What We Got Wrong About Depression
This summer, I read a study which upended everything that I learned in pharmacy school about depression.
Published in the journal, Molecular Psychiatry, this article concluded that there isn’t enough proof to support the serotonin theory of depression.(1) This theory, which has been widely held for decades, postulated that depression is caused by insufficient levels of the neurotransmitter serotonin in the brain. As such, the logical solution has been to give people medications to increase serotonin; profitable drugs like Prozac, Zoloft, Paxil, Celexa, and many others.
However, my journey into the world of functional medicine has opened my eyes to the pitfalls of relying solely on pharmacotherapy. Studies have pointed to the poor effectiveness of antidepressant medications (2), which makes sense because low serotonin is not the cause of this condition, but rather a symptom of an imbalance somewhere in the body. Therefore, simply increasing serotonin can’t be the only solution. Honestly, when I read this article, I couldn’t help but think: “Well…. Duh!” [insert face-plant emoji here].
Conventional treatment of depression is just another example of throwing drugs at symptoms and not addressing causes
The typical way that depression is treated is just another example of throwing drugs at downstream symptoms, but not actually getting to the true root cause(s) of illness. Conventional medicine often ignores the myriad of contributors to the development of depression: trauma, adverse childhood experiences, systemic inflammation, gut health, genetics, imbalanced immunity, social isolation, diet, and nutrient insufficiencies, just to name a few. Serotonin insufficiency is just a small piece of the big picture of depression.
Depression is a complex condition.
As such, the functional medicine approach is to address all the factors listed above, plus more.
Of particular interest to me is the fascinating role of diet and nutrition.
Tips for improving depression through nutrition:
1. Improve Diet Quality
The SMILES trial from a few years ago demonstrated that switching from a standard Western diet to a Mediterranean-style diet (with support from a nutrition professional) was an effective treatment for improving major depressive symptoms.(3) For those of you who appreciate stats, the NNT (number needed to treat) to achieve remission was 4.1, which is better than the NNT of 6.5 for the SSRI class of medications.(4) Yet, first-line therapy for depression continues to be SSRI therapy and dietary change is rarely recommended.
Optimizing diet quality should always be prescribed along with medication
Optimizing diet quality should always be prescribed in addition to medication therapy. If following the diet used in the SMILES trial, this means:
- Eat more fresh fruits and vegetables (Aim to fill at least ½ of your plate with vegetables),
- Choose whole grains instead of processed or white grain,
- Eat more fish, nuts & olive oil,
- Consume less processed foods and red meat, and
- Limit alcohol to two standard drinks per day.
2. Omega-3 Fatty Acids
There is evidence that consuming omega-3 fats can be helpful for improving depression and they are even recommended in Canadian treatment guidelines.(5,6) Omega-3 fats have anti-inflammatory properties and help to maintain healthy neuronal cell membranes. They also increase production of brain-derived neurotrophic factor (BDNF), a protein which promotes the growth of neurons and has been found to be low in people living with depression.(7)
Increase intake of omega-3 fatty acids by:
- Eating fatty, cold-water fish (8) several times per week or taking a fish oil supplement.
Fish and seafood are good sources of the omega-3 fatty acids EPA & DHA, with the former having greater efficacy in depression.
- Vegan sources of omega-3 fatty acids include flaxseed and walnuts, however these are less efficiently converted to the ideal forms of omega-3, so supplementation with algal oil is often necessary.
3. Antioxidants – Vitamins C and E, Selenium & Zinc
Chronic social, psychological, and physical stressors can lead to higher levels of damaging oxidative stress in people with depression. This results in depletion of the body’s supply of antioxidants. Eating foods rich in antioxidants has been found to be helpful in improving depressive symptoms. Antioxidants include vitamins C and E, as well as the many phytochemicals found in plants. Foods rich in selenium and zinc also help to support the body’s production of endogenous antioxidants. (5,9)
Ways to increase your antioxidant consumption:
- Aim to eat at least 1-2 servings of colorful fruits or vegetables with every meal and snack
- Drink 1-2 cups of green tea daily
- Enjoy a few squares dark chocolate (>70% cocoa)
- Enjoy a handful of nuts every day, including a couple of Brazil nuts, which are rich in selenium
- Top your food with seeds for a nice crunch (e.g., pumpkin, hemp, or sesame seeds)
- Consider eating more shellfish, which are rich in zinc (e.g., oysters, crab, shrimp, mussels)
4. Fiber, Prebiotics, Probiotics, and Fermented foods
There is a strong connection between the gut and the brain. More specifically, the microbial inhabitants of the intestinal tract affect brain function through direct communication via the vagus nerve, modulation of neurotransmitters (including serotonin), control of inflammation, and through production of nutrients such as vitamins and short-chain fatty acids.(5)
A healthy and diverse microbiome contributes to improved mood.
The gut microbiome thrives on fiber
To enhance the microbial health of your gut:
- Increase your intake of dietary fiber by eating more fruits and vegetables, nuts, seeds, legumes, and whole grains. Prebiotic supplements, like psyllium, can also be helpful. Your gut microbiome eats and thrives on fiber.
- Eat fermented foods like yogurt, kimchee, sauerkraut, miso, and kefir. These foods contain beneficial bacteria.
- Consider supplementing with probiotics. Strains that have shown efficacy in depression include L. helveticus R0052, B. longum R0175, L. plantarum 299v, and Bacillus coagulans MTCC 5856. (10)
This amino acid is required by the body to create serotonin, as well as the sleep hormone melatonin. It is an essential amino acid, which means that it must be obtained through food. People who do not eat enough protein containing tryptophan could be putting themselves at risk of depressive symptoms.
Good dietary sources of tryptophan include:
- Meat, fish, eggs, tofu, edamame, cheese, oats, and pumpkin seeds.
Of note, the efficacy and safety of tryptophan supplementation is not clear, so for now it’s best to focus on getting enough from the diet. (5)
6. B vitamins – Folate, B6, and B12
Folate is a B vitamin that has anti-depressive effects owing to its role in regulating enzymes which make neurotransmitters such as serotonin, noradrenaline, and dopamine. It also decreases homocysteine, a neurotoxic inflammatory protein.
To get adequate folate in your diet:
- Eat plenty of leafy green vegetables, fruit, and legumes
- Supplements are also available, however the methylfolate form is preferred due to its superior absorption, as well as the ability to cross the blood-brain barrier and bypass any folate enzyme genetic polymorphisms.
- Concurrent supplementation with vitamins B6 and B12 would also be useful as these similarly impact neurotransmitter production and homocysteine metabolism. (5,6)
Any of the above foods and nutraceuticals could be as adjuncts to medication therapy. There are also other nutraceuticals which have shown to benefit depression including saffron, SAMe, lavender, and DHEA. (6) Reach out to me directly if you’d like to learn more about these.
*Be sure to consult your doctor or pharmacist prior to starting any supplements or making dietary changes, as they might not be appropriate for you or could interact with your current medications*
LET’S CHAT if you need help figuring out the root cause of your symptoms
References and End Notes
8. My favorite sustainable & clean fish sources of omega-3’s are the SMASH fish: salmon, mackerel, anchovies, sardines, and herring. Here are additional resources for choosing safe seafood: www.seafoodwatch.org, https://www.epa.gov/fish-tech/epa-fda-advice-about-eating-fish-and-shellfish
The information contained in this article is intended for educational and entertainment purposes only. It is not to be construed as personalized nutritional advice nor intended to be a substitute for proper health and medical care. Please consult your physician or a qualified health care professional for support with your health conditions.