Lemon juice is said to be a healthy drink with potential disease-fighting properties.
It’s particularly popular in the alternative health community because of its supposed alkalizing effects. However, lemon juice has an unarguably low pH and should therefore be seen as acidic, not alkaline.
This article examines why some people consider lemon juice to be alkalizing, despite its acidic pH, and what that does to your body.
When discussing acidic versus alkalizing foods, it’s important to understand the concept of pH.
Put simply, pH is a rating of how acidic or alkaline a solution is on a scale from 0–14. A pH of 7 is considered neutral. Any pH value below 7 is considered acidic, and any pH value over 7 is considered alkaline (1, 2).
On the pH scale, the difference between adjacent numbers represents a tenfold difference in acidity. For instance, a pH of 5 is 10 times more acidic than a pH of 6 and 100 times more acidic than a pH of 7.
Because they contain a high amount of citric acid, lemons have an acidic pH.
Lemon juice has a pH between 2 and 3, which means it’s 10,000–100,000 times more acidic than water (1, 2, 3).
A food’s pH is a measure of its acidity. The pH of lemon juice falls between 2 and 3, meaning it is acidic.
The Alkaline Diet has gained popularity in recent years.
It’s based on the principle that the foods you eat may alter your body’s pH.
To set the record straight, there is no evidence to support the Alkaline Diet. According to research, the foods you eat have very little effect on the pH of your blood.
Nevertheless, the Alkaline Diet categorizes foods into three groups:
- Acidifying foods: meat, poultry, fish, dairy, eggs, and alcohol
- Neutral foods: natural fats, starches, and sugars
- Alkalizing foods: fruits, nuts, legumes, and vegetables
Proponents of the diet believe that eating large amounts of acidifying foods can cause your body’s pH to become more acidic, increasing your vulnerability to illness and disease.
For instance, many believe that your body steals alkaline calcium from your bones to buffer the acidifying effects of the foods you eat.
Some also believe that cancer grows only in acidic environments and that you can prevent or even cure it if you eat an alkaline diet.
Therefore, followers of this diet attempt to improve their health and reduce their risk of disease by limiting acidifying foods and favoring alkalizing ones instead.
Certain people believe that alkalizing foods lower their body’s pH, thereby promoting health and preventing disease.
Whether a food has an acidic or alkaline effect on the body has little to do with that food’s pH before it is digested.
Instead, it depends on whether acidic or alkaline byproducts are created once it is digested and processed by your body.
One method of estimating which type of byproduct a food will produce is the “ash analysis” technique.
In this method, foods are burned in a laboratory to simulate digestion. The pH of their ash is used to classify the foods as either acid or alkaline. Ash analysis is the reason foods are sometimes said to produce acid or alkaline “ash” (
However, ash analysis is an imprecise estimation, so scientists now prefer to use a different formula that grades foods based on their potential renal acid load (PRAL).
The PRAL of a particular food is the amount of acid that is expected to reach the kidneys after the body metabolizes that food (
Typically, the kidneys keep the blood’s pH constant by getting rid of excess acid or alkali through the urine.
Acidic nutrients such as protein, phosphorus, and sulfur increase the amount of acid the kidneys must filter out. Meats and grains, which tend to contain these nutrients, are therefore given a positive PRAL score (
On the other hand, fruits and vegetables are high in alkaline nutrients such as potassium, calcium, and magnesium. These ultimately reduce the amount of acid that the kidneys will need to filter out and are thus given a negative PRAL score (
Like other fruits, lemon juice produces alkaline byproducts once it has been metabolized. Therefore, it has a negative PRAL score.
This is why some people consider lemon juice to be alkaline even though it has an acidic pH before it is digested.
Once digested and metabolized, lemon juice produces alkaline byproducts, which make the urine more alkaline. This is why some people think of it as alkalizing, despite its acidic pH before it is digested.
Many proponents of the Alkaline Diet use pH test strips to check the alkalinity of their urine. They believe this helps them determine how alkaline their body truly is.
What they do not realize is that while lemon juice may make the pH of your urine more alkaline, it does not have the same effect on the pH of your blood.
According to research reviews published in 2013 and 2012, the foods you eat have a very limited effect on your blood pH (
Some much older studies estimated that you’d need to eat the equivalent of 18 pounds (8 kg) of oranges — which have an alkalizing potential similar to that of lemons — all in one sitting to increase your blood pH by just 0.2 (8,
Foods have such limited effects on the pH of your blood because your body needs to maintain pH levels from 7.35–7.45 for your cells to function properly (
If your blood pH values fall outside this range, you’re in a state called metabolic acidosis or metabolic alkalosis, which can be dangerous or even fatal if left untreated (
However, this rarely occurs, because your body is very good at preventing your blood pH values from falling outside the normal range. One of the ways it keeps the levels constant is by using your kidneys to filter out excess acids through your urine (
This is why your urine can become more acidic a couple of hours after you eat a large steak or less acidic after you follow a diet high in alkalizing foods (
Yet while the acidity of your urine can vary as a result of the foods you eat, the pH of your blood remains constant. So even if drinking lemon juice results in more alkaline urine, it’s unlikely to have any effect on the pH of your blood.
Lemon juice may have an alkalizing effect on your urine. However, contrary to the premise of the Alkaline Diet, it has very little influence on the pH of your blood.
Proponents of the Alkaline Diet seem to believe that the foods you eat can affect your health by influencing the pH of your blood. They generally claim that alkalizing foods prevent bone loss and can prevent or treat cancer.
However, as discussed above, this theory completely ignores the role your kidneys play in regulating the pH of your blood, among other methods your body uses to maintain pH (
In addition, contrary to popular belief, many large reviews have concluded that acidifying diets have no impact on calcium levels in the body (
In fact, several studies actually link high protein diets, which are thought to be acid-forming, with healthier bones (
As for the effects some people think acidifying foods have on cancer, studies show there is no direct link between the amount of acidifying foods you eat and your risk of developing the disease (
Nevertheless, an alkaline diet may offer some health benefits to certain individuals.
For instance, people with kidney disease usually need to restrict their protein intake. Consuming an alkaline diet may slightly decrease the need for this (
It may also reduce the risk of kidney stones in those prone to developing them (
However, more research on these purported benefits is needed before strong conclusions can be made.
Your body is designed to keep the pH of your blood within a narrow, healthy range. The foods you eat have very little effect on this pH.
Despite having very little alkalizing effect on the blood, regularly drinking lemon juice may promote several other health benefits.
For instance, lemon juice is high in vitamin C, a strong antioxidant that helps keep the immune system strong and prevents and fights disease (
One fluid ounce (30 ml) of lemon juice actually provides around 13% of your daily vitamin C requirement (
What’s more, drinking a vitamin C-rich beverage, such as lemon water, with meals may help increase your absorption of some minerals, including iron (
Lemon juice also contains small amounts of antioxidants that may help reduce the risk of heart disease by strengthening blood vessels, reducing inflammation, and preventing the accumulation of plaque (
In addition, some research suggests that regularly consuming lemon juice may help prevent the formation of certain types of kidney stones (
Regularly consuming lemon juice may strengthen the immune system, increase mineral absorption, reduce risk factors of heart disease, and prevent certain types of kidney stones.
Lemon juice has an acidic pH before it is digested. However, once metabolized by the body, it produces alkaline byproducts.
These alkaline byproducts can make your urine more alkaline but have very little effect on the pH of your blood.
Therefore, any health benefits lemon juice may offer are unlikely to come from its purported alkalizing effect.