Hemp (Cannabis sativa L.): A Comprehensive Reference
1. Identity and Botanical Classification
Botanical and Chemical Names
Hemp is derived from Cannabis sativa L., a member of the family Cannabaceae. The term "hemp" or "industrial hemp" conventionally refers to Cannabis sativa cultivars selected for low psychoactive content. THC is the substance primarily responsible for the psychoactive effects of cannabis; some cannabis plants contain very little THC, and under U.S. law these plants are considered "industrial hemp" rather than marijuana. The plant is also known in Chinese as dà má (大麻), and in classical pharmacopoeial literature it appears under the synonym Cannabis sativa subsp. sativa.
Cannabis sativa is one of the world's oldest cultivated plants. The plant has been used medicinally and recreationally for thousands of years; there are more than 550 chemical compounds in cannabis, with more than 100 phytocannabinoids identified, including Δ9-tetrahydrocannabinol (Δ9-THC).
Distinction from Drug-Type Cannabis
Cannabidiol (CBD) shares a common biosynthetic precursor with Δ9-THC and is the most abundant cannabinoid in hemp. The critical biochemical distinction between hemp and drug-type cannabis lies in the relative expression of THCA synthase versus CBDA synthase enzymes in the plant. Industrial hemp (Cannabis sativa L.) is cultivated for its low THC content (<0.3%), and is increasingly valued for its nutrient-rich seeds and broad applications in human nutrition. Since THC and CBD are found only in traces in hemp seeds, hemp seeds can be used in food applications because the psychoactive effects associated with cannabis are avoided.
Common Forms and Preparations
The hemp plant yields multiple distinct preparations used in nutrition and medicine:
- Hemp seeds (hemp hearts): Whole or dehulled seeds consumed as food; the hull is removed to produce the inner kernel (hemp heart).
- Hemp seed oil: Extracted by cold-pressing the seeds; retains the full fatty-acid and lipophilic-compound profile. Hemp seed oil is obtained in most cases by mechanical cold pressing of the seeds, but also by solvent extraction, microwave or ultrasound-assisted extraction, or by supercritical extraction using carbon dioxide.
- Hemp protein powder / isolate / concentrate: Products derived from processing the whole seed include oil, dehulled seeds, hulls, flour, cakes, meals, and proteins.
- Hemp flour: Ground defatted seed cake used as a food ingredient.
- Whole-plant / aerial-parts extracts: Including CBD-rich extracts derived from the flowers and leaves, distinct in composition from seed-derived preparations.
2. Traditional and Historical Use
East Asia
Hemp, called má (麻) in Chinese, was used in Taiwan for fiber starting about 10,000 years ago. The botanist Hui-lin Li wrote that "The use of Cannabis in medicine was probably a very early development. Since ancient humans used hemp seed as food, it was quite natural for them to also discover the medicinal properties of the plant." The oldest Chinese pharmacopeia, the (c. 100 AD) Shennong Bencaojing (神農本草經, "Shennong's Materia Medica Classic"), describes cannabis.
Hemp was used as a food source in ancient China; the Classic of Rites lists hemp seeds among the "five grains" that were a staple of ancient Chinese cooking, alongside soybeans, broomcorn, wheat, and foxtail millet. Hemp was often employed in ancient Chinese medicine; primarily the achenes (seeds) were used to treat maladies such as pain or mental illness. Traditional Chinese medical texts also recorded hemp seed preparations for constipation, malaria, rheumatism, and gout.
In 2000 BC hemp was so important to ancient China that it was considered one of the "five grains," cultivated crops thought to be sacred. From 200 BC to the late 1800s, hemp was used in the production of paper. Around 600 AD, hemp cultivation techniques were extensively covered in the ancient Confucian text "The Essential Arts for the People" (Qi Min Yao Shu).
South Asia
Cannabis has a long history in India, veiled in legends and religion. The earliest mention of cannabis has been found in the Vedas, or sacred Hindu texts, which may have been compiled as early as 2000 to 1400 BC. In Indian tradition, hemp preparations were used medicinally in multiple forms. Hemp flowers and leaves were also used to make teas and decoctions to treat pain, inflammation, fever, insomnia, and mental disorders.
