Vitamin C is one of the most studied vitamins, and one of the best known. You may think of it as the vitamin in oranges and grapefruits, and it is true that citrus fruits are great sources. Still, there are plenty of other foods high in vitamin C, and you might even get some benefits from taking supplements. In fact, vitamin C is one of the most common supplements that people take to boost health and immunity. This vitamin has a history dating back nearly 400 years, and its range of benefits is impressive.
The first hints of the existence of vitamin C were noticed in 1747. As an article in the “Annals of Nutrition and Metabolism” explains, sailors in the British navy had for years suffered from scurvy when they went on long voyages without seeing land. In a simple experiment, James Lind tried certain treatments for 12 sailors with scurvy. The only treatment that worked was eating lemons and limes. Since then, British navy sailors took limes on their voyages, and earned the nickname of “limeys.”
It took another few hundred years for vitamin C to be isolated from food. There were some other clues along the way, such as the presence of scurvy during the Irish potato famine. Eventually, within the range of 1928 to 1933, Albert Szent-Györgyi, Charles Glen King, and Norman Haworth isolated vitamin C and described vitamin C’s chemical structure.
So what does vitamin C do for the body, and what are the foods highest in vitamin C? What are the best vitamin C supplements, and how much vitamin C can you absorb? Here is the information you should know about vitamin C.
What is Vitamin C?
Vitamin C is a water-soluble vitamin that is essential in your diet. That means you need it for survival, and your body does not produce it on its own. Vitamin C is also called ascorbic acid. It is the most powerful antioxidant in your body’s plasma and tissues.
Types of Vitamin C
Vitamin C is available in food and in supplements. The form you get in both is often the same; it is L-ascorbic acid. Some supplements come in the form of ascorbic acid mineral salts such as calcium ascorbate and sodium ascorbate. These are not as absorbable as L-ascorbic acid, but they can be less harsh on your gastrointestinal tract. Some supplements have bioflavonoids and vitamin C, and the vitamin C in these supplements may not be as well absorbed. Finally, vitamin C is available as a topical cream to improve skin health.
What are the Benefits of Vitamin C?
Vitamin C has many roles in the body to keep you healthy. These are some of them.
It is an antioxidant vitamin
One of the most well-known roles of vitamin C is that it has antioxidant functions. This mean it fights oxidation in the body. Oxidative processes can be the result of chemical reactions with compounds called free radicals that your body can produce during regular metabolism or that can enter your body because of exposure to toxins. A major function of vitamin C is to fight free radicals.
This may sound a little abstract, but here is the punch line. Many common diseases are linked to oxidation. Less oxidation in your body can mean less risk of disease, and vitamin C may help protect you from many conditions. Vitamin C may lower your risk of developing cataracts, for example.
It can also lower your risk for heart disease because of its role in preventing oxidation of lipids, or fat-like molecules. In particular, the effects of vitamin C may include reducing the amount of cholesterol oxidation that occurs in your blood stream. Less oxidation of cholesterol means less likelihood of plaque building up in your arteries. Vitamin C may lower cholesterol levels by altering bile production and metabolism, too.
Vitamin C boost immunity and fights inflammation
Your immune system is responsible for keeping you safe from invaders. Vitamin C’s antioxidant actions strengthen your immune system in a few ways. First, it boosts production of certain types white blood cells, which are the ones that fight pathogens and other potentially dangerous substances that may get into your body. Vitamin C can raise your levels of certain types of white blood cells such as neutrophils, lymphocytes, and phagocytes, and it may increase levels of antibodies, which are designed to target specific pathogens to prevent infections.
The antioxidant effects of vitamin C are important in immunity, too. Vitamin C in white blood cells can protect them from free radicals, as well as from harmful substances that these white blood cells actually produce themselves, so that the white blood cells can continue to do their job of keeping you healthy. Vitamin C in white blood cells helps the antioxidant vitamin E regenerate so vitamin E is more powerful, too.
Vitamin C can improve heart health
Beyond its effects of possibly preventing atherosclerosis, or plaque building up in your arteries, vitamin C has other benefits for your cardiovascular system. People who have strokes appear more likely to be deficient in vitamin C than healthy individuals, which shows that vitamin C may have a protective effect in lowering your risk for stroke. Also, taking vitamin C may help lower high blood pressure or keep normal blood pressure in check. Vitamin C lowers inflammation, which may be another key in preventing heart disease and other chronic diseases such as type 2 diabetes and gout.
Vitamin C supports healthier skin
Vitamin C is a nutrient that is present in your skin. It is in both the epidermis, which is the top layer of your skin, and the dermis, which is the layer just under the epidermis. Having enough vitamin C can help protect against wrinkles and other signs of aging.
