The alkaline diet

You may have heard that, to protect your bones, you should eat more fruit and vegetables, and eat less protein. This is because some people believe foods high in protein can cause acidity in your bloodstream and damage your bones.

The suggestion is your body tries to neutralise the acidity in your blood by drawing calcium out of your bones. Calcium is an alkali, which neutralises excess acid. Theoretically, this could cause your bones to lose strength.

People who support the theory promote using your diet to influence the pH (level of acidity) of your bloodstream, so your body doesn't need to draw calcium from your bones. This is known as 'the alkaline diet'.

What does the alkaline diet look like?

Supporters of the alkaline diet suggest increasing your intake of fruit and vegetables and reducing the amount of protein from foods such as meat, grains and dairy. They recommend you should aim for an 80:20 ratio.

Does the alkaline diet work?

It’s true that eating plenty of fruit and vegetables has the potential to have an alkaline effect in the body and may help to balance out acid-forming foods.

However, it’s not been proven that following a strict alkaline diet, and restricting ‘acidic’ foods, lowers your risk of broken bones.

Claims that an alkaline diet is beneficial to bones first came from studies that were based on people with severe kidney disease. So these results may not be applicable to generally healthy people.

Risks associated with following the alkaline diet

Following the alkaline diet could cause you to miss out on important nutrition for your bones.

Milk and dairy products provide an inexpensive and easily available source of calcium. They also provide other valuable nutrients that are beneficial to bone health.

Reducing how much protein you eat could also put your bones at risk. Getting enough protein is essential for bone health, particularly as you get older.

We recommend the best way to protect your bones with the food you eat is by eating a healthy, balanced diet, with plenty of calcium and vitamin D.

How your body regulates acidity

Your body is designed to keep your blood pH within a narrow alkaline range. It does this very effectively, mainly through:

• your kidneys removing excess acidity in urine
• your lungs expelling ‘acidic’ carbon dioxide as you breathe.

These processes usually keep your body's acidity at the right level. And your body doesn't need to draw calcium out of your bones to neutralise the acidity in your bloodstream.

Testing your body's acidity

You may have seen testing kits that you can buy to check the acidity levels of your urine. Be aware these are unlikely to tell you much about the acidity of your bloodstream.

A reading showing high acidity in your urine doesn't prove high acidity levels in your blood, or possible damage to your bones.

Evidence shows eating an ‘acidic’ range of foods increases the acidity of urine. But there is no evidence that eating acidic foods alters blood pH much outside of the normal range.

Content reviewed: December 2019

(updated December 2021)

Also see:

• Vitamins, minerals and nutrients
• Are there any foods I should avoid?
• Calcium
• Vitamin D