Vitamin C Benefits: A Comprehensive Look

Vitamin C. You’ve been told about it ad nauseam since you were a child. Eat your oranges, you need your Vitamin C! It’s been hailed as both a helpful aid to combat the common cold, and as a life-extending wonder drug that fights cancers, diseases and illness. Which is it? We examine the scientific literature and provide a summary of the many benefits of Vitamin C.

Vitamin C is an essential nutrient and potent water-soluble antioxidant made internally by almost all living organisms on the planet – except bats, guinea pigs, and some primates, including humans. The fact that we can’t produce Vitamin C by ourselves means we need it from dietary sources, or we’ll become susceptible to diseases such as scurvy. But Vitamin C has also been shown to provide a myriad of other health benefits besides merely being essential to our survival. Some of the health benefits of vitamin C in summary form are presented below:

  • The progression of atherosclerosis can benefit from the antioxidant power of vitamin C intake, from preventing endothelial dysfunction and altering lipid profiles and coagulation factors to preventing blood vessel changes that can lead to strokes and other vascular catastrophes.
  • Vitamin C supplements can help to reduce cellular DNA damage and also help reduce inflammatory changes that allow a malignant cell to grow into a dangerous tumor.
  • Vitamin C supplements enhance the health-promoting effects of exercise and reduce exercise-induced oxidative damage.
  • Vitamin C supplements also combat the oxidative damage caused by smoking and exposure to tobacco smoke.
  • Vitamin C supplementation in sufficiently high doses has been shown to reduce the severity and duration of common colds and may mitigate the risk of serious respiratory conditions like asthma.
  • Vitamin C supplements can speed the clearance of the stomach disease-causing bacterium Helicobacter pylori and cut the risk of gastric cancer it causes.

If you want more detail about the specific studies and research that’s been done on this wonderous vitamin, we have more detail (lots more!) below.

Protection Against Colds and Flus

The first thing many people think of when vitamin C comes to mind is colds and flus. The long-standing adage is that an orange a day will help keep the cold and flu away. But how much of this is really true?

The research suggests that it is indeed mostly true, but it depends on certain factors. The biggest factor is the size of the dose. Researchers have found that smaller doses of vitamin C, up to about 500mg – the size of one typical vitamin C vitamin supplement tablet – have had negligible to small effects on test groups in reducing cold and flu severity and duration. But, ramp up the dose, and the science suggests that you really do see some significant benefits to taking vitamin C.

One study, The effectiveness of vitamin C in preventing and relieving the symptoms of virus-induced respiratory infections, published in 1999, administered a so-called ‘megadose’ of daily vitamin C to a test group, about 6000mg daily, while those in the test group were given a variety of standard pain relievers and decongestants, but no vitamin C supplementation.

The results were impressive indeed – at the study’s conclusion, the researchers reported that flu and cold symptoms in the test group decreased 85% compared with the control group after the administration of the ‘megadose’ of vitamin C. 85%? That’s a fantastic number when you think about it. That means almost all of the symptoms of a cold/flu were diminished after the high doses of vitamin C were taken. This is great news for those who want to avoid medication when getting sick. It seems all you need to do is pop about 8-10 vitamin C pills a day, and your cold will be annihilated by the sheer brilliance of that underrated little vitamin.

Another study, this one published by the Cochrane Review, suggested that vitamin C intake has a protective effect against colds and flus, particularly for those under heavy physical stress, showing that in five randomized trials of participants who were all under some form of physical stress, vitamin C intake reduced the incidence of the common cold by a whopping 50%. The study also showed that the vitamin is beneficial in smaller, more manageable doses. It suggested that regular doses of vitamin C of one gram per day or higher reduce the average duration of colds in adults by 8% and in children by 18%.

Oxidative DNA Damage

Vitamin C has been shown in a large number of studies to reduce DNA damage caused by factors such as exposure to environmental carcinogens. Now, this is a big one, because DNA damage is bad. Very bad. It can ultimately lead to genetic mutations and genomic instability, potentially resulting in the development of various cancers such as colon, breast, prostate cancer, and many others. It can also lead to undesirable conditions such as atherosclerosis, a condition in which the artery walls thicken due to an accumulation of fatty deposits. It goes without saying, then, that anything that can reduce the severity of this oxidative DNA damage should be looked at carefully.