Vitamin C plays some important roles in maintaining healthy skin. One function of vitamin C in your skin is to act as an antioxidant. In this way, vitamin C helps prevent your skin from photodamage, or harm to your skin caused by exposure to ultraviolet (UV) radiation from the sun.
Another of the important effects of Vitamin C in your skin is to allow the production of collagen, which is a type of tissue that holds your skin together. Vitamin C supplementation may even promote faster collagen production, which can result in better skin elasticity, or firmer and younger looking skin.
Vitamin C supports stronger bones
Vitamin C may not be one of the main minerals in bone the way calcium is, and it may not improve calcium absorption the way vitamin D does, but it can be just as important in keeping your bones from breaking.
About two-thirds of your bone structure consists of the hard mineral structure that you probably think of when you think of bones. The other third is a soft matrix that includes collagen, and that is where vitamin C comes in. You need vitamin C to allow for sufficient collagen production to support the hard mineral structure of bones. Lower vitamin C status is linked to lower bone density, which can put you at risk for osteoporosis and bone fractures.
Vitamin C makes you smarter
Well, maybe vitamin C does not actually make you stronger, but you definitely need this vitamin if you want to keep your brain in tip-top shape. One role of vitamin C in brain health is that you need it to produce GABA, which is a neurotransmitter that sends nerve signals from your brain to another part of your body, such as a muscle.
Another role is as an antioxidant, since vitamin C can protect against oxidative changes that can increase your risk of dementia. Finally, vitamin C can help prevent the build-up of heavy metals, such as lead and cadmium, which can be toxic to your brain.
Which are the Foods High in Vitamin C?
Fruits and vegetables are the foods highest in vitamin C. Peppers are the best sources of vitamin C. You can go for the heat, or go for sweet red, yellow, orange, and green bell peppers if you prefer. Each pepper has over 100 milligrams of vitamin C.
Leafy green vegetables, such as kale, spinach, and collards, are naturally rich. Other vegetables with a lot of vitamin C include tomatoes, cabbage, Brussels sprouts, broccoli, onions, and zucchini. And, while potatoes may get a bad rap sometimes, each medium potato actually has 17 milligrams of vitamin C.
Many fruits are also good sources. Citrus fruits are most famous for their vitamin C, and you can rest easy with choices such as oranges, tangerines, and grapefruits. Fruit juice works, too – start your day with a glass of orange juice, and you’ll get well over 100 percent of the daily value.
Berries are another group of foods rich in vitamin C. Strawberries, raspberries, blueberries, and blackberries help you get closer to your intake goals. Kiwis, mangoes, papayas, and other tropical fruits are rich sources. Even apples and pears have some vitamin C.
You can easily up your intake of vitamin C-rich foods with some of these tricks:
- Add strawberries or other berries to your oatmeal, cold cereal, or yogurt or cottage cheese.
- Toss in some tomatoes and onions when you scramble your morning eggs.
- Snack on bell pepper strips, sugar snap peas, and broccoli florets with your favorite dip.
- Grab an orange on your way out the door in the morning.
- Sneak spinach into soups and sauces.
- Pile on the tomato sauce when you have pasta, and add some cauliflower or broccoli to the sauce.
- Add tomatoes and bell pepper to sandwiches and wraps.
- Swap mashed potatoes for a baked potato with broccoli and Greek yogurt.
- Toss mandarin orange segments and sliced raspberries into salads.
- Top desserts such as ice cream, chocolate cake, or cheesecake with berries or kiwi slices.
- Order a side salad instead of a side of rice or pasta when you go out to eat.
Because vitamin C is mostly found in very healthy foods, eating a vitamin C-rich diet is a good indicator that your own diet is probably pretty healthy. In fact, some nutritionists look at vitamin C consumption from natural sources of vitamin C as a quick way to evaluate your diet. A good intake of fruits and vegetables high in vitamin C means that you are getting plenty of nutrients such as dietary fiber, vitamin C, potassium, and all kinds of phytonutrients, or plant nutrients, with a variety of benefits.
Eating more fruits and vegetables high in vitamin C is linked to multiple health benefits. You are less likely to get certain types of cancer, cataracts, heart disease, and Alzheimer’s disease with this kind of diet pattern. You are also more likely to be in better control of your weight.
Most animals are unable to produce vitamin C, which is why most of the foods rich in vitamin c are fruits and vegetables. Still, another of the foods highest in vitamin C is oysters. According to the USDA National Nutrient Database, each 3.5-ounce serving of these shellfish provides 16 milligrams of vitamin C, or 27% of the daily value.