Ancient Egypt and the Mediterranean
Evidence of hemp's health benefits can also be found in ancient Egypt; the Ebers Papyrus, a medical text dating back to 1500 BCE, mentions hemp as a treatment for inflammation and pain. By the 1st century CE, hemp's medicinal use had reached the Mediterranean; Greek physicians like Dioscorides and Galen wrote about its therapeutic properties. In ancient Rome, hemp was used to treat diseases such as gout, edema, and tumors.
Early Modern Europe and North America
Many 19th-century practitioners ascribed medicinal properties to cannabis after the drug found its way to Europe during a period of colonial expansion into Africa and Asia. Since the 19th century, disorders such as epilepsy, migraine, asthma, neuralgia, fatigue, and insomnia were treated using cannabis, with phytocannabinoids playing a vital role. In North America, the settlers of Jamestown, who arrived in 1609, brought hemp with them, and in the 1700s hemp was widely grown in the United States. Western countries frequently used hemp as medicine, and extracts of cannabis were found in the standard doctor's pharmacopeia.
3. Key Constituents and Active Compounds
Macronutrient Composition (Seeds)
Hemp seeds are a well-documented natural source of proteins, carbohydrates, and fats with high nutritional value. Whole hemp seeds contain 20–25% proteins, 20–30% carbohydrates, and 25–35% fats. They also contain fat-soluble vitamins, such as vitamins A and E, and minerals including potassium, magnesium, and zinc.
Proteins: Edestin and Albumin
Hemp seed is a high-quality plant-based protein source containing all nine essential amino acids. The protein content is primarily composed of edestin (60–80%) and albumin, both highly digestible and bioavailable. Glutamic acid is the most abundant amino acid (3.74–4.58% of the whole seed), followed by arginine (2.28–3.10% of the whole seed).
Edestin (also known as Edistin) is a highly digestible hexameric legumin protein and a seed storage protein with a molecular weight of 310 kDa. It is primarily found in hemp seeds and is a globular protein (biologically active) as opposed to a fibrous protein (structural). Globular proteins found in edestin are long peptide chains, precursors for biological proteins essential for life. Edestin is similar to serum globulin (blood plasma) and is capable of biosynthesizing antibodies (immunoglobulins).
The actual digestibility of hemp protein ranges from 87% to 91%, which is genuinely high. Hemp seeds do not contain trypsin inhibitors, compounds found in soybeans and many other legumes that interfere with protein digestion; without those antinutritional factors, hemp protein breaks down relatively easily in the digestive system. The Protein Digestibility-Corrected Amino Acid Score (PDCAAS) for hemp protein has been reported to range from 0.46 to 0.66 depending on processing and formulation. Although lower than animal proteins, these scores are comparable to other plant proteins such as legumes and grains. The sulfur-containing amino acids methionine and cysteine and lysine have been identified as limiting amino acids in hemp protein.
Lipids and Fatty Acids
Hemp seed oil is particularly rich in polyunsaturated fatty acids (PUFAs), providing substantial amounts of linoleic acid (LA, 18:2 n-6) and α-linolenic acid (ALA, 18:3 n-3), as well as smaller but physiologically relevant quantities of γ-linolenic acid (GLA, 18:3 n-6) and stearidonic acid (SDA, 18:4 n-3), fatty acids that are uncommon in most commonly consumed vegetable oils. Hemp seed oil also contains tocopherols and polyphenolic compounds with antioxidant potential.
A substantial amount of polyunsaturated fatty acids (PUFAs) not commonly found in vegetable oils has been reported. These include linoleic (ω-6) and α-linolenic acids (ω-3), comprising approximately 50% and 20% of the total fatty acids, respectively. Major components are PUFAs such as γ-linolenic acid (GLA), essential fatty acids (EFAs) especially linoleic acid and α-linolenic acid, and monosaturated fatty acids including oleic acid. Hemp seed oil is noted for its favorable ω-6 to ω-3 EFA ratio of 2–3:1.
