Guide to nutrient absorption: What you eat vs. what your body absorbs

Bananas are high in potassium. So if you eat a banana, your levels of potassium should go up immediately, right?

It is not quite so simple, says Reena Panjwani, a registered dietitian-nutritionist at BlueCross BlueShield of Tennessee. The nutrient levels in food and the amount of nutrients you actually absorb can be quite different.

“There are parts of every food that won’t get fully digested,” says Panjwani. “Your body won’t break down a mushroom to every molecule, or get every amino acid out of meats and proteins. Some nutrients go through your system undigested or unabsorbed, and that’s okay. The important thing is to understand how our bodies absorb nutrients and focus on putting healthy foods into it.”

How does nutrient absorption work?

Panjwani: Digestion starts as soon as you put food into your mouth.

Here are the basics steps of digestion and nutrient absorption:

Chewing introduces enzymes through saliva, which start to break down the chemical structure of food.
When food reaches your stomach, it mixes with powerful acid that breaks it down further.
Processed food reaches the small intestine, the body’s nutrient-absorption headquarters. Hundreds of thousands of villi (tiny brush-like structures) grab nutrients — fatty acids, glucose, amino acids, vitamins and minerals — from food.
Villi release these nutrients into your bloodstream.
Carrier proteins pick up the nutrients and deliver them to the cells that need them.
Once nutrients reach their assigned cells, carrier proteins help nutrients pass through the cellular membranes that guard each cell.

Are certain nutrients more easily absorbed than others?

Panjwani: Yes, some things are absorbed better when other nutrients are present.

Non-heme iron

Heme iron is a type of iron that can only come from animal proteins. It’s found in meat, poultry, seafood, and fish.
Non-heme iron, on the other hand, is found in plant-based foods such as grains, beans, vegetables, fruits, nuts and seeds.

Panjwani: While your body more easily recognizes and absorbs animal iron, non-heme iron isn’t absorbed as easily — however, eating it with foods that are rich in vitamin C can boost its absorption. So if you rely on plant-based foods for iron, be sure your meal also includes foods that are rich in vitamin C, such as citrus, strawberries, tomatoes, bell peppers or chili peppers.

Try:

Spinach salad (iron) with a lemony vinaigrette (vitamin C)
A berry smoothie (vitamin C) with kale (iron)
Beans (iron) with a squeeze of lime juice or diced tomatoes (vitamin C)

Panjwani: The good news is a lot of times you don’t really have to think about it because these foods go well together anyway.

Proteins & amino acids

Panjwani: Another thing people on plant-based diets need to consider is protein. There are two ways to ensure you’re getting enough:

Eat complete proteins, which contain all 9 essential amino acids. Complete plant-based proteins include quinoa, chia seeds, buckwheat, nutritional yeast and hemp.
Eat foods throughout the day that contain different amino acids so you get all 9 essential ones. Eat lentils to get isoleucine, brown rice to get leucine, lima beans for methionine and so on. As long as you aim to get all 9 over the course of the day, you’re in good shape.

What are amino acids? Exploring the 9 essential amino acids + the foods that have them

Lycopene

Panjwani: Lycopene is a carotenoid that gives tomatoes and strawberries their red color. It is also a powerful antioxidant. Tomatoes are high in lycopene, and studies show that lycopene is better absorbed when tomatoes are cooked, as in soups or sauces. Cooking has also been shown to boost its heart-healthy properties and cancer-fighting ability.

Does this mean you shouldn’t eat raw tomatoes? Absolutely not. Raw tomatoes are higher in vitamin C than cooked tomatoes, so your body wins either way.

Vitamin C

Panjwani: As I just mentioned, vitamin C decreases when food is heated.

To boost your vitamin C intake, add some raw dishes to your diet such as:

Broccoli salad with pecans and raisins
Sliced tomatoes with mozzarella and basil
Raw kiwi, strawberries, oranges or papayas

Fat soluble vitamins

Panjwani: Some vitamins are better absorbed when eaten with fat, including vitamins A, D, E and K.

Try:

Tomatoes (vitamins A and K) with olive oil or avocado (fat)
A leafy green salad (vitamin K) with dressing (fat)
Roasted or raw carrots (vitamin A) with yogurt or hummus (fat)

Panjwani: Vitamin D is important because it allows our bodies to absorb calcium. There aren’t a ton of dietary sources, which is why many people get it through sun exposure. But there are some foods that are rich in vitamin D and also naturally have fat, such as fatty fish (tuna, salmon), cheese and eggs.

Panjwani: Finally, there’s vitamin E, which we can get through nuts or nut butters — both of which naturally contain fat. If you can’t eat nuts, consider other sources of vitamin E such as beet or collard greens, spinach, pumpkin and red bell pepper.

Other absorption tips

Black pepper boosts the absorption of curcumin, a powerful antioxidant found in turmeric. Any time you cook with turmeric — for example, if you’re making Indian food — add some black pepper.
Try using hing, an Indian spice made from fennel resin and wheat, to foods that cause gas. Hing has been shown to help with the digestion of legumes, broccoli and other gas-causing vegetables.
If you’re low in iron or calcium, avoid drinking caffeine while eating iron- or calcium-rich foods. Caffeine can hinder the absorption of both.
Beans contain lectins and phytates which can hinder the absorption of certain minerals, but soaking and cooking beans reduces those effects.

Can you ever have too many nutrients?

Panjwani: Yes, and it typically occurs with supplement use. While excess vitamin C will simply be excreted in urine, vitamin D can be toxic when taken in high amounts. Getting nutrients through food is usually the best way to avoid an excess of any one nutrient. However, if you are low in a specific nutrient, supplements may be necessary. Just discuss them with your healthcare provider first. There are also certain nutrients to be mindful of with some medical conditions, but this would be something to discuss with a registered dietitian or health provider.

In general, how can we increase the levels of nutrients we absorb?

Panjwani: Eat local! Local vegetables and fruit will be higher in nutrients because they aren’t traveling as far to get to you. Grocery-store food often loses nutrients because there’s a long time between when it’s picked and when you buy it, bring it home and finally eat it. Community-supported agriculture, or CSAs, are also a great way to maximize the nutrients you’re getting.

In addition to eating local:

Store produce properly as soon as you bring it home to preserve its nutritional value.
Use frozen produce. Because fruits and vegetables are picked at their peak ripeness and flash frozen, their nutritional value is locked in.
Don’t get too caught up in food absorption rates.

Panjwani: While it’s interesting to know how food is broken down in our bodies, it’s much more important to focus on eating fruits and vegetables, and enjoying a variety of healthy foods without overthinking it.

Ashley Brantley

Ashley Brantley has been writing about food, culture and health for more than a decade, and has lived in three of Tennessee’s four major cities (Memphis, Nashville and Knoxville).