Tannin Levels in Teas: Powerful Antioxidants or Nutrient Blockers?

Have you ever taken a sip of tea and felt a bitter, dry coating in your mouth almost immediately? You can thank the tannin in the tea for that. Tannins are compounds classified as polyphenols, and they have positive and negative effects on your health, according to Cornell University.

While some tannins act as antioxidants and can help combat inflammation, protect your heart health and reduce your risk of developing cancer, others, like tannic acid, act as anti-nutrients, interfering with the way certain minerals, like iron, are absorbed. Most teas contain tannins, but some types of teas have higher amounts than others.

What Are Tannins?

Plants, like fruits, vegetables and herbs, contain compounds called "phytochemicals" that often get the credit for their health-promoting properties, according to Cornell University. There are lots of different phytochemicals, but one group that's found in high levels in tea is called tannins. More specifically, tannins belong to a group of phytochemicals (plant compounds) called polyphenols or phenolics.

Plants produce tannins as part of their defense system. When an animal (or human) eats the plant, the tannins give off a bitter, unpleasant taste that's an attempt to get the animal or human to stop eating. But it doesn't stop there. Tannins have a delayed negative effect, too.

Tannins also have a major effect on your nutrition and overall diet because they have an ability to bind with several macronutrients and other compounds involved in digestion, including:

• Carbohydrates
• Proteins
• Bacterial cell membranes
• Enzymes involved in food digestion

Tannins as Anti-Nutrients

Unlike some other compounds, tannins are heat-stable, meaning they aren't destroyed when you heat them up — like when making tea. According to a study in Preventive Nutrition and Food Science, tannins can block the digestion and absorption of proteins. They do this in one of two ways — either by making part of the protein unavailable or by inhibiting enzymes needed for your body to properly digest them.

Tannins also mess with the way your body absorbs iron. That's why avoiding excessive tea drinking is good for anemia. One study published in Cureus found that women who drink more tea tend to have higher rates of anemia.

If you drink too much tea and ingest too many tannins in your diet, it can also decrease the activity of enzymes in your digestive tract, negatively affecting your digestion as a whole. But tea isn't the only source of tannin. Fruit, red wine, and all types of coffee also contain significant amounts. According to an article in Foods, significant sources of tannins include:

• Grapes
• Apple juice
• Strawberries
• Raspberries
• Blackberries
• Pomegranate
• Plums
• Walnuts
• Peanuts
• Black-eyed peas
• Lentils

Tannins as Antioxidants

Tannins aren't all bad, though. Although they have the ability to mess up your digestion, according to Food Chemistry certain tannins may help reduce the risk of heart disease, prevent the formation of tumors and certain cancers, and help maintain a healthy gut microbiome.

Another report that was published in Frontiers in Nutrition also pointed out that tannins are anti-inflammatory and can decrease adipogenesis — a technical term for the creation of new fat cells. They've also been shown to help regulate blood sugar by improving the health of the cells in your pancreas (beta cells) that produce insulin (the hormone that you need to properly use the glucose, or sugar, in your blood), according to Cleveland Clinic.

Levels of Tannin in Tea

The amount of tannins in tea is a major factor in whether they act as antioxidants or behave more like anti-nutrients, according to a review published in Nutrients. Additional research is necessary to determine how much tea is beneficial.

Current Research in Nutrition and Food Science tested the levels of tannins in various types of tea. Black tea had the highest tannin concentration, ranging from 27 to 55 percent, while green tea had the lowest amount of tannins, at 13 to 21 percent. Oolong tea fell in the middle of black and green tea, clocking in at 18 to 41 percent. The oxidation process in producing black tea is a large factor in its higher tannin levels, as well as a contributing factor in its distinct flavoring.

Because of the possible negative health effects of tannin in tea, some suggest green tea as the best tea option, especially if you're drinking your tea with your meals or soon before or soon after eating. Steeping your tea for shorter time periods also reduces the levels of tannins.

Current Research in Nutrition and Food Science notes that there is no general recommendation for tannin consumption, but many consider 1.5 to 2.5 grams a day to be safe for the general population. The average American consumes approximately 1 gram of tannin per day.

Reducing the Effects of Tannins

But just because tannins have the ability to act as anti-nutrients doesn't mean that you have to avoid tea altogether. An older report in the Journal of Pharmacognosy and Phytochemistry advises drinking coffee and tea between meals instead of with them. It's also a good idea to spread out your consumption. Instead of drinking a cup of tea directly after your cup of coffee, try waiting a few hours and drinking some water in between.

You can also reduce the potential negative effects of tannins by adding some milk or lemon juice to your tea. This can neutralize the tannins so they don't affect the absorption of iron. You can also drink your tea along with foods that are rich in vitamin C, which also neutralizes the tannins. Here are some good sources of vitamin C, according to the National Institutes of Health:

• Bell peppers
• Broccoli
• Brussels sprouts
• Oranges
• Grapefruit
• Kiwi fruit
• Cantaloupe
• Strawberries
• Tomatoes
• Potatoes