Minor Bioactive Compounds
Hemp seed oil contains carotenoids (β-carotene, lutein, and zeaxanthin), tocopherols (α-, β-, γ-, and δ-tocopherol), phytosterols (campesterol and β-sitosterol), chlorophyll, and phenols (flavonoids and polyphenols).
Carotenoids are present in hemp seeds, with lutein being the most abundant, ranging from 1.4 to 3.4 mg/100 g in the whole seed. Lutein and zeaxanthin accumulate in macular cells, protecting against light-induced oxidative stress, indicating the potential of hemp seeds to contribute to maintaining ocular health.
Hemp seed oil offers approximately 80 mg/100 g total tocopherols, lipid-soluble compounds with strong antioxidant properties.
Cannabis sativa evokes its medicinal power from an array of secondary metabolites encompassing several chemical classes, including terpenoids and flavonoids. Cannabis is the sole botanical producer of cannabinoids, the class of terpenoids which interact with the mammalian endocannabinoid receptors. While the flowers and leaves contain substantial cannabinoids (CBD, THC, and more than 100 others), hemp seeds contain these only in trace quantities. Metabolites such as flavones and phenols are also contained in the seeds, contributing to their antioxidant properties with beneficial effects on human health, particularly on the cardiovascular system and/or the immune response.
4. Mechanisms of Action
The Endocannabinoid System (ECS)
The endocannabinoid system (ECS) consists of endogenous cannabinoids, their receptors, and metabolic enzymes that play a critical homeostatic role in modulating polyunsaturated omega fatty acid (PUFA) signaling to maintain a balanced inflammatory and redox state. The human brain responds to phytocannabinoids through cannabinoid receptors (CBx), which are part of the endocannabinoid system. The endocannabinoid system, made up of enzymes involved in the production and breakdown of endocannabinoids, cannabinoid receptors (CB1 and CB2), and endogenous ligands, is essential for preserving homeostasis in several physiological processes.
Hemp cannabinoids of THC and CBD groups show distinct but complementary actions through a variety of cannabinoid (CB1 and CB2), adenosine (A2A), and vanilloid (TRPV1) receptors; they also modulate PUFA metabolism within a wide variety of specialized lipid mediators that promote or resolve inflammation and oxidative stress. Beyond their effects on the endocannabinoid system, phytocannabinoids are studied for their ability to modify ion channels, neurotransmitter receptors, and antioxidative pathways.
The skin has its own endocannabinoid system. The ECS regulates cell growth and differentiation as well as immune and inflammatory responses. Phytocannabinoids can affect skin health. The endocannabinoids produced in the skin—N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG)—bind to the main endocannabinoid receptors CB1 and CB2, as well as other receptors including TRPV1 and PPARγ and PPARα from the Peroxisome Proliferator-Activated Receptors (PPAR) family.
Fatty Acid–Mediated Mechanisms
Whole food-based diets and dietary interventions linked to PUFAs of plant origin (hemp, flax, walnut, algae), as well as full-spectrum hemp oils, are increasingly used to support the ECS tone, promote healthy metabolism, improve risk factors associated with cardiovascular disorders, encourage brain health and emotional well-being, and ameliorate inflammation.
Omega-6 fatty acid linoleic acid is converted to arachidonic acid (AA), the precursor of inflammatory prostaglandins and leukotrienes, while ALA (omega-3) is converted to EPA and subsequently to DHA—the most biologically potent precursors of anti-inflammatory mediators. LA, before it converts to AA, goes through a stage of gamma-linolenic acid (GLA) and dihomo-gamma-linolenic acid (DGLA), both involved in the induction of anti-inflammatory eicosanoids.
Hemp seed oil has been demonstrated to include healthy polyunsaturated fatty acids, as well as antioxidant tocopherols and anti-inflammatory phytosterols. Inflammation has emerged as a leading pathophysiologic mechanism in atherosclerosis and other diseases, and the phytol and phytosterol content of hemp seed oil contributes to its recommendation as an interesting source of functional compounds.
