Vitamin C is one of the most well-known vitamins people think of when they think of immune support. But how does vitamin C help the immune system?


Why don’t we hear about scurvy anymore?

Before vitamin C was discovered, scurvy was a common disease that occurred in malnourished individuals. In the 1700’s it was much more challenging to get your hands on a variety of fruits and vegetables, and were especially scarce onboard ships.

Scottish surgeon, James Lind, gave his sailors lemon juice to see if it would improve their ailments. By 1795, Lind had nearly eliminated scurvy in the naval fleet. However, it wasn’t until over a hundred years later, in 1928, that Hungarian chemist Albert Szent-Gyorgi isolated vitamin C.


How does vitamin C support the immune system?

Vitamin C is considered an essential vitamin, which means that your body can’t produce it on its own, and therefore you need to get it from either food or supplements. Like the B-complex vitamins, vitamin C is water-soluble. The body doesn’t store water-soluble vitamins very well, which is why you must replenish your body with vitamin C every day.

One of the reasons vitamin C is so closely linked to the immune system is its role as a potent antioxidant. It helps both the innate and adaptive immune systems by protecting the body against oxidative stress.1 The innate immune system exists within the body from birth, and once activated against a specific type of antigen the immunity remains throughout the life. Adaptive immunity, on the other hand, is created in response to a foreign substance and can be lifelong or short.2


Which foods contain vitamin C?

As mentioned before, because vitamin C is an essential vitamin, it must be obtained through your diet either with foods or supplements. Although there are many delicious fruits and vegetables that are excellent sources of vitamin C in their raw form, you’d have to eat a lot to get the same benefits from a supplement. Fruits that contain vitamin C are oranges, grapefruits, kiwi, or strawberries, and vegetables rich in this vitamin are red bell peppers, broccoli, brussel sprouts, and cauliflower. However, you’d have to eat a lot of these fruits and vegetables to get the same therapeutic benefits that you would get from a vitamin C supplement.

Fruit Amount of vitamin C in mg
Red bell pepper (½ cup) 95 mg
Orange (1 medium-sized) 70 mg
Kiwi (1 medium-sized) 64 mg
Broccoli (½ cup) 50 mg
Strawberries (½ cup) 49 mg
Brussel sprouts (½ cup) 48 mg



What exactly is the difference between Ester-C® and regular vitamin C?

There are so many different forms of vitamin C out there that it can be overwhelming. At Sisu, we proudly use Ester-C® in many of our vitamin C products, but what exactly is the difference between Ester-C® and ascorbic acid, or regular vitamin C?

Put simply, Ester-C® is a patented version of vitamin C that is less-acidic and better-absorbed. Vitamin C is acidic and can cause stomach irritation for some people, so Ester-C® was created in response to this issue.

Studies also show that Ester-C® stays in the body in white blood cells for up to 24-hours, or up to two times longer than regular vitamin C.3

Some of our Ester-C® products include Sisu Ester-C® Chewable, Sisu Ester-C® Energy Boost™, and Sisu Ester-C® Supreme.


Can you have too much vitamin C?

According to the Council for Responsible Nutrition, vitamin C has low toxicity, and too much is not believed to cause any serious adverse effects. However, over 1000 mg per day may cause diarrhea, stomach pain, or flatulence related to unabsorbed vitamin C in the lower intestine.4


Vitamin C supplements

It’s important to give your body the best; that’s why Sisu offers a wide range of premium vitamin C supplements to support your individual needs.

Here are a few of our favourites:

Sisu Ester-C® 1000 mg: This high-potency vitamin C helps to maintain immune function. It is enhanced with citrus bioflavonoids, as well as acerola cherry extract and citrus fruit blend.

Sisu Kids’ Cold and Flu Rescue: In a delicious wildberry-flavoured chewable that your child will love, this supplement with echinacea helps fight off infections, especially of the upper respiratory tract. Also available for adults.

Sisu Ester-C® Energy Boost™: Immune-support has never tasted better with this easy-to-mix, flavoured drink mix. Each serving contains 1000 mg of Ester-C® and B vitamins for energy metabolism and electrolytes for hydration.


Summing up

Vitamin C is an essential nutrient that the body cannot make on its own, and therefore it must be consumed either through diet or supplements. There are many fruits and vegetables that contain vitamin C, but the easiest way to ensure you’re getting enough is to include a vitamin C supplement, such as Ester-C®, in your daily routine.


For monthly health and wellness tips sent directly to your inbox, sign up for our newsletter here!


Always read and follow the product label. Products may not be suitable for everyone.