Vitamin C and Acidity - What Form is Best?

Vitamin C: The Real Story, the Remarkable and Controversial Healing Factor

Vitamin C and Acidity - What Form is Best?

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Vitamin C - the Key for Good Health

Reprinted with permission from Orthomolecular Medicine News Service

(OMNS, December 8, 2009) Vitamin C is commonly taken in large quantities to improve health and prevent asthma, allergies, viral infection, and heart disease [1,2]. It is non-toxic and non-immunogenic, and does not irritate the stomach as drugs like aspirin can. Yet vitamin C (L-ascorbic acid) is acidic. So, a common question is, what are the effects from taking large quantities?

Ascorbic acid is a weak acid (pKa= 4.2) [3], only slightly stronger than vinegar. When dissolved in water, vitamin C is sour but less so than citric acid found in lemons and limes. Can large quantities of a weak acid such as ascorbate cause problems in the body? The answer is, sometimes, in some situations. However, with some simple precautions they can be avoided.

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Acid in the Mouth

First of all, any acid can etch the surfaces of your teeth. This is the reason the dentist cleans your teeth and warns about plaque, for acid generated by bacteria in the mouth can etch your teeth to cause cavities. Cola soft drinks contain phosphoric acid, actually used by dentists to etch teeth before tooth sealants are applied. Like soft drinks, ascorbic acid will not cause etching of teeth if only briefly present. Often, vitamin C tablets are coated with a tableting ingredient such as magnesium stearate which prevents the ascorbate from dissolving immediately. Swallowing a vitamin C tablet without chewing it prevents its acid from harming tooth enamel.

Chewable Vitamin C Tablets

Chewables are popular because they taste sweet and so are good for encouraging children to take their vitamin C [4]. However, some chewable vitamin C tablets can contain sugar and ascorbic acid which, when chewed, is likely to stick in the crevices of your teeth. So, after chewing a vitamin C tablet, a good bit of advice is to rinse with water or brush your teeth. But the best way is to specifically select non-acidic vitamin C chewables, readily available in stores. Read the label to verify that the chewable is made entirely with non-acidic vitamin C.

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Stomach Acidity

People with sensitive stomachs may report discomfort when large doses of vitamin C are taken at levels to prevent an acute viral infection (1,000-3,000 milligrams or more every 20 minutes) [1, 5]. In this case the ascorbic acid in the stomach can build up enough acidity to cause heartburn or a similar reaction. On the other hand, many people report no problems with acidity even when taking even 20,000 mg in an hour. The acid normally present in the stomach, hydrochloric acid (HCl), is very strong: dozens of times more acidic than vitamin C. When one has swallowed a huge amount of ascorbate, the digestive tract is sucking it up into the bloodstream as fast as it can, but it may still take a while to do so. Some people report that they seem to sense ascorbic acid tablets "sitting" at the bottom of the stomach as they take time to dissolve. It is fairly easy to fix the problem by using buffered ascorbate, or taking ascorbic acid with food or liquids in a meal or snack. When the amount of vitamin C ingested is more than the gut can absorb, the ascorbate attracts water into the intestines creating a laxative effect. This saturation intake is called bowel tolerance. One should reduce the amount (by 20-50%) when this occurs [1].

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Acid Balance in the Body

Does taking large quantities of an acid, even a weak acid like ascorbate, tip the body's acid balance (pH) causing health problems? No, because the body actively and constantly controls the pH of the bloodstream.

The kidneys regulate the acid in the body over a long time period, hours to days, by selectively excreting either acid or basic components in urine. Over a shorter time period, minutes to hours, if the blood is too acid, the autonomic nervous system increases the rate of breathing, thereby removing more carbon dioxide from the blood, reducing its acidity.

Some foods can indirectly cause acidity. For example, when more protein is eaten than necessary for maintenance and growth, it is metabolized into acid, which must be removed by the kidneys, generally as uric acid. In this case, calcium and/or magnesium are excreted along with the acid in the urine which can deplete our supplies of calcium and magnesium [6]. However, because ascorbic acid is a weak acid, we can tolerate a lot before it will much affect the body's acidity.

Although there have been allegations about vitamin C supposedly causing kidney stones, there is no evidence for this, and its acidity and diuretic tendency actually tends to reduce kidney stones in most people who are prone to them [1,7]. Ascorbic acid dissolves calcium phosphate stones and dissolves struvite stones. Additionally, while vitamin C does increase oxalate excretion, vitamin C simultaneously inhibits the union of calcium and oxalate. [1,2].

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Forms of Vitamin C

Ascorbate comes in many forms, each with a particular advantage. Ascorbic acid is the least expensive and can be purchased as tablets, timed release tablets, or powder.

  • The larger tablets (1000-1500 mg) are convenient and relatively inexpensive.
  • Timed-release tablets contain a long-chain carbohydrate which delays the stomach in dissolving the ascorbate, which is then released over a period of hours. This may have an advantage for maintaining a high level in the bloodstream.
  • Ascorbic acid powder or crystals can be purchased in bulk relatively inexpensively. Pure powder is more quickly dissolved than tablets and therefore can be absorbed somewhat faster by the body. Linus Pauling favored taking pure ascorbic acid, as it is entirely free of tableting excipients.

