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Nutrition + Health

Anti-Nutrients: Are They Actually Harmful?

August 21, 2020

I’ve been exploring the ins and outs of anti-nutrients over the past few weeks and thought it was worth exploring with you on the blog. I mean, the name alone, “anti-nutrients,” sounds a bit alarming. But are they really something we should be worried about? Let’s explore. First let’s define it. What are anti-nutrients? When […]

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I’ve been exploring the ins and outs of anti-nutrients over the past few weeks and thought it was worth exploring with you on the blog. I mean, the name alone, “anti-nutrients,” sounds a bit alarming. But are they really something we should be worried about? Let’s explore.

First let’s define it.

What are anti-nutrients?

When you think of nutrient dense foods you think of foods that are nourishing and healthy, right? Foods that are packed with minerals, nutrients and health benefits!

Anti-nutrients, on the other hand, are substances found in edible plants that reduce the availability or interfere with the absorption of nutrients from those same plants.  1 2

Why do they exist? 
According to Harvard Health, “Anti-nutrients are naturally found in animals and many plant-based foods. In plants, they are compounds designed to protect from bacterial infections and being eaten by insects.”

Anti-nutrients are basically a form of protection for plants and animals so they can continue to live and reproduce.

There is still a lot of research being done around the topic of anti-nutrients. But relatively speaking, experts are finding that most anti-nutrients aren’t harmful and if they are, there are ways you can disable them or reduce your exposure to them. 3 More on how to do this below.

Anti-Nutrients Leafy Greens

What foods contain the most anti-nutrients?

According to Harvard Health:

Phytates (phytic acid) is probably the most recognized anti-nutrient. This substance is found in whole grains, seeds (such as pumpkin/sunflower seeds), legumes, some nuts (cashews) and “can decrease the absorption of iron, zinc, magnesium, and calcium.” 4

The good news is you can counter this. “Foods rich in vitamin C, like leafy green vegetables or citrus fruits, can counteract phytate and increase iron absorption. And foods rich in vitamin A like sweet potatoes or berries can also help improve iron absorption.” 5

Oxalates, which are found in green leafy vegetables (spinach, kale, beets/beet greens, rhubarb, etc.), black tea, nuts/nut butters, can bind to calcium and prevent it from being absorbed. 67 People who have a history of calcium oxalate kidney stones should stick to a low-oxalate diet. Get more info on an oxalate-controlled diet here. Side note: According to Kathleen Robins, MS, RDN, CSSD, CSOWM, fat binds to calcium and can result in more oxalate being passed through kidneys so calcium supplements and limiting dietary fat can be helpful for those who frequently get oxalate renal stones.

Glucosinolates, which are found in cruciferous vegetables (broccoli, Brussels sprouts, cabbage, kale), can prevent the absorption of iodine, which may then interfere with thyroid function by  suppressing the thyroid gland’s ability to take up iodine and convert it into thyroid hormones. Those already with an iodine deficiency or a condition called hypothyroidism are most susceptible, shares Harvard Health. 8 9

Lectins, which are found in legumes (most commonly found in beans, peanuts, soybeans), whole grains, can interfere with the absorption of calcium, iron, phosphorus, and zinc.  Note: raw legumes (beans, lentils, peas, soybeans, peanuts) and whole grains like wheat contain the highest amounts of lectins. 10

Saponins, which are found in legumes and whole grains, can also interfere with normal nutrient absorption. 11

Tannins in tea, coffee, and legumes can decrease iron absorption. 12

Anti-Nutrients Legumes

Are anti-nutrients harmful?

Anti-nutrients can block some absorption, but, as Dietitian Beth Warren, MS, RDN, CDN states, “You would have to eat a large quantity for it to have a negative impact on your nutritional status.” 13

Secondly, most foods that contain anti-nutrients are also packed with amazing health benefits.

For instance, certain anti-nutrients such as lectins “can act as an antioxidant, which protects cells from damage caused by free radicals. They also slow down digestion and the absorption of carbohydrates, which may prevent sharp rises in blood sugar and high insulin levels.” 14

Glucosinolates, which can interfere with iodine absorption, are also believed to give cruciferous vegetables their cancer-fighting properties. 15

Phytates, reports Harvard Health, which can “interfere with the absorption of iron, zinc, magnesium, and calcium, have also been found to lower cholesterol, slow digestion, and prevent sharp rises in blood sugar. Basically, many anti-nutrients have antioxidant and anticancer actions, so avoiding them entirely is not recommended.” 16

Ultimately, the key is to eat a varied diet and of course, everything in moderation.

Harvard Health also suggests the following: “Avoid eating large quantities of foods containing anti-nutrients at one meal.” Rather, “eat a balanced diet throughout the day with a variety of foods. For example, instead of eating two cups of bran cereal with milk for breakfast, choose one cup of cereal with milk and one cup of fresh berries.” 17

How to reduce anti-nutrients

The good news is you can lower your consumption of anti-nutrients a variety of ways — cooking, soaking, sprouting, fermenting.

Cooking, according to Harvard Health, “especially with wet high-heat methods like boiling or stewing, or soaking in water for several hours, can inactivate most lectins.” 18

Take beans for example. To prepare them is to soften them, you must first soak and then boil them for several hours. This process alone disables the action of lectins.

One study, reports Healthline, “showed that boiling pigeon peas for 80 minutes reduced protease inhibitors by 70%, lectin by 79% and tannin by 69%.” 19

Anti-Nutrients

What about canned beans? Luckily, canned beans are cooked and packaged in liquid, so they are also low in lectins.20

Tip: You need to boil beans, and other types of food, in order to remove lectins. Raw beans simmered at low heat such as in a slow-cooker or undercooking the beans does not remove all the lectins. 21

Additionally, calcium oxalate is reduced by 19% to 87% in boiled green leafy vegetables. Steaming and baking are not as effective. 22

Another alternative is sprouting and/or fermenting whole foods before consuming them. Ill be exploring how to sprout foods in the next blog post!

Healthline put together a great guide to help you determine how best to reduce anti-nutrients from your diet:

Phytate (phytic acid): Soaking, sprouting, fermentation.
Lectins: Soaking, boiling, heating, fermentation.
Tannins: Soaking, boiling.
Calcium oxalate: Soaking, boiling.

In the end though, as long as you’re eating a diverse and wide variety of foods you shouldn’t have to worry about anti-nutrients. Now, if you’re someone who is prone to oxalate kidney stones, sufferers from iodine or calcium deficiency you’ll probably want to monitor which foods you’re consuming more closely. But, if you’re relatively healthy then just keep on eating your greens, legumes, and drinking that warm cup of tea!

 


Written by:

The Wise Consumer

Reviewed by:

Kathleen Robins
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