5. Scientific Evidence by Area of Use
5.1 Cardiovascular Health
Hempseed's cardiovascular benefits are potentially derived from its optimal 3:1 omega-6 to omega-3 fatty acid ratio and rich bioactive profile, including Îł-linolenic acid, tocopherols, phytosterols, and polyphenols.
Preclinical evidence: A 2025 systematic review critically evaluated the potential cardioprotective effects of hempseed, focusing on its impact on lipid metabolism, inflammation, oxidative stress, and other cardiometabolic markers. Preclinical studies suggest that hempseed can improve lipid profiles, reduce blood pressure, and reduce oxidative stress and inflammation, though clinical evidence remains limited and findings from animal models may not directly translate to human cardiovascular benefits due to physiological differences between species.
Human/clinical evidence: Research on hempseed oil in humans includes comparative fatty acid supplementation trials. A noted 2008 clinical study (Kaul et al., Journal of the American College of Nutrition) compared fish oil, flaxseed oil, and hempseed oil supplementation on cardiovascular parameters in healthy volunteers. Studies on hempseed protein, including a double-blind crossover study (Samsamikor et al., American Journal of Clinical Nutrition, 2024) compared hemp seed protein and its hydrolysate with casein protein in adults with hypertension, though findings from these studies require further independent replication.
Evidence strength: Despite promising findings, there is a need for long-term randomized controlled trials to establish the efficacy and safety of hempseed in diverse populations. The overall quality of direct human clinical evidence for hempseed and cardiovascular outcomes is currently preliminary.
Regarding thrombosis: In vivo (zebrafish) experiments demonstrated that 125 μg/mL hemp seed peptides significantly ameliorated ponatinib-induced thrombosis, with the anticoagulant effect partly attributed to upregulated expression of vegfr1 and downregulated expression of caspase-3 at the mRNA level. These findings propose hemp seed peptides as novel dietary antithrombotic agents—evidence currently restricted to animal models.
5.2 Skin Health and Atopic Dermatitis
Hemp seed oil's GLA content is the primary focus of dermatological research.
Key clinical trial (Callaway et al., 2005): A human crossover trial in patients with atopic dermatitis found that levels of both essential fatty acids (linoleic acid and α-linolenic acid) and GLA increased in all lipid fractions after hempseed oil supplementation, with no significant increases of arachidonic acid in any lipid fractions. It was suggested that these improvements resulted from the balanced and abundant supply of PUFAs in hempseed oil.
GLA mechanism in skin: In patients with atopic dermatitis, a reduced enzyme activity of delta-6-desaturase has been observed, leading to higher levels of LA and lower levels of GLA, resulting in lower concentrations of anti-inflammatory GLA and its metabolites. GLA is reportedly efficacious for treating transepidermal water loss (TEWL) and epidermal hyper-proliferation. In a study in which GLA-containing food was given to adults with dry skin or mild atopic dermatitis, beneficial effects on the TEWL index were recognized. The efficacy of GLA was demonstrated to be statistically significant especially in subjects with pro-inflammatory features, and the mechanism of improvement of skin barrier was associated with possible generation of anti-inflammatory metabolites from GLA.
Evidence strength: The evidence for hempseed oil specifically in atopic dermatitis is based on a small number of controlled trials, with GLA-rich oils (including but not limited to hemp) showing consistent but modest effects. Evidence is suggestive but not conclusive due to small sample sizes and short trial durations.
5.3 Anti-Inflammatory Effects
Hemp seeds contain bioactive compounds with antioxidant and anti-inflammatory properties. In addition to proteins and healthy fats, hemp seeds are rich in phytochemical compounds, especially terpenoids, polyphenols, and phytosterols, which contribute to their bioactive properties. Scientific studies have shown that these compounds possess significant antioxidant, antimicrobial, and anti-inflammatory effects, making hemp seeds a promising ingredient for promoting health.
