Analysis: These supplements are often seen as a way of slowing down some signs of ageing, but research studies and clinical trials are not conclusive
By Marina Navas, Trinity College Dublin
Collagen is a protein that is present in our skin, bones and cartilage. Production decreases with age, which results in a loss of skin elasticity and hydration along with the emergence of wrinkles. Considering this, collagen supplements are seen as a way of slowing down some signs of ageing - but can supplementation actually help replenish this lost collagen?
Collagen supplements are made from animals' bones, cartilage and skin. Collagen can be processed to obtain small protein fragments called collagen hydrolysates, which are easier to digest and absorb than the unprocessed collagen protein. These hydrolysates are the main ingredient of collagen supplements on store shelves.
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But clinical studies conducted with humans present some big limitations that should be considered before making a purchase. Originally scientists thought that when you eat a protein, like collagen, the amino acids that it is composed of are separated in the intestine and absorbed individually, but this is not fully true. Apart from individual amino acids, we can absorb groups of two and three amino acids, called peptides, which can have beneficial activities in our body.
When we take collagen hydrolysates, these peptides are absorbed into our blood. In studies with animal and cell models, these peptides can reach the skin and stimulate collagen production. These results are promising but studies in animals and cell models are not enough to say that collagen supplements can improve skin quality in humans. We need large, reliable clinical trials with human participants.
Clinical trials divide people into two groups, one receiving the treatment (in this case, the collagen supplement) and the other one receiving a placebo (a tablet or a drink which doesn’t contain collagen). The group that receives the placebo is called a control group. In this way, scientists ensure that the participants don’t know if they are receiving collagen or just a placebo. In one collagen study, the control group did not receive a placebo. So, those who were getting collagen knew they were, and this can influence the results. More trust-worthy studies are those where both the participants, and the doctors don’t know whether they’re getting or giving the treatment or the placebo.
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At the beginning of any clinical trial, both the treatment and the placebo groups need to be as similar as possible to single out the study variable. For example, imagine you wanted to test a pill to see if it can make people run faster. If you make the control group run a marathon first, the treatment groups are likely to run faster. The results cannot be attributed to the effect of the pill, but rather that the control group started with a disadvantage.
In some of the collagen studies, the group receiving the supplements had significantly worse skin quality at the beginning than the control group, and so they had more room for improvement. In this case, the two groups are not comparable, and we must interpret any positive outcome from these studies with caution.
It is also important to make sure that both groups are as similar as possible in terms of age. In a recent study, the placebo group was significantly older (32 to 48 years old) than the treatment group (31 to 37 years old). We know that skin quality worsens with age, so it would be unsurprising if at the end of the study the placebo group fared worse in many skin quality parameters.
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Another limitation of some clinical trials is that the comparison of outcomes is made within the treatment group. For example, the skin’s water content is compared between the people receiving collagen supplements at the end of the test and the people receiving the supplements at the beginning of the test. This can be misleading because of what statisticians’ call "regression to the mean". It indicates that there is natural variation in every outcome we measure, even if no treatment is given.
For example, the water content in your skin today is likely to be different to the water content in your skin next week. So, to make sure the difference in water content is due to the collagen supplements and not just to chance, it is necessary to compare the treatment group to a control group. This will reduce the chances of falsely concluding that the supplements work.
There are a few robust studies which demonstrate an improvement in skin elasticity of the forearm and the cheek, skin hydration, roughness and wrinkle count in the face. However, these studies are considered small, as the largest one enrolled just 85 people. If this was the case of a pharmaceutical drug, it would be necessary to test it in thousands of people to prove its efficacy.
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Moreover, it is not possible to extrapolate these positive results to the whole world’s population. This is because the age range was limited to 35 to 59 years old, some studies were conducted with Asian people and others with European people, which might react differently to the supplements, and the studies worked with women only. The trials which showed positive results lasted 8 weeks, so there is no way of knowing if the effects wear out over time, or for how long we should continue to take the supplement for a long-lasting effect.
Another issue is that the majority of collagen studies look at people who already display signs of natural aging such as wrinkles, have dry skin and low water content or were self-conscious about their skin appearance. Given this there is no way of knowing if collagen supplements can prevent the signs of skin aging if you start taking them at a young age, but only if they are effective to treat them once they are visible. It should also be noted that most clinical studies for supplements are financed by the same companies which sell said supplement. Inherently, they are more likely to report just the positive results.
Yes, some studies found a positive association between collagen supplements and skin quality. However, due to their limitations, there is not enough evidence to say that collagen supplements will improve the skin quality of the general population. This might change in the future, when larger, longer and more robust studies are available.
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Marina Navas is a PhD candidate with SSPC, the SFI Pharmaceutical Research Centre, at Trinity College Dublin.
The views expressed here are those of the author and do not represent or reflect the views of RTÉ
