One of the essential features of your digestive system is the absorption of key nutrients from food sources you eat and other supplements you take.
As someone who has researched and used various brands of vitamin supplements throughout a long fitness career, I’ve noticed that many of them make bold claims about their contents and health benefits.
But contrary to what people may expect, your digestive system does not absorb everything from them as efficiently as the branding makes it seem.
Quick Summary
- The absorption percentage of multivitamins can be between 10%-90%, depending on their quality, availability, and the amount the body requires.
- Some of the water-soluble vitamins absorbed in the small intestine are niacin, folic acid, biotin, riboflavin, thiamine, and Vitamin B6.
- Factors that prevent multivitamins from being properly absorbed are age, lack of bioavailability, smoking, and drinking.
How Much of a Multivitamin Is Actually Absorbed?
How much of a multivitamin is actually absorbed depends on the certain forms of vitamins and minerals in them, as well as various other factors. Also, the healthier your lifestyle, the better the rate of absorption.
Several factors related to the multivitamin supplements, your body, and your lifestyle and nutrition play a role in how much is actually absorbed.
How Does Your Body Absorb Vitamins?
Your body absorbs the vitamins in your intestines. After food gets into the stomach, hydrochloric acid and certain enzymes break down fats, proteins, and carbohydrates.
At this stage, the digestive system extracts the vitamins and minerals from the digested food and takes them into the bloodstream.
Nutrients from any vitamin and mineral supplements are absorbed in the small intestine [1]. Water-soluble vitamins synthesized by microbes in the large colon intestine are absorbed [2].
The following water-soluble vitamins from food are absorbed mainly in the small intestine:
- Folic Acid
- Thiamine
- Riboflavin
- Niacin
- Pantothenic acid
- Biotin
- Vitamins B6, B12, and C
Fat-soluble vitamins are absorbed by being incorporated into the bowels with other lipids. The body absorbs a compound or mineral and enters the intestinal absorptive cells (enterocytes) through diffusion [3].
In addition to the water-soluble vitamins mentioned, vitamin B12 is also primarily absorbed in the small intestine. Vitamin B12 requires a protein called intrinsic factor, which is produced in the stomach, to be absorbed effectively in the small intestine.
Vitamin A absorption and vitamin K absorption, occurs by being incorporated into the bile and other lipids. The body absorbs these vitamins in the small intestine, where they are taken up by the intestinal absorptive cells (enterocytes) through a process called diffusion.
“You take the healthiest diet in the world, if you gave those people vitamins, they would be twice as healthy. So vitamins are valuable”.
- Robert Coleman Atkins, American Physician & Cardiologist
What Stops Them from Being Absorbed Properly?
Various lifestyle choices and other factors are what usually stop vitamins from being absorbed properly. Let's take a closer look at some of them.
Lack of Bioavailability
Different compounds have different bioavailability — the degree and rate the body absorbs a compound or mineral.
A 2019 study showed that oil-based vitamin D capsules were a highly bioavailable supplement form of this nutrient [4].
Age
A 2002 study found that the intestine's ability to adapt to absorbing carbohydrates, lipids, amino acids, vitamins, and minerals decreases with age and may lead to further malnutrition [5].
Lack of Dietary Fat
If you lack fat in your diet, your body will not properly absorb specific vitamins.
For example, vitamin E is better absorbed by the body when consumed with dietary fat [6].
Smoking and Drinking
The nicotine from smoking tobacco negatively affects the body’s ability to absorb vitamins D and C, while drinking affects folate absorption [7].
Current Dietary Guidelines for Americans instruct that women should limit themselves to one drink and men to two [8].
It’s ultimately hard to put a number on how much each of these factors affects your body’s vitamin absorption capability. In my experience, it’s better to gravitate towards the side of it having an effect more significant than you think.
Related Article: How Long Does It Take for Multivitamins to Work?
How Can I Maximize My Multivitamin Absorption?
To maximize your multivitamin absorption, make sure they are made from natural products with high levels of purity and potency. You should also make sure your multivitamins have the following:
High Bioavailability
Look for brands with highly bioavailable forms of vitamins and minerals. Higher bioavailability means that your vitamins will be absorbed into your bloodstream more easily.
Ingredients like sugar and corn syrup are added to multivitamins as fillers. Like binders, fillers serve no nutritional benefit and will lead to unnecessary weight gain.
Healthy Diet
The best way to take your multivitamins is by combining them with healthy foods. A poor diet will affect your body’s absorption rate of multivitamins because it could lack the necessary complementary nutrients required for effective absorption.
For example, a person taking vitamin D supplements will not benefit from it if not eating calcium-rich foods [9].
All the vitamins and minerals your body requires are found in the food you consume.
Add Some Spice
Spicy foods contain thermo-nutrients — compounds that generate heat when digested.
In addition to boosting metabolism, thermo-nutrients are known to increase multivitamin and nutrient absorption [10].
Combination and Separation of Vitamins
To improve absorption rates, specific vitamins need to be taken together, whereas some combinations should be avoided.
For example, taking vitamin C and iron together is beneficial for iron absorption [11]. On the other hand, zinc and copper don’t absorb well when taken together as they compete for the same receptors [12].
Are the Nutrients in Multivitamin Supplements Absorbed?
Yes, but the effectiveness of the absorption rate is highly dependent on the brand of dietary supplements you consume and how healthy your lifestyle is.
Firstly, you can take steps to improve your lifestyle by eating a healthy diet and avoiding smoking and drinking excessively.
Secondly, if you’re going to take supplements, pick one of the premium brands of multivitamins that are high in bioavailability, most appropriate for your age, and preferably in liquid form.
Figuring this out independently is challenging, so talk to your physician and determine your specific requirements.
References:
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6631968/
- https://www.ncbi.nlm.nih.gov/books/NBK538510/
- http://www.vivo.colostate.edu/hbooks/pathphys/digestion/smallgut/absorb_lipids.html
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6631968/
- https://pubmed.ncbi.nlm.nih.gov/11977925/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4810759/
- https://pubmed.ncbi.nlm.nih.gov/1784736/
- https://www.dietaryguidelines.gov/sites/default/files/2021-03/Dietary_Guidelines_for_Americans-2020-2025.pdf
- https://www.bones.nih.gov/health-info/bone/bone-health/nutrition/calcium-and-vitamin-d-important-every-age
- Badmaev, Vladimir, Muhammed Majeed, and Lakshmi Prakash. "Piperine derived from black pepper increases the plasma levels of coenzyme Q10 following oral supplementation." The Journal of Nutritional Biochemistry 11.2 (2000): 109-113.
- https://nyaspubs.onlinelibrary.wiley.com/doi/abs/10.1111/j.1749-6632.1980.tb21325.x
- https://academic.oup.com/ajcn/article-abstract/34/9/1670/4693450
- https://www.webmd.com/healthy-aging/what-to-know-about-liquid-vitamins-after-60#1
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