Most anti-inflammatory mechanistic data derives from in vitro (cell culture) and preclinical (animal) studies. Research on hemp protein and inflammation is still in the early stages, but some preliminary findings show promise. Direct large-scale human trials isolating hemp's anti-inflammatory effect are not yet available.
5.4 Protein Nutrition and Metabolic Outcomes
Hemp protein has been evaluated as a high-quality plant protein source. Hempseed is a high-quality plant-based protein source that contains all nine essential amino acids required for human health. Human studies comparing hemp protein to benchmark animal or soy proteins have been conducted, with outcomes focused on amino acid bioavailability and satiety, but the number of well-powered randomized controlled trials remains limited.
Evidence strength: Preliminary; the nutritional composition is well-characterized, but human clinical outcome data for protein-specific effects (e.g., muscle protein synthesis, satiety) from hemp protein specifically is sparse.
5.5 Neuroprotection and Neurological Conditions
Clinical evidence links PUFAs and cannabinoids to changes in ECS tone, immune function, metabolic and oxidative stress adaptation, and overall maintenance of well-balanced systemic function. The phytocannabinoids present in whole-plant hemp extracts (predominantly CBD in industrial hemp) have been extensively studied for neurological conditions. The FDA has not approved the cannabis plant (as opposed to isolated CBD formulations) for any medical use. Evidence for hemp seed-derived preparations in neurological conditions is not yet established in human clinical trials.
6. Body Systems and Health Areas
- Cardiovascular system: Via PUFA-mediated modulation of lipid profiles, oxidative stress, blood pressure, and platelet function (primarily preclinical evidence).
- Integumentary system (skin): Via GLA-dependent support of skin barrier function and reduction of transepidermal water loss; ECS-mediated anti-inflammatory and regulatory effects in skin cells.
- Immune system: Via phytosterols, polyphenols, and fatty acids modulating eicosanoid production and cytokine balance; edestin's structural similarity to serum globulin proteins.
- Musculoskeletal system: Omega-3/omega-6 fatty acids and GLA studied in rheumatoid arthritis and musculoskeletal inflammation, though evidence is primarily for GLA-rich oils in general, not hemp oil specifically.
- Endocannabinoid system: The endocannabinoid system is involved in a host of homeostatic and physiologic functions, including modulation of pain and inflammation. Dietary PUFAs from hemp serve as precursors for endocannabinoid synthesis.
- Gastrointestinal system: Hemp seeds provide dietary fiber; traditional use included preparations for digestive complaints.
- Ocular health: Lutein and zeaxanthin from hemp seeds accumulate in macular cells, protecting against light-induced oxidative stress, with potential for reducing the risk associated with macular degeneration.
7. Dosage Forms and Dosages Reported in Studies
Dosage information in the scientific literature varies by preparation type and condition studied. The following are dosages as reported in cited sources:
- Hempseed oil (atopic dermatitis): The Callaway et al. (2005) trial in patients with atopic dermatitis used dietary hempseed oil as an oral supplement, with fatty acid plasma levels and dermatological outcomes assessed; the specific gram dosage used is reported in the full publication.
- GLA (general dermatological/anti-inflammatory use): Evening primrose oil (a GLA-rich oil, analogous to hemp in GLA content) at 4–6 g was administered daily for 12 weeks in atopic dermatitis patients. Hemp seed oil contains GLA at a lower concentration than evening primrose oil; equivalent GLA intake from hemp oil requires higher oil volumes.
- Hemp seed protein (hypertension): A double-blind crossover study (Samsamikor et al., Am J Clin Nutr, 2024; referenced via webmd.com vitamins monograph) compared hemp seed protein and its hydrolysate with casein in adults with hypertension, though specific gram amounts per day are reported in the primary publication.
- Hempseed (general dietary intake): Two to three tablespoons of hemp hearts (hemp seeds) sprinkled on food, blended into a smoothie, or stirred into oatmeal adds 7 to 10 grams of protein to a meal—a commonly reported dietary intake amount in nutritional contexts.
