I see you - working hard to build balanced meals out of a variety of vegetables, fruits, whole grains, healthy fats, and quality protein. It takes time, effort, and planning to put those vitamin and mineral-loaded meals together. You want to make sure you are getting the most out of these meals, right? I sure want that for you!
While you may be loading your plate with all of the right vitamins and minerals, you may not be getting the full benefit of all of the nutrient-dense foods you are eating. Many people are not absorbing all of the essential nutrients from their food, and as a result, some nutrients are going to waste. This may eventually lead to suboptimal nutrient levels or possibly even some vitamin and/or mineral deficiencies. According to a recent study published in the journal Nutrients, researchers found that “Nearly one-third of the U.S. population is at risk of deficiency in at least one vitamin, or has anemia.” The top five most common nutrient deficiencies were for Vitamins B6, B12, C, and D, and the mineral iron.
No need to worry though, there are some quick and simple ways to prepare meals in a way that maximizes your nutrient absorption. To help you better understand them, let's first do a quick overview of the main player involved in nutrient absorption - the digestive system.
The Digestive System's Role in Nutrient Absorption
Your digestive system is how your body takes the essential nutrients from your food and absorbs them so they can be used for growth, maintenance, energy, healing, and overall good health.
Fun fact: The amount of a nutrient that can be absorbed and used or stored in the body is called nutrient bioavailability. This describes how available the nutrient is for our biological use.
There are three main steps involved in processing the food we eat: 1) breaking it down/digestion, 2) absorbing the nutrients, and 3) eliminating what's waste. Breaking food down/digestion starts in the mouth. How well we chew our food can impact how much we absorb. Plus, there are enzymes in our saliva that help break down the carbohydrates in what we eat. Your stomach continues the process with acid and some more enzymes.
Ok onto step 2 - absorption. The majority of nutrient absorption happens in your intestines (both small and large but they play different roles). Our intestines are so long because this gives our bodies plenty of surface area for the digested food to interact with our intestinal cells. This is where we absorb the nutrients we need from the food we ate. In the small intestine, the cells that line the inside surface are responsible for nutrient absorption. The same is true in the large intestine BUT the helpful bacteria that live in your large intestine also play a role in absorbing certain nutrients!
Now for step 3 - whatever nutrients don’t get absorbed—because they weren’t broken down small enough, or were complexed with anti-nutrients, or because the digestive tract itself couldn’t do its best work—are eliminated as waste. It is natural and healthy to eliminate a lot of what you’ve eaten, but ideally, the waste should have very few nutrients left in it. You want most of the essential nutrients to be absorbed so your body can use them.
Why We Don't Always Absorb All The Nutrients We Should
There are several reasons why some important nutrients may end up in your waste. Here are a couple of examples:
food intolerances (which can contribute to leaky gut)
the presence of anti-nutrients (some food components bind certain nutrients, making them unavailable to our bodies -which is a reason why variety is so important in our diets!)
destroying vitamins in the cooking process
low stomach acid
inadequate digestive enzyme production
certain procedures and surgeries, such as bariatric surgery
malabsorption disorders
The good news is, there are several simple ways you can increase the nutrient bioavailability of your food! *Please note, if you are not absorbing enough nutrients due to a diagnosed medical condition and/or due to a surgical procedure, please consult with your physician and registered dietitian to help you develop a specific plan.
How to Increase Nutrient Bioavailability
Here are some nutrient-specific, simple strategies to help your digestive system get the most out of meals:
Vitamin C: enjoy these foods fresh and raw
Vitamin C is one of the most common vitamin deficiencies in the United States. Foods that are rich in vitamin C include fruits and vegetables. Some of the highest sources of vitamin C are bell peppers, citrus fruits, kiwis, broccoli, and strawberries.
Vitamin C is an antioxidant that is water-soluble and destroyed by heat. This means vitamin C levels are highest when the food is fresh and raw (or cooked as little as possible). To maximize the Vitamin C levels in your fruits and vegetables, try to eat them as fresh and raw as possible. If you enjoy them cooked, do so by lightly steaming or microwaving them.
Iron: enjoy iron-rich foods *with and without these...
Iron is the most common mineral deficiency in the United States. Some iron-rich foods are seafood, beans and lentils, liver, spinach, and tofu. Also, some breads and cereals are fortified with iron. But, not all iron-rich foods are equal. Iron is found in two different forms: heme (in animal-based foods) and non-heme (in plant-based foods). Heme iron is more bioavailable and therefore more easily absorbed than non-heme iron. This means that it is most difficult to absorb iron from plant-based foods, but there are some simple tips that you can use to absorb more.
Iron absorption can be enhanced when it is eaten with vitamin C-rich foods and away from tannin-containing drinks like tea and coffee. This means, enjoy your beans, lentils, spinach, or tofu with a vitamin C-rich food in the same meal. For example, add some bell peppers, orange wedges, or berries to your spinach salad. And enjoy your tea or coffee between your iron-rich meals rather than with them.
