No one can argue with the adage “you are what you eat” but that’s only if you absorb what you eat. Nutrient absorption is very important because it’s possible to eat a variety of highly nutrient-dense foods but not get the full benefit from these nutrients simply because they pass right through you and are not absorbed.
Not absorbing nutrients is similar to not consuming them in the first place. Nutrients can’t help your body if they never truly make it inside to do their job. Not absorbing enough of all the essential nutrients can create health problems if it leads to a deficiency. 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.
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. For example, Vitamin A has to reach your eyes to prevent night blindness and Vitamin C has to make it to the skin to heal wounds. The same goes for iron for your blood and energy levels, and calcium for your bones, muscles, and teeth. Before nutrients can get where they need to go, they first need to be removed from the food and absorbed into your body so that they can then be circulated to their destination.
In this blog post, I’ll share some strategies on how to make nutrients more absorbable. But first, a quick lesson on the nutrient absorption process.
Why some nutrients are harder to absorb?
Everyone needs to get enough of all of the essential nutrients for good health. This includes macronutrients (e.g., protein, carbohydrates, and healthy fats) and micronutrients (e.g., vitamins and minerals). Absorption and digestion of nutrients can be tricky because there are so many different foods and nutrients.
Fun fact: How much of a nutrient is absorbed and can be 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 to digesting the food you eat: breaking it down, absorbing the nutrients, and eliminating the waste. That’s why your digestive system provides a long, diverse journey for food to travel once it’s eaten. For example, your stomach is full of digestive juices (e.g., acid, enzymes) to break food into smaller pieces. Then, as your food starts moving through your small intestine, your liver and pancreas add alkaline bile (to neutralize the acid), as well as other enzymes to break down other components of food. Your small intestine is responsible for most—but not all—of the absorption of nutrients into your body. The final journey is through the large intestine that is home to your friendly gut microbes (helpful bacteria and other tiny microorganisms). These microbes can break down (or ferment) some of the toughest nutrients that have made it this far intact (some fibers). The large intestine also absorbs some nutrients and water.
Whatever nutrients don’t get absorbed—because they weren’t broken down small enough, or they were complexed with anti-nutrients, or the digestive tract itself couldn’t do its best work—is eliminated as waste. It’s natural and healthy to eliminate a lot of what you’ve eaten, but ideally the waste should have very little nutrition left in it. You want most of the essential nutrients to be absorbed so your body can use them for your best health.
Despite the diverse and complex processes that your body uses to absorb and digest as many nutrients from foods as possible, sometimes it can use some help. Some people have food intolerances or digestive issues that result in malabsorption of certain nutrients. Plus, there are some nutrient-nutrient interactions and anti-nutrients found in foods that can reduce your ability to absorb them.
The good news is research shows that there are some very interesting things that can increase nutrient bioavailability. By eating certain nutrients together—or apart, or certain foods cooked—or raw, you can enjoy the same foods, but in a more nutritionally efficient, bioavailable, way.
Simple strategies to boost nutrient absorption from the foods you enjoy
Vitamin C is one of the most common vitamin deficiencies in the U.S. Foods that are rich in Vitamin C include fruits and vegetables. Some of the highest sources of Vitamin C are bell peppers, citrus fruits (and their juices), kiwis, broccoli, and strawberries.
Vitamin C is an antioxidant that is water-soluble and destroyed by heat. This means that the 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 minimally by lightly steaming or microwaving them. Looking for some fun and nutritious ways to prepare your vegetables? Check out my blog post on Healthy greens to eat now: 5 not-so-basic leafy greens.
Iron is the most common mineral deficiency in the U.S. Some of the most iron-rich foods are meat, 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 more easily absorbed than non-heme iron. This means that the iron in plants is more difficult to absorb, but there are some simple tips that you can use to absorb more.
Iron absorption can be enhanced when consumed 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 or cook lentils with vegetables (see my cooking demo). Enjoy your tea or coffee—not with, but—between your iron-rich meals.
Vitamins A, D, E, and K
Vitamin A is found in liver, seafood, eggs, and fortified dairy. 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 with Vitamin C, Vitamin A is fat-soluble and becomes more bioavailable when orange and dark green plant-based sources are cooked.
Vitamin D is essential for bone health because it promotes absorption of calcium and is needed by bone cells for growth and repair, Vitamin D also helps reduce inflammation and helps to regulate the immune system and carbohydrate metabolism. Known as the sunshine vitamin because your skin makes Vitamin D 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.
Vitamin E is an antioxidant vitamin 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, 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.
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 olive oil or pairing them with a nutritious dip or dressing to help you absorb more of these essential fat-soluble vitamins.
The largest sources of calcium in the North American and European diets is from milk and dairy products. You can also get calcium from fruits and vegetables (e.g., kale, spinach, broccoli), as well as some 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 or going outside in the sun. Just be sure to have a regular supply of vitamin D (see the section above on fat-soluble vitamins for more information about Vitamin D). If you are on a dairy-free diet and have limited access to sunlight, a professional-grade supplement may be helpful.
Lycopene: Cooking tomatoes brings out this bioactive
Lycopene is similar to beta-carotene, but it is not considered an essential nutrient. Studies show that lycopene may help reduce 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 tomato paste, tomato sauce and tomato juice.
Like Vitamin A above, cooking tomatoes and enjoying them with a little bit of healthy fat can improve your absorption of lycopene.
Healthy eating is a little bit more than consuming nutritious foods, it’s also about absorbing the nutrients from those foods so they can be used in your body. With a few simple tips, you can get more benefits when you enjoy the same nutritious foods you usually do.
Eating Vitamin C-rich foods fresh and raw, and cooking foods rich in fat-soluble vitamins can help you absorb more of those essential nutrients. Eating fat-soluble vitamins with a bit of healthy fat, iron-rich foods with some Vitamin C (but not tea or coffee), and calcium-rich foods with some Vitamin D can also enhance absorption.
If you need help to maximize nutrient absorption to meet your health goals, consult a registered dietitian/nutritionist who can assess your diet and customize an eating plan for you.