Cannabis use is linked to lower levels of several vitamins and minerals, with the strongest human evidence pointing to vitamins C, E, and D, the B vitamin folate, and the mineral zinc. The mechanisms vary: some nutrients get consumed fighting the oxidative stress that cannabis smoke generates, others appear to be affected by how cannabinoids interact with absorption and metabolism, and still others drop because of the dietary habits that tend to accompany heavy use. The picture is more complicated than a simple checklist, though, because how you consume cannabis, how often, and what else is going on in your body all shape which deficiencies actually show up.
Vitamins C and E Take the Biggest Hit From Smoking
The most consistent finding across studies is that people who smoke cannabis have significantly lower blood levels of both vitamin C and vitamin E compared to non-smokers. A study of marijuana smokers in Nigeria found that serum levels of both vitamins were markedly reduced, and the longer someone had been smoking, the lower their levels dropped.1PubMed Central. Marijuana Smoke Inhalation and Potential Micronutrient Deficiencies among Nigerian Smokers A separate study on male cannabis smokers confirmed the same pattern, with statistically significant decreases in both vitamins compared to non-smoking controls.2Panacea Journal of Medical Sciences. Effect of cannabis smoking on Vitamin C and E levels of male cannabis smokers in Nnewi, Nigeria
The likely explanation is oxidative stress. Burning cannabis produces reactive oxygen species, the same unstable molecules generated by tobacco smoke. Your body uses antioxidant vitamins, especially C and E, to neutralize these molecules. When you inhale smoke regularly, you’re essentially burning through your antioxidant reserves faster than a typical diet can replenish them. Vitamins C and E are the front line of this defense, so they’re consumed first and most visibly.
This matters practically because both vitamins do more than just mop up free radicals. Vitamin C supports immune function, wound healing, and collagen production. Vitamin E protects cell membranes throughout the body. Chronic depletion of either can show up as frequent infections, slow-healing cuts, or dry, damaged skin, symptoms a daily smoker might not connect to their cannabis habit.
Vitamin D Drops in Heavy Users
Multiple studies have found that frequent cannabis users carry lower vitamin D levels than non-users. In a study of heavy cannabis users in the UK, average serum vitamin D was roughly 25 nmol/L compared to about 37 nmol/L in matched controls, a gap large enough to push many users into the range typically classified as deficient.3PubMed. Heavy Cannabis Use Is Associated With Low Bone Mineral Density and an Increased Risk of Fractures That same study found heavy users had lower bone mineral density and a higher risk of fractures, which tracks with what you would expect from chronically low vitamin D.
A Norwegian study of people with severe substance use disorders echoed the finding: those who frequently consumed cannabis had vitamin D levels about 5 nmol/L lower at baseline than those with less or no use.4Scientific Reports. Vitamin D status and associations with substance use patterns among people with severe substance use disorders in Western Norway The gap didn’t close over time during the study period, suggesting this isn’t a temporary dip that self-corrects.
Why cannabis would lower vitamin D isn’t entirely settled. Part of it may be behavioral: people who use cannabis heavily may spend more time indoors and get less sun exposure, which is the body’s primary source of vitamin D. But there are also hints of a more direct biochemical link. An animal study found that cannabidiol altered the expression of enzymes involved in vitamin D metabolism, increasing some and decreasing others in ways that could shift how the body processes the vitamin.5PubMed. Effects of Cannabidiol Interactions with CYP2R1, CYP27B1, CYP24A1, and Vitamin D(3) Receptors on Spatial Memory, Pain, Inflammation, and Aging in Vitamin D(3) Deficiency Diet-Induced Rats That’s a rat study, so direct translation to humans requires caution, but it suggests cannabis compounds may interfere with vitamin D at the metabolic level rather than just through lifestyle.
