Collagen is one of the most important structural proteins in the human body and is found in skin, bones, joints, muscles and many other tissues. However, the collagen content of the skin declines with age¹.
Many people therefore take collagen supplements. But the question arises: can you take collagen permanently or should you take breaks? Is there an ideal dosage and are side effects possible with long-term use? In this article, we look at the scientific findings on collagen supplementation and provide recommendations for safe use.
Can you take collagen permanently? Scientific findings
The function of collagen in the body
Collagen makes up around 25 to 30% of all body protein and is found in skin, tendons, ligaments, bone and cartilage, among other tissues². With age and UV exposure, the collagen-rich scaffolding of the dermis, the deeper layer of the skin, gradually breaks into fragments³.
Collagen is also available as a dietary supplement. But is there any scientific evidence that long-term collagen intake is safe?
Recommended daily dose of collagen
Studies have used daily amounts of between 2.5 and 15 g of collagen peptides⁴. Examples from studies:
- 2.5-5 g daily: the amount women aged 35 to 55 took in an eight-week study on skin elasticity⁵
- 10 g daily: the amount athletes took in a 24-week study on activity-related joint pain⁶
- 15 g daily: the amount older men with age-related muscle loss (sarcopenia) took in a twelve-week study in which they also did strength training⁷
What do studies say about long-term use?
To date, there is no evidence that long-term collagen supplementation is harmful to health.
Another study followed 25 participants who took 2.5 g of collagen peptides daily for 24 weeks: afterwards their nails grew 12% faster and broke 42% less often than at the start⁸. There was no comparison group without collagen, so the changes cannot be reliably put down to the collagen. An analysis pooling several studies with a placebo comparison group looked at how people with osteoarthritis (joint wear) rated their joint symptoms and pain on questionnaires while taking collagen⁹. In such questionnaires, people rate for themselves how severe their pain, stiffness and everyday limitations are. The participants had a medical condition; the analysis says nothing about healthy people.
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Long-term intake: what studies have measured
Skin
The dermis is made up largely of collagen. In one study, 69 women aged 35 to 55 took 2.5 or 5 g of hydrolysed collagen or a dummy product (placebo) daily for eight weeks. At the end, skin in both collagen groups was more elastic than with placebo. For skin moisture, the difference was too small to rule out chance⁵. Elasticity describes how well the skin springs back after being stretched; skin moisture, how much water the outer layer of the skin holds. One specific product was tested over eight weeks; the study does not show what happens with long-term use.
Joints and bones
Collagen is found in cartilage and bone; collagen peptides contain substantially more proline and glycine than other protein sources². In one study, postmenopausal women took 5 g of collagen peptides or a dummy product (placebo) daily for twelve months. With collagen, their bone density at the spine and the top of the thigh bone rose more than with placebo¹⁰. Bone density shows how much mineral the bone contains; doctors use it to estimate the risk of fractures. Only women whose bone density had already dropped with age were studied.
Hair and nails
Hair and nails are made of keratin, not collagen; collagen-rich connective tissue sits instead in the scalp and the nail bed. Collagen peptides supply amino acids such as proline and glycine that the body uses as raw material for its own proteins.
Gut
The intestinal lining is supported by collagen-containing connective tissue, and collagen peptides supply amino acids such as glycine and proline as raw material.
Possible risks or side effects of long-term use
Overdosing on collagen - is that possible?
An overdose of collagen is unlikely, as the body does not store excess collagen but breaks it down. Very large amounts can, however, upset your digestion.
Digestive complaints and intolerances
Some people report flatulence, bloating or heartburn after taking collagen. In such cases, it may help to take collagen with a meal or to increase the dose slowly.
Interactions with other nutrients or medications
Collagen hardly interacts with other nutrients or medications. Vitamin C contributes to normal collagen formation for the normal function of skin, bones and cartilage, so it is worth getting enough of it from your diet.
Other possible side effects of collagen
Collagen is generally considered well tolerated, but in some cases unwanted reactions can occur. Alongside digestive complaints and intolerances there are a few other side effects that appear less often but are still worth knowing about.
Collagen and skin reactions: can it trigger allergies?
Although collagen is usually well tolerated, there are reports of skin reactions such as itching, redness or mild rashes. This mostly affects people who are sensitive to particular collagen sources, such as fish collagen or bovine collagen.
If skin irritation occurs after taking collagen, it is worth switching to a different collagen source or pausing intake. Anyone with a known allergy to fish or beef proteins should consider vegan alternatives or specially filtered collagen products.
Can collagen affect blood sugar?
Some people wonder whether collagen affects blood sugar, especially when eaten with other foods. People with diabetes or insulin resistance should take collagen with a protein-rich meal and keep an eye on their blood sugar.
So far, however, there is no clear scientific evidence that collagen has a negative effect on blood sugar levels. If you are unsure, speak to a doctor.
How can you avoid side effects from collagen?
There are a few simple measures that can help improve tolerance and keep side effects to a minimum.
Pay attention to quality and additives
Not all collagen products are the same. Some contain artificial flavourings, sweeteners or additives that can cause gastrointestinal complaints or intolerances. High-quality collagen should be pure and free of unnecessary additions.
Combine collagen with vitamin C
Vitamin C contributes to normal collagen formation for the normal function of skin, bones and cartilage. If you like, combine your collagen with a source of vitamin C such as lemon juice, acerola or berries.
Increase the dose slowly if your stomach is sensitive
If you are taking collagen for the first time, start with a low dose (2–5 g a day) and increase the amount gradually. This helps your body get used to the new protein and avoids digestive problems.
Drink plenty of water
Because collagen is a highly concentrated protein, you should take in enough fluid. If you do not drink enough, you may notice mild digestive problems or constipation.
In closing: is taking collagen long term safe?
So far there is no evidence that taking collagen long term is harmful. Studies have mostly used 2.5 to 10 g of collagen a day. If you choose a high-quality collagen product and tolerate it well, nothing known so far speaks against taking it long term.