Supplement Interactions

Vitamin D3 + Vitamin K2 Research suggests Vitamin K2 helps direct calcium mobilised by Vitamin D3 to bones rather than soft tissue, potentially reducing arterial calcification risk. Magnesium + Vitamin D3 Magnesium is a cofactor in Vitamin D metabolism. Research suggests adequate magnesium is necessary for the body to activate and utilise Vitamin D3 effectively. Vitamin B12 + Vitamin C Some older research raised concerns about Vitamin C degrading B12, but modern studies indicate this is not clinically significant at normal supplement doses. Calcium + Vitamin D3 Vitamin D3 is essential for calcium absorption. However, combining high-dose D3 with high-dose calcium supplementation may increase the risk of hypercalcaemia. Research suggests monitoring total calcium intake (diet + supplements) to stay within recommended ranges. Omega-3 + Turmeric / Curcumin Research suggests curcumin and omega-3 fatty acids may have complementary anti-inflammatory effects. Both target overlapping inflammatory pathways through different mechanisms. Collagen + Vitamin C Vitamin C is an essential cofactor for collagen synthesis. Research indicates that without adequate Vitamin C, the body cannot properly hydroxylate proline and lysine residues needed for stable collagen formation. Iron + Vitamin B12 Both iron and Vitamin B12 are essential for red blood cell production. Deficiency in either can cause anaemia, and research suggests addressing both simultaneously when levels are low. Magnesium + Vitamin B6 Research suggests Vitamin B6 may enhance magnesium uptake into cells. A landmark study found the combination more effective for stress reduction than magnesium alone. Vitamin B6 + Zinc Zinc is involved in the conversion of pyridoxine to its active form (pyridoxal-5'-phosphate). Research suggests adequate zinc status supports B6 metabolism. Prebiotics + Probiotics Prebiotics serve as fuel for probiotic bacteria. Research suggests combining them (a 'synbiotic' approach) may enhance probiotic survival and colonisation in the gut. Chondroitin + Glucosamine Glucosamine and chondroitin are commonly combined for joint health. The GAIT trial suggested the combination may be particularly beneficial for moderate-to-severe knee pain. NAC + Vitamin C Both NAC and Vitamin C support the body's glutathione system. Research suggests they may have complementary antioxidant effects through different mechanisms. L-Theanine + Lion's Mane Research suggests L-theanine and Lion's Mane may have complementary cognitive benefits. L-theanine promotes calm focus while Lion's Mane supports nerve growth factor production. Creatine + Magnesium Research suggests magnesium may play a role in creatine metabolism and cellular energy production. Both are involved in the ATP energy system. CoQ10 + Omega-3 CoQ10 and omega-3 fatty acids may have complementary cardiovascular benefits. Research suggests both support heart function through different mechanisms. Selenium + Vitamin E Selenium and Vitamin E work together as part of the body's antioxidant defence system. Research suggests they have complementary roles in protecting cells from oxidative damage. Folate + Vitamin B12 B12 and folate are closely linked in the methylation cycle. Research indicates that B12 deficiency can trap folate in an unusable form, and supplementing one without the other may mask deficiency of the second. Boron + Vitamin D3 Emerging research suggests boron may help the body retain and utilise Vitamin D more effectively by inhibiting its degradation. Some studies indicate boron supplementation increases serum 25(OH)D levels. At very high D3 doses (>10,000 IU), this reduced clearance may theoretically contribute to Vitamin D excess. Magnesium + Vitamin B1 Magnesium is required for the activation of thiamine (B1). Research suggests that magnesium deficiency may impair thiamine utilisation even when B1 intake is adequate. Ashwagandha + Magnesium Ashwagandha and magnesium may have complementary effects on stress and sleep. Both are associated with cortisol reduction and relaxation through different pathways. Vitamin C + Vitamin E Research suggests Vitamin C can regenerate Vitamin E after it has neutralised a free radical, extending its antioxidant capacity. Omega-3 + Vitamin E Vitamin E may help protect omega-3 fatty acids from oxidation. Research suggests that high omega-3 intake increases the body's requirement for Vitamin E as an antioxidant. Calcium + Vitamin K2 Research suggests Vitamin K2 helps direct dietary and supplemental calcium to bones rather than soft tissues. This may reduce the risk associated with calcium supplementation. CoQ10 + Vitamin E CoQ10 and Vitamin E work together in the mitochondrial membrane as antioxidants. Research suggests CoQ10 can regenerate Vitamin E, similar to Vitamin C's role. Calcium + Magnesium Calcium and magnesium work together in muscle and nerve function. Research suggests maintaining a balanced ratio (roughly 2:1 calcium to magnesium) supports optimal function of both. Magnesium + Taurine Research suggests taurine and magnesium may have complementary effects on cardiovascular function