I’ve recently been asked by someone who is on the carnivore diet that why her stomach hurts after drinking green tea. She has been eating only animal-based food and has given up all non-carnivore drinks except for green tea. However, she found that her stomach would become sore after drinking green tea, especially when consumed on an empty stomach and this wasn’t something she had experienced before going carnivore.
In this post, I’ll share my findings on why you may experience a sore stomach after drinking green tea on an empty stomach.
Why green tea may cause stomach upset in some people?
Green tea may cause stomach pain and other discomfort in some people when they drink it on an empty stomach due to the plant toxins present in tea leaves.
Like all plants, tea tree doesn’t want its leave, flower or root to be eaten and it produces various toxins to deter predators.
Toxins or natural pesticides in green tea include compounds such as caffeine, tannin, oxalate, phytate, epigallocatechin-3-gallate which have been found to cause a number of health issues including: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
- Increased risk of insomnia, restlessness, tremors, and upset stomach
- Reduction in the absorption of non-heme iron, calcium and other minerals
- Interference with folate use in cells
- Causing oxidative stress and liver toxicity.
Although drinking green tea has not been associated with liver injury, green tea extracts have been found to cause toxic liver diseases in some individuals. More than 100 cases of liver injury attributed to green tea extract have been reported in the literature with a significant number of cases judged as severe or necessitated liver transplantation. [11, 12]
Possible side effects [of green tea] include nausea, vomiting, dehydration, lethargy, central nervous system stimulation such as dizziness, insomnia, tremors, restlessness, confusion, diuresis, heart rate irregularities and psychomotor agitation. Polyphones present in green tea may stain the teeth.Farooq and Nawab (2015)
There isn’t a lot of studies on the impact of having green tea on an empty stomach. However, it appears that the main cause of the potential discomfort or pain after drinking green tea on an empty stomach is the presence of two compounds in green tea: caffeine and tannins. [13, 14, 15]
Green tea contains caffeine, which can stimulate the production of gastric acid in the stomach and promotes gastro-oesophageal reflux. When you consume green tea on an empty stomach, the increased acid production can lead to irritation and discomfort, particularly if you are already prone to acid reflux or have a sensitive stomach. 
Tannins in green tea can also contribute to stomach pain and other discomforts. The astringent or bitter taste of tannins may promote the production of more gastric acid, potentially leading to pain and discomfort. 
Another characteristic of tannins that may upset your stomach is that they bind and precipitate proteins. Tannins first bind with proteins and then aggregate, resulting in the formation of the precipitate. They also bind with digestive enzymes and can adversely interfere with digestion and metabolism. [18, 19, 20, 21]
If you drink tea when there is still some food in your stomach, the food will cushion the impact that those plant compounds have on your stomach so you don’t feel their impact as much.
However, drinking green tea with food isn’t a good idea either. As mentioned above, the compounds in green tea like tannins, phytate and oxalate can interfere with the absorption of various nutrients. For example, tannins have been found to interfere with nutrition absorption, especially iron. People at risk of iron deficiency are advised to consume food rich in iron such as meat, fish and poultry and consume tea between meals instead of during the meal. [22, 23, 24]
“the tannins in green tea can form irresolvable bonds with iron in the body, rendering the iron hard to digest… the typical reduction in iron absorption from a food with a cup of tea in clinical studies is approximately 30-60 percent”Lindsey Goodwin of Vee Tea
My guess is that, because animal-based food is nutrient-dense and satiating, you don’t need to eat as often and, it’s likely that your stomach remains empty more often when you are on the carnivore diet than when you are on an omnivore or vegetarian diet. Hence, the effect of drinking green tea on your stomach may become more pronounced.
Our view is tea and coffee are not a good idea, whether you are on a carnivore diet or not. However, if you still want to drink green tea, below are a few suggestions:
- Don’t drink tea during or immediately after your main meal, wait for at least 1-2 hours after your meal to have your tea
- If your stomach is empty, have a small snack before drinking green tea
- Choose a lower-caffeine or decaffeinated green tea
- Shorten steeping times to reduce the concentration of caffeine and tannins in your tea.
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Disclaimer: The information in this post is for reference purposes only and is not intended to constitute or replace professional medical advice. Please consult a qualified medical professional before making any changes to your diet or lifestyle. Please check out our disclaimer for more detail.