Folate and the B Vitamin Question
Among the B vitamins, folate (vitamin B9) has the most concerning evidence. A population-level study in Newfoundland and Labrador found that plasma folate levels were negatively correlated with THC metabolite concentrations: higher THC exposure tracked with lower folate.6Clinical Chemistry. Relationship between legal recreational drug use with folate and vitamin B12 status in general adult population in Newfoundland and Labrador Interestingly, that same study found no association between cannabis use and vitamin B12 levels, suggesting the two B vitamins are affected differently.
Lab research offers a plausible mechanism for the folate connection. In a cell-line study modeling placental tissue, chronic THC exposure at physiological concentrations reduced folic acid uptake by about 20%.7PubMed Central. The grass isn’t always greener: The effects of cannabis on embryological development If something similar happens in the gut or other tissues, it could explain why people with higher THC levels end up with lower folate even if their dietary intake is adequate. The body is absorbing less of what it takes in.
The folate finding connects to another observation in cannabis users: elevated homocysteine. Homocysteine is an amino acid that your body normally converts using folate, B12, and B6. When those vitamins run low, homocysteine accumulates. A case report of two cannabis users documented exactly this pattern: elevated homocysteine alongside low vitamin levels, which improved with supplementation of folic acid, methylcobalamin, and pyridoxine (vitamins B9, B12, and B6).8PubMed Central. Management of Hyperhomocysteinemia, Low Vitamin Levels, and Low Cortisol in Cannabis Users: A Report of 2 Cases Elevated homocysteine is itself a risk factor for cardiovascular disease, so the downstream effects of even a modest folate dip can be clinically meaningful.
The B12 picture is muddier. While the Canadian population study found no link, a study of first-episode schizophrenia patients found that those who had abused cannabis had significantly lower B12 levels compared to non-users within the same patient group.9PubMed Central. Elevated homocysteine level in first-episode schizophrenia patients–the relevance of family history of schizophrenia and lifetime diagnosis of cannabis abuse It’s hard to untangle whether cannabis itself drove the B12 drop or whether the combination of schizophrenia, cannabis use, and generally disrupted nutrition all contributed. The honest read of the evidence is that folate appears more reliably affected by cannabis use than B12, but heavy users should be aware of both.
Zinc Drops While Copper Rises
Zinc is one of the minerals most consistently affected by cannabis use, and it shows up alongside an unusual twist: copper goes the opposite direction. In the Nigerian study of marijuana smokers, serum zinc was significantly lower while copper was significantly higher compared to non-smokers. The copper-to-zinc ratio was elevated, and this imbalance worsened with longer duration of use.1PubMed Central. Marijuana Smoke Inhalation and Potential Micronutrient Deficiencies among Nigerian Smokers Magnesium, by contrast, showed no significant difference between users and non-users in the same study.
A study comparing urinary trace element levels between people with substance use disorders and healthy controls reinforced the zinc finding. Healthy individuals had markedly higher urinary zinc and copper levels, while the substance use group showed accumulation of toxic elements like cadmium and lead.10PLOS ONE. Trace element levels: How Substance Use Disorder (SUD) contributes to the alteration of urinary essential and toxic element levels That study looked at mixed substance use rather than cannabis alone, so the zinc finding may partly reflect broader patterns of drug use and poor nutrition. Still, the convergence with the cannabis-specific data is suggestive.
The copper-to-zinc ratio deserves attention because it’s not just about having too little of one mineral. Zinc and copper compete for absorption in the gut, and an elevated ratio has been associated with increased inflammation and oxidative stress in other contexts. For cannabis users, this imbalance may compound the oxidative burden already created by smoking, amplifying the cycle of antioxidant depletion described earlier.
When Cannabis Hyperemesis Syndrome Creates Acute Deficiency
There’s one scenario where cannabis can cause a sudden, dangerous vitamin deficiency rather than a gradual slide: cannabis hyperemesis syndrome (CHS). This condition, which occurs in some long-term heavy users, causes severe, repeated bouts of nausea and vomiting that can last for days. The relentless vomiting depletes the body of nutrients it can’t replace fast enough, and thiamine (vitamin B1) is particularly vulnerable because the body stores very little of it.