and blood pressure regulation. Ashwagandha + Rhodiola Rosea Both are classified as adaptogens. Research suggests they may support stress resilience through complementary mechanisms — rhodiola primarily through stimulating pathways, ashwagandha through calming ones. Omega-3 + Vitamin D3 Research suggests omega-3 fatty acids and Vitamin D3 may have complementary anti-inflammatory and immune-supporting effects. The VITAL study examined their combined benefits. Iodine + Selenium Selenium and iodine work together in thyroid function. Research indicates selenium-dependent deiodinase enzymes are essential for converting T4 to the active T3 thyroid hormone. Milk Thistle + NAC Both milk thistle (silymarin) and NAC support liver health and glutathione production. Research suggests they may have complementary hepatoprotective effects. Selenium + Vitamin C Research suggests Vitamin C and selenium may have complementary antioxidant effects. However, very high-dose Vitamin C taken simultaneously may reduce selenite absorption. Creatine + Vitamin D3 Emerging research suggests combining creatine and Vitamin D3 may have additive benefits for bone health and muscle function, particularly in older adults. Ashwagandha + L-Theanine Both L-theanine and ashwagandha may support relaxation and stress reduction through different mechanisms. Research suggests they can be complementary in an anxiolytic stack. Magnesium + Melatonin Both magnesium and melatonin support sleep through different mechanisms. Research suggests magnesium may enhance melatonin production and improve sleep quality alongside it. Glutamine + Probiotics Research suggests glutamine supports intestinal barrier integrity, which may complement probiotic supplementation for gut health. Elderberry + Vitamin C Both elderberry and Vitamin C are commonly used for immune support. Research suggests they may have complementary effects on immune function. Vitamin C + Zinc Zinc and Vitamin C are frequently combined for immune support. Research suggests both independently support immune function and may have additive benefits. Boron + Calcium Emerging research suggests boron may reduce urinary calcium excretion, potentially supporting calcium balance and bone health. CoQ10 + Magnesium Both CoQ10 and magnesium are important for cellular energy production. Research suggests they support mitochondrial function through complementary mechanisms. CoQ10 + Vitamin B5 Pantothenic acid (B5) is a precursor to Coenzyme A, which is involved in CoQ10 biosynthesis. Research suggests adequate B5 may support the body's CoQ10 production. Magnesium + Vitamin K2 Research suggests magnesium may be important for Vitamin K-dependent carboxylation reactions. Both nutrients support bone health through different mechanisms. Probiotics + Vitamin D3 Emerging research suggests probiotics may enhance Vitamin D status. Some strains appear to improve 25(OH)D levels, possibly through gut-mediated mechanisms. Magnesium + Probiotics Emerging research suggests magnesium and probiotics may support gut health through complementary mechanisms. Magnesium oxide in particular has osmotic effects that can alter the gut environment. Ashwagandha + L-Tryptophan Both ashwagandha and L-tryptophan may support serotonin-related pathways. Research suggests they can be complementary for mood and sleep support. Magnesium + Vitamin B2 Both riboflavin (B2) and magnesium have been studied for migraine prevention. Research suggests the combination may be more effective than either alone. CoQ10 + Creatine Both CoQ10 and creatine support cellular energy production through the ATP system. Research suggests they may have complementary benefits for mitochondrial function. Omega-3 + Probiotics Emerging research suggests omega-3 fatty acids may positively influence gut microbiome composition, potentially complementing probiotic supplementation. Vitamin B1 + Vitamin B12 B vitamins generally work synergistically as a family. Research suggests B1 and B12 together support nervous system function through complementary mechanisms. Panax Ginseng + Rhodiola Rosea Both are adaptogenic herbs that may support energy and stress resilience. Research suggests they work through partially overlapping but distinct mechanisms. Glucosamine + Omega-3 Both glucosamine and omega-3 are used for joint health. Research suggests they may have complementary anti-inflammatory and structural benefits for joints. Turmeric / Curcumin + Vitamin D3 Research suggests curcumin and Vitamin D3 may have complementary anti-inflammatory and immune-modulating effects. Both influence NF-kB and other inflammatory pathways. Lion's Mane + Vitamin B12 Both Lion's Mane and Vitamin B12 support nervous system health. Research suggests they may be complementary for cognitive function and nerve health. Omega-3 + Taurine Both taurine and omega-3 have been studied for cardiovascular benefits. Research suggests they may have complementary cardioprotective effects. Saw Palmetto + Zinc Both saw palmetto and zinc are used for prostate health. Research suggests they may have complementary effects on 5-alpha-reductase activity. Biotin + Collagen