Depression is a global crisis that affects more than 280 million people today. It’s the leading cause of disability worldwide and contributes significantly to overall disease burden.1 Unfortunately, conventional medicine still relies on antidepressants as a first-line treatment, which oftentimes has intolerable side effects. This has led researchers to explore other factors that influence mental health, including diet.
One area gaining attention is the role of gut bacteria in mood regulation. A study from Massachusetts General Hospital and Harvard T.H. Chan School of Public Health has found that citrus fruits, particularly oranges, influence gut bacteria linked to neurotransmitters that regulate mood. While citrus has long been valued for its vitamin C content, this research suggests it may also support mental well-being by shaping the gut microbiome.2
How Does Citrus Support Gut Bacteria That Impact Mental Health?
Published in the journal Microbiome,3 the study analyzed data from the Nurses’ Health Study II (NHS2), a long-term study of over 100,000 women, to see how citrus affects mental health. They found that women who ate citrus regularly had lower rates of depression. Surprisingly, this effect was specific to citrus — other fruits, like apples and bananas, didn’t show the same benefit.
• Eating citrus is linked to a lower risk of depression — The study showed that higher citrus intake was associated with a 22% reduced risk of depression. This connection was linked to changes in gut bacteria, especially an increase in Faecalibacterium prausnitzii (F. prausnitzii), a beneficial bacterium with anti-inflammatory effects.
• A diverse gut microbiome supports mental health — Women who ate more citrus had higher gut microbial diversity and an increase in 15 specific bacterial species. Among them, F. prausnitzii stood out as the most strongly connected to lower depression rates. Women with higher levels of this bacterium had a lower risk of depression, while those with lower levels were more likely to experience symptoms.
• Findings were validated in a separate men’s study — To confirm the results, researchers examined data from 307 men in the Men’s Lifestyle Validation Study (MLVS). The study found that citrus intake was also associated with increased F. prausnitzii levels in men.
• Gut bacteria influence neurotransmitter production — F. prausnitzii plays a role in producing S-adenosyl-L-methionine (SAM), a compound that helps your body regulate mood-regulating neurotransmitters like dopamine. Lower SAM cycle activity was linked to a higher risk of depression, suggesting that gut bacteria may play a direct role in mental health.
• Citrus intake is linked to lower expression of a specific enzyme in the colon — Higher SAM cycle activity was linked to lower levels of monoamine oxidase A (MAOA) in the colon. MAOA is an enzyme that breaks down neurotransmitters like serotonin and dopamine. It plays a key role in regulating mood and stress responses. Having lower MAOA activity may help maintain balanced neurotransmitter levels, preventing mood swings and overstimulation.
• Citrus contains plant compounds that nourish good gut bacteria — Researchers identified naringenin, formononetin, and hesperidin as key citrus compounds that help F. prausnitzii thrive. These flavonoids, found in whole citrus fruits, support gut health by reducing inflammation and feeding beneficial bacteria that influence brain function.
• The role of citrus in depression management — According to the study’s lead author, Raaj Mehta, an instructor in medicine at Harvard Medical School and a physician at Massachusetts General Hospital, comparing citrus to traditional antidepressants, such as selective serotonin reuptake inhibitors (SSRIs), is difficult. He noted:
“… [W]e’re talking about preventing depression, and those drugs are usually used to treat depression once a person is already experiencing it. In the future, eating citrus could perhaps be part of a strategy for managing depression that also involves these more traditional pharmaceuticals. But more research is needed before we can conclude that.”4
To learn more about how gut influences your mental health, read “Gut Health’s Impact on Mental Well-Being.”
Does Eating Ultraprocessed Food Increase Your Depression Risk?
In related news, a study published in JAMA Network Open5 examined the impact of ultraprocessed food consumption on depression risk. This research adds to growing evidence from Harvard T.H. Chan School of Public Health and Brigham and Women’s Hospital, reinforcing the connection between diet and mental health.
• Eating more ultraprocessed foods significantly increases depression risk — Researchers analyzed data from over 31,000 middle-aged women and found that those who ate the most ultraprocessed foods had a 49% higher risk of developing depression compared to those who ate the least. This association remained even after adjusting for factors like exercise, smoking, alcohol intake, and overall diet quality.
• Reducing ultraprocessed food intake lowers depression risk — The study found that women who cut back on ultraprocessed foods by at least three servings per day had a significantly lower risk of developing depression. Those who continued eating high amounts of ultraprocessed foods had worse mental health outcomes, while those who gradually reduced their intake saw improvements.
