Analysis and toxicological evaluation of Cannabinoids in hemp food products-a review

Abstract

After having abolished the prohibition of the cultivation of the species Cannabis sativa L. (so-called fibre hemp) with minor content of the psychoactive Δ 9 -tetrahydrocannabinol (THC), a wide variety of hemp food products is currently offered on the market. In this review, an introduction to the botany of the hemp plant and the current law situation in Germany and the European Union is presented. A survey of the analytic techniques used to verify compliance with the guidance values is given and the THC content of hemp food products is discussed in regard to its toxicology. In particular, the forensic-toxicological aspects regarding the influence of hemp food on drug tests are described.

Full text

Electron. J. Environ. Agric. Food Chem.
ISSN 1579-4377 812
ISSN: 1579-4377
ANALYSIS AND TOXICOLOGICAL EVALUATION OF CANNABINOIDS IN
HEMP FOOD PRODUCTS - A REVIEW
Dirk W. Lachenmeier and Stephan G. Walch
Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weißenburger Str. 3, D-76187 Karlsruhe, Germany
Web-address: http://www.cvua-karlsruhe.de, E-Mail: Lachenmeier@web.de
KEYWORDS
Hemp food, fibre hemp, Cannabis sativa L., cannabinoids, tetrahydrocannabinol (THC), forensic
toxicology, drug tests
ABSTRACT
After having abolished the prohibition of the cultivation of the species Cannabis sativa L. (so-called fibre
hemp) with minor content of the psychoactive Δ9-tetrahydrocannabinol (THC), a wide variety of hemp
food products is currently offered on the market. In this review, an introduction to the botany of the hemp
plant and the current law situation in Germany and the European Union is presented. A survey of the
analytic techniques used to verify compliance with the guidance values is given and the THC content of
hemp food products is discussed in regard to its toxicology. In particular, the forensic-toxicological
aspects regarding the influence of hemp food on drug tests are described.
INTRODUCTION
Hemp containing food products are currently experiencing a revival. After the legalization of fibre-hemp
cultivation, hemp food products, mostly sold in esoteric stores, were consumed due to supposed
psychoactive properties associated with a potential content of Δ9-tetrahydrocannabinol (THC). Since the
mid 1990s, hemp food has gradually expanded into the natural product market and is increasingly found
in natural food stores for positive nutritional and health benefits. In 1995, the first hemp food product on
the market was hemp oil [1]. Nowadays various hemp food products are available, e.g. hemp leaves (tea),
hemp seeds, hemp oil, flour, beverages (beer, lemonade), and cosmetic products. In the meantime a
flourishing trade is establishing itself via the internet.
After a short description of the hemp plant and an introduction into hemp foodstuff, the analytical
possibilities to determine THC in food samples are described. The THC content of hemp food products is
discussed in regard to its toxicology and possible influence on forensic drug tests.
HEMP – Cannabis sativa L.
The hemp plant Cannabis sativa L. (Cannabaceae), which is a very old culture plant, comes from the
restrained wides of Central Asia until Northwest India. Their shoot axis fibres were already used in the
second millennium BC in China, especially for the there invented paper manufacturing [2, 3] (Fig. 1).

