{"id":53632,"date":"2024-09-11T10:00:00","date_gmt":"2024-09-11T17:00:00","guid":{"rendered":"https:\/\/foodrevolution.org\/?p=53632"},"modified":"2026-09-14T05:09:01","modified_gmt":"2026-09-14T12:09:01","slug":"ultra-processed-foods-and-depression","status":"publish","type":"post","link":"https:\/\/foodrevolution.org\/blog\/ultra-processed-foods-and-depression\/","title":{"rendered":"The Sad Diet: Ultra-Processed Foods and Their Impact on Depression"},"content":{"rendered":"

There\u2019s an awful lot of depression going around these days. From 1990 to 2017, depression rates skyrocketed<\/a> by 50%, and experts predict that the numbers will keep increasing<\/a>.<\/strong><\/p>\n

In the US, depression has reached epidemic proportions: almost 30%<\/a> of people report having been diagnosed with depression at some point in their lives.<\/p>\n

And that\u2019s just clinical depression, meaning symptoms severe enough to satisfy the diagnostic criteria for the condition. Many more people suffer from subclinical depression \u2014 struggling with persistent feelings of sadness, low energy, and emotional distress without having a formal diagnosis.<\/p>\n

So what\u2019s causing so many people to be depressed or just plain down? Psychiatrists tend to view depression as the result of a chemical imbalance in the brain and often prescribe medications that affect chemical pathways.<\/p>\n

Recently, researchers have identified a strong link<\/a> between gut bacteria and the development of depression through the gut-brain axis<\/strong>, a bidirectional communication channel between the central nervous system and the enteric nervous system (which you can think of as a mini-brain in your gut).<\/p>\n

The food you eat ends up in your gut, where it feeds different types of bacteria. Some bacteria love sugar, others prefer fat, and still others get their kicks from fiber. Whichever kind you feed increases, while the others decline or even disappear.<\/p>\n

Certain foods are better for our guts than others (hello, fiber!). But modern industrialized diets don\u2019t tend to prioritize gut-friendly foods. Instead, they’ve been replaced with calorie-rich and nutrient-poor foods. Specifically, the amount of ultra-processed foods<\/a> and sugar-sweetened beverage options consumed has grown exponentially, particularly in more economically well-off countries<\/a>.<\/p>\n

So, if diet quality has gone down and depression rates have gone up, is it possible that there\u2019s a connection between the rise of ultra-processed foods and depression<\/a>?<\/strong><\/p>\n

Let\u2019s explore the evidence. In this article, we\u2019ll examine the relationship between ultra-processed foods, food\u2019s impact on the gut-brain axis, and depression. And we\u2019ll look at what you can do to add more good vibes to your life.<\/p>\n

What Are Ultra-Processed Foods?<\/h2>\n
\"Abstract
iStock.com\/Muharroimi Souvanny<\/figcaption><\/figure>\n

In 2016, the Food and Agriculture Organization of the United Nations adopted NOVA, a food classification system.<\/p>\n

NOVA identifies four classes of foods as follows:<\/p>\n

    \n
  1. Unprocessed and minimally processed foods<\/li>\n
  2. Processed culinary ingredients<\/li>\n
  3. Processed foods<\/li>\n
  4. Ultra-processed foods<\/li>\n<\/ol>\n

    Public health researchers define ultra-processed foods<\/a> as \u201cindustrial formulations that are mostly or entirely made from industrial ingredients, with little or no whole foods.\u201d<\/strong> They tend to be high in energy (calories) and contain unhealthy fats, refined carbohydrates, added sugars, and salt. They are also engineered to \u201cintensify sensory impact<\/a>,\u201d which is a fancy way of saying they are formulated to taste so good that you can\u2019t stop eating them.<\/p>\n

    Ultra-processed foods also tend to be low in protein, dietary fiber, micronutrients, and other bioactive compounds (like antioxidants). In some cases, they may contain no intact whole foods whatsoever.<\/p>\n

