By Dr. Mercola
Vitamin C is a water-soluble vitamin, which means your body doesn't store it. Unlike most other mammals, humans do not have the ability to make vitamin C, which means you need to consume it via your diet.
Vitamin C has numerous functions in the human body, including acting as an essential cofactor in enzymatic reactions. In this way, it plays a role in your body's production of collagen, carnitine (which helps your body turn fat into energy), and catecholamines (hormones made by your adrenal glands), for starters.
Vitamin C is also used by your body for wound healing, repairing, and maintaining the health of your bones and teeth, and plays a role in helping your body absorb iron.1 However, it's vitamin C's role as an antioxidant that it is most well known for.
As a powerful antioxidant, vitamin C is known to block some of the damage caused by DNA-damaging free radicals. Over time, free radical damage may accelerate aging and contribute to the development of heart disease and other health conditions. It's through this antioxidant effect that it's thought vitamin C may play a role in protecting heart health – perhaps as much as exercise.
Vitamin C May Be as Helpful to Your Heart as Walking
A daily dose of vitamin C may have a similar effect as walking on a protein called endothelin-1, which promotes the constriction of small blood vessels. The study, which was presented at the American Physiological Society's 14th International Conference on Endothelin, involved 35 sedentary, overweight, or obese adults.2
Those who took a daily time-release dose of vitamin C (500 milligrams, mg) reduced endothelin-1-mediated vessel constriction as much as those who walked daily. Endothelin-1 activity is known to be higher in those who are overweight and obese.
This makes small blood vessels more prone to constricting, which increases the risk of heart disease. As noted by the Daily Mail:
"[T]he team concluded that vitamin C supplementation represents an effective lifestyle strategy to reduce ET-1 mediated vessel constriction in overweight and obese adults," particularly since many people do not engage in recommended levels of daily physical activity.3
Vitamin C Is Well Known for Helping Your Blood Vessels to Relax
Vitamin C is a simple intervention that can have far-reaching effects for heart health, even beyond its affect on endothelin-1, in part because of its role in vasodilation. As explained by the Linus Pauling Institute:4
"The ability of blood vessels to relax or dilate (vasodilation) is compromised in individuals with atherosclerosis. Damage to the heart muscle caused by a heart attack and damage to the brain caused by a stroke are related, in part, to the inability of blood vessels to dilate enough to allow blood flow to the affected areas.
The pain of angina pectoris is also related to insufficient dilation of the coronary arteries. Impaired vasodilation has been identified as an independent risk factor for cardiovascular disease.
Many randomized, double-blind, and placebo-controlled studies have shown that treatment with vitamin C consistently results in improved vasodilation in individuals with coronary heart disease.
It also occurred in those with angina pectoris, congestive heart failure, diabetes, high cholesterol, and high blood pressure. Improved vasodilation has been demonstrated at an oral dose of 500 mg of vitamin C daily."
Even beyond vasodilation, a study published in the American Heart Journal revealed that each 20 micromole/liter (µmol/L) increase in plasma vitamin C was associated with a 9 percent reduction in heart failure mortality.5
According to Dr. Andrew Saul, editor of the Orthomolecular Medicine News Service, if everyone were to take 500 mg of vitamin C per day — the dose required to reach a healthy level of 80 µmol/L — an estimated 216,000 lives could be spared each year.
Vitamin C Is One Reason Why Vegetables Are So Good for Your Heart
Most people are aware that eating fresh vegetables and, to some extent, fruits, may benefit your heart health. However, researchers recently teased out one such benefit from the crowd, revealing that a primary reason why people who eat lots of fruits and vegetables have a lower risk of heart disease and early death is because of their high vitamin C levels.
A Danish study that followed more than 100,000 people found those with the highest intake of fruits and vegetables had a 15 percent lower risk of developing heart disease and a 20 percent lower risk of early death compared with those with the lowest intakes.6
The study also revealed that those with the highest plasma vitamin C levels had significantly reduced rates of heart disease and all-cause mortality. The researchers explained:7
"… [W]e can see that the reduced risk is related to high vitamin C concentrations in the blood from the fruit and vegetables… our data cannot exclude that a favorable effect of high intake of fruit and vegetables could in part be driven by high vitamin C concentrations."
Vitamin C May Lower Your Blood Pressure and Help Keep Arteries Flexible
Adding on to vitamin C's strong role in heart health, people who eat a diet rich in antioxidants like vitamin C may have a lower risk of high blood pressure.
Research published in the journal Hypertension revealed a "strong association between vitamin C concentrations, an indicator of fruit and vegetable consumption, and a lower level of blood pressure."8
Vitamin C is also known to slow down the progression of hardening of the arteries (atherosclerosis). It may help keep your arteries flexible and prevents damage to LDL cholesterol. People with low levels of vitamin C are at increased risk of heart attack, peripheral artery disease, and stroke, all of which can stem from atherosclerosis.9
Beyond Heart Health: Why Else Do You Need Vitamin C?
