The hypothalamic–pituitary–gonadal axis (HPG axis) plays an important role in the development and regulation of a number of the body’s systems, such as the immune and reproductive systems. Fluctuating hormone levels cause changes in the hormones that are produced by each gland and as a result have a variety of widespread and local effects in the body. The HPG axis can be influenced by lifestyle and dietary factors such as stress, inadequate sleep, illness, the use of certain medications including hormones, as well as poor dietary habits. This axis can also be subject to disorders such as hypothalamic–pituitary failure or
Although interfacing with clinical data can even make our heads spin at times, it’s important to have an understanding of what actually makes a good, viable study.
Unfortunately, many publications report the bioavailability of curcuminin without actually distinguishing between free form curcumin, curcumin metabolites, and total curcuminoids (curcumin, DMC, BDMC).
This will inevitably skew what was actually measured in sample blood, versus what is reported in the corresponding publication. Don’t forget about our little friend Beta-glucuronidase either, seeing the use of this enzyme further skews results generating false values for Free Form Curcumin. For the sake of accuracy, simple honesty, and the varying potency of each form, it is critical that all of the forms are clearly distinguished and measured correctly. These details can be confirmed in the materials and methods section of a study.
Here is a loose outline of what a curcumin study looks likes to help you imagine the process:
- A set dose of a curcumin is administered to human subjects once a day.
- Blood samples are collected before curcumin is administered at very specific intervals over the course of 24 hours.
- The concentrations of curcuminoids are measured in order to plot a concentration time curve.
Results include the following:
- Cmax (Concentration maximum) is when a drug reaches its peak concentration in the blood after administration. This is depicted by the highest point on a graph.
- Tmax (Time maximum) is the time a substance takes to reach maximum concentration.
- AUC (Area Under the Curve) is the overall amount of a therapeutic agent in the bloodstream after a dose. The AUC is dependent on the dose and the rate of elimination from the body.
Some other important keys to a well-designed study are: human subjects, the number of subjects, and appropriate controlled variables.
The human league should be the only league when it comes to study subjects. Although there is merit in animal studies, humans are not rats, mice, or any other kind of animal. We have entirely different anatomy, physiology, and biochemistry. Thus, data from a different species cannot accurately show what happens within humans in all cases. This is why healthy human volunteers are used in bioavailability studies to increase accuracy by removing factors such as disease, medication, smoking and other lifestyle influences.
When it comes to sample size, the more the merrier. Although some studies with smaller samples are still very well-designed and executed, it is even better when more subjects are involved.
Larger sample sizes offer higher accuracy, seeing the result is demonstrated many more times. This is a standard that all studies should strive for.
The importance of specific scientific controlled variables is critical to a well-designed study. Unbiased studies incorporate positive and negative controls, including placebos, randomization, blind and double-blind experiments.
Making Sense of Curcumin Bioavailability Claims
This is where things can get a little technical. Instead of hiding behind altered data and complex arguments, let’s clarify the research associated to some of the popular curcumin forms on the market. As mentioned, every curcumin on the market has a bioavailability study that companies base their absorption claims on, i.e. 100x more bioavailable.
Before comparing any two products, there are a few points to take into consideration. In general, studies investigating bioavailability of curcumin have focused on exploring the fold increase in comparison to standard Curcumin-95, which we know has very poor bioavailability. AUC (area under the curve) is considered the best method to use in any comparison. While comparing to a standard is a good reference point, the AUC method is dose dependent; therefore, it is not possible to conclude with any accuracy what the effect of an increase or decrease in dose will have on the AUC.
Again, many publications report the bioavailability of curcuminin without actually distinguishing between free form curcumin, curcumin metabolites, and total curcuminoids (curcumin, DMC, BDMC). However, in Schiborr et al., (2014), each individual curcuminoid (curcumin, DMC, BDMC) was investigated separately. Using this same methodology, Kumar et al., (2016), highlight that CurQfen is 270x higher than standard curcumin.