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Glandular trichomes, especially densely on the underside of the leaves along the leave veins and in the
area of the inflorescence, are found on the whole surface of the plant besides seeds and roots. These
contain resin consisting from 80 to 90% of cannabinoids as well as essential oils, high-polymeric phenols,
terpenes and waxes [4,5]. The cannabinoids belong to the chemical class of terpenophenolic compounds
that only occur in the hemp plant. The psychoactive compound is Δ9-tetrahydrocannabinol (THC).
Besides 60 other known cannabinoids, cannabidiol (CBD) and cannabinol (CBN) are further main
components [6] (Fig. 2). In reference to the content of THC, it is possible to distinguish between drug
hemp and fibre hemp. The phenotypes of Cannabis sativa are characterized by the ratio of
(THC+CBN)/CBD [7-10] (drug hemp > 1; fibre hemp < 1). Recently it was described, that the
simultaneous determination of THC, CBD and CBN in hemp containing food products and following
calculation of the Cannabis-phenotype-ratio allows the discrimination between fibre and drug hemp, even
as a food ingredient [10].
Figure 1. Hemp, Cannabis sativa L., drawing of the plant, inflorescences, fruit and seed (drawing by W. Müller [3]).
Tea is made of the leaves of the hemp plant, while flour and oil are made of the seed.
The biggest glandular trichomes are found in the bloom regions of the female hemp plant and in particular
on the leaves of the seed hulls. The content of cannabinoids correlates with the quantity of the glandular
trichomes [4,5]. Generally, all plant parts with the exception of the seeds can contain cannabinoids.
Therefore traces of cannabinoids determined in hemp seed products result from contamination with
cannabinoid rich plant parts. The concentration of THC in the seeds depends on the type of plant (fibre or
drug hemp) as well as on the degree of contamination at the harvest. Therefore, the tidiness of the seeds
plays the most decisive part in the concentration of THC in the seeds. The largest proportion of THC can
be found on the surface of the seed coat. As a consequence only very low THC concentrations are found
in the inside of the seeds (less than 2 mg/kg with drug hemp and less than 0.5 mg/kg with fibre hemp)
[11]. For the application as food products it must be made sure that the THC content of the seeds is not
increased by impurities, neither with THC-rich plant parts, nor by corresponding cultivation conditions
[12].
Especially the flowers of the female plants excrete a cannabinoid-rich resin from the glandular trichomes,
that is named hashish (THC-content 0.5-7%), while the inflorescences stuck together with resin are
commonly called marihuana (THC-content 5-20%) [2,13]. Drug hemp is usually grown illegally or by
chance as a by-product of the cultivation of hemp [2].

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Because of the drug problem, the breeding of plants with low THC-content was started in France and in
the former Soviet-Union in the 1970s, followed by Hungary in the beginning of the 1980s [14]. Present
day, fibre hemp species show, in the European Union (EU) guidelines corresponding THC-content of less
than 0.2%. Even the selection of phenotypes with less than 0.05% THC was successful [14, 15].
Psychoactive effects with the consumption of fibre hemp plant parts could not be observed [16].
O
OH
Δ9-tetrahydrocannabinol (THC)
HO
OH
cannabidiol (CBD)
O
OH
cannabinol (CBN)
Figure 2. Structure of THC, CBD und CBN, the main cannabinoids of hemp (Cannabis sativa L.).
Besides the phenotype of the plant, the cannabinoid content depends strongly on the climatic
circumstances of the cultivation. Some authors observed both with drug hemp and with fibre hemp higher
THC-contents in warmer and dryer continental areas than in maritime climate [17-19]. The Cannabis
plants are developing more glandular trichomes in these areas and therefore produce more cannabinoids
[4]. Bazzaz et al. [20] showed a significant reduction of the cannabinoid-content for both tropic and
temperate origins with rising temperature. Older examinations proved that the resin-content of the plants
depends less on the climate but for the most part on the hemp species, therefore, the cultivation of THC
rich hemp for pharmaceutical purposes is also possible in Central Europe [21,22]. It can not be excluded
either, that low content THC species can develop high concentrations under certain cultivation conditions
[23]. Generally, huge deviations can be observed in the resin and fibre content of the species Cannabis, so
that it is often unclear whether the deviation’s origin is the genetically difference or the difference in the
environmental conditions [24].
The hemp plant is primarily a fibre supplier. As by-product, the fruits, small round nuts (usually called
hemp seeds), are usually harvested and are sold traditionally as bird or fish feed. Because of their fat

