catalogue of research proving the benefits of cranberries — in particular for tackling urinary tract infections (UTIs), such as a study in the American Journal of Clinical Nutrition in 2016 that showed drinking a ‘cranberry juice beverage’ lowered the number of UTIs in women who’d recently had the infection.
In just the past four months alone studies have suggested that cranberries in various forms can improve our memory, lower levels of harmful cholesterol and potentially reduce the risk of heart disease
Put together, it makes quite the case for eating more cranberries or regularly downing a glass of cranberry juice.
But these studies have one thing in common — other than being about cranberries; they are funded, at least in part, by the cranberry industry. Does it matter? As we shall discover, it’s a question that polarises the scientific community. And one that has implications for research into other foods, and whether we do really need them.
Cranberries were first used by Native Americans for medical purposes but started to attract scientific interest for their potential to prevent UTIs in particular in the late 1980s and 1990s. In the years that followed women have religiously been drinking cranberry juice in the belief that it helped prevent UTIs. And for years their doctors even recommended it.
‘As a junior doctor in the late 1990s, I was told to suggest cranberry products to patients who had catheters to help prevent urinary tract infections,’ says Dr Cat Anderson, an NHS GP who runs a UTI clinic in Newcastle-under-Lyme.
Meanwhile, nearly a third of women say they drink cranberry juice to treat a UTI.
Much of the research being done on cranberries has been supported by the cranberry industry.
Take, for example, two of the recent impressive studies. The first, which linked cranberry consumption to improved memory and lowered ‘bad’ cholesterol, was conducted by the University of East Anglia and involved 60 healthy individuals who were given a daily 4.5g freeze-dried cranberries (the equivalent of 100g of fresh cranberries) or a placebo for 12 weeks. The researchers found that the cranberries had a ‘significant’ impact on memory and levels of ‘bad’ LDL cholesterol.
Put together, it makes quite the case for eating more cranberries or regularly downing a glass of cranberry juice. But these studies have one thing in common — other than being about cranberries; they are funded, at least in part, by the cranberry industry. Does it matter?
Meanwhile, two months previously, in March 2022, King’s College London published a study in the journal Food & Function that showed eating cranberries can ‘significantly affect vascular health even in people with low cardiovascular risk’ — again, the study participants had powdered cranberries equivalent to 100g fresh cranberries or a placebo, but this time for a month.
In both cases the researchers declared that they were ‘supported’ by the Cranberry Institute. Founded in 1951, this U.S.-based not-for-profit organisation aims to ‘further the success of cranberry growers and the industry in the Americas through health, agricultural and environmental stewardship research as well as cranberry promotion and education’.
Its members include well-known brands such as the world’s biggest cranberry producer, Ocean Spray, as well as Fruit d’Or based in Quebec, Canada, and Cape Cod Select — and needless to say it is very keen to publicise any benefit cranberries might offer.
The website offers a library of more than 600 studies showcasing cranberries’ potential for health. The studies highlight the fruit’s potential role in everything from ‘urinary tract health to antimicrobial activities, cardiovascular and type 2 diabetes, and anti-cancer properties’. How much the institute puts into research it doesn’t say, but it outlines that ‘research efforts’ are done on ‘behalf’ of members.
But, separately, in 2017 Ocean Spray alone announced it was committing $10 million (around £8 million) over five years for research into ‘cranberry’s antimicrobial benefits’ and how this might reduce the need to use antibiotics.
It was Ocean Spray that funded the 2016 UTI study, as well as the recent study into tooth decay. The firm’s website proclaims cranberries as ‘one of Mother Nature’s super fruits’ with ‘well-documented health benefits’ that can play ‘an important role in a balanced diet and healthy lifestyle’.
Yet its product range includes whole cranberry sauce (which has 33g of sugar per 100g) and a Sparkling Pink Cranberry (with a serving suggestion to pour it over ice with vodka).
But the question raised by the burgeoning cranberry product market is this: should Ocean Spray or any other food company be paying for health research?
Is there a danger that this skews the market — in other words, other foods may provide a slew of benefits, it’s just that they don’t have the weight of an industry actively looking for them?
As Dr Kirsten Brandt, a senior lecturer in food and human nutrition at Newcastle University, explains: ‘Say you have the walnut industry, for example; if it works together it may invest in research to support walnut’s health properties — but the reality is there is no scientific reason to believe they are any better than, say, hazelnuts.’
She adds that industry funding ‘skews the financing towards studies that are likely to provide a positive marketing advantage rather than studies for the general good’.
‘Companies are doing the best they can — it’s the system that incentivises the wrong decisions.’
