Several readers have inquired about PQQ foods and whether diet alone is sufficient to obtain enough pyrroloquinoline quinone to be biologically effective. The answer — relative to what is known about optimizing growth in rodent nutritional growth experimental models — is probably yes. However, some rather broad assumptions have to be made, because of the limited amount of data regarding the forms of PQQ in different foods.
For perspective, Dr. Steinberg out of the University of California, Davis has presented data that suggests PQQ is needed at ~200-400 micrograms per kilogram of dry food. Given that most lactating mammals have the same vitamin and mineral requirements, when those amounts are expressed on a food energy or dry food weight basis, one might infer humans — who consume about 300 to 500 grams of dry food per day (about 2000 Kcal) — need up to 100-200 micrograms of PQQ per day. You can learn more about the benefits of PQQ by clicking here.
In the section, Pyrroloquinoline quinone and CoQ10, we previously discussed that pyrroloquinoline quinone exists as salts or as complex derivatives of amino acids, imidazolopyrroloquinolines, and abbreviated IPQs. For PQQ consumed in the diet (even as a supplement), much of it is converted to IPQ (Pyrroloquinoline Quinone Improves Growth and Reproductive Performance in Mice Fed Chemically Defined Diets). In human milk, the ratio of IPQ to PQQ was estimated to be about 8:1 (Characterization of Pyrroloquinoline Quinone Amino Acid Derivatives by Electrospray Ionization Mass Spectrometry and Detection in Human Milk). In foods, it is reported that the ratio under assay conditions may be closer to 2:1 (Simple and Sensitive Method for Pyrroloquinoline Quinone (PQQ) Analysis in Various Foods Using Liquid Chromatography/Electrospray-Ionization Tandem Mass Spectrometry). Regrettably, tissue preparation, acidity or alkalinity, and temperature can impact and alter PQQ and IPQ values. For example, under alkaline conditions (above pH8) almost all pyrroloquinoline quinone is converted to derivatives when PQQ is introduced into a complex mixture or environment.
PQQ Foods *
* In addition to the values taken from published papers, some of the values are from conference reports or abstracts presented at meetings. As noted in the main body copy, there is a lot of variability. Kamazama et al. in their 1995 Biochemistry Journal paper report ~0.06 micrograms as the PQQ concentration in dried skim milk per 100 grams of milk solids. However, later in an abstract of a paper presented at the Biochemical Society Transactions in 2000 in England, they report detection and quantization of IPQ in human breast milk at 0.14 to 5.5 microgram/100 mL of fresh milk or 1.4 to 55 micrograms per 100 grams of milk solids. Given the variability, my estimates are in line with the data reported in Characterization of Pyrroloquinoline Quinone Amino Acid Derivatives by Electrospray Ionization Mass Spectrometry and Detection in Human Milk, i.e. ~140-180 micrograms (PQQ +IPQ) per 100 g of milk solids. Moreover, Fluckinger et al. reported that the PQQ concentration of milk is 15-150 micrograms/100 mL or 150 to 500 micrograms/100 grams of bovine milk solids. For the Fluckinger assays PQQ was separated and then measured using a 16-channel electrochemical detector, a highly precise and sensitive procedure. All other assay involved sophisticated separation and mass spectrometer for detection, also highly precise and sensitive. The information above is also derived from the work of Kumazawa et al. (Levels of pyrroloquinoline quinone in various foods). Some of the values are higher than corresponding values for foods analyzed by Noji et al. (Simple and Sensitive Method for Pyrroloquinoline Quinone (PQQ) Analysis in Various Foods Using Liquid Chromatography/Electrospray-Ionization Tandem Mass Spectrometry). Although the number of foods analyzed is small, an important finding is that PQQ has been observed in all tissues analyzed to date in both plants and animals.
