It was one of the most popular fad diets of recent decades – rocketing to fame in 2013 after a single tweet from Victoria Beckham.
‘Love this healthy eating cookbook!!’ gushed the former Spice Girl turned fashion designer, alongside a picture of the recipe book Honestly Healthy.
Beckham was, at the time, almost as famous for her slender frame and strict eating habits as she was for her pop and fashion careers – and within a year, the book, which outlined ‘how to eat the alkaline way’, was a No. 1 bestseller with a sequel in the works.
The alkaline diet quickly gained a celebrity following, including actress and wellness guru Gwyneth Paltrow, Friends star Jennifer Aniston and supermodel Elle Macpherson.
The approach divided foods into two categories: acidic or alkaline.
Foods said to ‘produce acid’ when digested – such as meat, poultry, dairy, eggs, processed foods and alcohol – were claimed to make the body more acidic, disrupting its natural pH balance. This, advocates warned, could lead to a range of problems, from low energy and poor memory to headaches, muscle pain and insomnia.
So-called alkaline foods, meanwhile – including fresh fruits, vegetables, nuts, legumes and whole grains – were said to restore the body’s pH balance, improving health problems and even slowing the aging process.
By cutting out acidic foods, alkaline diet advocates claimed, dieters could prevent everything from fatigue, bloating and acne to serious illnesses such as heart disease, the bone-thinning condition osteoporosis, arthritis and even cancer.
Victoria Beckham, who was famed for her slender frame and rigid eating habits, pictured in 2003
Gwyneth Paltrow is said to be a fan of the alkaline diet, which aims to cut out acidic foods
Supermodel Elle Macpherson was also a fan of the diet, which helps to restore the body’s pH balance
But just as quickly as it became a worldwide phenomenon, the diet fell from grace, as experts cast doubt on the science behind it.
Leading doctors refuted the idea that blood pH could be changed by diet – or that eating this way could prevent cancer.
Any benefits, they countered, were likely due to the fact that many of the ‘acidic’ foods followers were told to avoid – including sugar and processed foods – were less healthy, while ‘alkaline’ foods included plenty of fresh fruits and vegetables.
In 2017, the ‘naturopathic doctor’ credited with inventing the diet, Robert Young, was sentenced to prison for practicing medicine without a license – and was later accused of defrauding terminally ill cancer patients by ‘treating’ them with infusions of baking soda.
Now, more than a decade after its controversial heyday, pioneering research is bringing the alkaline diet back into the spotlight.
Recent studies suggest that a diet low in acid-producing foods may reduce the risk of conditions including osteoporosis, type 2 diabetes and kidney disease.
Unlike the vague, detox-like claims of the past, the modern approach is based on a measurable concept called potential renal acid load, or PRAL.
This estimates the amount of acid the kidneys must excrete after food is metabolized.
That acid comes from the breakdown of certain nutrients, particularly protein and phosphorus, which generate compounds such as sulfuric and phosphoric acid as waste products.
Foods with a negative PRAL, including fruits, vegetables and legumes, are considered alkalizing because they produce fewer acidic by-products.
In contrast, meat, dairy and refined grains typically have a positive PRAL, meaning they generate a greater acid load and are classified as acid-forming.
Researchers believe that repeatedly placing a higher acid load on the body over many years may contribute to chronic disease – not, as advocates of the original alkaline diet claimed, because these foods meaningfully change the body’s pH level.
And while some experts warn the claims may still be overstated, others believe this evidence-based version of the diet could be part of the answer to the obesity crisis.
‘The more alkaline foods you eat, the easier it is for the body to lose weight,’ says Washington, DC-based endocrinologist Dr Hana Kahleova. ‘We know that GLP-1 medications [such as Mounjaro] are an effective way to lose weight, but they’re also expensive, have side effects and can cause people to lose a significant amount of muscle.
‘Some people may even end up worse off than when they started.