Kirsten Brandt is among those who believe that food companies shouldn’t be funding research into their products.
‘It’s well known that if you take 50 publications sponsored by industry and 50 from studies without industry sponsorship, you will find nearly 100 per cent of the industry-sponsored ones beneficial to the product — a much bigger proportion than those not sponsored by industry,’ she told Good Health.
‘Some say they are putting their fingers on the scale [to weigh research in their favour] somehow. I think that isn’t actually the case. However, industry will have a different decision process about which study they do. They will generally not want to support research that is based on some idea that may or may not work.’
She adds that they will only do trials ‘when their advisers — good scientists — tell them that if they do this trial it will most likely have a positive effect. That means they will have more successful studies simply by avoiding trials where the outcomes are uncertain’.
Cranberries were first used by Native Americans for medical purposes but started to attract scientific interest for their potential to prevent UTIs in particular in the late 1980s and 1990s. In the years that followed women have religiously been drinking cranberry juice in the belief that it helped prevent UTIs. And for years their doctors even recommended it
The potential for bias is by no means confined to cranberry research. When Anita Rao, an associate professor of marketing at Chicago University in the U.S., examined the outcomes of industry-sponsored and non-industry-sponsored research into 20 different wholegrains (from wild rice to amaranth), she found that industry-backed research generally was 3.2 per cent more positive in its findings on the health benefits than non-industry sponsored research.
However, research involving grains with ‘heavy industry funding’ such as corn, wheat and rice was almost 9 per cent more positive than non-industry funded research, she reported in the journal Quantitative Marketing and Economics in 2021.
‘These are not bad studies,’ Anita Rao told Good Health. ‘These are scientific, gold-standard, randomised placebo-controlled studies — but they are likely to be painting a rosier picture when it is positive. So they don’t report findings wrongly, but they write it in a more positive way.’
When researchers from Deakin University in Australia sifted through studies published in the top ten most-cited nutrition journals in 2018, they found that 13 per cent had ‘industry involvement’.
The authors of the study, published in the journal PLoS One, wrote: ‘Given the potential competing interests of the food industry on the one hand, and scientific and population health interests on the other, it is important to explore mechanisms that can safeguard the integrity and public relevance of nutrition research, and ensure they are not undermined by the influence of the food industry.’
However, at a time when public finances are stretched, is it not reasonable that industry is increasingly relied on to pay for science? After all, even the most basic trial testing a product such as hazelnuts on a group of people over a reasonable period, say a few months, can cost £200,000 to £500,000 (according to Kirsten Brandt).
Gunter Kuhnle, a professor of nutrition and food science at Reading University, readily admits ‘lots’ of his work is ‘industry funded’ — although he hasn’t conducted cranberry research — but says in the right circumstances it can make sense to have industry involvement.
‘The type of science we [in nutrition research] do is expensive to undertake. We need compounds on a large scale and if you don’t get government funding then the only option is to go to industry,’ he says. ‘If you’re testing cranberry juice and you want to compare it to the outcome with a placebo, you can’t use lemonade — you need something that’s the same colour and with the same fibre content, for example, and often the only people who can provide that are the makers of the food you are trialling.’
He gives the example of beetroot juice — it’s thought the nitrate in beetroot can reduce blood pressure by helping relax blood vessel walls. To test its effectiveness, it needs to be compared to the outcomes of people given beetroot juice without nitrate.
‘It’s then that you are going to need the expertise of the industry itself to provide a juice without nitrate,’ says Professor Kuhnle. ‘If you follow all the rules and the guidance, then industry involvement is fine.’
However, he adds, ‘problems arise when trials are not used to get information but to promote the product’. Or what we might understand as marketing.
There is no doubt that, like other fruit, cranberries have health merits. They are, for example, rich in proanthocyanidins (PACs), antioxidants with anti-viral, antibacterial and other properties.
A review in the journal Biomedicine & Pharmacology in 2019 concluded that PACs can ‘help to protect the body from sun damage, improve vision, improve flexibility in joints, arteries and body tissues such as the heart, and improve blood circulation by strengthening capillaries, arteries, and veins’.
Indeed, PACs are not, however, unique to cranberries, and are found in a variety of fruits such as blackcurrants and blueberries, as well as nuts such as walnuts. The review spelt out that cranberries aren’t even the richest source — that accolade (for fresh weight), goes to chokeberries, rose hips and cocoa products.
Cranberries have, however, gained interest as a treatment for UTIs as some research suggests that their PACs can prevent bacteria sticking to the walls of the bladder.
