Low Zinc Levels Linked to Depression – Does Your Vegan Diet Contain Enough Zinc?

by L Matthews on January 6, 2014

zinc deficiency and depression in vegansNew research from the University of Toronto adds weight to a link between zinc deficiency and depression, which is worrying for vegans as this is a mineral that can sometimes be lacking in poorly planned vegan diets. As it is thought that it takes a while for absorption of zinc from plant-based foods to be upregulated in new vegans, the first six months to a year of veganism could be even tougher if you’re already suffering from depression.

The research, published in the December 15th issue of Biological Psychiatry (74:872-878), is a meta-analysis carried out across 17 studies looking at levels of zinc in the peripheral blood of 1643 depressed and 804 non-depressed (control) individuals. What Walter Swardfager, PhD, from the Sunnybrook Research Institute, University of Toronto, Canada, and colleagues found was that mean peripheral blood–zinc concentrations were lower by approximately 1.85 µmol/L in depressed individuals compared with control participants.

Zinc and Mental Health

As we should all know by now, association doesn’t equal causation so the researchers aren’t saying that zinc deficiency causes depression. Instead, the clinicians called for further investigation into the links beteen zinc status and mental illness, specifically depression, based on their own analysis of a number of studies over the past few decades. Not all of the studies looking at zinc levels and depression have found such a link but many have and zinc has also previously been linked to an elevated incidence of schizophrenia and eating disorders.

Zinc Deficiencty-Induced Depression

This latest analysis adds to earlier evidence from interventional studies in animals that found that those fed a diet lacking in zinc began to exhibit depressive-like behaviour, subsequently reversed by zinc supplementation. Indeed, those who are depressed and who are given zinc supplements alongside their antidepressant medications have been seen in some cases to have a more rapid and effective response to the treatment.

More Severe Depression and Zinc

Those suffering from the most severe forms of depression tended to have the greater differences in zinc levels in this analysis. While this study alone does not provide sufficient evidence to suggest a dose-dependent effect of zinc on depressive symptoms more recent studies looking at zinc monotherapy are adding weight to that hypothesis. Of course, it’s also important to note that ingesting a large amount of zinc can itself cause problems, including compromising copper status, which would then compromise the production of collagen, among other things, and decrease bone health.

Ten of the studies included in this review were conducted in psychiatric institutions, seven were from community samples, the average age of the individuals was 37.7 and 34.4% were male. Psychiatric inpatients showed the greatest effect of zinc, and the link was strongest in the studies with the highest methodological quality.

The Link Between Zinc and Depression

Explanations as to why zinc and depression may be linked include mechanisms such as antioxidant defence provided by the mineral, as well as zinc’s influence on immunity and hormone balance. Zinc is also important in maintaining healthy cognitive function especially as concerns the hippocampus and cortical glutamatergic systems that are involved in helping us remain adaptable and resilient to external stressors.

Zinc and EFAs

Zinc is also a key mineral for hundreds of enzymatic processes in the body, including the formation of essential fatty acids (EFA), particularly long-chain fatty acids such as docosahexanoic acid (DHA) and eicosapentanoic acid (EPA) which can be lacking a vegan diet. The human body is able to synthesise such fatty acids given the right ingredients but this conversion may be compromised in some individuals. Flaxseed, chia seeds, and especially algal oil are good ways for vegans to meet their EFA needs but it is vital to also have zinc, vitamin C, vitamin B6 and a range of other nutrients in order to form the longer chain DHA and EPA from plant-based omega 3.

EFAs and Cognitive Health

Disturbances in EFA levels have been linked to impaired cognitive function, such as attention deficit hyperactivity disorder (ADHD), autism, and depression. In addition, fatty acid metabolic dysfunction can affect the health of our blood vessels, leading to impaired circulation, cardiovascular disease (a common comorbidity of major depressive disorder) and even to ischaemic stroke, and possible forms of dementia like Alzheimer’s disease.

Zinc Deficiency and Veganism – Raising Awareness and Supporting Vegans

While the results of this meta-analysis do appear to confirm a link between low levels of zinc and depression it is important to note that some of the studies involved paid little heed to diet, alcohol, and to the use of medications (even to antidepressants) in some participants. Thus, the data is not foolproof and should be viewed in light of such limitations.

Evidence is mounting, however, to suggest a range of potential pathological connections between zinc deficiency, depression, and cognitive dysfunction. Whether zinc status becomes useful in diagnosing depression and monitoring treatment, or whether it actually becomes a part of treatment itself remains to be seen. What we do know, however, is that it makes sense to pay attention to your zinc status as a new vegan and even if you’re an old hand at veganism. It may be that some of the cases of lapsed vegans involving fatigue, depression, and disenchantment with the vegan ‘lifestyle’ could be connected to zinc deficiency-induced depressive symptoms. So, if you know someone making the switch to veganism help them out with some tasty zinc-rich snacks and meals!