‘Instead, more people need to start making changes to their diet. Low-fat, vegan foods can help reduce the risk of diabetes, lower stress levels and help shed excess fat without muscle loss.’
A study of alkaline eating, led by Dr Kahleova alongside researchers from the University of Utah and George Washington University, found it helped participants lose nearly a pound a week.
The trial compared an alkaline-heavy, low-fat vegan diet with the Mediterranean diet, which includes meat, fish and olive oil. Sixty-two overweight adults tried both diets for four months each.
There was no calorie restriction on either diet – participants could eat until they were full.
While on the alkaline diet, participants lost an average of 13.2 pounds over 16 weeks. The Mediterranean diet, on the other hand, resulted in no significant weight loss.
The results, says Dr Kahleova, could be a game changer for people struggling with obesity.
She says: ‘On the Mediterranean diet, participants saw their blood pressure go down. But on the vegan diet their blood pressure dropped, their insulin sensitivity and blood lipids improved, and they lost fat while gaining muscle.’
This occurs, claims Dr Kahleova, because eating more acid-producing foods may trigger the release of the stress hormone cortisol. The theory is that the body has to work harder to maintain its tightly controlled acid-base balance, potentially pushing cortisol levels higher.
High levels of cortisol have been linked to changes in metabolism, increased appetite and greater fat storage, particularly around the abdomen.
‘The body has an amazing capacity to correct any fluctuations in pH – but we’ve only started to realize how much stress this can put on the body,’ says Dr Kahleova. ‘The more alkaline foods you consume, the fewer stress hormones are released and the easier it becomes to lose weight.’
However, Dr Susan Lanham-New, Professor of Human Nutrition at the UK’s University of Surrey, says the weight-loss benefits of alkaline eating shown in the trial may be overstated.
‘The study showed that changes in dietary acid load were associated with changes in body weight,’ she explains. ‘But adjusting for energy intake lowers that statistical significance. Those on the vegan diet were simply eating less.’
Despite this, says Dr Kahleova, even when the difference in calories was taken into account, higher consumption of alkalizing foods was linked to greater weight loss.
‘A reduction in dietary acid load was still associated with weight loss, independent of the calories consumed,’ she insists.
A 2017 study by the University of São Paulo in Brazil found that eating a diet high in acid-producing foods – and low in alkaline-producing foods – may contribute to a condition known as low-grade metabolic acidosis, which has been linked to inflammation and impaired kidney function.
Another paper, published this year in the International Journal of Cardiology Cardiovascular Risk and Prevention, linked a higher dietary acid load to a type of thickening of the arteries associated with heart disease.
A high dietary acid load has also been linked in some research to a greater risk of osteoporosis – the bone-thinning condition.
In general, Professor Lanham-New adds, dietary acid load is a concept with the potential to be very exciting.
‘What we have seen so far is that dietary alkalinity has been shown to have positive effects on a range of health outcomes. We just need more research into it.’
But a vegan diet – or one with fewer dairy and animal products – can come with its own challenges, says registered nutritional therapist Grace Kingswell.
‘It’s no surprise that when people go vegan they start to immediately feel better, because all of a sudden they’ve cut out processed food and are eating far more fruits and vegetables,’ she explains.
‘But we know that long term, there’s a real risk of nutrient deficiencies when following a vegan diet.’
Getting enough protein is also essential. The nutrient is fundamental for maintaining muscles and other tissues and plays an important role in blood sugar control and many other processes throughout the body.
‘Unless you do a vegan diet very well, it’s really hard not to be nutrient deficient,’ warns Ms Kingswell.
But reducing your dietary acid load doesn’t require an all-or-nothing approach.
‘There’s no need to obsess over it,’ insists Dr Kahleova. ‘The aim isn’t to only eat alkaline foods – it’s more like a shift towards more alkaline eating that we need.’
And after all, even Gwyneth Paltrow admits that she (occasionally) eats pasta now.
