Depression is not just feeling sad. It is low mood most days, loss of interest in things you used to enjoy, poor sleep or too much sleep, low energy, poor concentration, and a sense of worthlessness that does not lift with rest. It can last weeks, and it can stop you functioning at work, at home, and with people you love. If you cannot function, or you are thinking about suicide, please get professional help now. No supplement in this piece is a substitute for that.

I start with labs because a few deficiencies can look like depression, and fixing them is the cheapest win in this whole field. Folate, B12, vitamin D, iron, and thyroid all belong in the check. Low folate in particular tracks with poorer antidepressant response. Folate is needed to make SAMe, and SAMe is needed to make serotonin, dopamine, and noradrenaline. Low B12 can cause fatigue, fog, and low mood before anaemia ever shows up. Low vitamin D tracks with depression, though the causal story is still open. Low thyroid can feel exactly like depression, slow, cold, tired, foggy. If those are off, fix them first, with your clinician, and retest in 12 weeks.

EPA dominant omega-3 has the strongest evidence of any supplement for depression. A 2019 meta analysis of 26 randomised trials, 2,160 people, found omega-3 reduced depressive symptoms with a small to moderate effect, which became larger and more consistent in trials using formulas that were at least 60 percent EPA at 1 g a day or more, mostly as add ons to antidepressants. DHA dominant products did not work. Benefit appears greatest in people with raised inflammatory markers such as C-reactive protein. Studied dose is 1 to 2 g of EPA per day from a fish oil with EPA at least 60 percent of total omega-3, for 8 to 12 weeks. It helps as an add on, not instead of treatment. It can interact with blood thinners, so check if you take warfarin, aspirin, or clopidogrel.

Saffron is the surprise. At least 12 randomised trials, mostly 6 weeks long at 30 mg a day, have tested standardised saffron extract in mild to moderate depression. Meta analyses find a large effect over placebo and no significant difference from fluoxetine 20 mg or imipramine 100 mg in head to head trials, with fewer side effects. Lopresti and Drummond, 2014, pooled 6 trials and reached the same conclusion. The mechanism, crocin and safranal acting on serotonin, dopamine, inflammation, and oxidative stress, is at least testable. The caveat is real. Many trials come from Iranian research groups where saffron is a major industry, and independent replication in diverse populations would strengthen confidence. Saffron is serotonergic, so do not combine it with an SSRI, SNRI, MAOI, or tramadol without prescriber coordination. Do not use it if you are pregnant.

SAMe, S-adenosyl-L-methionine, is a naturally occurring compound involved in methylation throughout the body, including in the synthesis of monoamine neurotransmitters. It has been used as a prescription antidepressant in several European countries for decades. A 2014 trial compared SAMe 1,600 to 3,200 mg a day to escitalopram 10 to 20 mg a day in major depressive disorder and found no significant difference in response rates. A 2010 trial found SAMe helped as an add on for people who had not responded to an SSRI. Studied dose is 800 to 1,600 mg a day, on an empty stomach, split twice daily. It can trigger mania in bipolar disorder, which is a serious safety concern for self prescribers. It can also interact with serotonergic drugs, and it can cause stomach upset and insomnia if taken late.

L-methylfolate is the active form of folate that crosses the blood brain barrier directly. Papakostas and colleagues, 2012, tested 15 mg a day as an add on to SSRI in patients who had a partial response, and found significant improvement versus placebo, with the benefit most pronounced in patients with evidence of underlying folate insufficiency. L-methylfolate is FDA approved as a medical food for depression at 7.5 to 15 mg a day as an adjunct. It is not a general mood supplement for people with normal folate. It needs a prescriber, because high dose folate can mask B12 deficiency, and it can interact with methotrexate and some epilepsy drugs.

Magnesium is the quiet one. A 2023 meta analysis found significant reductions in depression scores with a large effect size. In an open label randomised trial, 248 mg of elemental magnesium a day produced a clinically meaningful drop in both depression and anxiety scores within a fortnight, and it worked regardless of starting level. The mechanism runs through the HPA axis, which regulates your stress response, and through GABA, your calm neurotransmitter. Magnesium is also a cofactor for ATP, so low magnesium can feel like low energy as well as low mood. Give it two to four weeks if you are low, and do not expect it to fix depression that comes from thyroid or trauma.

Zinc is worth checking if you have not responded to an antidepressant. Studies show significant improvements in Beck Depression Inventory scores when zinc 25 mg daily is combined with antidepressants. Zinc deficiency is associated with increased depression risk, and zinc is involved in NMDA receptor signalling, which is the same system ketamine targets. Do not take high dose zinc long term without a clinician check, because it can trap copper in the gut and cause anaemia and low white blood cells. High dose zinc above 40 to 50 mg a day for weeks or months is the range where that risk rises.

Vitamin D is the one with the strongest correlation and the shakiest causal story. A 2023 meta analysis found vitamin D supplementation reduced depressive symptoms, with stronger effects in people who were actually deficient and had existing depression. Large trials like VITAL-DEP found no significant effect on depression prevention in people who were not deficient. So test first. If your 25 hydroxyvitamin D is below 50 nmol per litre, repletion to roughly 30 to 50 ng per mL often helps how you feel in general. If you are already sufficient, extra vitamin D does not reliably lift mood.

What I would do, if you are already on an antidepressant and still feel low, is ask your clinician about one add on at a time, for 6 to 8 weeks, with one score tracked, like PHQ-9 each week. EPA 1 to 2 g a day, or L-methylfolate 15 mg a day, or zinc 25 mg a day if you are low, are the three with the best add on data. Do not stop your antidepressant abruptly to try a supplement. That can cause withdrawal and rebound, and it can make depression worse.

This is education, not medical advice. It is not a diagnosis, and it does not replace professional care.

Sources: Liao and colleagues, Translational Psychiatry, 2019, PMID 31383846. Lopresti and Drummond, Human Psychopharmacology, 2014, PMID 25384672. Mischoulon and colleagues, Journal of Clinical Psychiatry, 2014, PMID 24500245. Papakostas and colleagues, American Journal of Psychiatry, 2012.