Vitamin C benefits your health in a variety of ways. Of course, its role in reducing the duration and severity of flu is most well-known. But your body needs and uses vitamin C for many other functions besides giving your immunity a boost. You need vitamin C for collagen synthesis, tissue repair, proper absorption of iron, wound healing and maintaining the health of your bones, teeth and eyes.
Vitamin C is also a powerful anti-oxidant, that makes it beneficial in conditions caused by oxidative stress and inflammation. Now, a new study published in BMC Cardiovascular Disorders showed that these anti-oxidant properties may also be responsible for reducing the risk of atrial fibrillation (irregular heart beat) in patients after cardiac surgery. This is a relevant finding as the development of atrial fibrillation after cardiac procedures is linked with serious complications such as increased risk of stroke, longer stays in the intensive care unit and hospital and other poor outcomes such as heart attack, heart failure and even death.
The benefits of vitamin C for heart health has already been widely explored (and we are going to discuss these benefits and underlying mechanisms in a while). But first, let’s understand what is atrial fibrillation and why vitamin C may be helpful in preventing this condition in high risk patients.
Vitamin C lowers atrial fibrillation risk after heart surgery
Your heart has 4 chambers; two upper chambers (right and left atria) and two lower chambers (right and left ventricles). These chambers work in co-ordination with each other to pump oxygenated blood to the body. Let’s see how it works:
- The right atrium receives de-oxygenated blood from the body and pumps it to the right ventricle.
- The right ventricle pumps this oxygen-poor blood to the lungs, where lungs supplies oxygen to the blood.
- The left atrium receives oxygen-rich blood from the lungs and pumps it to the left ventricle.
- The left ventricle pumps the oxygen-rich blood to the body through aorta.
- Once the body has used all the oxygen from the circulating blood, it is pumped back into the right atrium of the heart. And the cycle goes on.
In a healthy state, your heart beats to a regular rhythm. But in atrial fibrillation (AF), the upper chambers beat out of tune with the lower chambers of the heart, leading to fast, irregular beats. This condition can cause blood clots, stroke, heart failure and other heart-related complications. The symptoms often include heart palpitations, shortness of breath and general fatigue.
What triggers AF?
The risk of atrial fibrillation typically increases with age but many stressful conditions such as high blood pressure, diabetes, previous heart condition, smoking and obesity are all risk factors for AF. In addition, it is also commonly observed after cardiac surgery procedures.
What did the study find?
The goal of this systematic review was to analyse the role of vitamin C in preventing atrial fibrillation (AF) in patients considered high risk for developing AF, for example, those undergoing cardiac surgery. The study concluded that “vitamin C may prevent post-operative atrial fibrillation in some countries outside of the USA, and it may also shorten the duration of hospital stay and ICU stay of cardiac surgery patients.” 
How vitamin C may help in cardiac surgeries?
Studies show that oxidative stress and inflammation may be important mechanisms in the development of post-operative atrial fibrillation. . As a powerful anti-oxidant that can scavenge free radicals and lower inflammation, vitamin C sounds a great possibility. And that’s what the above-mentioned study found.
In addition, cardiac surgery is associated with acute ischemic and reperfusion injury, which happens when blood supply is restored to the heart tissue (reperfusion) after a period of lack of oxygen (ischemia). While early restoration of blood flow is required to prevent any further damage to the tissue, unfortunately this process also triggers free radical release – causing oxidative stress and inflammation. Now, this adds another dimension to the role of vitamin C in protecting cardiac surgery patients from oxidative stress and the resulting onset of post-operative AF.
Another 2017 meta-analysis also indicates that vitamin C treatment shows significant decrease in postoperative AF . However, the review noticed no association with the length of ICU stay or the length of hospital stay after cardiac surgery.
The findings of this 2015 study also chimed with these results. The study concluded that “Vitamin C can decrease the length of hospital stay, drainage volume in the ICU and in the first 24 postoperative hours, intubation time and some complications in patients after cardiac surgery; perhaps by decreasing inflammatory factors.” 
In fact, there is good evidence that vitamin C is overall good for heart health, mostly because of its ability to work as a potent antioxidant and its ability to improve endothelial functions. Let’s have a closer look.
Vitamin C works as an antioxidant:
Free radicals cause oxidation of LDL cholesterol in the arteries. Studies show that it is this oxidized cholesterol that is the main culprit in the process of plaque formation. Oxidized LDL particles stimulate the immune system to start a vicious cycle of inflammatory reactions that eventually lead to the build-up of plaque in the arteries. Vitamin C, as an antioxidant, can inhibit the oxidation of LDL cholesterol and consequently reduces the risk of atherosclerosis, heart attack and stroke.
Vitamin C improves endothelial functions:
Collagen is the most abundant protein present in all your connective tissues such as bones, skin, ligament, nerves, organs and your blood vessels. Collagen lends strength, support and elasticity to these tissues. Vitamin C works as an essential co-factor in the synthesis of collagen, keeping blood vessels and the endothelium (inner lining of blood vessels) strong and healthy. You need a well-functioning, resilient endothelium to prevent oxidized LDL cholesterol and other toxins to infiltrate and hold onto the vessel wall, where they can promote inflammation and plaque build-up. Vitamin C increases the availability of nitric oxide (NO) in the blood vessels.  When it comes to your endothelial and cardiovascular health, NO plays a very important role. Most importantly, it relaxes blood vessels, increasing blood and oxygen flow through the arteries. This helps to reduce blood pressure.
Vitamin C improves type 2 diabetes symptoms
Elevated blood sugar levels in type 2 diabetes damage both small and large blood vessels, causing extraordinary damage to the entire vascular system. That is why diabetic patients are at a high risk of developing complications of the heart, eyes and kidneys. Cardiovascular disease, peripheral arterial disease (blocked blood vessels in the legs due to plaque deposits) and nerve damage are the main causes of death and disability in people with diabetes. How does vitamin C help? It lowers blood glucose and lipids levels in patients with type 2 diabetes, reducing the risk of associated complications. 
- Prevents oxidation of LDL cholesterol, a key step in the formation of plaque in the arteries.
- Makes nitric oxide more available in the arteries, which improves endothelial functions and relaxes blood vessels. All of this helps in regulating blood pressure, a major risk factor in heart disease.
- Facilitates collagen synthesis, a process that makes arteries healthier and stronger, thus less prone to oxidative damage and resulting plaque formation
- Harri Hemilä, Timo Suonsyrjä. Vitamin C for preventing atrial fibrillation in high risk patients: a systematic review and meta-analysis. BMC Cardiovascular Disorders. 2017.
- AS Tahhan et al. Association between oxidative stress and atrial fibrillation. Heart Rhythm. 2017.
- X Hu et al. Efficacy and safety of vitamin C for atrial fibrillation after cardiac surgery: A meta-analysis with trial sequential analysis of randomized controlled trials. International Journal of Surgery. 2017.
- Sadeghpour et al. Impact of Vitamin C Supplementation on Post-Cardiac Surgery ICU and Hospital Length of Stay. Anesth Pain Med. 2015.
- Mortensen et al. Does vitamin C enhance nitric oxide bioavailability in a tetrahydrobiopterin-dependent manner? In vitro, in vivo and clinical studies. Nitic Oxide. 2014.
- Ardekani et al. Effect of vitamin C on blood glucose, serum lipids & serum insulin in type 2 diabetes patients. The Indian Journal & Medical Research. 2007