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content of 30-35%, they are also used for the extraction of oil. A green, middle strong drying oil is
accumulated on that occasion, whose glycerides consist to 40-60% of linolic acid and to 14-28% of
linolenic acid [2].
HEMP AS FOOD
All parts of the hemp plant are completely usable (Fig. 3). Besides the application of seeds and leaves as
foodstuff, the usage of hemp in the manufacturing of textiles or paper is also possible. The press residue
of oil extraction is used as animal feed. The most promising product of the Cannabis cultivation to be
utilized as food is the seed and its derived products [25]. The protein of the hemp seed contains all 8
essential amino acids in the necessary proportions for the human nutrition [25, 26].
Hemp
(Cannabis
sativa L.)
Leaves
Flowers
Fibres Seeds
Flour
Foodstuff
Animal Feed
Edible OilTeaDrugsPaperTextiles
Figure 3. Possibilities of the industrial use of hemp.
Hemp oil contains the highest proportion of unsaturated fatty acids of all vegetable oils and contains
nutritional valuable essential fatty acids (approx. 75%) [26, 27] A problem is, that the unsaturated fatty
acid molecules are susceptible against oxidation, especially when they are exposed to light or heat [28].
Therefore, hemp oil shows an essentially shorter shelf life in comparison to other cold-pressed oils like
olive oil. This disadvantage makes the commercial exploitation of hemp oil difficult [25, 29]. Further on,
hemp oils are avoided by many consumers because of the unfamiliar taste and smell [28].
The application of hemp as food is currently restricted, because the available hemp species were bred in
regard to a high fibre production not in regard to a high seed yield [30]. The oil content of the fruits varies
between 9 and 34%. The most important breeding goal is, therefore, to obtain ripe seeds under Central
European conditions [14]. There is still some breeding potential especially in regard to an increase of the
gamma-linolenic acid content, as well as increasing the tocopherol content for the anti-oxidation
protection of the oil [29].
FOOD LEGISLATION
The THC maximum limit for hemp (measured in the upper third of the plant) has been gradually lowered
from 0.5% (1984) to 0.2% (since 2002) [31]. In Switzerland, all plant types of Cannabis can be grown
legally and varieties with high THC content are usual. However, THC content limitations were applied
for hemp food [28]. After decontrol of the fibre-hemp cultivation in 1996 [32], in Germany the former

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federal institute for health protection of consumers and veterinary medicine (BgVV, today: Federal
institute for risk assessment, BfR) estimated a provisional tolerable THC intake of 1-2 µg/kg/day [12].
From these estimations the following precautionary guidance values for THC in hemp-containing foods
were derived in the year 2000: beverages (alcoholic and non-alcoholic): 5 µg/kg, edible oil: 5000 µg/kg,
other food: 150 µg/kg [33].
The hemp cultivation for fibre production is subsidized in the European Union. The International
Narcotics Control Board (INCB, an organ of the United Nations) determined that a considerable market
for hemp food developed parallel into the expansion of the hemp cultivation in the EU, although the
effects of these products on health are not yet adequately researched. Moreover, the use of hemp seeds or
leaves in the food industry is seen to be problematic in regard of contributing to the overall benign image
of Cannabis as a drug. Hemp foods are not necessary for nutrition, anyway [12,34]. None of these
products can therefore be promoted by an EU allowance. In view of the biological similarities between
hemp that is used for industrial purposes and such from which psychotropic substances are gained, the EU
executes regular controls in order to test, whether the allowance encourages the illegal hemp cultivation.
With most cultivators, the THC content is controlled annually. Therefore, it is guarantied that only seed of
varieties with a low THC content according to the maximum limits is used. It turned out, that through the
new, intensified regulations the risk of the cultivation of high-content THC species is not disposed of
once and for all, but reduced to a negligible level [34].
ANALYSIS OF THC IN HEMP FOOD
Gas chromatography coupled with mass spectrometry (GC/MS) is the method of choice for the
determination of cannabinoids in hemp food products [10, 11, 28, 35-46] (Tab. 1). In singular cases thin-
layer chromatography [47], liquid chromatography coupled with UV and fluorescence detection [48] or
mass spectrometry [27] were used, as well as immunochemical screening methods [37, 39, 42, 49]. As
official community method [50] for the quantification of THC in hemp species, the gas chromatographic
separation and detection by flame ionisation is commonly used.
Table 1. Methods for the analysis of different hemp food products
Matrix Sample preparation Method
Limit of
detection Ref.
Hemp beer SPE, derivatization (methylation) GC-MS 1 µg/l [36]
Hemp beer SPE, derivatization (BSTFA) GC-MS
Immunoassay 1 ng/ml [42]
Hemp oil FFE (methanol) GC-MS [43,45]
Hemp oil FFE (methanol)
SPE GC-MS 1 mg/kg [41]
Hemp oil FFE (acetonitrile)
SPE, possibly derivatization (MSTFA) GC-MS
Immunoassay [44]
Hemp tea FFE (petroleum ether) GC-FID
GC-MS [38]
Seeds FFE (chloroform/methanol (99:1),
hexane/ethyl acetate (9:1)), SPE
GC/MS [11]
Seeds FFE (benzol) TLC [47]
Different hemp
food products FFE (methanol or ethyl acetate) GC-MS
Immunoassay [37,39,40,67]
Different hemp
food products FFE (methanol,
methanol/dichloromethane (9:1, v/v)) HPLC-UV
HPLC-FD 0.01 ng [48]
Different hemp
food products FFE (hexane), saponification GC-MS 12.9-17.3 µg/kg [46]
Different hemp
food products HS-SPME, on-fibre derivatization
(MSTFA) GC-MS 0.01-0.05 mg/kg [10]
LLE: liquid-liquid-extraction, GC: gas chromatography, FID: flame ionisation detector, MS: mass spectrometry, TLC: thin-layer
chromatography, SPE: solid-phase extraction, HS-SPME: headspace solid-phase micro extraction, BSTFA: N,O-Bis-trimethylsilyl-
trifluoroacetamid, MSTFA: N-Methyl-N-trimethylsilyl-trifluoroacetamid

