The richest man, the greatest bowler or the highest scoring student is popular and remembered while the second-highest or the second-best (Despite losing it by seconds or few points) is neither remember nor applauded by most. We do this with nutrients such as vitamins too remembering only those that have the maximum nutrient ignoring the rest. So, what’s your first thought on the mention of the word Vitamin C? Its none other than oranges which have monopolized vitamin C for centuries together being depicted as the trademark source for this vitamin despite the fact that kiwis and bell peppers are also enriched with this nutrient. Vitamins are organic compounds that must be acquired from the diet we eat due to two main reasons-one, because the organism doesn’t have the enzyme necessary to synthesize it or two, because it cannot produce them in sufficient quantities. Our body is a magic land that’s been fully equipped to fight against health calamities with its inbuilt nutrient stores and inflowing nutrient additions that happen. Surprisingly, humans cannot synthesize vitamins such as A, B1, B2, B5, B6, B7, B9, B12, E and K but can readily produce B3 and D. Vitamin C is quite contrasting in this regard that while it can be synthesized by most of the vertebrates and invertebrates humans are unable to do it on their own. It’s quite intriguing given that we belonged to a species that once were producing vitamin C on their own. Evolution not only changed the synthesis of vitamin C from the kidney to the liver once in bids and once in mammals it also brought about a strong genetic evolution where mammals such as gorilla, apes and our very own humans lost the magical power to produce vitamin C internally!
Vitamin C Synthesis
The biosynthetic pathway includes multiple steps and in each one a substrate is converted into a product in a reaction catalysed by an enzyme. Different animals, birds and amphibians go through all these steps successfully which enables them to produce vitamin C successfully but humans cannot perform the last step of Vitamin C biosynthesis-conversion of l-gulono-g-lactone into ascorbic acid catalysed by enzyme gulonolactone oxidase. While the gene that codes for the enzyme is present in humans it is not active due to multiple mutations that’s nullified its presence. If one looks at the chain of species that’s lost this ability it includes humans, gorillas, chimps, orangutans and some monkeys indicating that the genetic flaw could have happened initially in one of our primate ancestors. Evolution is the process where the survival of the fittest happens and if so, species with vitamin C synthesis ability should have survived through but the opposite has happened.
Vitamin C regulates a key stress-induced transcription factor H1F1α, a protein, which when activated oversees the expression of hundreds of stress-related genes. Insufficient vitamin C levels trigger activation of H1F1 α. When regulation of vitamin C levels is in our hands, we can foresee H1F1α activation. The protein becomes active in the presence of a deficiency and less active when vitamin C levels meet requisite criteria. Hence, we can modulate the protein expression by getting to know about our nutrition status and performing the required action thereon.
Discovery of Vitamin C
The death of millions of sailors to scurvy (occurring as a result of acute vitamin C deficiency) shed light on this vitamin and this is an often-retold story. Though James Lind, in his first controlled clinical trial showed that scurvy (he called it as lassitude) could be treated with citrus fruits the remedy was not taken seriously until after several decades. You can even quote scurvy as the hallmark disease of vitamin C characterized by symptoms resulting from loss of collagen that weakens connective tissues which include hair loss, swelling/bleeding gums leading to teeth loss, spotting in the skin seen as a result of bleeding and bruising from broken blood vessels and delayed healing of skin-related wounds. The prevalence of the disease is extremely rare now and has almost disappeared from developed countries. Still, it can occur in individuals having access to limited food varieties.
Vitamin C is a water-soluble vitamin known primary for its role in supporting a healthy immune system and has been touted as a great antioxidant due to which it has been widely proposed and promoted as a means to cure/treat various health conditions.
Cancer: Epidemiologic evidence suggests that vitamin C intake lowers the risk of certain types of cancers but there are other studies that don’t prove so. Most of the clinical trials show that modest supplementation of vitamin C alone or in combination with other nutrients aren’t a safety belt against cancer. Vitamin C has the ability to limit the formation of carcinogens such as nitrosamines, optimize immune responses and prevent oxidative damage thereby safeguarding the body against cancer. It has been observed that plasma concentration of vitamin C is lower in those with cancer compared to others.
There have been studies on cancer patients to see whether administering this vitamin could prolong their life or improve their quality of life. Here too studies showed conflicting evidences but other emerging studies suggest that the route (oral or intravenous) of vitamin C administration could bring about changes. Intravenous administration produces better results compared to oral administration but further research is needed to check whether supplementing the body with vitamin C might interfere with chemotherapy and radiation.
Cardiovascular Disease: Oxidative damage is a primary contributor of cardiovascular disease and intake of aplenty fruits and vegetables rich in antioxidants has the property to reduce the risk of cancer. Vitamin C is a good antioxidant that helps to reduce monocyte adherence to the endothelium, improve endothelium-dependent nitric oxide production and vasodilation and reduce vascular smooth-muscle-cell apoptosis, which helps to prevent plaque accumulation that can lead to atherosclerosis. Here again, studies that dwell on the effect of vitamin C intake on cardiovascular disease show conflicting results and results from most clinical trials too don’t have promising results.
Age-related Macular Degeneration (AMD) and cataracts: These are two of the common problems that can result in vision loss in ageing adults. Vitamin C is seen as the solider in shining armour against both of these conditions as their underlying cause is none other than oxidative stress. There are studies supporting and denying the effect of high levels of vitamin C in protecting individuals against these conditions. But we do have the landmark age-relate eye disease study (AREDS) which showed that people at high risk for the disease who consumed 500mg/day of vitamin C alongside beta-carotene, vitamin E and zinc helped cut down the progression of advanced AMD by 25% and visual acuity loss by 19%. What is sure is that vitamin C intake does not pave way for occurrence of AMD but it might as well slow progression of the disease in people at a high risk of developing advanced AMD.
