While it’s important to know which foods are high in nutrients, it’s not enough. You also have to consider how much of what you eat is actually making it into your body. There are things about you and things inside of foods that block or enhance vitamin and mineral absorption. This blog post goes over how you can get the most out of the foods you eat and explains how food choices and food preparation affect the availability of nutrients.
Bioavailability – At-A-Glance
- Bioavailability measures the amount of an ingested nutrient available for use or storage.
- Nutrient absorption is impacted by your age, gender, health status, body composition, and how much you need a particular nutrient.
- The health of your gut microbiome and gut lining impacts the absorption of nutrients.
- Some foods contain antinutrients (i.e., oxalates, lectins, phytic acid) that decrease the absorption of other nutrients.
- Anitnutrients are more common in plant-based foods than animal-based foods. Therefore, humans tend to absorb nutrients better from animal foods than from plant foods.
- Soaking or boiling can reduce certain antinutrients.
Most Nutrients in Foods DON’T Make It Into Your Body – Here’s Why [Video]
In this video, you’ll learn…
- An explanation of bioavailability.
- The four factors that impact your body’s ability to absorb nutrients.
- Two of the best ways to ensure your body absorbs and uses nutrients.
Eating a nutrient-dense diet is one thing. It is another to absorb those nutrients. Take calcium for example. Cheese and spinach are packed with calcium.
An ounce of grated Parmesan cheese contains 242mg of calcium. A cup of cooked spinach contains 260 mg. However, even though the serving of spinach has more calcium than the cheese, that doesn’t mean that extra calcium will get inside you. In fact, a measly 5% of the calcium from spinach will be absorbed and used.
If you’re lucky, 40% of calcium from cheese will get absorbed and used.
This measure of the amount of an ingested nutrient that becomes available for use or storage in the body is called bioavailability.
Absorbable Nutrients: A Problem of Bioavailability
When discussing poorly absorbed nutrients, the concern is with micronutrients like vitamins and minerals more than macronutrients.
It would be great if there were an easy-to-read bioavailability chart that made it clear what percentage of each food nutrient gets inside of you. Unfortunately, that cannot be a reality because so many variables affect bioavailability. Factor number one is you.
Impact Factor #1: You
There are many things that are just part of your life that affect nutrient absorption. These include your age, gender, health status, body composition, and how much you need a certain nutrient.
People absorb nutrients at different rates. Therefore, while conventional wisdom tells us that the highest-nutrient foods are the best, that is only the first step. We also have to ensure the nutrients are properly absorbed so they can be used or stored. To ensure this, there are two considerations: the gut microbiome and the strength of the gut lining.
Gut Microbiome and Gut Lining
Most of us are familiar with the gut microbiome and the fact that a healthy gut full of friendly bacteria supports good absorption of nutrients. Just as important to your metabolic health is the integrity of the gut lining. That lining creates a barrier that separates the contents of the gut from the bloodstream.
A major factor in keeping that barrier strong is the layer of mucus coating the inner wall. That coating provides a home for beneficial bacteria called Akkermansia that feed off of proteins called mucin.
You want that to happen because when the Akkermansia consumes mucin, your body responds by producing more of it, which replenishes and strengthens this protective layer. Low levels or a lack of Akkermansia in the gut is linked with a thin mucus layer, which has been associated with obesity, diabetes, inflammation, and metabolic disorders.
Impact Factor #2: Antinutrients
Nutrient bioavailability not only differs between individuals, it also varies among foods. At the beginning of this post, I mentioned that calcium from spinach is much less bioavailable than calcium from cheese. This is due to antinutrients found in spinach called oxalates.
Oxalates are just one form of antinutrient. The mechanism by which they affect nutrient absorption varies. But in general, they bind to nutrients, preventing their absorption through the intestine.
Oxalates are high in spinach, almonds, beans, and potatoes. As you may have guessed, they bind to calcium and block it from being absorbed. If you are prone to kidney stones, your doctor may have told you to avoid oxalates because they can form crystals as they pass through the kidneys on their way out of your body.
Lectins are another type of antinutrient. They are high in whole grains as well as legumes, like beans, peanuts, and soybeans. They also interfere with the absorption of calcium and with the absorption of minerals like iron, phosphorus, and zinc.
Phytic acid or phytates are the other antinutrients that get attention. This type is found in grains, legumes, nuts, and seeds and binds to minerals, blocking their absorption.
One thing that may have jumped out at you as I went through foods that contain oxalates, lectins, phytates, and other antinutrients is that they are common in plant foods.
You may think it feels like a mistake of Mother Nature to put antinutrients in plants. However, these compounds are there so the plant can defend itself against threats like fungi, bacteria, and insects.
Because of these antinutrients, we tend to absorb nutrients better from animal foods than plant foods. But I don’t want the takeaway to be that plant foods should be avoided.
“Antinutrient” is a scary-sounding term, but I don’t want you to leave this post feeling scared to eat. Leafy greens, nuts, seeds, and so on contain many nutrients that your body will absorb and use. Would I recommend an all-spinach, all-day-long diet? No.
It is best to avoid eating large amounts of the foods I mentioned in a single sitting, whether you are prone to a disorder or not. But when eaten in smaller quantities, a healthy individual will gain more health benefits than consequences, and the preparation of these plant foods can affect bioavailability.
Impact Factor #3: Cooking and Food Prep
A narrative review published in 2020 outlines preparation tips for reducing antinutrients. For example, oxalates dissolve in water, so you can reduce the oxalates in foods like almonds, beans, and spinach by soaking them or boiling them in water. Lectins and phytates can also be reduced in these ways (1).
Impact Factor #4: Food Source
Still, when it comes to bioavailability, animal foods outperform plant foods. For example, heme iron from animal-based foods is better absorbed than non-heme iron from plants (2).
Some nutrients obtained from animal sources enhance the absorption of other nutrients. For example, salmon and eggs are rich in vitamin D and contain fat that helps your body absorb calcium and fat-soluble vitamins.
There are complementary nutrients in many plant foods. For instance, vitamin C enhances the absorption of non-heme iron, and we get vitamin C from various fruits and vegetables (2).
The takeaway is this. There are compounds in foods that block the absorption of certain nutrients. There are also compounds that enhance the absorption of other nutrients. The lists are long and complicated, but they shouldn’t make you fearful of eating.
Taking in a variety of whole foods and optimizing your gut health are the best ways to ensure your body absorbs and uses nutrients.
Thank you for reading and have a wonderful week!
(1) Petroski, Weston, and Deanna M. Minich. “Is there such a thing as “anti-nutrients”? A narrative review of perceived problematic plant compounds.” Nutrients 12.10 (2020): 2929.
(2) Ems, Thomas, Kayla St Lucia, and Martin R. Huecker. “Biochemistry, iron absorption.” (2017).
About the Author
Becky Gillaspy, DC, is the author of The Intermittent Fasting Guide and Cookbook and Zero Sugar / One Month. She graduated Summa Cum Laude with research honors from Palmer College of Chiropractic in 1991.