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lVitamin C is a nutrient humans cannot live without. Although ascorbic acid can be readily obtained from fresh fruits and vegetables, the levels necessary to optimize health and vitality may not be achievable in food alone. Recognizing this, millions of people worldwide regularly supplement their daily intake of this essential vitamin with nutritional supplements, functional foods and beverages enhanced with vitamin C. However, many vitamin C advocates do not fully comprehend the many benefits of year-round supplementation with this essential nutrient and how it can protect their whole body.

Vitamin C has been making news ever since Nobel Prize winning scientist Linus Pauling extolled its virtues in fighting the common cold.

Since then, this essential nutrient has demonstrated remarkable benefits in strengthening the immune system, maintaining healthy joints and supporting vision, cognitive and cardiovascular functions.

Vitamin C is a powerful water-soluble antioxidant that neutralizes health damaging and disease inducing free radicals that result from everyday activities and are exaggerated by stress, disease, sunlight and pollution.

Mechanism of Action

Vitamin C readily undergoes reversible oxidation and reduction and functions as a buffer against cell damage from health zapping free radicals.[1,2,3] As a specific electric donor, vitamin C also appears to participate in the synthesis of brain neurotransmitters, pituitary peptide hormones and the hormones that help the body respond to stress. It also enhances the antioxidant activity of vitamin E, a fat-soluble free radical scavenger. Vitamin C regulates iron distribution and storage through its regulation of the ratio of ferratin to hemosiderin. It helps convert tryptophane to 5-hydroxytryptophan (5HTP). It also possesses anti-histamine activity and may help reduce some inflammatory reactions. Finally, vitamin C can help rid the body of heavy metal toxins, including mercury, lead, cadmium and nickel.

Scurvy is the classic disease associated with vitamin C acid deficiency. Symptoms include fatigue, anaemia and bleeding into the skin, muscles and joints. Secondary infections and loosening of teeth, cerebral haemorrhage, high fever, convulsions and death can occur in the late stages of this disease.

Cardiovascular Protective Effects

Optimum supplementation with vitamin C and other essential nutrients may provide a basic therapeutic means for the prevention and successful management of cardiovascular dysfunctions. Smoking, stress, unhealthy diets, birth control pills, hormone replacement therapy and certain chemicals will increase free radical formation and increase the body's requirement for vitamin C. Nevertheless, the most well recognized cardiovascular utility of vitamin C lies in its ability to function as a potent water-soluble antioxidant.[4]

Facts

• Heart disease is the leading killer of American men and women;
• Since 1984, the number of cardiovascular deaths for females has exceeded those of males;
• 52% of the American population has cholesterol levels over 200;
• One out of every four Americans has high blood pressure that can be controlled by diet.[5]

Mechanism of Action

Vitamin C plays an important role in the prevention of cardiovascular diseases. Although not confirmed in vivo, in-vitro studies suggest that vitamin C not only inhibits oxidation of low-density lipoprotein (LDL) particles, but also regenerates alpha-tocopheroyl[6,7] and improves endothelial cell function. An insufficient intake of vitamin C over time may eventually lead to the decreased stability and elasticity of the vessel walls as well as increased infiltration and deposition of cholesterol, white blood cells and fibrin within the vessel wall. As small lesions develop on the new surfaces of arteries and cholesterol and other repair factors accumulate on the walls, this 'plaque' can detach and travel through the blood stream to block a major blood vessel in the heart or brain resulting in a heart attack or stroke.

Research

In a study of 26 men and 8 women between 28 and 76 years of age with congestive heart failure, it was found that vitamin C improved vessel function by inhibiting endothelial cell death.[8] Vitamin C may enhance endothelial function that inhibits artery clogging and lowers blood pressure.[9] In a study conducted at UCLA, it was reported that men that took 800mg of vitamin C daily had a 41% reduction in mortality from cardiovascular disease compared to men who only took 60mg of vitamin C daily. The study also reported that men consuming the larger amounts lived an average of 6 years longer than the men who consumed 60mg.[10]

The June issue of Stroke featured a study in which scientists measured vitamin C blood levels of middle aged men with no history of disease and then monitored them for 10 years. The men with the lowest plasma vitamin C levels showed an increased risk of stroke, especially among hypertensive and overweight men.[11] An analysis of First National Health and Nutrition Epidemiologic Follow-up Study by Nhanes (1971-1992) data showed that high dietary and supplementary vitamin C was protective against cardiovascular disease.[12]

A paper from the Harvard School of Public Health and the Harvard School of Medicine provides very strong evidence supporting the role of vitamin C in reducing the risk of coronary heart disease. A 16-year follow up of more than 85,000 female nurses found a 27% reduction in the risk of CHD with a total vitamin C intake equal to or more than 360mg per day as compared to less than 93mg per day. The reduction of risk seemed stronger among women using at least 400mg of supplemental vitamin C daily.[13]