Common Cold: We come to the most popular theory behind vitamin C intake-using it as a means to prevent common cold or as a treatment option for those suffering from it. Neighbours and family members often advice those suffering from inadmissible episodes of cold frequently to consume plenty of oranges-a fruit that actually aggravates cold. Oranges are said to provide protection against the disease reducing the chances of occurrence when we eat them beforehand as they improve the immune system-and cold is a manifestation of a compromised immune system. A meta-analyses of 29 placebo-controlled trials which administered 200 mg or more of vitamin C doses orally showed the following results: prophylactic use of vitamin C supplementation had no effect on the incidence of common cold on the general population but had a modest effect in reducing the duration by 8% in adults and 13% in kids besides optimizing severity of symptoms. This has been the most promising evidence till date as common cold causes 23 million lost days of work annually and even a slight improvement could lead to better results. But trials including marathon runners, skiers and soldiers who undergo severe practise and are exposed to extreme cold environments showed that prophylactic use of vitamin C (between 250 mg/day to 1 g/day) reduced occurrence of cold by 50%. Treating common cold with vitamin C is ineffective. Studies do show that megadoses (above 500 mg) of vitamin C don’t have any effect on common cold but might be able to decrease the severity and duration of the problem.
If you want to reap the benefits of vitamin C against common cold it should become a part of everyday your lifestyle-consuming fruits and vegetables rich in this nutrient-and not some kind of a tablet that you take at the start of the symptoms. Though we do have studies showing that massive supplementation of vitamin C can help prevent common cold it is not feasible in real life-as the doses prescribed are 8000 mg/day and at doses above 400 mg/day vitamin C is excreted via urine and doses above 2000 mg/day bring on symptoms such as nausea, diarrhoea, abdominal pain and disrupt blood test results too. Though the research and contradictions on using vitamin C as an effective aid against common cold has been going on for more than 70 years manufacturing companies and certain people in the health industry have taken advantage of this claim in selling out their supplements and products.
What to Eat?
As we know oranges are an excellent source of vitamin C and there are other fruits and vegetables that are richly packed with this nutrient. This includes strawberry, broccoli, cantaloupe, Brussels sprouts, kiwis, red and green bell peppers, tomatoes, potatoes, lemon and grapefruit. While vitamin C is not naturally present in grains it is added to some fortified breakfast cereals.
It is normally advisable to eat fresh fruits and vegetables in their raw form for maximized benefits and there is no exception with citrus fruits as well. Vitamin C can be destroyed by heating and cooking. Hence, it is advisable to avoid cooking them at high temperatures for a prolonged time. As this is a water-soluble vitamin there are greater chances for it to become dissolved with the cooking liquid and get lost forever when we don’t consume the dish along with the liquid. It is advisable to use quick heating methods or even use minimal water (stir-frying or blanching) to preserve the nutrients in the food. But, for ultimate benefits it is recommended to consume them in raw form choosing those that are fully ripe (for more benefits) and thankfully most of the produce rich in vitamin C taste great in raw form. Vitamin C intake improves the absorption of non-heme iron, the type of iron found in plant foods such as beans and quinoa, and consuming vitamin C-rich foods in combination with iron-rich foods in the same meal can be a double bonanza, for vegetarians especially whose only source of iron are plant-based foods.
Vitamin supplements are also widely prescribed and taken in the form of ascorbic acid, sodium ascorbate, calcium ascorbate and other mineral ascorbates.
Recommended Doses of the Vitamin
The 2001-2002 National Health and Nutrition Examination Survey (NHANES) the recommended mean intake levels for individuals include 105.2 mg/day for adult males and 83.6 mg/day for females. For children and adolescents between 1 and 18 years of age the recommendations are between 75.6 mg/day and 100 mg/day. In case of newborn babies, breastmilk contains sufficient vitamin C levels needed by the child. When observed, you will notice that the recommended levels of vitamin C has increased from 10mg/day to almost 100 mg/day over the years.
Though its recommended to eat at least five servings each of fruits and vegetables not many fulfil this requirement and despite the availability of vitamin C in various produces not many consume them too. Almost 35% of adults take multivitamin supplements and12% take exclusive vitamin C supplements. Even 29% of kids take some form of dietary supplement that contains vitamin C.
The upper limit recommendations include 2000 mg daily beyond which the person might suffer from side effects such as diarrhoea, nausea, abdominal cramps, increased formation of kidney stones in those with kidney disease or history of kidney stones, increased levels of uric acid and increased absorption of iron which doesn’t affect normal individuals. But in those suffering from hemochromatosis it could case tissue damage.
Though supplements and foods are absorbed equally it is always better to consume recommended levels in the form of natural fruits and vegetables as these foods contain essential vitamins and minerals alongside vitamin C that have a positive influence on health.
The Mystery of Vitamin C: https://www.nature.com/scitable/topicpage/the-mystery-of-vitamin-c-14167861/
Vitamin C: https://www.aoa.org/patients-and-public/caring-for-your-vision/diet-and-nutrition/vitamin-c
Can Vitamin C Prevent a Cold? https://www.aoa.org/patients-and-public/caring-for-your-vision/diet-and-nutrition/vitamin-c
Vitamin C Physiology: the Known and the Unknown and Goldilocks: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4959991/
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