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The result, which is obtained with the described gas chromatographic method, is called the “total THC
content”. Following a recommendation by the BgVV, this result is used for the assessment of hemp food
products. Besides THC itself, precursors are determined, which can be transformed into THC under
certain circumstances. The most important precursor acid is Δ9-tetrahydrocannabinolcarboxylic acid
(THCA). At higher temperatures, this acid can be transformed into THC, by a simple decarboxylation.
THCA has no psychoactive effect, therefore the pragmatic reason for its co-quantification is, that with the
usually applied gas chromatographic method the co-determination is not avoidable. A further argument is
the possibility of a growing THC content in hemp food products, if these products are heated. Even if
other methods are used, THCA has to be transformed into THC before the determination or in-situ.
Especially the determination by high-performance liquid chromatography (HPLC) can result in a too low
total THC content. Using HPLC, no decarboxylation as with the gas chromatographic method by the high
temperatures of the injector and column, occurs [51]. Before HPLC analysis a thermal decarboxylation
can be conducted, which transfers THCA quantitatively into the neutral THC without the possibility of
oxidative cannabinol formation [51-54]. Another approach is the simultaneous determination of THC and
THCA [55]. A gas chromatographic separation of THC and THCA is possible after a pre-analytical
derivatization.
a) Alkaline
hydrolysis
(
5 min
)
Hemp
sample
+ ISTD
+ NaOH
A
gitator with
heater (90°C)
sample: position 1
MSTFA: position 2
SPME-needle
attached to
autosampler
fibre holder
b) Headspace
extraction
(
25 min
)
25 µl
MSTFA
c) On-fibre
derivatization
(
2 min
)
d) Desorption
in GC injector
(
4 min, 250°C
)
Figure 4. Procedure for a fully automated analysis of hemp food samples with alkaline hydrolysis,
headspace solid-phase microextraction (HS-SPME), on-fibre derivatization and GC-MS
according to Ref. [10].
As sample preparation the traditional liquid/liquid extraction (LLE) is used, which is time intensive and
solvent consuming. For liquid matrices (e.g. hemp beer, hemp oil) the solid phase extraction (SPE) is
recommended for sample preparation [36, 41, 42, 44]. As an alternative to the established sample
preparations, the headspace solid-phase microextraction (SPME) can be used. In spite of the marginal
volatility of the cannabinoids and the possible phenolate formation in the alkaline setting, this class of