Researcher Gladys Block, Professor of Health Nutrition at the University of California, Berkeley, demonstrated in a group of healthy men that those with the lowest vitamin C blood levels had diastolic blood pressure – the pressure exerted in blood vessel walls when the heart rests between beats – higher than those who had the greatest intake of vitamin C.[14]

Based on a pilot study using carotid ultrasound testing, Dr. Paul Ward showed that high vitamin C supplement users had 'remarkably' healthy carotid arteries. In fact, when adjusted for other factors such as age, elevated homocysteine, LDL cholesterol and glucose, the high vitamin C users appeared to have less carotid pathology than the general population.[15]

It has been suggested in observational studies[16,17] that the best approach may be a multi-nutrient supplement plus vitamin A, C or E.[18,19] However among high-risk individuals studied in the UK,researchers concluded that antioxidant vitamins did not produce any significant reduction in the 5-year mortality from, or incidence of any type of vascular disease.[20] This study did not involve healthy people.

Vitamin C and Vision

There is substantial scientific evidence that generous intake of vitamin C and other antioxidants may help reduce oxidative damage to the eye, thereby preventing or slowing the progression of eye disease. Vitamin C is a small water-soluble molecule that can penetrate the layers of the lens to readily deliver its antioxidant properties to this relatively isolated organ. It also appears that the active accumulation of vitamin C in the lens and aqueous humour is striking – vitamin C concentrations are 20 times higher than those found in plasma.

Facts

• Age-related macular degeneration (AMD) is the leading cause of blindness in people older than 65 in the United States and Europe;[21]
• Cataracts are the leading cause of decreased vision in Americans older than 65 and the leading cause of blindness in the world;[22]
• Diabetic retinopathy affects more than 5.4 million American adults;[23]
• Open-angle glaucoma, the most common form, affects about 3 million Americans.[24]

Mechanism of Action

According to the National Centre for Health Statistics about 20-30% of adults 70 years or older have some sort of visual impairment. Without proper nutrition, eye health can deteriorate, leading to AMD, cataracts and even glaucoma. People with diabetes must pay special attention to maintaining eye health to avoid diabetic retinopathy.

Research

The normal healthy eye contains a higher level of vitamin C than any other organ of the body except the adrenal glands.[25] Studies have shown a decreased level of vitamin C in the aqueous humour as well as the overall body when cataracts are forming.[26] Vitamin C also has been shown to control sugar imbalances that often play a roll in cataract formation. Most studies have found consistent associations between higher dietary or plasma vitamin C and a reduced risk of cataracts. Researchers have also found that as little as 300mg of vitamin C daily can protect against cataracts by preventing photo oxidation of the lens and absorbing UV light.[27] Several studies have shown that large doses of vitamin C can significantly reduce inter-ocular pressure by increasing blood osmolality, reducing aqueous production, improving aqueous flow and supporting collagen.[28]

It appears however, that long-term supplementation is important to influence the concentration of vitamin C in the lens. For example, in the Nurses' Health Study, women who took vitamin C supplements for ten years or longer had a significantly reduced risk of cataracts, while there was minimal benefit with less than 10 years of use.[29] There appears to be 60% lower risk among people using multi-vitamins containing C or E for more than 10 years.[30]

One observational study found that those with the highest levels of the antioxidant selenium, vitamin C and vitamin E had a 70% lower risk of developing macular degeneration than those with the lowest levels of these nutrients.[31] Another study, the Age-Related Eye Disease Study (AREDS), sponsored by the National Eye Institute showed that those at high risk of developing advanced stages of AMD reduced their risk by 25% when treated with a combination of vitamin C, vitamin E, beta-carotene and Zinc.[32]

In the Roche European American Cataract Trial (REACT), a supplement containing beta-carotene and vitamins C and E slowed the progression of cataracts.[33] Since free radical damage is implicated in the development of diabetic retinopathy, the use of antioxidants has been investigated. A mixture of selenium, vitamin E, vitamin A and vitamin C were given for several years to 20 people with diabetic retinopathy. During that time, 19 of the 20 showed either improvement or no progression of the disease.[34]

Because free radical damage, due to smoking and sunlight is a risk factor for AMD, antioxidants have been extensively investigated as nutrients important in preventing or slowing down its progression. Smoking increases free radical formation, decreases levels of vitamin C and impedes blood flow to the eye and thus increases the risk of vision loss from macular degeneration and cataracts.[35]

Vitamin C and Collagen

The importance of vitamin C on structure and function of bone and connective tissue has been known for centuries. Without dietary vitamin C, the human animal cannot properly synthesize collagen. Without collagen, connective tissue is weak and bone mineralization is defective.