A published case report described a CHS patient who developed Wernicke’s encephalopathy, a serious brain condition caused by thiamine deficiency. Brain imaging showed the characteristic pattern of damage, and the patient recovered rapidly after receiving intravenous thiamine.11PubMed Central. Wernicke’s Encephalopathy Secondary to Cannabis Hyperemesis Syndrome Wernicke’s encephalopathy is typically associated with alcoholism, so seeing it in a non-alcoholic cannabis user caught clinicians off guard. The case underscores that CHS is not just uncomfortable; it can create the conditions for life-threatening nutrient depletion.
Most cannabis users will never develop CHS. The condition appears to require heavy, daily use over months or years, and even then only a subset of users are susceptible. But for anyone who experiences cyclical vomiting episodes linked to cannabis use, the risk of thiamine and other nutrient depletion is real and warrants medical attention rather than simply waiting it out.
Why Route of Consumption Matters
Most of the human studies showing vitamin depletion specifically examined people who smoke cannabis. This is an important detail because smoking introduces a variable that edibles, tinctures, and vaporizers do not: combustion products. The oxidative stress pathway that depletes vitamins C and E is driven by reactive molecules in smoke. If you consume cannabis through edibles, you’re removing that entire mechanism from the equation.
That said, the effects that appear to be driven by THC or other cannabinoids directly, such as reduced folate uptake and possible interference with vitamin D metabolism, would theoretically apply regardless of how you consume cannabis. A THC molecule absorbed through the gut from an edible enters the same bloodstream and reaches the same tissues as one inhaled from smoke. The dose may differ, and the metabolic pathway of first-pass liver processing may alter the cannabinoid profile, but the active compounds still interact with your cells.
In practical terms, this means that switching from smoking to edibles would likely protect against the antioxidant depletion (vitamins C and E) and possibly the zinc and copper imbalances associated with smoke exposure. It would not necessarily protect against folate disruption, vitamin D changes, or the effects of CHS. The evidence base for non-smoking routes is thin, though, because researchers have overwhelmingly studied smokers. Until more data on edible-only users accumulates, drawing sharp lines about which deficiencies are route-specific remains somewhat speculative.
Dietary Habits and Confounding Factors
One of the persistent challenges in this research is separating what cannabis does biochemically from what cannabis users tend to do behaviorally. Heavy cannabis use is associated with altered eating patterns, including increased calorie intake (the stereotypical “munchies” are real) but not necessarily increased nutrient density. Eating more chips and fast food will not replace the folate, zinc, or vitamin C that may be getting depleted.
Research has examined the dietary patterns of cannabis users, finding that the relationship between cannabis use and diet is complicated. Cannabis acutely increases appetite, but the food choices made while high tend toward energy-dense, nutrient-poor options. Over time, this pattern can create a paradox where calorie intake is adequate or even excessive while micronutrient intake lags behind. Earlier research on the nutritional effects of marijuana, heroin, cocaine, and nicotine found that addictive drugs broadly affect food intake behavior, taste preferences, and body weight, with specific nutrient status changes developing alongside each substance.12Frontiers in Psychology. A daily diary investigation of cannabis use and its diet and exercise correlates
Lifestyle factors add further confusion. Heavy cannabis users may be more likely to use tobacco concurrently, drink alcohol, sleep irregular hours, or have less outdoor activity, all of which independently affect nutrient status. The Norwegian study that found lower vitamin D in cannabis users, for instance, studied people with severe substance use disorders, a population facing many overlapping nutritional challenges. Isolating the independent effect of cannabis from everything else in a heavy user’s life is genuinely difficult, and most studies acknowledge this limitation.
None of this means the vitamin depletion findings are artifacts. The oxidative stress mechanism from smoking is well-established chemistry, the cell-line data on folate uptake doesn’t depend on diet, and the consistency of the vitamin D finding across different populations is hard to explain away. But it does mean that a person who uses cannabis occasionally and otherwise eats well is at a very different risk level than a daily smoker with a poor diet. Context shapes the actual impact more than the molecule alone.
