Lemon juice is said to be a healthy drink with disease-fighting properties.
It is 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 value that rates 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.
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 falling between 2 and 3, which makes it 10,000–100,000 times more acidic than water.
Bottom Line: 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 is 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 one of 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 believe that eating high 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 the body steals alkaline calcium from your bones to buffer the acidifying effects of the foods you eat.
Some also believe that cancer only grows in acidic environments and that it can be prevented or even cured 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.
Bottom Line: 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 to estimate which type of byproduct a food will produce is known as the "ash analysis" technique.
Foods are burned in a laboratory to simulate what happens during digestion. The pH of their ash is used to classify the foods as either acid or alkaline. Ash analysis is the reason why foods are sometimes said to produce acid or alkaline "ash" (1).
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 (, , ).
Normally, 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 despite the fact that it has an acidic pH before it is digested.
Bottom Line: Once digested and metabolized, lemon juice produces alkaline byproducts, which make the urine more alkaline. This is why it is thought of 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 fail to realize is that, while lemon juice may make the pH of the urine more alkaline, it does not have the same effect on the pH of your blood.
In fact, several studies show that the foods you eat have a very limited effect on blood pH (, , ).
To illustrate how little, researchers estimate 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 (1, ).
The reason foods have such limited effects on the pH of your blood is because your body needs to maintain pH levels between 7.35–7.45 for your cells to function properly ().
If your blood pH values fall outside this normal range, you're in a condition called metabolic acidosis or metabolic alkalosis, which can be dangerous or even fatal if left untreated (9).
However, this rarely occurs because your body is very good at preventing blood pH values from falling outside the normal range. One of the ways it keeps levels constant is by using the kidneys to filter out excess acids through the urine (10).
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, this is unlikely to have any effect on the pH of your blood.
Bottom Line: 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 have the ability to 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, a comprehensive review reports 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.
Bottom Line: 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 23% of your daily vitamin C requirements (22).
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 (23).
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 (24, 25).
In addition, some studies report that regularly consuming lemon juice may help prevent the formation of certain types of kidney stones (, , , ).
Bottom Line: 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.