Facts

• 45 million Americans suffer the daily aches and pains caused by joint inflammation and/or brittle bones;[36]
• Osteoarthritis affects 43 million Americans;[37]
• Rheumatoid Arthritis attacks 2 million Americans, with 75% of sufferers women;[38]
• 55% of the US population aged 50 years or older has low bone mass and faces an increased risk of developing osteoporosis and related fractures.[39]

Mechanism of Action

Vitamin C is known to stimulate procollagen, enhance collagen synthesis and stimulate bone cell formation. Evidence is growing that the synthesis, maintenance and repair of connective tissue and bone are not optimized with ordinary intake of essential vitamins and minerals, especially in the elderly. Diseases of connective tissue and the skeleton, such as arthritis and osteoarthritis are rampant among the elderly whose nutritional status is compromised by poor diet, lowered nutrient absorption and altered metabolism. In addition, there may be an increasing requirement for precursor molecules that the younger body is capable of manufacturing in sufficient supply whereas the older body cannot in the face of stress and aging.

Research

Evidence from a large study revealed that OA sufferers with the highest intake of vitamin C had a reduced risk of cartilage loss and disease progression. Although high intake of vitamin C did not reduce the incidence of osteoarthritis, there was a three-fold reduction in the risk of progression of the disease in those with arthritis of the knees.[40] Another study found that RA patients consistently showed low levels of vitamin C in their white blood cells.[41] It was shown in a multi-centre double-blind, placebo-controlled trial of 133 OA patients that a non-acidic form of vitamin C significantly reduced pain compared to a placebo.[42] A pilot study by UK researchers showed that only 8% of patients with complex regional pain syndrome (CRPS), a poorly understood condition that causes crippling pain, developed swelling compared to 22% who did not take the supplements.[43] A rat model study noted that inflammatory arthritis resulted in a decrease in vitamin C levels,[44] suggesting that the vitamin C has been spent in the process of reducing inflammation or neutralizing free radicals.

There are many reports that vitamin C levels are closely related to bone mineral density (BMD).[45,46,47] Long term use of vitamin C supplements was associated with higher BMD among women who had never used oestrogen in any postmenopausal years[48] as well as currently using concurrent oestrogen therapy and calcium supplements.[49]

Vitamin C may be an essential co-factor in maintaining periodontal health.[50] In a poll conducted by the American Academy of Periodontology's website (www.perio.org) three out of four periodontists recommend that their patients increase their intake of vitamin C to promote healthy gums. A vitamin C deficiency increases the permeability of the oral mucosa to endotoxins.[51] In fact, people who get too little vitamin C suffer a slightly higher incidence of gum disease. Vitamin C enhances the mobility of infection fighting white blood cells and a deficiency is associated with a host of immune responses.[52] Studies have shown that animals placed on a diet deficient in vitamin C exhibit severe adverse changes in oral tissue.[53-57]

Vitamin C appears to keep periodontal tissues healthy in smokers by maintaining and repairing connective tissue. However, higher doses of vitamin C do not appear to minimize periodontal damage associated with cigarette smoking. Chewing on ordinary vitamin C tablets, however can erode dental enamel and irritate sensitive gum tissues.

Vitamin C and The Skin

Vitamin C is the most abundant antioxidant found naturally in the skin. It is important in neutralizing free radicals and may help prevent certain forms of cancer and accelerated aging. Vitamin C is depleted when the skin is exposed to sun, pollution or smoking. Even minimal UV exposure can decrease vitamin C levels in the skin by 30%, while exposure to the ozone layers of city pollution can decrease levels by 55%.

Age-related free radical damage not only depletes the body's natural antioxidant defences, but also leads to degeneration of the skin's blood circulation, which is responsible for removing waste products and replenishes nutrients that maintain the flexibility and resilience of the connective tissues. Declining levels of vitamin C in the skin make the tissue susceptible to free radical damage and slow down the repair and synthesis of collagen.

Facts

• 40-50% of Americans who live to age 65 will have skin cancer at least once;[58]
• One million cases of curable basil and squamous cell cancers occur annually;[59]
• 7,400 Americans die each year from melanoma.

Mechanism of Action

Vitamin C helps reduce the effects that free radicals formed from UVB and UVA rays, pollutants and smoke have on the skin and its supporting structures. Vitamin C inhibits the activity of enzymes that destroy the capillary wall, thus helping maintain dermal blood supply. It also supports the production and regeneration of collagen to help maintain skin tone and texture.

