Vitamin C is the go-to nutrient for keeping your immune system strong, but when you're taking supplements, you want to make sure you're actually getting what you need. That's why you may be wondering whether you need vitamin C injections or if oral supplements will do the trick.
While injections may be the better choice if you're extremely deficient in vitamin C or if you're trying to target a certain health condition, oral supplements are highly effective for most people. That being said, not all oral vitamin C supplements are created equally, so it's helpful to understand the difference between them. Of course, as with any new supplements, always talk to your health care provider before adding vitamin C to your routine.
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You absorb more vitamin C from injections, but they're not as convenient to take (or as easily accessible) as over-the-counter oral supplements. Since oral supplements are still highly absorbable (especially liposomal varieties), injections aren't necessary for most general health needs.
Oral or Injection?
Injectable supplements, like vitamin C, are often considered superior to oral versions because of how they're absorbed in the body. Injections bypass the digestive system and move right into the blood, while oral supplements have to make it past the stomach and into the small intestine before they can enter your bloodstream.
There are a lot of factors that alter how much of the vitamins and minerals you consume actually make it into your blood. The amount your intestines absorb, the way vitamins and minerals are transported through tissues and kidney re-absorption all play a role in determining how much vitamin C actually gets into your body. To answer the question of whether oral or injection is a better option, researchers compared the different administration routes. Here's what they found:
- A study from a January 2012 issue of Nutrition Journal reported that oxidative stress and subjective measurements of fatigue improved within two hours after participants were given vitamin C injections. What's interesting here is that the vitamin C levels in the blood were at a level previously reported to be 70 times more than the levels achieved by oral supplements.
- A systematic review, published in Nutrients in May 2019, investigated whether vitamin C could help improve health markers in those with cancer. Researchers looked at 19 studies and concluded that the mode of delivery appeared to be a deciding factor in the effectiveness of vitamin C. Most of the studies that showed positive results used intravenous vitamin C; the studies that didn't show any effect used oral supplements. The researchers also said this may suggest that the digestive system can't absorb all of the vitamin C from oral supplements.
- A review that was published in Oral Diseases in January 2016, indicated that bioavailability from intravenous vitamin C is 100 percent because the vitamin bypasses the digestive tract. However, researchers also concluded that bioavailability of oral supplements is very high (near 100 percent) when patients who are deficient in vitamin C are given small doses throughout the day, rather than one large dose all at once.
The Linus Pauling Institute broke this down a little further, explaining that 100 percent of the oral vitamin C you take is absorbed when you're taking up to 200 milligrams at a time. When oral doses go above 500 milligrams, less vitamin C is absorbed (and most of the excess is removed from your body when you urinate), although this isn't the case with injections. That's why blood levels go higher with intravenous vitamin C.
However, since the RDA for vitamin is 75 to 90 milligrams per day and your body can absorb up to 200 milligrams at a time from oral supplements, then taking oral vitamin C will still allow more than 200 percent of your daily requirement to be absorbed. For most people, this is plenty. Of course, if you have a vitamin C deficiency or an underlying health problem that could benefit from extra vitamin C, your doctor may recommend that you get an extra dosage through injections.
Read more: What Are the Benefits of Buffered Vitamin C?
Choosing an Oral Supplement
Now that you have a good grasp on how the method of delivery affects absorption rates of vitamin C, it's also a good idea to familiarize yourself with the different types of oral vitamin C supplements to make sure you're getting the most bang for your buck. The Linus Pauling Institute points out that vitamin C oral supplements in the form of liquid, tablets and chewable tablets are all equally, and well, absorbed. However, "timed-release capsules" are about 50 percent less effective.
Researchers from a June 2016 study in Nutrition and Metabolic Insights worked on finding a middle-ground between injections and oral supplements. Although the study was small, including only 11 adults, the researchers reported that liposomal vitamin C was more effective at raising blood levels of vitamin C than other types of oral vitamin C supplements, including unencapsulated doses.
A July 2019 report in the Journal of Liposome Research backed up these findings and added that lipsomes encapsulate the vitamin C and prevent it from breaking down in the digestive tract. They also slow down the vitamin's release and improve absorption.
So what's the bottom line? Although you can absorb more vitamin C from injections, they're really only necessary if you have an extreme vitamin C deficiency or you're working to correct an underlying health issue. Most people can get what they need from oral vitamin C supplements. To increase the amount of vitamin C you absorb from oral supplements, choose a liposomal variety and space out your intake throughout the day.
- Linus Pauling Institute at Oregon State University: "Vitamin C"
- Nutrition and Metabolic Insights: "Liposomal-Encapsulated Ascorbic Acid: Influence on Vitamin C Bioavailability and Capacity to Protect Against Ischemia–Reperfusion Injury"
- Oral Diseases: "Vitamin C: The Known and the Unknown and Goldilocks"
- Linus Pauling Institute at Oregon State University: "The Bioavailability of Different Forms of Vitamin C (Ascorbic Acid)"
- Journal of Liposome Research: "New Oral Liposomal Vitamin C Formulation: Properties and Bioavailability"
- Nutrition Journal: "Intravenous Vitamin C Administration Reduces Fatigue in Office Workers: A Double-Blind Randomized Controlled Trial"
- Nutrients: "The Effect of Vitamin C (Ascorbic Acid) in the Treatment of Patients With Cancer: A Systematic Review"