Fat-soluble vitamins: A, D, E, and K
Vitamin A is found in liver, seafood, eggs, and fortified dairy products. Pro-vitamin A (beta-carotene) is found in fruits and vegetables, especially orange ones like sweet potatoes and carrots, and dark green leafy ones like spinach and kale. Because of the way beta-carotene is stored in the plant cells, not all of it is as bioavailable as vitamin A in animal-based foods. Unlike vitamin C, vitamin A is fat-soluble and becomes more bioavailable when orange and dark green plant-based sources are cooked, especially with some fat like avocado or olive oil.
Vitamin D is essential for bone health because it promotes the absorption of calcium and is needed by bone cells for growth and repair. Vitamin D also helps reduce inflammation, helps to regulate the immune system, and also helps regulate carbohydrate metabolism. Known as the sunshine vitamin because your skin makes it when exposed to UV light, vitamin D is also naturally found in a few foods. These foods include seafood, mushrooms exposed to UV light, egg yolks, and some fortified dairy products.
Vitamin E is an antioxidant that is necessary for protecting cells from oxidants to prevent or delay chronic diseases. Vitamin E is also essential for your immune system. Foods with high levels of vitamin E include whole grains, nuts and seeds (and their butters), and oils (e.g., wheat germ oil, sunflower oil, and peanut butter).
Vitamin K comes in two forms: K1 is in dark green leafy vegetables, broccoli, soy, and herbs. Vitamin K2 is mostly made by bacteria, so it’s found in fermented foods like yogurt, cheese, and sauerkraut. Vitamin K is essential for proper blood clotting and bone metabolism. *Please note, if you are taking any blood thinners, be sure to talk to your prescribing doctor before changing the amount of vitamin K you eat.
These four fat-soluble vitamins can be fairly bioavailable on their own, but a simple tip can help enhance absorption even more: get enough healthy fat. This means cooking your vegetables with a bit of healthy oil or pairing them with a nutritious dip or dressing to help you absorb more of these essential fat-soluble vitamins.
Calcium: be sure to have adequate vitamin D
The largest sources of calcium in the North American and European diets are milk and dairy products. You can also get calcium from fruits and vegetables (e.g., kale, spinach, broccoli), as well as mineral water. Some of the plant sources of calcium have lower bioavailability because they contain anti-nutrients like oxalate and phytic acid. The amount of calcium absorbed from these foods is increased with vitamin D intake. While you don’t need to get vitamin D in the same meal as a calcium-rich one, getting enough vitamin D every day is key—whether that means eating vitamin D-rich foods with a bit of healthy fat, staying on top of your supplementation, and/or going outside in the sun.
Lycopene: cooking tomatoes brings it out
Lycopene is similar to beta-carotene, but it is not considered an essential nutrient. Studies show that lycopene may help reduce the risk of heart disease and some cancers like prostate cancer. Lycopene is a health-promoting antioxidant found in red and dark green fruits and vegetables such as tomatoes, pink grapefruit, and watermelon. The main sources of lycopene are cooked tomato products like ketchup, tomato juice, and pasta sauce.
Like vitamin A, cooking tomatoes and enjoying them with a little bit of healthy fat can improve your absorption of lycopene.
Putting it All Together
Healthy eating is not just about what you eat, but how well you're reaping the benefits of the nutrients you are consuming! If you need help getting enough of all of the essential nutrients to reach your health goals, consult a registered dietitian for some more guidance.
References
Bird, J. K., Murphy, R. A., Ciappio, E. D., & McBurney, M. I. (2017). Risk of Deficiency in Multiple Concurrent Micronutrients in Children and Adults in the United States. Nutrients, 9(7), 655. https://doi.org/10.3390/nu9070655 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5537775/
Cleveland Clinic. (n.d.). Malabsorption. https://my.clevelandclinic.org/health/diseases/22722-malabsorption
Coe, S., & Spiro, A. (2022). Cooking at home to retain nutritional quality and minimise nutrient losses: A focus on vegetables, potatoes and pulses. Nutrition bulletin, 10.1111/nbu.12584. Advance online publication. https://doi.org/10.1111/nbu.12584 https://pubmed.ncbi.nlm.nih.gov/36299246/
Harvard T.H. Chan School of Public Health. (n.d.). Are anti-nutrients harmful? The Nutrition Source. https://www.hsph.harvard.edu/nutritionsource/anti-nutrients/
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National Institute of Diabetes and Digestive and Kidney Diseases. (n.d.). Your digestive system & how it works. https://www.niddk.nih.gov/health-information/digestive-diseases/digestive-system-how-it-works
National Institutes of Health. (2021, March 26). Vitamin C: Fact Sheet for Health Professionals. Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/
National Institutes of Health. (2021, March 26). Vitamin E: Fact Sheet for Health Professionals. Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/VitaminE-HealthProfessional/
National Institutes of Health. (2021, March 29). Vitamin K: Fact Sheet for Health Professionals. Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/
National Institutes of Health. (2021, June 15). Vitamin A and Carotenoids: Fact Sheet for Health Professionals. Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/
National Institutes of Health. (2022, April 5). Iron: Fact Sheet for Health Professionals. Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/
National Institutes of Health. (2022, August 12). Vitamin D: Fact Sheet for Health Professionals. Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
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