Tea Guides

Last updated: October 2026

Not reliably. A 2025 field trial on oolong trees in China found theanine fell by 58% from the lowest garden to the highest, and the authors credited soil, not altitude. Other studies run the other way. Our Ilam greens and whites grow at 5,500 ft, and we won't quote a theanine figure until we have tested our own leaf.

If you would rather judge the cup than the chemistry, start with the Tea Sampler Kit ($30 CAD): ten teas in 5g bags from all four of our farms in Ilam and Taplejung, grown at 5,000–6,000 ft, every one naturally free of bitterness. Taste first. Then read on for why we stopped saying "altitude means more theanine."

Does high altitude really raise theanine in tea?

The claim is repeated so often it feels like settled fact: cooler mountain air slows the leaf, theanine builds up, the cup turns sweet. The research is less tidy. A 2025 paper by Ren and colleagues opens by citing earlier literature that says exactly this, and then tests it. They sampled 50-year-old Lingtou Dancong oolong trees at three altitudes in one tea garden on Fenghuang Mountain, Guangdong, and measured the leaf by HPLC. Theanine fell significantly as altitude rose. The highest plot came in 58.2% lower than the lowest. Caffeine fell too, by 24.8%. The theanine-to-caffeine and theanine-to-catechin ratios, which the authors use as sweetness indices, were best at the bottom of the hill. Their conclusion was that soil chemistry, rather than altitude itself, mainly regulated quality there (Ren et al., 2025).

One garden and one cultivar cannot overturn the older view. It does show the older view is not a law.

Why do other studies find the opposite?

Because the effect points different ways in different places. A 2025 metabolomics study of green tea at an estate in Central Java, Indonesia, found theanine higher at the higher of two elevations, though the paper's own results text calls the difference slight. The authors set their result against Korean and Chinese studies that went in other directions and put the split down to local climate. They also sampled a single rainy-season month, so it is a snapshot (Wahyuni et al., 2025).

Taiwan's Tea and Beverage Research Station describes its official high-mountain oolong as lower in bitter catechins and higher in sweet-tasting components such as theanine and soluble nitrogen (TBRS, n.d.). That is a description of a named, regulated category of Taiwanese oolong. It is not a rule for every tall hill.

Read together, these say what the Fenghuang trial says. Altitude stands in for a bundle of conditions, and the bundle changes from mountain to mountain.

What else changes theanine in the leaf?

Soil and feeding, at the least. In the Fenghuang data, soil total potassium was positively correlated with leaf theanine, and the richness of the soil's fungal community tracked theanine closely (r = 0.80) (Ren et al., 2025). A ten-year trial in Fujian went further. Long-term nitrogen fertilizer lifted leaf theanine from 6,812 to 20,477 µg per gram of fresh leaf, about threefold, in a low-lying plot growing one cultivar. The authors speculate that the rise came from more glutamic acid being available as raw material, not from busier theanine genes (Chen et al., 2021).

So a leaf can be rich in theanine because of how its soil is fed, whatever its height above sea level. We are not claiming either explanation for our farms. We do not have the data.

So what do we actually claim about our teas?

Three things we can stand behind, and one we can't. Our Organic Light Green Tea, Floral Green Tea, Fresh White Tea and Floral White Tea all come from Farmers Tea Co. in Malate, Ilam, a certified organic farm at 5,500 ft. Each is naturally free of bitterness, which is what we taste in the cup and what we put on the label. We can name the farm, the elevation and the district, because we buy directly from the farm.

What we can't claim is a mechanism. We have not had our leaf assayed for theanine, so we have no number to give you, and the research above says a number is what you would need before crediting altitude. We have repeated the altitude line ourselves in the past. This is the correction.

How should you brew these teas for the softest cup?

Use cooler water and short steeps: 75–80°C for the greens, 75°C for the whites, two to three minutes. These leaves forgive an extra minute better than most green teas do, so a slightly long steep will not turn the cup harsh.

All four are grown on a certified organic farm. Both white teas come from Farmers Tea Co. in Ilam and nowhere else.

Which one should you order after the sampler?

For an everyday green, the Organic Light Green Tea ($20 CAD for 50g) is the easy pour. For the gentlest cup in our range, and the one we'd pour after dinner, the Floral White Tea ($10 CAD for 25g) is the lowest in caffeine we make.

Frequently Asked Questions

Does high-altitude tea have more L-theanine?
Not reliably. A 2025 field trial on Fenghuang Mountain oolong found theanine fell as altitude rose, and the authors credited soil chemistry. A 2025 Java study found it slightly higher at the higher elevation. Results depend on the mountain, cultivar and soil, so altitude alone does not predict theanine.

Why do so many tea brands say altitude raises theanine?
It is repeated in older literature and is partly true in some places, such as the Taiwanese high-mountain oolong that Taiwan's research station describes as higher in theanine. The problem is stating it as a rule. We repeated it ourselves before reading the 2025 field trial, and we have stopped.

Do Nepal Hills teas contain L-theanine?
Every true tea contains it, ours included. What we have not done is measure how much. Our greens and whites come from Farmers Tea Co. in Malate, Ilam, at 5,500 ft, and we will not quote a theanine figure until our own leaf has been tested.

What else affects theanine in tea leaves?
Soil and feeding both appear to. In the Fenghuang data, soil potassium and fungal richness tracked leaf theanine, and a ten-year Fujian trial found long-term nitrogen fertilizer raised theanine about threefold in one lowland plot. Each study covers one cultivar and place, so none transfers to our farms.

Are Nepal Hills teas bitter?
No. Every tea we sell is naturally free of bitterness. Brew greens at 75–80°C and whites at 75°C for two to three minutes, and the cup stays soft. Our Organic Light Green Tea from Farmers Tea Co., grown at 5,500 ft in Ilam, is a good first green for anyone who has written the category off.

Which Nepal Hills tea is best in the evening?
The white teas are the gentlest in our range, and Floral White Tea is the lowest in caffeine. Both whites come from Farmers Tea Co. in Malate, Ilam, at 5,500 ft. Brew at 75°C for two to three minutes. We make no sleep or health promises, only a soft, low-caffeine cup.

External sources cited above:
Ren, X., Lin, M., Liu, J., Khan, W., Zhao, H., Sun, B., Liu, S., & Zheng, P. (2025). Effects of altitude on tea composition: Dual regulation by soil physicochemical properties and microbial communities. Plants, 14(11), Article 1642. Read the study
Wahyuni, D. S. C., Putri, R. K., Arniyanti, A., Audita, S. H., Choiri, S., Hadi, S., et al. (2025). Metabolomic study on Indonesian green tea (Camellia sinensis L.) cultivation. Pharmacognosy Journal, 17(3), 331-341. Read the study
Tea and Beverage Research Station, Ministry of Agriculture, Taiwan (R.O.C.). (n.d.). High-mountain Oolong tea. Read the page
Chen, Y., Wang, F., Wu, Z., Jiang, F., Yu, W., Yang, J., et al. (2021). Effects of long-term nitrogen fertilization on the formation of metabolites related to tea quality in subtropical China. Metabolites, 11(3), 146. Read the study

Bhaskar Dahal is the founder of Nepal Hills Tea, a Canadian direct-trade specialty tea company sourcing single-origin loose-leaf teas from Ilam and Taplejung, Nepal.