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compounds is reproducibly extractable out of the headspace by SPME. This is possible, because the
lipophilic compounds have a comparatively high octanol/water distribution coefficient and therefore
posses a high affinity to the unpolar polydimethylsiloxane (PDMS) SPME-fibre [56-58]. A totally
automated HS-SPME method for the determination of THC, CBD and CBN in all kinds of hemp food
products was recently introduced by Lachenmeier et al. [10] The food samples are hydrolysed after the
addition of the deuterated internal standard with sodium hydroxide and directly analysed by HS-
SPME/GC-MS. As already mentioned the adsorption of THC to the SPME-fibre is achieved by a PDMS
coating. After the adsorption of the analytes, the SPME-fibre is treated with N-dimethyl-N-trimethylsilyl-
trifluoro-acetamid (MSTFA) for derivatization in the headspace (on-fibre derivatization) of the sample.
After this solvent free extraction and derivatization process, desorption is achieved by the penetration of
the SPME-fibre into the hot injector of the GC/MS system (Fig. 4). By the extraction out of the
headspace, matrix interferences are minimalised. A typical HS-SPME chromatogram of a hemp food
sample is given in Fig. 5. A special advantage of the automated method is the time saving factor in
comparison to the traditional methods like liquid/liquid extraction. The SPME method is easy to handle
and provides the same reproducibility and sensitiveness as conventional methods, while at the same time
it is solvent free and only needs small sample amounts.
CBD
13.00 14.00 15.00 16.00 17.00
0
6000
12000
18000
24000
30000
36000
42000
Zeit (min)
A
bundance
THC CBN
12.00
Figure 5. Typical HS-SPME/GC/MS-SIM-chromatogram of a hemp tea containing 15.5 mg/kg THC, 47.1 mg/kg
CBD and 1.36 mg/kg CBN according to Ref. [10] (m/z 390,337,371,386,367,368).
THC-CONTENT OF HEMP FOOD PRODUCTS
Hemp food products, even those made of fibre hemp, commonly contain analysable THC amounts.
Earlier analysis of hemp oil revealed a wide range of concentrations, between 11.5-117.5 mg/kg [44] and
7-150 mg/kg [40]. A Swiss working group reported the highest found concentrations in oil: 4.1-880
mg/kg [48], 3-1500 mg/kg [41], and even 2-3568 mg/kg [28]. They obviously examined products made of
drug hemp.
In hemp tea THC contents of 1020-1480 mg/kg [48] and 5000 mg/kg [38] were discovered in the leaves
and between 1.0 mg/kg [48] und 2.4 mg/kg [38] in the respective tea infusions. Low THC concentrations
were only found in beverages, such as beer (0.004-0.016 mg/l [36]) and liqueur (0.02 mg/l [39]), as well
as in seed (0-12 mg/kg [11], 3.9-5.2 mg/kg [48]). Besides the earlier studies of the year 1996-2000, no
current data about the THC content of hemp food products are available. The CVUA Karlsruhe, part of
the German official food control system, analysed the THC content of 19 hemp food products in 2004.
The samples were mainly taken from drug stores and natural food stores (67%), some from conventional
stores and a few directly from the manufacturer. Only 33% of the samples were taken in so-called head
shops or in esoteric shops. In 15 products (79%) THC was detected, while in the remaining 4 samples no
THC was found. In comparison to earlier experiments the THC contents determined in the recent years

