How can you tell if a substance is safe?
There are different values that will tell you how safe an ingredient is. The easiest is the Tolerable Upper intake, abbreviated as UL. This is a limit, set by the (American) government, under which an ingredient is considered safe. However, not everything has a UL. You can also look at the NOAEL of an ingredient: the maximum tested dose that causes no side effects . Sometimes these values are only available for animals because these types of research test the boundary of what is safe. Whilst this may seem strange, there are very reliable calculation methods to convert these results into values that are safe for humans. If no information from clinical trials is available that has tested the maximum dose that causes side effects, then you can look at the highest dose that has been investigated without any side effects. In this article we examine the most reliable and available of these methods for each ingredient.
Acetyl-L-Carnitine (500 mg)
There are several studies in which the NOAEL is converted to a minimum of 24 grams of Acetyl-L-Carnitine for an average person of 80 kilos . In a dose of FLVX is 500 mg.
Caffeine (100 mg)
The European Food Safety Agency and the US National Academies of Science, among others, conclude that for healthy individuals a caffeine intake of up to 400mg per day poses no health risks [4,5,6]. In addition, the EFSA states that you can safely take up to 200mg of caffeine at a time without health risks.
Caffeine is the only substance in FLVX that you can build a tolerance for. You can circumvent this by regularly taking a break from caffeine intake.
L-Theanine (200 mg)
Research shows that at a dose of up to 4000mg per kg bodyweight in rats there were no side effects . Converted to a human quantity (the so-called HED)  this is approximately 4400 mg for a person of 80 kg. The company Suntheanine even performed research that showed that a human dose of 7200 mg had no side effects. In FLVX there is 160 mg of L-theanine.
Rhodiola Rosea (300 mg)
There is no UL published for Rhodiola Rosea because it is an herb, but there is a lot of research into the use of this herb for different purposes, with dosages being tested up to 680 grams. These studies show that in clinical trials with humans there are no side effects that are clinically relevant .
Methylcobalamine (B12, 500 mcg)
This is the most easily absorbed form of vitamin B12. B12 and a number of other vitamins an UL is deliberately not determined because they generally do not cause side effects even at very high doses. The NOAEL is 1000 micrograms. In several studies doses of 1000 mcg per day was used without side effects . In another study, 1000 mcg per day was used in combination with other B vitamins without side effects for 5 years .
Methylfolaat (B11, 400 mcg)
Methylfolate is a very bio-absorbable form of folate, also known as vitamin B9 (but as methyl folate it is called B11). Folate proves to be safe even in extremely high doses. In general, doses of 5,000 to 15,000 mg are tolerated without significant side effects .
Vitamin B6 (20 mg)
B6 can lead to neuropathic problems in high doses. The lowest dose where this is reported is 200mg. This is also the NOAEL. FLVX contains 20 mg.
Want to read more about these ingredients and their safety?
There are a number of sources available where scientific research is brought together and summarised in plain english. Examine.com is one of these, and contains extensive information about almost every possible substance. In addition, WebMD and Mayo Clinic are also reliable sources of information.