Buffered Ascorbate

A fraction of a teaspoon of sodium bicarbonate (baking soda) has long been used as a safe and effective antacid which immediately lowers stomach acidity. NOTE: Make sure to only use aluminum-free baking soda (such as Bob's Red Mill Baking Soda). When sodium bicarbonate is added to ascorbic acid, the bicarbonate fizzes (emitting carbon dioxide) which then releases the sodium to neutralize the acidity of the ascorbate.

Calcium ascorbate can be purchased as a powder and readily dissolves in water or juice. In this buffered form ascorbate is completely safe for the mouth and sensitive stomach and can be applied directly to the gums to help heal infections [8]. It is a little more expensive than the equivalent ascorbic acid and bicarbonate but more convenient. Calcium ascorbate has the advantage of being non-acidic. It has a slightly metallic taste and is astringent but not sour like ascorbic acid. 1000 mg of calcium ascorbate contains about 110 mg of calcium.
Other forms of buffered ascorbate include sodium ascorbate and magnesium ascorbate [9]. Most adults need 800 - 1200 mg of calcium and 400-600 mg of magnesium daily [6]. The label on the bottle of all these buffered ascorbates details how much "elemental" mineral is contained in a teaspoonful. They cost a little more than ascorbic acid.

Buffered forms of ascorbate are often better tolerated at higher doses than ascorbic acid, but they appear not to be as effective for preventing the acute symptoms of a cold. This may be because after they are absorbed they require absorbing an electron from the body to become effective as native ascorbate [1]. Some of types of vitamin C are proprietary formulas that claim benefits over standard vitamin C [9].

Liposomal Vitamin C

Recently a revolutionary form of ascorbate has become available. This form of vitamin C is packaged inside nano-scale phospholipid spheres ("liposomes"), much like a cell membrane protects its contents. The lipid spheres protect the vitamin C from degradation by the environment and are absorbed more quickly into the bloodstream. Liposomes are also known to facilitate intracellular uptake of their contents, which can cause an added clinical impact when delivering something such as vitamin C. This form is supposed to be 5-10 fold more absorbable than straight ascorbic acid. It is more expensive than ascorbic acid tablets or powder.

Ascorbyl Palmitate

Ascorbyl palmitate is composed of an ascorbate molecule bound to a palmitic acid molecule. It is amphipathic, meaning that it can dissolve in either water or fat, like the fatty acids in cell membranes.

It is widely used as an antioxidant in processed foods, and used in topical creams where it is thought to be more stable than vitamin C. However, when ingested, the ascorbate component of ascorbyl palmitate is thought to be decomposed into the ascorbate and palmitic acid molecules so its special amphipathic quality is lost.

It is also more expensive than ascorbic acid.

Natural Ascorbate

Natural forms of ascorbate derived from plants are available. Acerola, the "Barbados cherry," contains a large amount of vitamin C, depending on its ripeness, and was traditionally used to fight off colds. Tablets of vitamin C purified from acerola or rose hips are available but are generally low-dose and considerably more expensive than ascorbic acid. Although some people strongly advocate this type, Pauling and many others have stated that such naturally-derived vitamin C is no better than pure commercial ascorbate [2,9].

Bioflavonoids are antioxidants found in citrus fruits or rose hips and are thought to improve uptake and utilization of vitamin C. Generally, supplement tablets that contain bioflavonoids do not have enough to make much difference. For consumers on a budget, the best policy may be to buy vitamin C inexpensively whether or not it also contains bioflavonoids.

Citrus fruits, peppers, and a number of other fruits and vegetables contain large quantities of bioflavinoids. This is one more reason to eat right as well as supplement.


[1] Hickey S, Saul AW (2008) Vitamin C: The Real Story, the Remarkable and Controversial Healing Factor. ISBN-13: 9781591202233
[2] Pauling L (1986) How to Live Longer and Feel Better, by Linus Pauling (Revised version, 2006) ISBN-13: 9780870710964
[3] Handbook of Chemistry and Physics (2004), CRC Press, ISBN-13: 978-0849304859
[4] (Ideas on how to get children to take vitamin C.)
[5] Cathcart RF (1981) Vitamin C, titrating to bowel tolerance, anascorbemia, and acute induced scurvy. Med Hypotheses. 7:1359-1376.
[6] Dean C (2006) The Magnesium Miracle. (2006) ISBN-13: 9780345494580
[8] (Healing gums with buffered ascorbate.)
See also: Riordan HD, Jackson, JA (1991) Topical ascorbate stops prolonged bleeding from tooth extraction. J Orthomolecular Med, 6:3-4, p 202. or
[9] (Information about different forms of vitamin C)

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Editorial Review Board:

Carolyn Dean, M.D., N.D.
Damien Downing, M.D.
Michael Gonzalez, D.Sc., Ph.D.
Steve Hickey, Ph.D.
James A. Jackson, PhD
Bo H. Jonsson, MD, Ph.D
Thomas Levy, M.D., J.D.
Jorge R. Miranda-Massari, Pharm.D.
Erik Paterson, M.D.
Gert E. Shuitemaker, Ph.D.

Andrew W. Saul, Ph.D., Editor and contact person. Email: [email protected]

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