VITAMIN C (SUPPLEMENTS)
Vitamin C is a vitamin. Some animals can make their own vitamin C, but people must get this vitamin from food and other sources. Good sources of vitamin C are fresh fruits and vegetables, especially citrus fruits. Vitamin C can also be made in a laboratory.
Most experts recommend getting vitamin C from a diet high in fruits and vegetables rather than taking supplements. Fresh-squeezed orange juice or fresh-frozen concentrate is a better pick than ready-to-drink orange juice. The fresh juice contains more active vitamin C. Drink fresh-frozen orange juice within one week after reconstituting it for the most benefit. It you prefer ready-to-drink orange juice, buy it 3 to 4 weeks before the expiration date, and drink it within one week of opening.
Historically, vitamin C was used for preventing and treating scurvy. Scurvy is now relatively rare, but it was once common among sailors, pirates, and others who spent long periods of time onboard ships. When the voyages lasted longer than the supply of fruits and vegetables, the sailors began to suffer from vitamin C deficiency, which led to scurvy.
These days, vitamin C is used most often for preventing and treating the common cold. Some people use it for other infections including gum disease, acne and other skin infections, bronchitis, human immunodeficiency virus (HIV) disease, stomach ulcers caused by bacteria called Helicobacter pylori, tuberculosis, dysentery (an infection of the lower intestine), and skin infections that produce boils (furunculosis). It is also used for infections of the bladder and prostate.
Some people use vitamin C for depression, thinking problems, dementia, Alzheimer’s disease, physical and mental stress, fatigue, and attention deficit-hyperactivity disorder (ADHD).
Other uses include increasing the absorption of iron from foods and correcting a protein imbalance in certain newborns (tyrosinemia).
There is some thought that vitamin C might help the heart and blood vessels. It is used for hardening of the arteries, preventing clots in veins and arteries, heart attack, stroke, high blood pressure, and high cholesterol.
Vitamin C is also used for glaucoma, preventing cataracts, preventing gallbladder disease, dental cavities (caries), constipation, Lyme disease, boosting the immune system, heat stroke, hay fever, asthma, bronchitis, cystic fibrosis, infertility, diabetes, chronic fatigue syndrome (CFS), autism, collagen disorders, arthritis and bursitis, back pain and disc swelling, cancer, and osteoporosis.
Additional uses include improving physical endurance and slowing aging, as well as counteracting the side effects of cortisone and related drugs, and aiding drug withdrawal in addiction.
Sometimes, people put vitamin C on their skin to protect it against the sun, pollutants, and other environmental hazards. Vitamin C is also applied to the skin to help with damage from radiation therapy.
HOW DOES IT WORK?
Vitamin C is required for the proper development and function of many parts of the body. It also plays an important role in maintaining proper immune function.
The richest natural sources are fruits and vegetables, and of those, the Kakadu plum and the camu camu fruit contain the highest concentration of the vitamin. It is also present in some cuts of meat, especially liver. Vitamin C is the most widely taken nutritional supplement and is available in a variety of forms, including tablets, drink mixes, crystals in capsules or naked crystals.
Vitamin C is absorbed by the intestines using a sodium-ion dependent channel. It is transported through the intestine via both glucose-sensitive and glucose-insensitive mechanisms. The presence of large quantities of sugar either in the intestines or in the blood can slow absorption.
While plants are generally a good source of vitamin C, the amount in foods of plant origin depends on: the precise variety of the plant, the soil condition, the climate in which it grew, the length of time since it was picked, the storage conditions, and the method of preparation.
The following table is approximate and shows the relative abundance in different raw plant sources. As some plants were analyzed fresh while others were dried (thus, artifactually increasing concentration of individual constituents like vitamin C), the data are subject to potential variation and difficulties for comparison. The amount is given in milligrams per 100 grams of fruit or vegetable and is a rounded average from multiple authoritative sources:
The overwhelming majority of species of animals and plants synthesise their own vitamin C, making some, but not all, animal products, sources of dietary vitamin C.
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Vitamin C is most present in the liver and least present in the muscle. Since muscle provides the majority of meat consumed in the western human diet, animal products are not a reliable source of the vitamin. Vitamin C is present in mother’s milk and, in lower amounts, in raw cow’s milk, with pasteurized milk containing only trace amounts. All excess vitamin C is disposed of through the urinary system.
The following table shows the relative abundance of vitamin C in various foods of animal origin, given in milligram of vitamin C per 100 grams of food:
Vitamin C chemically decomposes under certain conditions, many of which may occur during the cooking of food. Vitamin C concentrations in various food substances decrease with time in proportion to the temperature they are stored at and cooking can reduce the Vitamin C content of vegetables by around 60% possibly partly due to increased enzymatic destruction as it may be more significant at sub-boiling temperatures. Longer cooking times also add to this effect, as will copper food vessels, which catalyse the decomposition. Research has also shown that fresh-cut fruits don’t lose significant nutrients when stored in the refrigerator for a few days.
Vitamin C supplements
Vitamin C is the most widely taken dietary supplement. It is available in many forms including caplets, tablets, capsules, drink mix packets, in multi-vitamin formulations, in multiple antioxidant formulations, and crystalline powder. Timed release versions are available, as are formulations containing bioflavonoids such as quercetin, hesperidin and rutin. Tablet and capsule sizes range from 25 mg to 1500 mg. Vitamin C (as ascorbic acid) crystals are typically available in bottles containing 300 g to 1 kg of powder (a teaspoon of vitamin C crystals equals 5,000 mg).
Artificial modes of synthesis
Vitamin C is produced from glucose by two main routes. The Reichstein process, developed in the 1930s, uses a single pre-fermentation followed by a purely chemical route. The modern two-step fermentation process, originally developed in China in the 1960s, uses additional fermentation to replace part of the later chemical stages. Both processes yield approximately 60% vitamin C from the glucose feed.