To only classify vitamin C as a nutrient for your heart would be doing your health a disservice. Vitamin C is considered an anti-aging vitamin and actually reversed age-related abnormalities in mice with a premature aging disorder, restoring healthy aging.10
Vitamin C even plays a role in brain health, as it is necessary to make certain neurotransmitters, including serotonin.11 It has also been found to play a role in preventing the common cold, cancer, osteoarthritis, age-related macular degeneration, asthma, and more. Vitamin C may also be useful for:12
Boosting immune system function Improving vision in people with uveitis (inflammation of the middle part of the eye) Allergy-related conditions, such as eczema and hay fever Treating sunburn Alleviating dry mouth Healing burns and wounds Decreasing blood sugar in diabetics Fighting viral illnesses, such as mononucleosis Maintaining healthy gums
In the video above, you can also hear from Dr. Ronald Hunninghake, an internationally recognized expert on vitamin C who has personally supervised more than 60,000 intravenous (IV) vitamin C administrations. Dr. Hunninghake explained:
"The way to really understand vitamin C is to go back to the writings of Irwin Stone who wrote The Healing Factor, which was a fantastic book written in the 70s about vitamin C. He points out that every creature, when they are sick, greatly increase their liver's or their kidney's production of vitamin C. But humans, primates, and guinea pigs have lost that ability.
We still have the gene that makes the L-gulonolactone oxidase enzyme that converts glucose to vitamin C but it's non-functional. We have to get our vitamin C from the outside: from food. When we give vitamin C intravenously, what we're doing is recreating your liver's ability to synthesize tremendous amounts of vitamin C… So I always look upon high dose vitamin C as nature's way of dealing with crisis in terms of your health."
IV vitamin C is used for a variety of illnesses, notably as an adjunct to cancer treatment and for chronic infections, such as cold, flu, or even chronic fatigue.
What Are the Best Food Sources of Vitamin C?
Many people associate citrus fruits with vitamin C – and they are a good source, but they're far from the only one. Many vegetables as well as non-citrus fruits also contain vitamin C, so you can usually get plenty from your diet as long as you're eating well. Particularly rich sources of vitamin C include:
Sweet peppers Chili peppers Brussels sprouts Broccoli Artichoke Sweet potato Tomato Cauliflower Kale Papaya Strawberries Oranges Kiwifruit Grapefruit Cantaloupe
You can also squeeze some fresh lemon or lime juice into a glass of water for a vitamin-C-rich beverage. And if you're concerned you're not eating enough fresh produce, consider juicing. For more information, please see my juicing page. Getting your vitamin C from food sources is ideal, as the vitamin C will work in synergy with other nutrients and compounds in the food. As reported by the George Mateljan Foundation:13
"Antioxidants in foods tend to work together in important and synergistic ways to provide protection against free radical damage. The most well-known of these connections is that between vitamin E and vitamin C. Specifically, vitamin C helps to protect vitamin E in people, such as smokers, who have chronic overproduction of free radicals. Similarly, we see the flavonoid class of plant-based antioxidants helping to make the free radical protection from vitamin C that much stronger.
This is great news, given that the foods that are most flavonoid-rich also tend to be among our better vitamin C sources. This synergistic protection is but one of many potential explanations for why the health benefits of plant-based diets cannot be replicated by nutrient supplements."
When taking an oral vitamin C, you also want to be mindful of your dosing frequency. Dr. Steve Hickey, who wrote the book Ascorbate, has shown that if you take vitamin C frequently throughout the day you can achieve much higher plasma levels. So even though your kidneys will tend to rapidly excrete the vitamin C, by taking it every hour or two you can maintain a much higher plasma level than if you just dose it once a day (unless you're taking an extended-release form of vitamin C).
Signs of Vitamin C Deficiency
In the US, serious vitamin C deficiency is rare, however many people do have low levels.14 If you're elderly, for instance, you may have higher requirements for vitamin C, as aging may inhibit absorption. Smokers may also require more vitamin C due to the increased oxidative stress from cigarette smoke. Signs that you may need more vitamin C include:15
Dry and splitting hair Gingivitis (inflammation of your gums) Bleeding gums Rough, dry or scaly skin Decreased wound-healing rate Easy bruising Nosebleeds Decreased ability to ward off infection
Generally speaking, if you're regularly eating multiple servings of vegetables and fruits daily, your vitamin C levels are probably OK. However, keep in mind that the fresher the vegetables, the more vitamin C they'll contain. According to George Mateljan foundation:16
"The same thing that makes vitamin C so important — its ability to protect against free radical damage — also makes it very prone to damage by heat, oxygen, and storage over time… The vitamin C content of food will start to decline as soon as it is picked, even though this decline can be slowed down and minimized by cooling and retention of the food in its whole form. But a fresh, vitamin C-rich vegetable like broccoli — if allowed to sit at room temperature for 6 days — can lose almost 80 percent of its vitamin C…
Long-term storage of vegetables can cost a significant amount of vitamin C. Kept frozen for a year, kale can lose half its vitamin C or more. Canning is even more detrimental, with 85 percent of the original vitamin C lost over the same year. While cooking will lower the amount of vitamin C in most foods… the amount of vitamin C lost will vary widely by cooking method. For example, basket-steaming broccoli for 15 minutes will reduce the vitamin C content by nearly one quarter."
So eat vegetables as often as you can, but try to make sure they're fresh and either raw or lightly cooked. As an alternative, you can also try making fermented vegetables at home. The vitamin C in sauerkraut(fermented cabbage) is about six times higher than in the same helping of unfermented cabbage approximately one week after fermentation begins, so it's an excellent way to boost your vitamin C intake.