What Type of Acid Is in Tomatoes?

The acid in tomatoes can be beneficial for many bodily functions, including energy release and reduced risk of certain ailments. Citric acid, ascorbic acid and malic acid are all found in tomatoes, and all of these provide help to the body's cellular functions.

The primary acids in tomatoes are citric and malic acid. (Image: Serghei Starus / EyeEm/EyeEm/GettyImages)

Tip

The principal acids found in tomatoes are citric, ascorbic and malic acids, all of which play key roles in the production and release of energy.

Malic Acid in Tomatoes

The most prominently found acids in tomatoes are citric, malic and ascorbic acid. Otherwise known as vitamin C, ascorbic acid is key to the production of proteins in the body. Lemons, limes, oranges and grapefruits all contain high levels of citric and ascorbic acid, whereas the best source for malic acid is apples.

Malic acid is often paired with citric acid to create an effective antimicrobial, but in food it is often used to provide a distinct, sour taste to products like sour candies and fruit drinks as an additive. It is often used to mask bitterness and provide foods with a tart taste.

As a food additive, malic acid quantities have to be carefully maintained as too much or too little can encourage product deterioration. Therapeutically, malic acid has been used to treat ulcers and wounds, as well as used intravenously in the treatment of liver disorders. It has also been used in a variety of drug trials to treat depression and hypertension.

At all stages of tomato ripening, citric acid remains the dominant acid. However, in the earlier stages malic acid is at its most prominent. This is why unripened tomatoes often taste more sour, because the malic acid is more abundant. In addition to this, citric acid gradually declines following the ripening of the tomato, but the malic acid content remains consistent throughout even after the tomato has fully ripened. This is what maintains the sharp — or acidic — flavoring.

The acidity of products is often measured using the pH scale, with acidity at one end and alkaline at the other, the center being neutral. The scale goes from zero to 14 — with zero the most acidic and 14 the most alkaline. Neutrality usually sits at the 6 or 7 mark.

Canned tomatoes and tomato paste tend to be the most acidic, with readings sitting at 3.5 at their highest acidity. You should avoid these foods if you struggle with acid reflux or high stomach acid. The most alkaline tomatoes are those that have been strained or vine-ripened.

Warning

Dietary alterations can help you reduce acid, especially if you are experiencing negative symptoms such as stomach cramps or acid reflux. Tomatoes are high in acid, so avoid them if these symptoms arise. If symptoms continue despite dietary alteration, contact your health care professional.

Citric Acid in Tomatoes

Citric acid is the most commonly found natural acid in tomatoes. Citric acid is often used in food flavoring and as a preservative due to its ability to kill bacteria. It is particularly used in soft fruit drinks to provide that sharp flavor. In addition to this, it is integral to the citric acid cycle in the body. This process pathway provides nearly two thirds of all energy in the human body, so it's an important acid to keep the body topped up on.

Citric acid can be a highly beneficial to your overall health as well. A December 2014 literature review published in the Korean Journal of Urology found that an increased intake of citric acid was linked to a reduced chance of developing kidney stones. This occurs because citric acid binds to urinary calcium, reducing the supersaturation of urine that can lead to kidney stones. Citric acid also binds to calcium oxalite crystals, preventing the excessive growth of crystals that would otherwise result in stones.

Along with a reduced chance of kidney stones, increased consumption of citric acid has been linked to a reduced risk of gout. According to the Mayo Clinic, gout occurs when uric acid is not dissolved in the blood properly, so it builds up and eventually forms painful crystals that cause inflammation in joints and may eventually result in a gout attack.

An older study published in the journal Endocrine Research in 2010 tested a total of 70 subjects and found that increased citric acid intake also increased the acidity of urine and the excretion of uric acid, meaning that uric acid was less likely to build up and form crystals that could lead to gout. Because tomatoes are high in citric acid, adding them to your diet may provide similar benefits.

Ascorbic Acid in Tomatoes

Ascorbic acid, more commonly known as vitamin C, is found in significant quantities in tomatoes. It's a highly beneficial vitamin for the body due to its role in cell maintenance and repair.

According to MedlinePlus, vitamin C is necessary for:

  • The production of particular proteins that make up skin, tendons, ligaments, and blood vessels

  • The healing of injuries and wounds

  • The repairing and maintenance of teeth, bones and cartilage

  • The healthy absorption of iron

The human body is not able to create and store vitamin C independently, so it's highly important that you get as much as you can through dietary means. Sources of ascorbic acid go beyond tomatoes alone; it is actually quite common.

Sources of vitamin C include:

  • Cantaloupe
  • Citrus fruits and juices, such as orange and grapefruit
  • Kiwi fruit
  • Mango
  • Papaya
  • Pineapple
  • Strawberries, raspberries, blueberries, and cranberries
  • Watermelon
  • Broccoli
  • Brussels sprouts
  • Cauliflower
  • Green and red peppers
  • Spinach
  • Cabbage
  • Turnip greens
  • Sweet and white potatoes
  • Winter squash

Now you don't need to go and binge on any of these items just because the body doesn't produce ascorbic acid independently, but adding them and keeping them in your diet will certainly help keep levels high and boost your overall health.

Tip

As much as 13.7 milligrams of a 100-gram serving of tomatoes is made up of ascorbic acid, making them a significant source of this beneficial acid.

Sugar in Tomatoes

The most common sugars found in tomatoes are glucose and fructose, both of which play a key role in the production and release of energy in the body. The sugar in tomatoes is directly linked with the acidity, as they increase together. A May 2018 study in the journal MethodsX found that the quantity of citric acid in tomatoes increased at the same rate as quantity of fructose and glucose, demonstrating their link.

Glucose is the main source of energy — many complex sugars and carbohydrates become glucose once they have been broken down through the digestive process. Glucose from dietary sources, such as the glucose in tomatoes, is absorbed, transported to the liver where it is metabolized and released into the bloodstream. Your body's tissues then extract glucose from the blood and use it as energy, keeping tiredness and fatigue at bay.

The process of metabolizing glucose in the liver requires insulin. Fructose on the other hand, also found in tomatoes, does not require insulin. For this reason, fructose is often easier for people with diabetes to tolerate, as it does not affect the blood levels of glucose and energy can be released without needing insulin.

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