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were considerably lower. The reduced limit of THC in seeds seems to have the desired effect on the hemp
food products.
The results of the CVUA Karlsruhe are confirmed by a publication that appeared lately in which 30 hemp
food products were examined [10]. Only in isolated cases, the infringement of the THC limit was
described. The THC content of hemp tea ranged from 4.37 to 15.53 mg/kg in the Cannabis leaves and
from 0.04 to 0.23 mg/kg in the tea infusion, exceeding the upper limit of the German guidance value for
beverages.
High contents of THC, beyond the guidance value of 0.15 mg/kg for other foods, were determined in
seeds and flour (0.29-1.07 mg/kg), thin slices (0.20 mg/kg) and Cannabis pastilles (0.16 mg/kg). One oil
sample with 11.48 mg/kg also exceeded the guidance value for edible oils of 5 mg/kg. However, the
majority of the analysed samples revealed THC concentrations below the guidance values in the range
0.01-4.44 mg/kg. In two beverage samples (a soft drink and beer), THC could not be detected, whereas in
all samples CBD and CBN were present. The prescribed use of certificated fibre hemp seed by the EU
and the increase of controls of manufacturers obviously lead to a significant decline of THC
concentrations in hemp food products. In the USA was also reported that through a more careful cleaning
of the seed, since 1998, a significant decline of THC concentrations was achieved [59]. The maximum
THC content in nowadays purchasable hemp food products [10] are ten to hundred fold lower than the
ones found in the studies of the 90´s [28,38,40,41,44,48]. In respect to the own analysis results of the
CVUA Karlsruhe between 1998 and 2003 and taking into account the values described in literature, a
significant linear decrease in the THC concentrations of hemp tea (N=19, R=-0.73, p<0.0001) and hemp
oil (N=60, R=-0.23, p=0.05) was observed. On the other hand, in the case of the food products seeds
(N=27, R=-0.29, p=0.13) and beverages (N=34, R=-0.21, p=0.22) no decrease in respect of the 5% level
of significance was provable.
FOOD-TOXICOLOGICAL ASPECTS
In humans, after oral application of drug hemp products (hashish, marihuana), a multiplicity of adverse
effects can be observed [12,60] 10 to 20 mg of THC are regarded as effective intoxication dose at an
inhalative application. THC is rapidly metabolised to 11-hydroxy-Δ9-tetrahydrocannabinol (11-OH-
THC), which is further metabolised to the main metabolite 11-nor-Δ9-tetrahydrocannabinol-9-carboxylic
acid (THC-COOH). This carboxylic acid is eliminated in equal parts in free form and as glucuronide in
the urine. THC and 11-OH-THC are both psychoactive, while THC-COOH and its glucuronide do not
show any pharmacological activity. The metabolite THC-COOH and especially its glucuronide have
relatively long half-lifes up to eight days. These substances tend to cumulate in the body if regularly
consumed. High concentrations can only be determined in persons, who regularly consume hashish and
marihuana. Even after the habit of regular drug use is abandoned, these metabolites can be detected in
blood for some weeks and in urine for more than three months [13].
The resorption of orally administered THC varies strongly interindividual as well as in regard of total
content and resorption rate [61]. This should be one of the reasons for the individually very different
perceived psychotropic effects. A single oral dose of 20 mg of THC caused symptoms as tachycardia,
conjunctival irritations, “high feeling” or dysphoria within 1-4 hours in adults. One in five adults
developed these symptoms after a single dose of 5 mg. A marihuana cigarette contains approximately 30-
50 mg of THC [62].
In 1996/1997, some cases of intoxications with hemp foods were reported in Switzerland. 4 cases of
accidentally THC intoxication were described by Meier and Vonesch [62]. After consumption of a salad
that was prepared with hemp oil, gastrointestinal irritations and perceptual disturbances occurred. The
used oil showed a THC content of 1500 mg/kg, which is significantly over the Swiss maximum limit.
One portion of the edible oil (13 g) contained 20 mg of THC. This is a concentration that can easily cause
the described symptoms. As a cause for the high content of the oil a mistake in the manufacturing process
was assumed [48].