- CBD from hemp (drug interaction study): A clinical trial at Washington State University (sponsored by NIH ODS and NCCIH) is investigating two different doses of CBD given as a hemp product and their effects on the blood concentrations of the antiplatelet drug clopidogrel. The specific CBD doses under investigation are detailed in the trial protocol (NCT06192589).
8. Safety Considerations and Drug Interactions
THC Contamination in Commercial Hemp Products
Hemp seeds are popular for their high nutrient content, and strict regulations are in place to limit the amount of potentially harmful phytocannabinoids, especially Δ9-THC. In Canada, this limit is 10 μg of Δ9-THC per gram of hemp seeds (10 ppm), and other jurisdictions follow similar guidelines. Research has discovered that Δ9-THC concentrations in some consumer-grade hemp seeds could be as high as 1250% of the legal limit, with phytocannabinoid amounts dependent on extraction procedure employed. Hemp seeds have been found to contain 0–12 μg Δ9-THC per 1 g of seeds, and majority of Δ9-THC is located on the surface of the seeds; fluctuations in Δ9-THC content in different replicates of the same type of seeds could be the result of degree of contamination on the outside of the seeds.
Analysis of 413 hemp-based products (mostly CBD oils) on the German market confirmed that 48 products (12%) contained Δ9-THC above the lowest observed adverse effect level (2.5 mg/day). It may be assumed that adverse effects of some commercial CBD products are based on a low-dose effect of Δ9-THC, and the safety, efficacy, and purity of commercial CBD products is highly questionable.
Interactions with Anticoagulants and Cardiac Medications
Hemp seeds may interact with certain medications including anticoagulants. Studies have shown that hemp seeds reduce blood clotting, which can interact with prescription blood thinners. The seeds may also interfere with cardiac glycosides (heart drugs) such as digoxin. These medications help to maintain a healthy heart rate, and hemp can do the same; combining the two may lead to bradycardia, a slower-than-normal heart rate.
Despite increasing use of cannabis products, the pharmacokinetic interaction potential with pharmaceutical medications remains understudied. Previous pharmacokinetic studies have yielded convincing evidence that CBD significantly inhibits the activity of the drug metabolizing enzyme cytochrome P450 (CYP) 2C19. This inhibition has implications for any co-administered medication that relies on CYP2C19 for metabolism. An NIH-funded clinical trial (NCT06692933, Washington State University) is actively investigating the effect of hemp-derived CBD on blood concentrations of clopidogrel (Plavix®), an antiplatelet drug metabolized by CYP2C19.
Hemp seeds may enhance the effects of certain diuretics, triggering the body to flush out too much potassium, which can lead to dangerously low potassium levels.
Allergic Potential
Hemp seed allergies are uncommon but real. Reactions can range from mild skin symptoms to, in rare cases, anaphylaxis. The likely allergens are the same storage proteins that make hemp nutritious: edestins and vicilin-like proteins. Research has identified cross-reactivity between hazelnut and hemp seed proteins, with hazelnut-sensitized individuals showing immune responses to hemp seed extracts. The clinical significance of this overlap is still being studied.
Regulatory Classification
The Agricultural Improvement Act (Farm Bill) of 2018 removed hemp (defined as cannabis and derivatives of cannabis with extremely low concentrations of THC) from the definition of marijuana in the Controlled Substances Act. Hemp products remain subject to regulation under the Federal Food, Drug & Cosmetic Act, and the growing CBD products market raises various safety concerns, especially with long-term use.
Pregnancy and Lactation
There is not enough clinical research to show that hemp is safe either orally or topically for women who are pregnant or breastfeeding.
General Safety Profile of Hemp Seeds
At ordinary dietary amounts, hemp seeds and hemp seed oil have an established history of safe consumption as a food. Agronomic practices and environmental factors considerably influence the seed's nutritional profile. The possibility of drug interactions, direct toxicities, and contamination with active pharmaceutical agents are among the safety concerns about dietary and herbal supplements. Although there is a widespread public perception that herbs and botanical products are safe, research has demonstrated that these products carry the same dangers as other pharmacologically active compounds.
References
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