Research is underway at the Scottish Crop Research Institute in the interest of creating a strain of yeast that can synthesise vitamin C in a single fermentation step from galactose, a technology expected to reduce manufacturing costs considerably. By 2008 only the DSM plant in Scotland remained operational outside the strong price competition from China. The world price of vitamin C rose sharply in 2008 partly as a result of rises in basic food prices but also in anticipation of a stoppage of the two Chinese plants, situated at Shijiazhuang near Beijing, as part of a general shutdown of polluting industry in China over the period of the Olympic games.
Health Canada evaluated the effect of fortification of foods with abscorbate in the guidance document, Addition of Vitamins and Minerals to Food, 2005. Health Canada categorized abscorbate as a ‘Risk Category A nutrients’. This means it is either a nutrient for which an upper limit for intake is set but allows a wide margin of intake that has a narrow margin of safety but non-serious critical adverse effects. Health Canada recommended a minimum of 3 mg or 5 % of RDI in order for the food to claim to be a source of Vitamin C and maximum fortification of 12 mg (20 % of RDI) in order to be claimed “Excellent Source”.
Vitamin C is one of the safest and most effective nutrients, experts say. It may not be the cure for the common cold (though it’s thought to help prevent more serious complications). But the benefits of vitamin C may include protection against immune system deficiencies, cardiovascular disease, prenatal health problems, eye disease, and even skin wrinkling.
A recent study published in Seminars in Preventive and Alternative Medicine that looked at over 100 studies over 10 years revealed a growing list of benefits of vitamin C.
“Vitamin C has received a great deal of attention, and with good reason. Higher blood levels of vitamin C may be the ideal nutrition marker for overall health,” says study researcher Mark Moyad, MD, MPH, of the University of Michigan. “The more we study vitamin C, the better our understanding of how diverse it is in protecting our health, from cardiovascular, cancer, stroke, eye health [and] immunity to living longer.”
“But,” Moyad notes, “the ideal dosage may be higher than the recommended dietary allowance.”
HOW MUCH VITAMIN C IS ENOUGH?
Most of the studies Moyad and his colleagues examined used 500 daily milligrams of vitamin C to achieve health results. That’s much higher than the RDA of 75-90 milligrams a day for adults. So unless you can eat plenty of fruits and vegetables, you may need to take a dietary supplement of vitamin C to gain all the benefits, Moyad says. He suggests taking 500 milligrams a day, in addition to eating five servings of fruits and vegetables.
“It is just not practical for most people to consume the required servings of fruits and vegetables needed on a consistent basis, whereas taking a once-daily supplement is safe, effective, and easy to do,” Moyad says. He also notes that only 10% to 20% of adults get the recommended nine servings of fruits and vegetables daily.
Moyad says there is no real downside to taking a 500-milligram supplement, except that some types may irritate the stomach. That’s why he recommends taking a non-acidic, buffered form of the vitamin. “The safe upper limit for vitamin C is 2,000 milligrams a day, and there is a great track record with strong evidence that taking 500 milligrams daily is safe,” he says.
Vitamin C plays an essential role in the production collagen in the body, which is a type of protein needed by various different tissues including the skin, tendons, ligaments, blood vessels, bones and cartilage. It is known for its role in the process of tissue growth and repair.
Additionally, vitamin C is an antioxidant, which can help to neutralize free radicals in the body. This is important as free radical build up in the body over time is associated with advanced aging and health conditions such as cancer, heart disease and arthritis.
It also helps in the prevention of some potentially fatal diseases such as scurvy and may help to reduce the duration of symptoms of the common cold.
When dietary consumption of vitamin C is insufficient, the production of collagen is interrupted and cannot replace collagen needed, resulting in the breakdown of tissues.
This leads to a health condition known as scurvy, which can be directly caused by Vitamin C deficiency. Symptoms of scurvy may include:
- Muscle pain, particularly in legs
- Joint pain
- Redness on skin
- Swollen gums and possible bleeding
All vitamin C needed for normal bodily functions needs to come from daily dietary consumption, as it cannot be produced or stored in the body.
Although vitamin C deficiency and resulting symptoms of scurvy are uncommon in today’s society, the prevalence is higher in particular populations that have less access to fresh fruit and vegetables. People who are elderly, drug-dependent or have a low income are more likely to suffer.
Consuming high quantities of vitamin C is not considered to be a great health concern as it is a water-soluble vitamin that is excreted in the urine when taken in excess. However, it may cause symptoms with high doses (greater than 2000 mg daily) such as:
Vitamin C also increases the absorption of iron from food. While this can be a beneficial aspect in some populations, people with hemochromatosis will be more likely to build up iron in the body and should avoid vitamin C supplementation.
Additionally, pregnant women should not be advised to take large doses of vitamin C, as the infant may experience rebound scurvy at birth due to the drop in vitamin C intake.
The Common Cold
Vitamin C is often promoted to help in the prevention and treatment of the common cold. However, the scientific evidence supporting this recommendation is conflicting.
It appears that taking several doses of vitamin C throughout the day when initial symptoms of a cold present may be effective at shortening duration and severity of symptoms. Taking vitamin C as a preventative method, however, has not been shown to reduce the frequency of the common cold.
Although the recommended dietary intake remain in debate, most practitioners agree approximately 45-90 mg/day is an appropriate amount in most populations. Increased doses for use to treat the common cold range from 200 to 2000 mg/day usually split into three doses.
Vitamin C can be found in a variety of fresh fruit and vegetables including:
- Brussels sprouts
- Kiwi fruit
- Leafy greens
Most people can easily reach the recommended daily intake of vitamin C by consuming a normal diet with sufficient fruit and vegetables.