Biotin and collagen are both commonly used for hair, skin, and nail health. Research suggests they support these tissues through different mechanisms. L-Theanine + Magnesium Both magnesium and L-theanine promote relaxation without sedation. Research suggests they may have complementary calming effects through different GABA-related mechanisms. Elderberry + Zinc Both elderberry and zinc are used for immune support, particularly during cold season. Research suggests they may have additive antiviral and immune-stimulating effects. Chromium + Vitamin B3 Both niacin and chromium are involved in glucose and lipid metabolism. Research suggests chromium as part of the glucose tolerance factor (GTF) may work with niacin to support insulin sensitivity. Collagen + Zinc Zinc plays a role in collagen synthesis and wound healing. Research suggests adequate zinc is important for the body to effectively utilise supplemental collagen. Maca + Zinc Both maca and zinc are associated with reproductive health and hormone support. Research suggests they may have complementary effects on testosterone and fertility. Omega-3 + GLA (Omega-6) Research suggests a balanced ratio of omega-6 to omega-3 fatty acids is important for managing inflammation. GLA (gamma-linolenic acid) is an anti-inflammatory omega-6, unlike most omega-6 fats. CLA + Omega-3 CLA (conjugated linoleic acid) and omega-3 are both fatty acids that may support body composition. Research suggests they may have complementary effects on fat metabolism.

Iron + Vitamin C Vitamin C significantly enhances non-heme iron absorption. Studies indicate it can increase iron uptake by 2-3 times when taken together. Omega-3 + Vitamin A Vitamin A is fat-soluble. Research suggests taking it with omega-3 or other fat sources significantly improves absorption.

Iron + Zinc Research indicates that zinc and iron compete for absorption via the DMT1 transporter when taken simultaneously. Studies suggest this can reduce absorption of both minerals by 30-50%. Calcium + Iron Calcium can significantly inhibit non-heme iron absorption. Studies show reductions of 40-60% when taken together at doses above 300mg calcium. Magnesium + Zinc High-dose magnesium and zinc may compete for absorption when taken simultaneously. The effect is most pronounced at higher supplemental doses. Calcium + Zinc Research suggests calcium may inhibit zinc absorption when taken simultaneously at high doses. The interaction is more significant with supplemental calcium than dietary calcium. Iron + Manganese Iron and manganese compete for the same intestinal transporter (DMT1). Research suggests high iron intake can reduce manganese absorption and vice versa. Folate + Zinc Some research suggests high-dose zinc supplementation may impair folate absorption, though the evidence is mixed and dose-dependent. Calcium + Chromium Research suggests calcium carbonate may reduce chromium absorption when taken simultaneously. Chromium picolinate appears less affected. Iron + Turmeric / Curcumin Research suggests curcumin may chelate iron, potentially reducing its absorption. This may be beneficial for those with iron overload but problematic for those with iron deficiency. Calcium + Manganese Calcium and manganese may compete for intestinal absorption. Research suggests high calcium intake can reduce manganese bioavailability. Iron + Vitamin E Research suggests inorganic iron (ferrous sulfate) may oxidise and reduce Vitamin E in the gut. This interaction is less relevant with chelated iron forms. Copper + Iron Copper and iron have a complex absorption relationship. Research suggests high-dose iron can reduce copper absorption, though copper is also needed for iron metabolism. NAC + Zinc NAC's thiol group can chelate zinc and other minerals in the gut. Research suggests taking NAC separately from mineral supplements may optimise absorption of both. Calcium + Omega-3 At high doses, calcium may form insoluble soaps with fatty acids (including omega-3), potentially reducing absorption of both. This is mainly a concern at very high calcium doses. Selenium + Zinc At high doses, zinc and selenium may compete for absorption. However, at typical supplement doses, research suggests they are compatible and even complementary for immune function. Calcium + Potassium Very high calcium intake may affect potassium balance, though this interaction is typically only significant at very high supplemental calcium doses. Iron + Probiotics Iron supplements may create an unfavorable gut environment for certain probiotic strains. Research suggests unabsorbed iron in the colon can alter the gut microbiome. Chromium + Iron Research suggests iron and chromium may compete for absorption when taken simultaneously, particularly at higher doses. Iodine + Iron Iron deficiency can impair thyroid function and iodine utilisation. Research suggests that iron deficiency reduces the effectiveness of iodine supplementation for thyroid health. Collagen + Iron Certain amino acids in collagen (particularly glycine) may form complexes with iron that affect absorption. Research on this specific interaction is limited.

