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L-Lysine vs L-Theanine (For Anxiety And Cold Sores)

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So 2020 is the year you wanna get healthy.

That’s awesome! I’m pleased for you.

There’s just one (big) problem…

You have 100s of different supplements to pick from. So how do you choose?

Well, in my Supplement Comparison Guide, I take 2 supplements and put them against each other on their benefits, drawbacks, price and so much more.

The goal isn’t to pick a “winner”, but to help you choose which one is best for you.

Up next, we have L-Theanine vs L-Lysine.

Let’s get started!

What is L-Theanine?

L-Theanine is a non-essential amino acid that’s found naturally in tea leaves.

So tea is the most common source of L-Theanine for most people.

Thanks to its sedative properties, lots of people use L-Theanine to help unwind and relieve stress.

It’s one of my favorite nootropic supplements as it’s safe, cheap and good for you.

What is L-Lysine?

L-Lysine is an essential amino acid.

This means it’s critical for human health, but the body can’t produce it so you need to get it from food or supplements.

(This is where L-Lysine differs from L-Theanine.)

L-Lysine plays an important role in the production of L-Carnitine – a nutrient which allows fatty acids to be used for energy.


Benefits of L-Theanine

L-Theanine may help improve sleep quality

When it comes to health and wellbeing, many people seem to forget that sleep is a vital component.

Personally, I think this is due to a lack of understanding of how important sleep is.

I’ve been experimenting with a handful of supplements to improve my sleep, such as:

  • Holy Basil
  • L-Theanine
  • Phosphatidylserine
  • California Poppy Extract

I had my best ever sleep when combining Holy Basil and Phosphatidylserine, or when using L-Theanine on its own.

(California Poppy Extract didn’t resonate with me. It may be effective for other people, but for me? Not so much.)

So how could I tell that L-Theanine improved my sleep?

Well, I measure my sleep quality on 2 factors:

  • How deep my sleep is
  • How long it takes me to fall asleep

L-Theanine improved both these factors for me!

(Related reading: Is Phosphatidylserine Good For Sleep And Insomnia?)

L-Theanine may reduce caffeine jitters

You really can’t beat that first gulp of a warm, aromatic coffee in the morning.

You know the one I’m talking about…

The one that fills you with joy even if it’s a Monday.

But sometimes, the caffeine rush that follows can ruin my day.

Whether it’s jitters, anxiety or pounding headaches, my body will tell me when it’s had too much caffeine.

But when I take L-Theanine in the morning alongside my cup of Joe, these effects are hardly noticeable!

L-Theanine may boost cognitive function

Lots of people use L-Theanine for its brain enhancing properties.

In other words, they use it as a nootropic.

L-Theanine can help improve mental function by amplifying your alpha brain waves, which can boost creativity.

Benefits of L-Lysine

L-Lysine may improve bone health

Calcium is an important mineral for bone health and preventing osteoporosis.

Interestingly, research shows that L-Lysine can help increase calcium absorption in your gut.

Also, a study of 30 women found that L-Lysine reduces the amount of calcium lost in urine.

So by improving the absorption of Calcium and preventing the loss of Calcium, L-Lysine may be a suitable supplement for those wanting to improve bone health.

L-Lysine may help reduce anxiety

Did you know that over 40 million American adults suffer from anxiety-related disorders?

This makes anxiety the most common mental disease in the US.

The good news is L-Lysine may help reduce anxiety.

For example, a study of 50 people found that L-Lysine (used alongside L-Arginine) lowered cortisol levels and anxiety in the subjects.

Another study found that using wheat flour enriched with 4.2g of L-Lysine reduced anxiety scores in Syrian males under stress.

(Related reading: Does Phosphatidylserine Improve Anxiety Symptoms?)

L-Lysine may protect against cold sores

Cold sores are pus-filled blisters that appear on the lips of sufferers.

Not only can they be painful, but they can also affect your mental health by making you anxious of your appearance.

Research shows that people who suffer from cold sores may benefit from L-Lysine supplementation.

In a study of 30 people, an L-Lysine containing cream was applied to the cold sores of the subjects.

After only 6 days, 87% of the subjects had their cold sores cleared by the cream.

Another study showed that taking 1g of L-Lysine daily reduced the amount of cold sores in 26 people who were susceptible to cold sores.


L-Theanine Cost

L-Theanine is typically sold in capsules or as a powder.

Here are some standard prices for these:

  • Powder: $10 for 100g
  • Capsules: $20 for 100

L-Lysine Cost

L-Lysine is usually sold in capsules or tablets.

Typical prices for these are:

  • Tablets: $9 for 100
  • Capsules: $7 for 100

Side Effects

L-Theanine Side Effects

It’s generally safe to take L-Theanine supplements and to drink teas which contain L-Theanine.

But if you drink too much tea, you might experience the following effects from the high caffeine content:

  • Nausea
  • Irritability
  • Upset stomach

L-Lysine Side Effects

Like L-Theanine, L-Lysine is usually safe when taken at its recommended dosage.

But it can cause the following side effects in some people:

  • Nausea
  • Diarrhea
  • Upset stomach


My L-Theanine Recommendation: Nootropics Depot L-Theanine Powder

Click to see on Amazon


An epic L-Theanine supplement that’s in powdered form.

Ideal for those who enjoy the freedom to choose how much L-Theanine they’d like to take.

What I like about it

A great feature of this product is that it only contains 100% L-Theanine powder.

In other words, you’re not wasting your hard-earned cash on cheap fillers and additives, which manufactures often include to make more profit.

Also, if you follow the recommended serving size, then each purchase will last you many years, making this product fantastic value for money.

(Following the serving size, each tub provides a whopping 2500 servings!)

And the fact that it’s a powder means you can experiment with the dosage to see what suits you.

(Some of you will notice better results from a smaller dosage, while others will be more suited to a higher dosage.)

Potential Drawbacks

While powdered supplements are my preference, some people may prefer the convenience of taking capsules.

If that’s you, then this supplement probably isn’t for you.

Check price and read more reviews of Nootropics Depot L-Theanine on Amazon.

My L-Lysine Recommendation: Country Life L-Lysine

Click to see on Amazon


A cheap and cheerful L-Lysine supplement mixed with Vitamin B6.

Country Life L-Lysine gets Vitalized Future’s seal of approval.

What I like about it

A great feature is that this L-Lysine is mixed with Vitamin B6, which helps your body utilize it better.

This makes it more effective than other L-Lysine supplements out there.

Also, the dozens of fantastic reviews show that this is tried and tested L-Lysine supplement that’s loved and used by many people.

In fact, a lot of people have used this supplement to avoid cold sores with successful results.

So at its low price, this supplement is great value for money making it a top budget buy.

Potential Drawbacks

According to the Amazon reviews, some customer has experience stomach pains after taking this supplement.

Check price and read more reviews of Country Life L-Lysine on Amazon.

The Verdict

Thanks a bunch for staying to the end of this L-Theanine vs L-Lysine showdown.

I hope it’s been an enjoyable read!

Hopefully, you now have a good idea of which of the 2 amino acids you’re going to use, but if you’re still on the fence, then here’s what I’d go for:

You might prefer L-Theanine if:

  • You want better sleep
  • You want to improve your mental function
  • You’re a coffee lover, but hate caffeine jitters

You might prefer L-Lysine if:

  • You suffer from anxiety
  • You suffer from cold sores
  • You want to improve your bone health

Hope this helped!

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