It's been celebrated by celebrities - fans are said to include Victoria Beckham, Gwyneth Paltrow and Jennifer Aniston - but debated by experts, who say that although the diet may work, it might not be for the reasons that the creators claim.
So what actually is the alkaline diet, and more important, can it really help you to lose weight and improve your health? Here's what you need to know...
What is the alkaline diet?The diet revolves around the idea that eating acidic food has a negative effect on your digestion, increasing bloating and generally making you feel lethargic because the kidneys are working overtime to break down the acids in food.
The aim of the diet is to keep the pH of your food at between 7.35 and 7.45 because that's when your body functions best.
The diet suggests you eat 80% non-acidic foods and then meat on top, making up the additional 20% of your meal. It means your meals don't have to be really boring and you can include some high-protein food, despite the fact that most of these are pretty high on the pH scale.
One of the most popular versions of the alkaline diet is the Honestly Healthy Alkaline Programme, set up by Sienna Miller's sister and chef Natasha Corrett. The plan is intended to reduce bloating, help you lose weight and make you feel more awake, and can even relieve any aches and pains you may be suffering with.
What foods can I eat?As we've mentioned, most meats are acidic, so it's best to stick to raw vegetables with a little meat for some protein. Some of the lowest acid foods include fennel, broccoli, artichoke, asparagus, beetroot, kale, spinach, watercress and cauliflower.
Some foods, such as spinach, can be alkaline when raw but become acidic when cooked, so you should also be aware of how foods can changes when exposed to heat.
Nuts and sunflower seeds are good for a snack, while dates, figs, grapefruit, lemon and lime top the fruit list. Although grapefruit, lemon and lime are all acidic when you eat them, they change to alkaline when digested. For a bit of extra sustenance, brown rice and quinoa can help bulk things out and give a good hit of fibre.
Big no nos are dairy, wheat, fish, shellfish, coffee, tea, sugar, fizzy drinks and alcohol.
How can I check whether something's acid or alkaline?If you really want to take this diet on seriously, you should invest in a pH testing kit. If you have an iPhone, the pHood app (available for £1.49 from the App Store) has a comprehensive list of almost every food's pH score.
What other effects does the diet have?According to the authors of the book Honestly Healthy, the diet can improve energy levels and memory and help prevent headaches, bloating, heart disease, muscle pain and insomnia. Although not scientifically proven, it's thought minimising acidic food can also help with arthritis, diabetes and cancer. You may also notice your skin is in better condition if you increase your intake of nuts.
What does a typical menu look like?Breakfast could be bircher muesli made with soya milk, or scrambled eggs on raw spinach and rye bread. Lunches are typically soups or salads, and dinner could be, for example, gnocchi made with pumpkin instead of potato, or a vegetable bake. If you're hungry, snack on protein-rich nuts or a serving of fruit.
What do the experts say?Which the alkaline diet does promote the consumption of healthy foods like fruits, vegetables, proteins and healthy fats like nuts, there is debate over the science behind the diet.
Natural nutritionist Amy Morris says: 'Many chronic illnesses have a common root cause – inflammation. Many people respond well to a diet that is low in inflammatory agents, and have eased their many aches and pains associated with inflammation by switching to a plant-based diet. Animal based diets can be too challenging to some, due to animal protein being highly inflammatory as it is very acidic. Whereas even some plant-based foods that are acidic, they are much less so than animal protein with the majority being alkalising. Thus, helping the body to achieve its preferred pH which is 7.2.'
However, nutritionist Dr. Sarah Schenker argues: 'There aren't any pros to the alkaline diet, there isn't any scientific evidence behind this diet and eating different foods has no effect on the pH of the body. This is something that is closely regulated within the body itself.'