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INFLUENCE OF HEMP FOOD ON FORENSIC DRUG TESTS
The presence of THC in hemp containing food stuff raised not only the problem of psychoactive effects,
but it also lead to concerns about the validity of positive results of drug tests [63]. Positive results in
blood- and urine analyses can have grave consequences for the person in question. Generally, a positive
result in such tests is interpreted as evidence for previous consumption of Cannabis in the form of hashish
or marihuana. For groups of people, who have to prove drug abstinence, such a misinterpretation can have
grave consequences. On the other hand, attempts to justify one's behaviour in court by claiming that the
positive test was caused by hemp food consumption are possible nowadays.
First studies after emergence of hemp food products, containing significantly higher THC levels than
nowadays, described positive results in forensic-toxicological drug tests for hashish and marihuana after
the consume of hemp oil [37,41,64-67] and other hemp food stuff [38,40]. Most of the studies were
conducted in 1996-1997 with THC concentrations of more than 50 mg/kg. For example, after few hours
of oral administration of hemp oil (151 µg/ml THC), THC-COOH could be detected in urine. After the
application of 40-90 ml oil, THC-COOH could be detected in urine for up to 80 hours. THC serum levels
up to 6 ng/ml were determined after intake of 40 ml of hemp oil [37,40, 67].
With the gradual reduction of THC in hemp food, also a reduction of its metabolites in the urine of the
consumers could be observed. In a study in 2001 with a maximum content of 5 mg/kg of THC and a daily
intake of up to 0.6 mg THC, no positive urine tests were obtained [59]. In a recent study [10] after the
consume of 6 cups (0.2 l) of hemp tea (0.23 mg/kg THC) over a duration of 2 hours, no THC metabolites
were found in the urine of six probands using an immunochemical standard screening method. This
confirms previous results of other working groups that excessive consume of currently available hemp
food products (e.g. hemp beer) does not cause positive urinalyses [36, 39, 42, 44, 59, 68-70]. Only the
consumption of hemp food products with high THC contents, which are no longer available on the
market, can produce positive results [71, 72]. In cosmetic products as hemp shampoo, the THC content is
negligible, so that no influence on forensic-toxicological hair analyses could be proven [70, 73-75].
Nowadays one can assume that fibre hemp products do not influence forensic-toxicological drug tests, if
these products comply with the effective limits.
FOOD REGULATORY ASPECTS
The lowest orally administered dose of THC, which after repetitive application causes the described
effects in adults, is 2.5 mg/day. This is equal to the administration of approximately 40 µg per kg of
bodyweight and day, if a bodyweight of 60 kg is assumed. Food products leading to the uptake of such or
higher doses, if they are daily consumed have to be judged as being eligible to threat the consumers’
health and should therefore be objected. To eliminate uncertainties, such as a variation in the individual
sensitivity, kinetic specialties (redistribution, long half-life) or interaction with other hemp or food
ingredients or certain drugs, the BgVV advises that a daily uptake of 1-2 µg/kg of bodyweight should not
be exceeded. This advised uptake limit is 20 – 40 fold lower than the lowest known effective dose [12].
Marginal violations of the limit can usually be tolerated. Samples, which exceed the limit twice, have to
be estimated as being deteriorated. Hemp food products, which extremely exceed the limit and therefore
contain amounts of THC that are close to the lowest, known effective dose have to be judged as unfit for
consumption. The CVUA Karlsruhe is of the opinion that the labelling of some products as “THC free” is
a deception of the consumer, because a significant concentration of THC can be found in all the products.
Also products with low hemp content but with a special stress on nutritional value of hemp should be
rated likewise.
CONCLUSION
Critical product groups that should be intensively observed by the official food control in the future are
especially so called hemp teas, because they are made of the glandular trichomes rich leaves, in which the
cannabinoids are accumulated. Next to the covering leaves of the inflorescence, they contain the highest

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concentration of cannabinoids. The similarities between these products and marijuana, which is likewise
made of dried plant parts of the hemp plant (drug hemp), can lead to a belittlement of Cannabis as illicit
drug. The fear remains, even if after the excessive consumption of fibre hemp no psychoactive effects or
influence on forensic drug tests can be observed. Nutritional or organoleptical benefits, which could
justify the consumption of such products, couldn’t be proved either. It should be a goal to work towards
Europe-wide applicable limits for THC in food products, which could then replace national guidelines.
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