When It Comes To Vitamin C Absorption, Form & Function Matter
Supplements can feel kind of complicated. You have to decide not only which supplements to add to your wellness routine and which brand to buy from but also understand some of that "science-y stuff" so you can be sure the nutrient will be absorbed in your system to reap its intended benefits.
For some vitamins, that means taking the supplement with food or a fat; for others, it just means taking it at a certain time of day.
When it comes to vitamin C, knowing how the essential nutrient is absorbed and utilized can be the difference between closing the vitamin C insufficiency gap (which affects 42% of the U.S. adult population1, by the way) and all of that good vitamin C going down the drain (literally).
So, let's break down how one overlooked vitamin is absorbed by the body and what you can do to make sure your body makes the most of this immune-supporting, collagen-promoting antioxidant.*
How does the body use vitamin C?
First, a reminder about what vitamin C does. Even though vitamin C is colloquially synonymous with immune support, this vitamin does more than just help you feel your best.*
"Vitamin C is a water-soluble vitamin that also serves as an antioxidant. It supports several important functions within the body—including proper immune system function, tissue healing, collagen formation, maintenance of bones and cartilage, and optimal absorption of iron. Due to its antioxidant capacity, it also serves to combat oxidative stress within the body,"* says Alexander Michels, Ph.D., clinical research coordinator at the Linus Pauling Institute at Oregon State University.
RELATED: How Much Vitamin C Should I Take?
How is vitamin C absorbed?
"Vitamin C is absorbed in the small intestine, where there's a group of different proteins there that can take it up," explains Michels. That's easy enough—so what's all the fuss about vitamin C absorption, then?
Well, the vitamin C in foods (and many supplements) is a form called ascorbic acid. According to Michels, the potential challenge with absorption of ascorbic acid (at high doses) is that it's easily saturated—take a concentrated amount of vitamin C in this form at one time and you're unlikely to absorb the excess.
However, here's the important distinction: When the intestine is faced with lower levels of ascorbic acid (i.e., less than about 400 milligrams), an active transport system absorbs the vitamin C (i.e., moves the nutrient through the gut and into the bloodstream, to where it's needed in the body).
As soon as these active transports become overwhelmed, passive diffusion takes over to absorb the rest of the vitamin C (which is a fairly inefficient process). The truth is that absorption isn't as easy as it sounds, and the fact that ascorbic acid appears to have a ceiling for absorption, that can make it difficult to glean all the benefits of higher potency formulas (if they feature the ascorbic acid form).
Plus, vitamin C is water-soluble2, meaning it dissolves in water (as the name suggests), but this type of vitamin can't be stored in your body for later use.
You may be more familiar with the process of fat-soluble vitamins—including D, E, A, and K—which are absorbed and stored in tissue. Alternatively, excess water-soluble vitamins are discarded, leaving you to start fresh every day.
Your body can handle around 300 to 400 milligrams of the purely ascorbic acid form of vitamin C at a time according to Michels (which is a genuinely useful, lower dose found in foods, multivitamins, and other multi-ingredient complexes), but with higher doses, less is absorbed.
"This is more than enough capacity to absorb most of the vitamin C you get from food, but supplements can be a different story," he explains. Because of the saturation phenomenon, the rest of that valuable vitamin C from an ascorbic acid supplement, for example, will theoretically be flushed down the toilet (i.e., you'll just pee it out).
RELATED: Mood Support, Hormone Balance & 5 Other Surprising Vitamin C Perks*
How to optimize absorption
When you're taking a supplement, you want to make sure that your body actually uses it. If you're taking purely ascorbic acid (at doses above 300 to 400 milligrams per serving), Michels recommends maximizing your vitamin C absorption by splitting up your dose of vitamin C throughout the day.
"Take it in two or three doses," he reports. That way, your system can more intentionally and actively absorb all of that essential C.
When it comes to taking a higher dose of vitamin C (since much of the scientific studies3, particularly for vitamin C's impact on immune response, are at 500 milligrams, 1,000 milligrams, and higher) and making sure you're absorbing most of those milligrams, choosing the right form of vitamin C is the key. mindbodygreen's vitamin C potency+ utilizes a unique and clinically researched trio of vitamin C, lipids, and citrus bioflavonoids for this exact reason.
PureWay-C™ is the scientifically advanced form in this premium, vegan vitamin C product, delivering a vitamin-C-lipid-citrus bioflavonoid complex developed by scientists to increase vitamin C absorption and prolong blood and tissue retention of vitamin C.*
Essentially, it combines citrus bioflavonoids (the compounds in fruits like oranges) with lipid metabolites (i.e., fatty acids from rice bran), which allows for C to pass through the lipid membranes of cells more easily.
And boom—the result is a 233% higher cellular absorption rate4 of vitamin C than ascorbic acid.*† Because it is more rapidly absorbed, it leads to higher serum vitamin C levels5 (i.e., promoting vitamin C sufficiency most effectively!) as well as a greater reduction of oxidative stress markers.*†
When you don't have a trusty friend who majored in chemistry to explain to you why lipid metabolites and citrus bioflavonoids allow for better vitamin C absorption and stability, doing the dirty work (aka the research) about the processes of essential vitamins yourself is crucial to make sure you aren't flushing your supplements down the drain.*
The key to vitamin C is to check on your dosage, time doses of ascorbic acid throughout the day, and make sure your supplement is doing some of that absorption work for you (like mbg's vitamin C potency+).* When you know more about your supplements, your supplements can actually do much more for you.
Josey Murray is a freelance writer focused on inclusive wellness, joyful movement, mental health, and the like. A graduate of Wellesley College, where she studied English and Creative Writing, her work appears in Women’s Health, Cook & Culture, and more. By expressing her own vulnerability, she writes with warmth and empathy to help readers find self-compassion and true wellness that’s sustainable for body, mind, and planet.