There is another natural source of vitamin C that may be surprising. The grain known as amaranth provides 2 milligrams, or 4 percent of the daily value in each cup of cooked grain, and sprouted wheat is also a source of vitamin C. Amaranth and sprouted wheat are whole grains with additional beneficial nutrients such as dietary fiber and potassium.
How Much Vitamin C Do You Need?
The recommended dietary allowance or recommended daily intake for vitamin C is 90 milligrams a day for men, and 75 milligrams a day for women. These values assume you do not smoke. If you are a smoker, your needs are about 35 milligrams a day higher, or 125 milligrams for men and 110 milligrams for women.
The RDA of vitamin C is set based on the amount of vitamin C you need to keep the concentration in your neutrophils (a type of white blood cell) high without excreting too much vitamin C in your urine. While this amount is sufficient to prevent any deficiency symptoms, a higher daily intake level is almost certainly necessary to get the greatest decrease in chronic disease risk.
The daily value for vitamin C is set at 60 milligrams per day. This is the basis for the percentages that you will see on nutrition labels of food packages. The value of 60 milligrams is based on the previous RDA, which was 60 milligrams a day before being raised to its current values.
Who is at Risk of Vitamin C Deficiency?
Among the groups at greatest risk of vitamin C deficiency are people who smoke. Smoking leads to more free radicals and the potential for more oxidation in your body because of the toxins in cigarette smoke. Because of the greater number of free radicals, your body uses vitamin C more quickly if you are a smoker, so you need more of it.
Individuals who are malnourished are at risk for vitamin C deficiency. This can happen if you do not eat a sufficient, balanced diet, which can occur if you are on a restrictive diet or you have undergone weight loss surgery or another procedure that limits the types and amounts of foods you can eat.
People who do not eat enough fruits and vegetables are also at risk for deficiency. This is rare in the United States among healthy adults, but it can occur occasionally in children and older adults. In developing countries, vitamin C deficiency can occur in poorer populations who eat a grain-based diet and have limited access to fresh fruits and vegetables throughout the year.
People taking certain medications need to up their intake of vitamin C compared to the standard recommendations. Birth control pills with estrogen, for example, can lower your levels of vitamin C. If you take aspirin regularly, which is commonly prescribed to reduce stroke and heart attack risk, your body may excrete more vitamin C, leaving you with a greater need.
Signs of Vitamin C Deficiency
Scurvy is the most severe form of vitamin C deficiency. Symptoms are the result of lack of collagen production. You might notice bleeding gums, easy bruising, bleeding under your skin, anemia or fatigue and weakness, and joint pain. Scurvy is almost unheard of in the United States since you can prevent it with only 10 milligrams a day of vitamin C, which is about the amount in half a tomato.
Why Use Vitamin C Supplements?
The most obvious reason to use vitamin C supplements is to prevent deficiency if you are worried that you are low in vitamin C. Because vitamin C is water-soluble, your body does not store extra. Instead, you eliminate it via your urine. That means that taking vitamin C supplements tends to be relatively safe for most individuals, although it is always a good idea to ask your doctor before taking any supplement.
Vitamin C supplements can also help restore your vitamin C levels if you are already depleted. For example, a study in the “Journal of the American College of Nutrition” looked at individuals who were in a rehabilitation program for alcohol abuse problems. Researchers provided participants with vitamin C among other supplements. The participants who were deficient in vitamin C at the beginning of the study had significant improvements in their vitamin C levels after 21 days of supplementation.
One of the most common reasons to use vitamin C supplements has to do with the common cold. People use vitamin C supplements to prevent colds, reduce the severity of the symptoms of a cold, or get over their colds faster. The idea comes from the role of vitamin C in immune system functioning. Linus Pauling was a proponent of high dose vitamin C to mitigate colds. So far, it appears that vitamin C supplementation may help you get over your cold 8 to 14 percent faster than without supplements, according to the Linus Pauling Institute.
It does not seem to prevent colds for most people, but you might want to consider a vitamin C supplement if you are an endurance athlete such as a long-distance runner. People who take vitamin C after extensive exercise are less likely to catch a cold. Be warned, though, that vitamin C does not seem to have effects once you already have symptoms.
Using vitamin C supplements can also be beneficial if you have low iron stores. Vitamin C helps your body absorb iron from plant-based foods and from supplements. This type of iron is known as non-heme iron, and absorption is lower than absorption of the heme iron that you get from animal based foods such as meat and shellfish. To increase iron absorption, you can take vitamin C at the same time as you take an iron supplement or when you eat a meal with non-heme iron sources, such as spinach, beans, and potatoes. Vitamin C also helps improve zinc absorption.
Some athletes look to vitamin C as part of their regimen to improve muscle recovery. The idea comes from observations that intense exercise causes mild damage to muscles. There is not yet concrete evidence that vitamin C protects muscle against normal damage related to exercise or speeds recovery after a workout, but you might want to keep vitamin C in your routine to be sure you are fighting free radicals as best you can.