Vitamin C has long been proven to show significant antioxidant action through a number of in vitro experiments (those conducted on isolated cells or organs), which may not provide a complete indication of the effect of the vitamin on the body as a whole, but at the very least demonstrates that it does have a measurable and noticeable effect on the oxidation process.

One particular area that Vitamin C has been studied extensively is in oxidative DNA damage caused by N-Nitroso compounds. These are a class of carcinogenic compounds that occur widely in the environment and can be formed endogenously from the interaction of ingested nitrate or nitrite with secondary amines. One particular form of N-Nitroso compound is N-Nitrosamines, a potent food-derived genotoxin that has been associated strongly with cancer development. N-Nitrosamines are so potent that they have been proven to be carcinogenic to a wide variety of animals, as the table below indicates. They are commonly found in foods such as cured meats, fried bacon, dried fish, and pickled vegetables, among others.

A number of in-vitro studies have indicated that vitamin C in the bloodstream reduces N-Nitrosamine induced oxidative DNA damage by up to 94% in certain cells, at a level of 10µM, which roughly corresponds to vitamin C intake of about 100mg daily – an amount easy to achieve just through eating 3-5 fruits and vegetables per day. About 90% of
vitamin C in the average diet comes from fruit and vegetables. In addition, the studies showed that vitamin C was able to reduce DNA strand breaks (33%) and oxidative DNA damage in purines (12%) and in pyrimidines (35%) induced by H2O2. Among the possible mechanisms involved in the anticarcinogenic effects of vitamin C are the inhibition of CYP450 activities, the enhancement of detoxification pathways that convert the reactive compounds to less toxic and more easily excreted products, alteration of cell proliferation, stimulation of the repair of carcinogeninduced DNA damage and free radical scavenging efficiency.

Keep in mind however that as many of these studies were performed in-vitro, it might not be as simple as popping a few vitamin C pills each day to achieve the anticarinogenic effects outlined above. It could be vitamin C working in tandem with several other important nutrients or compounds obtained in fruits and vegetables, and indeed several investigations have demonstrated that vitamin C and other chemopreventive compounds added in combination are more protective and provide more benefits that when added singly.

Cancer

Thanks to its potent antioxidant effects, the benefits of Vitamin C extend to a reduction in risk in contracting certain types of cancers. We’ll briefly mention some of the more important studies that have shown a correlation between vitamin C intake and cancer benefits. A study conducted in Canada in 2011 on published in BMC Cancer in 2011 suggested that vitamin C intake in post-menopausal women reduced the risk of breast cancer by up to 21%, and that antioxidant intake in general (from any sources) for a period of 10 years or longer had a 54% reduced likelihood of contracting breast cancer.

Another very extensive study, published in the online journal Gut followed 23,000 men and women between the ages of 40 to 74 over an 18 year period. Each one of the 23,000 participants kept a food diary, detailing the food they ate each day, how much they ate, and even the preparation methods used. Researchers analyzed each of the food diaries and calculated an approximate ‘nutrient value’ score for each participant’s food intake.

By the end of the study, 86 of the participants had unfortunately developed pancreatic cancer, which has the lowest survival rate of any cancer. It’s particularly nasty because it’s often difficult to diagnose and is very difficult to remove even once found.

The researchers concluded that of the participants, those who had the highest levels of vitamin C, E and selenium consumption had a reduced risk of developing pancreatic cancer by 67%. In the closing notes of the study, the authors suggested that a 67% reduced risk roughly corresponds to an 8% prevention rate of pancreatic cancer.

If this isn’t enough evidence for you to show that vitamin C can at least potentially play a beneficial role in preventing cancer, then we have more scientific studies to show you.

One of the largest studies ever conducted on cancer was the European Prospective Investigation into Cancer and Nutrition (known as EPIC). It began in 1992 and involved 521,483 individuals across 10 European nations. A recent update on the study, published in the journal Carcinogenesis in November 2006, stated ‘The results of this study show, in a prospective setting, an inverse association of GC (gastric cancer) risk with high levels of plasma vitamin C and suggest an interaction with the intake of red and processed meats, whose consumption may elevate endogenous N-nitroso compound production.’

So the study essentially suggested that high levels of vitamin C intake combined with a reduced consumption of red and processed meats can lead to a significant risk reduction for developing gastric cancer. Good news indeed for the status of our favorite vitamin – tick another off on the list of vitamin C benefits.

