L-Hydroxyproline: Benefits, Side Effects, Best Time to Take It & More

L-Hydroxyproline

(Hydroxyproline)

Evidence: Very Low
Possible Benefits: Low
Safety: Reasonable

What is L-hydroxyproline?

L-hydroxyproline is a non-essential amino acid. As a supplement, it is often used for improving the production of collagen. Unfortunately, there are very few studies on hydroxyproline and it doesn’t seem to have any benefits outside of correcting a hydroxyproline deficiency to produce enough collagen. This article is about the main benefits of L-hydroxyproline, its potential side effects, the best time to take it, and more.

What does L-hydroxyproline do for the body?

Since L-hydroxyproline is a non-essential amino acid, you do not need to consume it to survive. However, this amino acid still plays an important role in human health.

The main function of L-hydroxyproline is forming collagen molecules and supporting collagen stability.

This leads to many potentially beneficial effects, such as forming connective tissue, repairing skin damage and wounds, healing the gut lining, and repairing joints.

Possible benefits

All of the potential benefits mentioned below are dose-dependent. Generally, the higher the dose, the more pronounced the effects are. However, they do reach a plateau at a certain point. We will discuss the best dosing protocol later in this article.

Correcting impaired collagen production – Those who cannot produce enough collagen due to a hydroxyproline deficiency are likely the only ones to benefit from a hydroxyproline supplement. As far as we know today, there don’t seem to be any other benefits of supplemental L-hydroxyproline.

Possible side effects

These side effects are dose-dependent. The risk for them increases (often linearly but sometimes exponentially) as you increase the dose. Some of the side effects only apply to very high doses.

Amino acid imbalance – Essential and non-essential amino acids should be kept in balance as they act synergistically in many ways. Too much of one amino acid can sometimes cause side effects if there isn’t enough of another amino acid. For example, this principle applies to glycine and methionine, lysine and arginine, and the BCAA trio. There are many other proven and unproven examples. Food or a protein powder is usually a better choice for getting enough amino acids unless you have a specific goal in mind targeted by a particular amino acid/s.
Toxicity – While acute toxicity has never been reported, taking high amounts of L-hydroxyproline could lead to chronic toxicity and cause some health problems. To prevent chronic toxicity, it is best to stay below 1 gram a day unless you have a great reason to take more.
Contamination – Contaminated supplements are uncommon in the USA and other well-regulated countries. However, if you wish to buy products from China, India, or other countries without strict regulations, beware that the supplements may be contaminated. Either way, you need to choose the brand you order from wisely. It is highly recommended to check the certificates or read through some reviews for the specific product before you buy it. The FDA (Food and Drug Administration) has the power to regulate dietary supplements but can only do so after they have been on the market for a while. That’s because supplement companies are not obligated to announce to the FDA when releasing a new product on the market. The FDA has to discover the product and test it for potential impurities, which can take a lot of time. During that time, the supplement can be sold on the market even if it’s impure. Also, supplement companies can change their manufacturers without announcing it to the FDA.

Who should not take L-hydroxyproline?

You should probably avoid taking the supplement if you:

get enough hydroxyproline from food
experience a severe adverse reaction after taking the amino acid
are on a tight supplement budget (since there are more cost-effective supplements on the market for most people)

Who will benefit the most?

You should consider taking the supplement if you:

consume very little protein (less than 0.3 grams/pound of body weight)
are over 60 years old and/or don’t produce enough collagen

How much L-hydroxyproline should you take?

There is almost no scientific data on L-hydroxyproline supplementation and what the right dose would be. This segment is mostly speculative.

Since this amino acid can be found in food or synthesized in the body, you may already get sufficient amounts without taking it as a supplement. About 0.36 grams of protein/pound of body weight should generally be enough to prevent any symptom deficiency.

If you plan to take L-hydroxyproline as a supplement, 500 mg appears to be the best daily target for most people. This amount should provide most of the benefits without meaningful side effects.

People with impaired collagen production due to a hydroxyproline deficiency may benefit from doses higher than 500 mg.