In the above table, Column A indicates some of the currently available sources for pyrroloquinoline quinone (for which compositional values have been obtained). Column B are amounts taken mostly from the Kumazawa et al. paper, but are expressed as micrograms of PQQ per 100 grams of food (~1/4 lb) and not as nanograms per grams of food (as they were originally reported). Next, in column C, the amounts in column B are multiplied by 5-10 to obtain an estimate of micrograms of PQQ per 100 grams of dried foods or so-called food solids (e.g., given that most of the food items mentioned contain at least 75% water or more). Column D requires making some guesses. As noted, some researchers have reported that IPQ is 5 to 8 times greater than the amount of PQQ in tissues. While others have reported a low ratio of 2 to 3 for IPQ to PQQ. Thus, the apparent IPQ + PQQ values given in Column D range from the lowest to highest amounts obtained by multiplying arbitrarily the values in Column C by 2 or 8. Column E is even trickier. It represents the estimated amounts consumed per day for an “ideal” person consuming a maintenance diet of 2000 calories per day. Regarding the diet consumed, the values for the major food categories are based on the estimated amounts consumed per day (on a dry weight basis) derived from values given in the USDA publication, Profiling Food Consumption in America. The question is whether a typical selection of food can yield the minimum amount that corresponds to optimizing growth in animal models, i.e. about 100-200 microgram per day.
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Regarding various conclusions, the first is that much better data is needed. However, setting aside that concern and assuming the actual values for pyrroloquinoline quinone in PQQ foods may be at the median (middle) of the estimates provided, one can guess that a typical intake in humans is indeed about 0.3 mg or 300 micrograms of pyrroloquinoline quinone per day or more. That amount is very much in line with the amount of pyrroloquinoline quinone or PQQ + IPQ needed to stimulate growth in animals. It is also an amount that is found in human milk, which is always a good starting point for assessing a need related to growth or maintenance.
So what can we conclude about PQQ foods?
In the paper by Kumazawa et al. Levels of pyrroloquinoline quinone in various foods it is stated that probably the PQQ in animal tissues are derived at least in part from their diet and that the levels of pyrroloquinoline quinone in plant tissues are in the aggregate about 10 times those in animal tissues. In a review by Rucker et al. Potential physiological importance of pyrroloquinoline quinone, the same conclusion was reached, particularly given that stomach microflora does not make an abundance of PQQ. The data also begs the question do we need supplements and if so how much? Many of the PQQ products sold are in the 10-20 mg range. As indicated in the section — PQQ Dosage, What size pyrroloquinoline quinone pills should I take? — we discuss that the reasonable pyrroloquinoline quinone dosage, like many supplements, for an active adult is probably the result of an arbitrary decision.
It can be confidently speculated that pyrroloquinoline quinone (PQQ) was present throughout the earliest phases of biological conception. This is because compounds with the properties of PQQ are present in stellar dust. Cometary grains are considered to be the precursors of organic materials in early life on the earth. It can also be argued that compounds with the properties of PQQ would have been important in initiating the early chemical processes important to evolution.
Consequently, for animals and humans, there appears to have been continuous exposure to PQQ-like compounds. PQQ’s chemical properties are novel, somewhat like combining the best attributes of the vitamins:
- ascorbic acid
- pyridoxine (vitamin B-6)
…into one molecule. Under appropriate conditions, PQQ is capable of catalyzing repeated oxidation and reduction reactions on a per molecule or molar basis hundred of times more efficiently than ascorbic acid and is capable of modifying amino acids to produce products, such as those that result from B-6 dependent enzymes. Moreover, PQQ is very stable to heat and harsh chemical environments. Pyrroloquinoline quinone is also water soluble. The potential number of catalytic cycles (number of repeated reactions) depends very much on chemical stability. PQQ does not easy self-oxidize or destruct, which is not the case for many bioactive quinone-containing compounds (e.g. the red wine and chocolate bioflavonoids) or so-called enediols, such as ascorbic acid). Although PQQ (both the oxidized and reduced forms) is not an effective antioxidant in aqueous-based environments. PQQ in lipid solvents or when amino acids are present in aqueous systems is a very powerful antioxidant and used as a “gold standard” in chemical-based assays. The facts surrounding pyrroloquinoline quinone cofactor biochemistry are unique, novel, and are fundamental to PQQ’s ability to perform unique and novel biological applications.
As a final point, unlike many dietary factors and biofactors, the pyrroloquinoline quinone found in PQQ foods (and its derivatives) are sustained in tissues and seem to play a fundamental role related to energy metabolism. In this regard, the need for PQQ might vary depending on your desired outcome.