Research

Swedish researchers found that antioxidants such as vitamin C when applied to the skin have a protective effect in treating allergic reactions that involve the production of free radicals.[60] A French study conducted at the University Hospital of Saint-Jacques, Beschon, France, documented that vitamin C cream can reverse the signs of photo-aging through the production of new collagen.[61]

Vitamin C and Immunity

Although many nutrients are necessary for a healthy immune system, vitamin C is probably the most common one associated with maintaining healthy immune function. It was Dr. Linus Paulings' book, Vitamin C and the Common Cold, that first created awareness of vitamin C's immune strengthening properties.[62] According to researchers at the University of Colorado at Boulder, older adults may be able to combat oxidative stress in their tissues by loading up with vitamin C.[63] There is also evidence that vitamin C helps reduce oxidative stress in passive smokers.[64]

Facts

• SARS, AIDS, West Nile Virus and some 200 cold and flu viruses threaten our existence;[65]
• Stress and its negative effects on the body has surpassed the cold virus as the most common problem in North America;[66]
• Electromagnetic radiation from cellular phones, power lines, hair dryers, electric blankets and a depleted ozone layer affect immune function.[67]

Mechanism of Action

Health is dependant on a strong, functioning immune system, which in turn rests on the balance in the body between free radicals and antioxidants. As an antioxidant, vitamin C neutralizes the free radicals formed as white blood cells destroy pathogens and is thus important in suppressing symptoms of secondary infection. Vitamin C has been shown to increase the activity of specific white blood cells that ingest and destroy bacteria, yeast and certain cancerous cells. It can increase activation, proliferation or cytotoxicy of natural killer (NK) cells that help control viral and bacterial infections as the spread of cancerous growth (metastasis).[68] Vitamin C helps maintain the healthy mucus membranes lining of the respiratory and intestinal tracts.[69]

Research

The recognition of vitamin C as a cold and flu-fighting nutrient has been controversial since Pauling's work almost 30 years ago. In the early 90s, a retrospective analysis was published that seemed to give credence to Paulings' earlier work.[70] A recent survey conducted by Zila Nutraceuticals in Ohio last winter showed that "74% of the residents reported no symptoms commonly associated with colds" while on a twice daily course of 500mg of Ester-C calcium ascorbate (a patented form of vitamin C). A previous survey in the UK demonstrated that Ester-C reduced the incidence of colds and shortened the duration of its symptoms.[71] Other work has shown the positive effects of vitamins C and E in affecting immune response.[72] Vitamin C's repairing effect on vitamin E may potentiate its activity.[73]

Because of vitamin C's ability to support the body's immune system and its free radical fighting properties, there have been many investigations into its use in preventing cancer. There is indeed much data to support the important role of specific antioxidants in reducing the risk of certain forms of cancer and are with further investigations.[74-82]

There is no cure for AIDS, but advances in drug therapy as well as a better understanding of the role that nutrition plays in supporting a damaged immune system have made it a treatable disease. Vitamin C is a critical nutrient for people with HIBV and AIDS. It helps suppress replication of the HIV virus and appears to protect the brain from toxicity that occurs in the late stages of the disease. There is evidence that vitamin C deficiency may contribution to aids-related dementia.[83,84]

Conclusion

Given the typical level of stress today combined with the typical diet, vitamin C supplementation is absolutely essential for optimum health and vitality. Fortunately, more consumers are becoming aware of the important role that vitamins play in maintaining health and preventing disease. Vitamin C is one of the most important vitamins required by the body – it is essential for a plethora of physiological functions that maintain life. The current RDI is 75mg for women, 90mg for men with an additional 35mg recommended for smokers. These levels are assumed to provide cellular saturation to reduce the risk of heart disease, stoke, joint dysfunction, visual and cognitive impairments and cancer in healthy individuals. Stress, smoking, disease, sunlight and environmental pollutants deplete the body of ascorbic acid and increase its need in the diet.

There is well-documented peer-reviewed research that demonstrates vitamin C's many heath benefits, including properties as an antioxidant, anti-atherogenic, anti-carcinogenic, immunomodulator nutrient as well as its role in preventing the symptoms of colds and flu. It is a very safe vitamin, especially in a non-acidic form. In fact, in-vivo data clearly shows that excess ascorbic acid does not induce kidney stone formation, excess iron absorption or pro-oxidation. As more human in-vivo studies are completed, its role in not just supporting health, but promoting vitality will be better appreciated.

Further Information

For information about vitamin C products, call the Nutri Centre on Tel: 020-7436 5122 (supplement orders & information centre); Tel: 020-7323 2382 (book orders & library services); or visit Nutri Centre on-line at www.nutricentre.com

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