Great Vegan Zinc Sources

Some great vegan zinc sources include pumpkin seeds, cashews, sunflower seeds, and wheatgerm, along with spinach, peanuts, sesame seeds, and even alfalfa sprouts. Many processed vegan foods, including granola, faux meat products, and non-dairy milks are fortified with zinc and can help you meet your daily zinc goals. So, while zinc deficiency may be linked to depression, and zinc deficiency is arguably more likely on a poorly planned vegan diet compared to a well-planned omnivorous diet, there are plenty of ways to lessen your risk and be a happy and healthy vegan.

For more on zinc and vegan diets check out:

Great vegan zinc sources
Zinc and sexual health
Signs of a zinc deficiency.

UPDATE (Sept. 13th 2014):

A 2012 review looked at four randomised controlled trials investigating the use of zinc supplements alone or as an adjunct to conventional antidepressant therapy. Lai et al. found that zinc significantly lowered depressive symptoms scores when combined with standard antidepressant therapy, while stand-alone zinc supplementation had a less clear impact on depressive symptoms but was suggestive of potential benefits.

A more recent trial looked at zinc monotherapy for depressive symptoms in people considered overweight or obese. Solati et al. randomly assigned 50 people to receive either a 30mg zinc supplement daily or a placebo for 12 weeks. They used the well-regarded Beck depression inventory II to assess depression severity at the start of the study and after 12 weeks and also examined serum levels of zinc and brain-derived neurotrophic factor (BDNF).

The zinc supplementation significantly increased serum zinc and BDNF levels compared to placebo and while both groups had lower BDI scores at the end of the study, those taking zinc had a significantly greater reduction in their BDI score. Those with an initial score of 10 on the BDI had a decrease in their score while those with a score below 10 (i.e. who weren’t experiencing depressive symptoms) had no change following zinc supplementation.

In addition to suggesting a greater benefit of zinc supplementation for those with a BDI over 10, another interesting finding from this study was that serum BDNF levels were significantly inversely correlated with the severity of a person’s depression, i.e. the higher their serum BDNF level the less severe their depression. At baseline (i.e. at the beginning of the study), there was a significant positive correlation between serum BDNF and zinc levels. The authors’ concluded that zinc supplementaion improved mood in overweight and obese people, most likely by increasing serum BDNF levels.

Lai J, Moxey A, Nowak G, Vashum K, Bailey K, McEvoy M. The efficacy of zinc supplementation in depression: systematic review of randomised controlled trials. J Affect Disord. 2012 Jan;136(1-2):e31-9. doi: 10.1016/j.jad.2011.06.022. Epub 2011 Jul 27.
Solati Z, Jazayeri S, Tehrani-Doost M, Mahmoodianfard S, Gohari MR. Zinc monotherapy increases serum brain-derived neurotrophic factor (BDNF) levels and decreases depressive symptoms in overweight or obese subjects: A double-blind, randomized, placebo-controlled trial. Nutr Neurosci. 2014 Jan 7. [Epub ahead of print]

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Leave a Comment

{ 2 comments… read them below or add one }

Walter Swardfager September 13, 2014 at 07:53

Thank you for this useful and informative summary for those adopting a vegan lifestyle.

There is one statement about which I would advise caution; the finding that “Those suffering from the most severe forms of depression tended to have the greater differences in zinc levels” was inferred because studies that had larger differences in blood zinc levels between depressed and non-depressed subjects had depressed patients with more severe symptoms. To infer “a possible dose-dependent response for zinc supplementation” may be misleading since supplementation was not studied in that paper.

There is currently no consensus on what a healthy zinc intake would be for those suffering from depression, and more is not necessarily better. Our study provided little insight into diet and supplementation and dose-finding studies for brain health are still needed.

Generally, it is not considered beneficial to supplement minerals above the “recommended daily intake”; however, vegetarians, and vegans especially, are a special case, requiring a zinc intake over 50% higher than that recommended for omnivores. The reason for this is that while plant sources (beans, grains and seeds) contain zinc, they also contain phytates that sequester zinc and prevent its absorption by the body. To reduce the binding of zinc by phytates, beans, grains, and seeds can be soaked in water for a few hours before cooking them, or allowing them to sit after soaking until they start to sprout. Also, the body can absorb more zinc from leavened grains than unleavened grains because leavening breaks down phytates – so in general, breads can be better sources of zinc that crackers.

Walter Swardfager

L Matthews September 13, 2014 at 10:55

Hi Walter,

Thanks for reading and for your insightful comment! It’s always good to be reminded of the need for careful language use so I really appreciate the prompt to go back and reassess how I wrote this post.

As you can see, I’ve added a little extra research, including a study of which I’m sure you’re already aware, where zinc monotherapy was studied in relation to brain health and depression.

Thanks for the great work you do and for taking the time to comment on this article!

Leigh

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