Dr Oghenekome Gbinigie, a GP and a researcher at Oxford University, has been researching the role of cranberries and UTIs and says there’s ‘good evidence that cranberry extract helps to block the binding of E.coli [which most commonly causes UTIs] to the lining of the bladder, which could, in theory, help to prevent a UTI’.
In 2020, Ocean Spray petitioned the U.S. medicines regulator, the Food & Drug Administration, to allow it to claim cranberries could reduce the risk of UTIs in healthy women. The regulator ruled that the ‘limited and inconsistent’ evidence was enough only to allow a ‘qualified health claim’.
In terms of juice (which must be at least 27 per cent juice), manufacturers can make claims such as ‘limited and inconsistent scientific evidence shows that by consuming one serving [8oz] each day of a cranberry juice beverage, healthy women who have had a urinary tract infection may reduce their risk of recurrent UTI’.
Yet on a Q&A on its website, the Cranberry Institute goes further, saying: ‘Drinking 8-16oz of cranberry juice cocktail each day is recommended to maintain urinary tract heath and prevent urinary tract infections.’
And there remain questions over how some of the science behind such claims came to be.
For example, the 2016 study on UTIs, published in the American Journal of Clinical Nutrition, was not only ‘supported by Ocean Spray Cranberries Inc’, but two of the six authors listed on the study were ‘employees of Ocean Spray Cranberries Inc’.
In a press release, the company described the study as a ‘landmark’. It said that 240ml of cranberry juice a day ‘reduces symptomatic UTIs by nearly 40 per cent in women with recurrent UTIs — suggesting a significant reduction in the need for antibiotics’.
In 2017 Christina Khoo, director of emerging science at Ocean Spray and one of the authors of the 2016 study, was reported as saying: ‘We went into this trial with the utmost care with how the study should be run. It’s unfortunate that there is the perception that, just because it’s funded by a company, that it’s not a good study.’
Yet previous research has been much less convincing. In 2012, Cochrane — the authoritative UK body that asks independent experts to review existing studies — concluded: ‘Although some small studies demonstrated a small benefit for women with recurrent UTIs, there were no statistically significant differences [in preventing infections] when the results of a much larger study were included.’ (Such findings led to a change in doctors recommending cranberry products to patients with catheters, says Dr Anderson.)
However, much of the research on cranberries as a preventative involves using capsules, not juice.
As for using cranberries for treating patients, in 2020 Cochrane said that ‘at the present time, there is no good quality evidence to suggest that it is effective for the treatment of UTIs’. Yet almost a third (27 per cent) of women who develop a UTI try cranberry juice to treat it, according to a survey of more than 2,000 women published in the British Journal of General Practice in 2015.
Dr Anderson says: ‘Cranberries are mentioned more than anything else by people who have a UTI for the first time — the marketeers have been very successful.’
She says she has patients who try cranberry ‘and it may help a bit, but it’s not all some people think it is’. ‘The danger is that people then go and grab cranberry juice off the supermarket shelves — which is often loaded with sugar,’ she says. ‘And when it comes to infections, we know that sugar can make things worse.’
Dr Anderson also warns that people who try cranberry, whether in juice or capsule form, should be aware of its potential interactions with some medicines, such as the blood thinner warfarin (it may thin the blood too much).
Dr Gbinigie adds that there have been problems with how some UTI studies have been conducted. ‘Some have not specified the amount of PACs they used, and others have a very high dropout rate [up to 55 per cent] due to people struggling to drink large quantities of cranberry juice over long periods,’ she told Good Health.
But Professor Kuhnle warns against ‘dismissing’ industry-funded nutrition research out of hand.
‘It’s easy to say company X produces food that’s unhealthy and that they just do these studies to polish their image. It’s an accusation that sticks very quickly.’
However, he wants the research focus to be more on the compounds in foods, rather than the actual products, to be clearer about whether it’s the compounds that are improving health.
Others, such as Kirsten Brandt, would like to see all research being paid for by the public purse. ‘At the moment the system isn’t working very well,’ she says.
‘I think we should stop expecting industry to finance these studies, particularly for health benefits that are naturally caused by food, such as cranberries, and are not as a result of industry’s inventions.’
Bill Frantz, executive director of the Cranberry Institute, told Good Health: ‘The Cranberry Institute health research programme is, and has always been, under the oversight of a scientific advisory board of five independent researchers with the highest ethical standards.
‘The Cranberry Institute board and partner boards, such as the Cranberry Marketing Committee, vote to decide which projects get funded. The Cranberry Institute Scientific Advisory Board helps choose the area(s) of research and ranks projects on merit. This process ensures that the research is not biased from start to finish.
‘I can say unconditionally that publication in a scientifically peer-reviewed journal is of the highest standards or it would not be published.’