Atherosclerosis

Vitamin C has also been implicated in lowering risk factor for atherosclerosis, a nasty condition in which the artery walls thickens as a result of the accumulation of fatty materials such as cholesterol and triglyceride. Atherosclerosis can lead to an increased chance of a heart attack or stroke, and the biggest contributing factor to developing it is the oxidation of lipids in LDLs (Low-density lipoprotein, otherwise known as bad cholesterol) that become trapped in the extracellular matrix of the subendothelial space. Researchers from Oregon State University conducted a study on vitamin C intake and the toxins that result from fat metabolism, and how vitamin C could react with and neutralize the toxic byproducts of human fat metabolism.

Fred Stevens, an assistant professor from the university, said of the study: “This is a previously unrecognized function for vitamin C. We knew of vitamin C as an antioxidant that can help neutralize free radicals. But this new discovery indicates it has a complex protective role against toxic compounds formed from oxidized lipids, preventing the genetic damage or inflammation they can cause. Prior to this study, we never knew what indicators to look for that would demonstrate the protective role of vitamin C against oxidized lipids. Now that we see them, it becomes very clear how vitamin C can provide a protective role against these oxidized lipids and the toxins derived from them. And this isn’t just test tube chemistry, this is the way our bodies work.”

So while the study is careful to avoid claiming outright that vitamin C can reduce atherosclerosis risk, the signs are indeed positive that the vitamin may have a beneficial role in protecting against damaging lipid oxidation.

Another study related to the benefits of vitamin C and atherosclerosis was conducted in 2003 by a group of scientists at the University of Kuopio, Finland, and the results were published in the journal Circulation. The study was conducted on a group of 520 participants who were divided into two groups, one group given daily supplementation of vitamins E and C and the other group on regular, non-supplemented diets. The results over the 3-year study suggested that the combination of vitamin E and slow-release vitamin C slowed down atherosclerotic progression.

Human Reproduction

Believe it or not, researchers have also suggested that vitamin C plays a very important role in the female reproductive system as well. Vitamin C has been strongly correlated with fertility through its essential role in hormone secretion, gamete production and gonadal tissue remodeling. Vitamin C is known to be essential for collagen synthesis in the body, as well as hormone secretion, gamete production and gonadal tissue remodeling.

In human reproduction, collagen synthesis is important for follicular development (the phase in which follicles in the ovary mature), luteum development and the remodeling of the ovulated follicle. In vitro studies on culture systems supplemented with vitamin C (ascorbic acid) showed an increased number of intact follicles, implying an increased potential of
basal lamina expansion during development. While we are getting into the very technical side of things now, just know that the basal lamina is an important part of the ovary which helps regulate cell proliferation, influences cell metabolism and survival, and organizes proteins in the adjacent plasma membrane.

Vitamin C may also provide a benefit to the human reproductive system through its strong antioxidant properties. There is substantial scientific literature (referenced below) to suggest that oxidative stress plays a negative role in the female reproductive process, and that the body has elevated requirements for antioxidants during gestational development. Deficiencies in antioxidants during pregnancy, as well as a placental oxidant-antioxidant imbalance have been shown to adversely affect fetoplacental unit development. Vitamin C intake can therefore play a key role in protecting fetal tissues from abnormalities.

How Much Do I Need?

This handy table provides the recommended daily amounts of Vitamin C, as per the US Office of Dietary Supplements.

Note that these are the minimum recommended amounts to prevent seeing adverse effects from a Vitamin C deficiency. In order to get many of the health benefits as described in the above sections, you’ll need to significantly increase your dosage from these amounts.

Life Stage Recommended Amount
Birth to 6 months
40 mg
Infants 7-12 months
50 mg
Children 1–3 years
15 mg
Children 4-8 years
25 mg
Children 9-13 years
45 mg
Teens 14-18 years (male)
75 mg
Teens 14-18 years (female)
65 mg
Adults (male)
90 mg
Adults (female)
75 mg
Pregnant Teens
80 mg
Pregnant Women
85 mg
Breastfeeding Teenagers
115 mg
Breastfeeding Women
120 mg

By this stage, you are hopefully convinced that vitamin C benefits the human body in a multitude of ways, filling an essential role as a cofactor in enzymatic reactions in the body and providing a strong dose of antioxidant goodness. There’s still more fascinating research out there on vitamin C’s health benefits – I will put up another article in the next few weeks detailing some even more profound studies on the effects of vitamin C on human health and wellbeing.


photo credit: Denise Cross Photography via photopin cc

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