Are acidic foods harmful to health?

The following article presents the claims and investigates the evidence to help people decide whether a low-acid or acid-free diet is the right choice for them.


People should be aware of some background information, regarding how acid and alkaline substances interact with the body, before deciding whether avoiding acidic foods is beneficial or not:

Measuring acidity and alkalinity

Measuring the pH values of foods and drinks is how people determine the acidity or alkalinity of them.

The pH values can range from 0 to 14 with distilled water having a pH of 7, or neutral. Other types of water with impurities or minerals may have a slightly different pH value.

Anything below pH7 is acidic while anything above ph7 is alkaline.

pH levels in the body

Different parts of the human body have different pH levels. Within the digestive system, pH values range from extremely acidic to slightly alkaline.

Differences in pH levels within the different organs and body fluids allow them to fulfill their particular function:

Human blood should be slightly alkaline with a pH ranging from 7.35 – 7.45.

A pH level in the blood that exceeds these limits in either direction will drastically impair metabolic processes inside the body.

The acid-ash hypothesis suggests that excessively acidic diets are bad for overall health.

Researchers based the hypothesis on the premise that foods that have been metabolized by the body leave behind a chemical residue known as ‘ash.’

When combined with body fluids, this ‘ash’ can be either acid-forming or alkali-forming, which could cause a reaction in the body.

According to the hypothesis, foods containing acid-forming substances lower the pH level of the blood, causing an accumulation of acid.

The body then compensates for this loss by leaching alkaline minerals, specifically calcium, from the bones and excreting them in the urine.

Supporters of the acid-ash hypothesis claim that regular and prolonged consumption of acid-forming foods increases mineral bone loss, thereby increasing the risk of conditions, such as osteoporosis.

Foods containing acid-forming substances include:

  • meat
  • grains
  • dairy
  • unsprouted beans
  • sunflower and pumpkin seeds
  • nuts
  • carbonated drinks
  • alcohol
  • coffee and other caffeinated drinks
  • sweeteners
  • refined table salt
  • tobacco

Foods that promote alkalinity, or ‘base-forming’ foods, are thought to prevent or counteract the effects of excess acid in the body. These foods include most fruits and vegetables.

Even citrus fruits, which are initially acidic, promote alkalinity once metabolized.

Proponents of the acid-ash hypothesis encourage regular pH testing of the urine as a means of monitoring the pH level of the body.

This information is then used to inform a person’s dietary choices.

Another reason people may choose to avoid acidic foods is due to concerns that they may cause or aggravate certain digestive disorders, such as acid reflux gastroesophageal reflux disease, otherwise known as GERD.

While acidic fruits and vegetables, such as citrus fruits, can irritate upper gastric disorders, these conditions are also likely to be exacerbated by foods high in fats.

The following foods are known triggers of acid reflux and GERD:


Contrary to the acid-ash hypothesis, there is no evidence to suggest that acidic foods are harmful to health. It is simply not possible to alter the pH of the blood through diet alone. A blood pH that is excessively acidic or alkaline indicates a serious underlying medical issue.

Despite this, so-called alkalizing diets consisting mainly of fruits and vegetables are abundant in vitamins, minerals, and antioxidants. People can achieve many benefits for their overall health by increasing their intake of these foods. However, these benefits are not related to alterations in blood pH.

People who are most likely to benefit from a reduced-acid diet are those for whom acidic foods are believed to trigger an upper gastric disorder or symptoms.

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