Should collagen supplements be taken with meals or an empty stomach?

Different collagen supplements and products have different preferences and opinions about the best time to take collagen.  The most general consensus, is collagen supplements should be taken on an empty stomach.  

But what does “on an empty stomach” mean exactly?

There are many people who claim taking collagen supplements work on an empty stomach providing them with the best collagen effect and results. Many people abide by this method because you need stomach acid to digest proteins, so in theory taking collagen on an empty stomach ensures you will be able to better break down the collagen.

A study conducted by researchers of USA proved that taking collagen on an empty stomach prior to bedtime provides the best results. This collagen study checks the effect of collagen in patients suffering from rheumatoid arthritis. Significant pain reduction reported by this study including morning stiffness, stiffness following periods of rest, pain that worsens with use of the affected joint and loss of joint range of motion and function. The subject received a single oral daily dose of 10 mg UC-II on an empty stomach prior to bedtime for 42 consecutive days. Moreover, the study confirmed that pepsin is necessary to break down the collagen. Pepsin is produced in the stomach and is one of the main digestive enzymes in the digestive systems of humans, where it helps digest the proteins. It will be in larger amount when the stomach is empty.

So in summary, this collagen research indicates taking collagen on an empty stomach to be effective.  

Similarly, a study conducted in Japan reported the efficacy of collagen in sleep deprivation. The study found that oral ingestion of glycine (present in collagen) before bedtime, empty stomach, significantly improve the quality of sleep. The study found a significant concentration of glycine in cerebrospinal fluid and plasma that is associated with the decline in core body temperature. A decline in core body temperature is associated with improvement in sleep quality. So, the breakdown of collagen is necessary if you want to convert collagen into glycine. Again, it is better to use collagen on an empty stomach or after 2 to 3 hours of a meal.  

Further supportive information can be obtained from the following articles:

https://www.ncbi.nlm.nih.gov/pubmed/12837047

https://www.jstage.jst.go.jp/article/jphs/118/2/118_11R04FM/_article