The upper safety limit for hydroxyproline is not well-established. To stay on the safe side, don’t take more than 1 gram daily unless you have a great reason to do so. Higher amounts may cause problems if you take the supplement for a prolonged period.

Food sources of L-hydroxyproline

Hydroxyproline is found in all whole foods that contain dietary protein.

The amount of L-hydroxyproline per gram of protein varies from food to food but a general rule of thumb is that the more protein you eat, the more proline you are getting from food.

The easiest way to find out exactly how much hydroxyproline or other amino acids you are getting from food is with Cronometer.com. This free app allows you to track all vitamins, minerals, and more.

Best time to take L-hydroxyproline

Like most other amino acids, L-hydroxyproline is water-soluble, so you don’t have to take it with food to absorb it well. Taking the supplement with food is better if it causes stomach upset when you take it on an empty stomach.

Whether you take the supplement in the morning or the evening doesn’t matter much. It should not interrupt your sleep in any way.

If you practice time-restricted eating, take this amino acid during your eating window to guarantee it won’t break your fast.

Unless it feels too impractical, spread the daily dose into 2+ smaller doses throughout the day.

Interactions

Other amino acids
Essential and non-essential amino acids should be kept in balance as they act synergistically in many ways. Too much of one amino acid can sometimes cause side effects if there isn’t enough of another amino acid. For example, this principle applies to glycine and methionine, lysine and arginine, and the BCAA trio. There are many other proven and unproven examples. Food or a protein powder is usually a better choice for getting enough amino acids unless you have a specific goal in mind targeted by a particular amino acid/s.

Where to buy L-hydroxyproline

Amazon is the best option for ordering L-hydroxyproline supplements in most countries. They offer some very affordable products backed by many positive reviews. Also, you can choose from a wide range of brands without having to search through other markets on the internet.

Beware some brands display the dosage per serving instead of per pill or capsule. Therefore, you may accidentally buy something less potent than you intended. Do not fall for this marketing trick.

FAQ

You can take the amino acid daily and do not need to cycle it. However, it is certainly not a problem if you don’t take it daily. Not taking the supplement every once in a while could lead to better absorption. That is yet to be proven or disproven.

All of these options are fine. The two most important things to consider are the price and dosing. Powders are almost always the cheapest form. However, you may need a highly accurate scale to dose them correctly (preferably 0.001g). You can get one for as little as $20 from Amazon. Dosing the powders also takes some time that can add up over months or years. The disadvantage of capsules is that they often contain bovine gelatin, which rarely comes from an ethical source.

Yes. Most amino acids, including L-hydroxyproline, absorb and digest well if you take them before falling asleep. The supplement should not impact sleep quality in any significant way.

This amino acid should not become harmful once it exceeds the expiration date but can lose potency over time.

Keep the supplement in a cold, dark, and dry place, and it should remain just as potent for many months or even years.

While toxicity is rare, too much L-hydroxyproline in the system can cause some health problems, often related to causing an imbalance in other amino acids. It is best to stay below 1 gram a day to prevent these side effects.

You may need more of this amino acid if you:
– eat very little protein (less than 0.3 grams/pound of body weight)
– are over 60 years old and/or don’t produce enough collagen

The half-life of hydroxyproline in the body is about 5 hours. This amino acid stays in your system for about 1-2 days after you consume it.

In the long term, you need to take the supplement for about 2-4 weeks to begin noticing the benefits.

You can easily find vegan-friendly L-hydroxyproline pills and powders but always check the label to be sure. If you buy the amino acid in a capsulated form, beware that the capsules often contain animal-based gelatin. Instead, find a brand that puts its products into cellulose capsules.

Like most other amino acids, L-hydroxyproline is water-soluble, so you don’t have to take it with food to absorb it well.

L-hydroxyproline should not break a fast unless you take a very high dose at once. If you practice time-restricted eating, take this amino acid during your eating window so it doesn’t break your fast.

References

Most of the information provided in this guide is supported by scientific research that can be found and verified in the PubMed medical library. We highly encourage you to use the library to verify anything said in this article. We excluded from consideration studies that are either confounded or have a high conflict of interest.

TABLE OF CONTENTS