Melatonin + Vitamin B12 B vitamins, particularly B12 and B6, may promote alertness and energy. Research suggests taking them in the morning rather than alongside melatonin in the evening. Melatonin + Vitamin B6 Vitamin B6 is involved in melatonin synthesis (converting tryptophan to serotonin to melatonin). However, B6's energising effects in the evening may interfere with sleep onset. L-Theanine + Valerian Both valerian and L-theanine have calming effects. Research suggests combining them may produce a cumulative sedative effect, which is desirable at bedtime but could cause excessive drowsiness during the day. Ashwagandha + Valerian Both ashwagandha and valerian have sedating properties. Research suggests their combined use may enhance sedation, which is beneficial for sleep but may cause excessive drowsiness. Melatonin + Rhodiola Rosea Rhodiola is considered a stimulating adaptogen. Taking it alongside melatonin may produce conflicting effects — one promotes alertness, the other sleep. Panax Ginseng + Melatonin Ginseng has stimulant-like properties. Research suggests taking it at the same time as melatonin may create opposing pharmacological effects. Maca + Melatonin Maca may have mild energising effects. Research suggests taking it in the morning rather than in the evening with melatonin to avoid conflicting effects. L-Tryptophan + Melatonin L-tryptophan is converted to serotonin and then melatonin in the body. Taking both may be redundant and could potentially lead to excessive serotonergic effects. Ashwagandha + Panax Ginseng Ginseng is a stimulating adaptogen while ashwagandha is calming. Research suggests they can be complementary if timed appropriately, but simultaneous use may produce conflicting effects. Iron + NAC NAC's thiol group can chelate iron in the gut. Research suggests separating them for optimal absorption of both, though NAC may also have hepatoprotective benefits against iron-induced oxidative stress. Melatonin + Valerian Both valerian and melatonin promote sleep. Combining them may produce excessive sedation in some individuals. Research suggests starting with one and adding the second cautiously. Ashwagandha + Melatonin Both ashwagandha and melatonin can promote sleepiness. Research suggests their combined use may enhance sedation, which is beneficial for sleep but should be dosed carefully.

Copper + Zinc Long-term zinc supplementation above 40mg/day can deplete copper levels, potentially leading to copper deficiency anaemia. This is well-documented in clinical literature. Copper + Vitamin C Very high-dose Vitamin C (>1500mg/day) may reduce copper absorption over time. Research suggests monitoring copper status if taking megadose ascorbic acid long-term.

Vitamin A + Vitamin D3 Both Vitamin A and D3 are fat-soluble and stored in the body. Research suggests high-dose retinol (preformed Vitamin A) may antagonise Vitamin D's bone-protective effects. Vitamin A + Vitamin E Both are fat-soluble vitamins stored in the body. Research suggests excessive supplementation of both together increases the risk of exceeding safe upper limits. Vitamin B3 + Vitamin B6 If taking individual B6 alongside a B-complex or multivitamin containing B6, the combined dose may exceed the tolerable upper limit (25mg/day in the UK, 100mg/day per EFSA). Chronic high-dose B6 may cause peripheral neuropathy. Selenium + Vitamin A Both selenium and Vitamin A (retinol) have relatively narrow safety margins. Research suggests monitoring total intake from all sources to avoid exceeding upper limits. Iron + Vitamin A Both iron and Vitamin A (retinol) are stored in the liver. Research suggests excessive supplementation of both may increase liver burden, particularly in individuals not deficient. Folate + Vitamin B6 When supplementing individual B vitamins alongside a B-complex, total doses may exceed intended amounts. Particularly for B6, which has a well-established UL, and folate, where high doses may mask B12 deficiency. Vitamin D3 + Vitamin E Both are fat-soluble vitamins that accumulate in adipose tissue. Research suggests monitoring combined intake from multiple supplement sources to avoid exceeding upper limits.