Vitamin A and Cannabinoid Interactions at the Molecular Level
Vitamin A gets less attention in the cannabis-nutrition discussion, partly because the evidence sits at a more basic-science level. Researchers have identified that a cannabinoid compound called abnormal cannabidiol (abn-CBD) acts as an inhibitor of a protein called CRBP1, which plays a key role in transporting and processing retinol (the active form of vitamin A) inside cells. X-ray crystal structures showed that abn-CBD binds to this protein with high affinity, and experiments demonstrated that it could modulate the flow of retinoids through the vitamin A cycle in living animals.13PubMed Central. Abnormal Cannabidiol Modulates Vitamin A Metabolism by Acting as a Competitive Inhibitor of CRBP1
Abnormal cannabidiol is not the same as the CBD sold in consumer products; it’s a synthetic isomer used in research settings. Whether the cannabinoids present in typical cannabis produce the same effect on vitamin A transport proteins hasn’t been established in humans. The finding is worth knowing about because vitamin A is critical for vision, immune function, and cell growth, and because it suggests there may be cannabinoid-vitamin interactions we haven’t fully mapped yet. But claiming that smoking weed depletes your vitamin A based on this evidence alone would be getting ahead of the science. File it under “plausible mechanism, not yet confirmed in people.”
Pregnancy Deserves Special Mention
The folate finding takes on heightened urgency during pregnancy. Folate is essential for neural tube development in the first weeks of pregnancy, and even modest deficits during this critical window increase the risk of serious birth defects like spina bifida. The cell-line study showing that THC reduced folic acid uptake by about 20% used a model of placental tissue, which means the disruption may occur precisely where nutrient transfer to the developing fetus happens.7PubMed Central. The grass isn’t always greener: The effects of cannabis on embryological development
This is concerning because cannabis use during pregnancy has been increasing in many countries, partly driven by the perception that cannabis is “natural” and therefore safe, and partly because some people use it for morning sickness. If THC is simultaneously reducing folate absorption while the fetus desperately needs folate for normal development, the combination is particularly risky. Standard prenatal vitamins include folic acid for exactly this reason, but if THC is impairing the uptake mechanism itself, supplementation alone may not fully compensate. Anyone who is pregnant or planning to become pregnant has a strong reason to avoid cannabis beyond the other well-documented concerns about THC exposure during fetal development.
What You Can Do About It
If you use cannabis regularly and are concerned about nutritional gaps, the practical steps are straightforward. For vitamins C and E, eating a diet rich in fruits, vegetables, nuts, and seeds can help offset the extra oxidative demand, especially if you smoke. Citrus fruits, bell peppers, strawberries, and broccoli are strong vitamin C sources. Almonds, sunflower seeds, and avocados cover vitamin E. If you smoke heavily, a standard multivitamin that includes both may be reasonable insurance.
For vitamin D, the usual advice applies with extra emphasis: get regular sun exposure, eat fatty fish or fortified foods, and consider supplementation if blood tests show your levels are low. Given that multiple studies have found heavy users running levels in the deficient range, asking your doctor to check your 25-hydroxyvitamin D is worthwhile if you consume cannabis frequently.
Folate is available in leafy greens, legumes, and fortified grains, and supplementation is cheap and widely available. For zinc, oysters, beef, pumpkin seeds, and lentils are good dietary sources. Monitoring the copper-to-zinc ratio is trickier without blood work, but avoiding supplemental copper unless directed by a doctor is a sensible default for cannabis users given the evidence that copper tends to run high in this group.
Switching from smoking to non-combustion methods is probably the single change with the broadest nutritional benefit, since it eliminates the oxidative stress pathway that drives depletion of C, E, and likely zinc. It won’t address everything, but it removes the biggest single driver of antioxidant loss from the equation.