Cancer results from abnormalities in cells that can occur for many reasons, including oxidative damage due to the activity of free radicals. Given its role as an antioxidant and knowing that cancer is linked to oxidation, it is no surprise that researchers have, for decades, looked to vitamin C as a way to fight cancer.
The National Cancer Institute explains that vitamin C is a promising tool in the fight against cancer. In vitro – that is, in the laboratory test tube rather than in people – vitamin C reduces cell proliferation or stops the growth of cancerous cells in the case of cells that produce cancer in the prostate, skin, colon, pancreas, and liver.
The benefits may translate to in vivo – or in people – situations. High doses of vitamin C during cancer treatment have shown promise in clinical trials. Some patients receiving high dose vitamin C, including intravenous vitamin C, during cancer treatment have fewer side effects and better tolerance to treatment.
Still, vitamin C is not a guaranteed cure for cancer. One research study published in the British Journal of Cancer looked at links between vitamin C and survival among women who were diagnosed with breast cancer. The study involved 3,405 women and it followed them over the course of 23 years. The women who had higher dietary intakes of vitamin C from natural sources were more likely to survive over the course of the study. However, there was no effect of vitamin C from supplements.
Topical vitamin C for your skin can be a good idea if you believe your collagen is weakening and you are already getting plenty of foods rich in vitamin C. The reason is that once you already top off your levels in your bloodstream, the levels in your skin no longer increase. That means vitamin C pills will not help your skin. Topical creams can provide the extra vitamin C that you are looking for in your skin.
Vitamin C can be a very promising supplement for a variety of benefits. Because of the mixed research and everyone’s individual situation, it is best to ask your doctor what form of vitamin C to take and how much you should have.
Who Shouldn’t Take Vitamin C Supplements?
Most healthy individuals can safely take vitamin C supplements as long as you talk to your doctor first, but some groups should be a little more cautious. As always, pregnant and breastfeeding women need to think twice before taking any supplement. The other groups who need to be wary of vitamin C supplements include people on various medications or who take certain herbs that interact with vitamin C.
Vitamin C can lower blood pressure, so you should be especially careful if you are on blood pressure lowering medications or if you have trouble with low blood pressure. Vitamin C also interacts with blood thinners, such as Coumadin or warfarin and aspirin. If you have diabetes and take insulin or other medications that affect blood sugar, vitamin C can change your blood sugar levels.
How Much is Too Much Vitamin C?
Vitamin C is relatively safe at doses that are somewhat higher than the RDA, but too much vitamin C can be harmful. The tolerable upper level of intake, or UL, is the amount you can safely consume each day without experiencing health problems. For adults, this amount is 2,000 mg per day, or more than 20 times the RDA. More than this may be toxic, although some studies find that even amounts up to 10 grams of vitamin C per day, or 10,000 mg, are safe. Ingesting this extremely large amount of vitamin C puts you under the risk of kidney complications, so it is generally not advised.
Vitamin C Toxicity Symptoms/Side Effects
Vitamin C appears to be one of the safest nutrients you can take. There have not been any proven toxic effects of too much vitamin C when taken at regular doses. Some people have reported birth defects, atherosclerosis, and vitamin B12 deficiency as a result of too much vitamin C, but these seem to be isolated incidents and not the norm.
Some of the other possible side effects of vitamin C can include dehydration, heartburn, diarrhea, and dizziness. You should know that when you stop taking high doses of vitamin C, your levels will drop below normal even if you continue taking normal amounts of the vitamin. Some of the most common side effects are gastrointestinal. You might have diarrhea, an upset stomach, and cramping of your stomach.
Vitamin C toxicity may occur if you take supplemental vitamin C over the UL for a long period of time. Since vitamin C is broken down into oxalate during the digestive process, some people suspect it can increase your risk of developing calcium oxalate kidney stones. Still, the evidence is not clear, and vitamin C may not cause kidney stones.
Vitamin C is an antioxidant vitamin that has many benefits and a good safety profile. Lots of nutrient rich fruits and vegetables have vitamin C, but some experts think even higher amounts may be better. Ask your doctor about taking vitamin C and choosing the best supplement for your needs.
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- Glutathione and Immunity
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Article reviewed by:
Absolvent of the Comenius University in Bratislava, Slovakia, Faculty of Pharmacy. Zuzana holds a PhD. in Pharmacognosy and Botany, during the course of which she worked on two projects studying medicinal plants, their active constituents and their effects on the human body. A trained pharmacist with 3 years experience and a first author of three publications, she is currently working on continuing her study of medicinal plants at University of Vienna, Austria.
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