• The worst ultraprocessed foods for mental health — The study identified certain categories of ultraprocessed foods that had the most harmful effects on mental health, including:
◦Artificially sweetened drinks
◦Low-fat and sugar-free processed snacks
◦Frozen ready-to-eat meals
◦Highly processed grain products (e.g., packaged cereals, flavored instant oatmeal)
◦Processed meats (e.g., deli slices, hot dogs)
Take a deeper dive into the dangers of ultraprocessed foods to your health in “Frequent Ultraprocessed Food Consumption Raises Mortality Risks, Especially in Women.”
Five Strategies to Improve Your Gut for Better Mental Health
Taking steps to restore your gut microbiome is a proactive way to support your mental health. Below are five key strategies to improve gut function, starting with removing obstacles that harm mitochondria, restoring cellular energy production, and then reintroducing beneficial carbohydrates and bacteria.
1. Remove vegetable oils from your diet — If you eat out frequently or consume processed foods, you’re likely consuming too much linoleic acid (LA) from vegetable oils like sunflower, safflower, soybean, and canola. These oils disrupt mitochondrial function, impair cellular energy production, and damage gut health.
Switch to healthier fats like butter, ghee, or tallow instead. Removing vegetable oils allows your mitochondria to function efficiently, helping your gut maintain an environment where beneficial bacteria can thrive.
2. Reduce exposure to endocrine disruptors and electromagnetic fields (EMFs) — Common household plastics and products contain endocrine-disrupting chemicals that interfere with hormones and mitochondrial function.
At the same time, constant exposure to EMFs from wireless devices weakens mitochondria and reduces cellular energy production. Lowering your exposure to these toxins helps restore gut health by improving mitochondrial function.
3. Optimize your carbohydrate intake — Your body needs about 250 grams of carbohydrates daily for optimal cellular energy production, but the type of carbs matters, especially if you have gut issues. If your gut health is severely compromised, gradually introduce whole fruit, white rice, or juice with pulp into your diet before moving on to starches and fibrous vegetables.
If you’re physically active, you may need more carbs, but introduce them slowly. Too much fiber too soon will feed pathogenic bacteria that release endotoxins, which can lead to digestive discomfort.
4. Introduce Akkermansia supplements wisely — Akkermansia muciniphila is a key gut bacterium that strengthens the gut barrier, but most people have very low levels. If you’ve already eliminated vegetable oils for at least six months, consider adding a timed-release Akkermansia supplement to help restore your gut.
However, don’t rush into supplementation if you’re still consuming processed foods that damage your microbiome. Prepare your gut first by eliminating vegetable oils, then introduce Akkermansia through timed-release capsules or microencapsulation technology to ensure it reaches your colon effectively.
5. Be patient and allow your gut to heal — Healing your gut is a process — it requires removing harmful toxins, reintroducing the right nutrients gradually, and supporting beneficial bacteria. By making these deliberate, consistent changes, you create a thriving gut microbiome, leading to better mental health, improved digestion, and long-term wellness. Patience is key, but each small step helps restore your body’s natural balance and resilience.
What to Do if Someone You Know Is Depressed
One of the most supportive things you can do for a friend or family member struggling with depression is to help them adopt healthier eating and lifestyle habits. Making positive changes can be especially challenging when someone feels deeply depressed or suicidal, so offering guidance and encouragement can make a meaningful difference.
• If you or someone you know is in crisis, immediate help is essential — You cannot focus on long-term solutions while in the middle of a crisis.
• If you have thoughts of suicide or feel desperate, call the National Suicide Prevention Lifeline at (800) 273-TALK (8255), dial 911, or go to the nearest hospital emergency department. Help is available — reach out.
Frequently Asked Questions (FAQs) About Citrus, Gut Health, and Depression
Q: How does eating citrus help with depression?
A: Citrus fruits contain compounds that support beneficial gut bacteria, especially F. prausnitzii, which is linked to lower depression rates. These bacteria help regulate serotonin and dopamine, the neurotransmitters that control mood.
Q: What is the connection between gut bacteria and mental health?
A: Your gut bacteria influence neurotransmitter production, inflammation levels, and brain function. An imbalance in gut bacteria leads to higher levels of inflammation, which is linked to depression and anxiety.
Q: Why are ultraprocessed foods bad for mental health?
A: Ultraprocessed foods increase inflammation, disrupt gut bacteria, and interfere with serotonin and dopamine production. Artificial sweeteners, processed snacks, and packaged meals have been linked to a higher risk of depression.
Q: How can I improve my gut health to support my mood?
A: Eliminate vegetable oils, reduce processed food intake, eat whole foods like citrus, and consider gut-supporting bacteria like Akkermansia muciniphila. Managing stress and avoiding toxins like endocrine disruptors and EMFs also help restore gut balance.
Q: How long does it take to see improvements in mental health by changing my diet?
A: It varies, but many people notice mood improvements within weeks of removing harmful foods and adding gut-supporting nutrients. Consistency is key — restoring gut health takes time, but each step strengthens your overall well-being.