    So what are some examples of ultra-processed foods? They\u2019re all around us, including most packaged snacks, soft drinks, candy, ice cream, cookies, pastries, cakes, frozen meals, a significant share of breakfast cereals, and packaged bread. While meat is unprocessed, processed meat products, such as sausages, burgers, and hot dogs, are considered ultra-processed (as are many plant-based versions of the same type of products).<\/p>\n

    That\u2019s a long list, but how much do they really contribute to people\u2019s diets? It turns out a lot: Ultra-processed foods account for almost 60% of all calories<\/a> consumed in the US, and their presence is increasing in other countries<\/a> as well.<\/strong><\/p>\n

    \"Worst<\/p>\n

    The Role of the Gut-Brain Axis in Mood<\/h2>\n

    So, what does all this have to do with rising rates of depression?<\/p>\n

    Your gut microbiota is the collection of bacteria, archaea, and eukarya that colonize your GI tract. The unhealthy components often found in ultra-processed foods have been shown<\/a> to directly cause changes in gut microbiota functions.<\/strong> This can, in turn, impact multiple organs, including the brain, through the gut-brain axis (the bidirectional connection<\/a> through which your gut bacteria and neurons can chat and collaborate).<\/p>\n

    One of the functions of your gut bacteria is to modulate the creation and function of neurotransmitters<\/a>. These are chemicals that allow neurons to communicate with each other throughout your body, especially in your brain. They\u2019re also chemical messengers that regulate emotions, motivation, and movement.<\/p>\n

    The gut bacteria coordinate their work with your central nervous system using the neurotransmitters GABA, dopamine, norepinephrine, serotonin, and histamine.<\/p>\n

    As we\u2019ve seen, the foods you eat can contribute to either good or bad gut bacteria formation. If you eat ultra-processed foods, for example, you can bring about gut dysbiosis<\/a> (basically, an unhealthy imbalance among the different types of bacteria in your gut) due to some particularly unhelpful ingredients.<\/p>\n

    Ingredients That May Negatively Impact the Microbiome<\/h2>\n

    So let\u2019s get specific \u2014 what are the particular ingredients in ultra-processed foods that have the worst impact on your gut bacteria and mood? There are three main categories: free sugars and artificial sweeteners, unhealthy fats, and artificial additives and preservatives.<\/p>\n

    Free Sugars and Artificial Sweeteners<\/h3>\n
    \"Granulated
    iStock.com\/aryutkin photo<\/figcaption><\/figure>\n

    We have to distinguish free sugars (also called \u201cadded sugars\u201d) from natural sugars found in fruits and other sweet foods like sweet potatoes and beets. Natural sugars are bound with fiber and water and tend to be good for us \u2014 in fact, they\u2019re one of your body\u2019s preferred energy sources.<\/p>\n

    On the other hand, free sugars have had their fiber and water stripped away. In nature, you rarely find free sugars outside of honeybee hives (and those bees will make sure you think twice before taking their honey).<\/p>\n

    How much free sugar are we eating? In the US, among people who are the highest consumers of ultra-processed foods, almost 20%<\/a> of total calories come from free sugars.<\/strong><\/p>\n

    One of the many reasons to limit free sugars is that they can harm your gut microbiome. Specifically, they can negatively impact the synthesis<\/a> of important products of gut bacteria called short-chain fatty acids (SCFAs)<\/a>. This, in turn, can compromise the integrity of your intestinal barrier, leading to chronic inflammation<\/a> that often fuels metabolic conditions.<\/p>\n

    Because sugars can be so bad for you, many people prefer products sweetened with artificial sugar substitutes<\/a>. Unfortunately, researchers are discovering that these chemicals may actually have a very problematic effect on your gut microbiome. A 2022 study found<\/a> that just 10 weeks of sucralose (aka Splenda) consumption led to a significant increase in concentrations of harmful bacteria and a decrease in beneficial ones.<\/strong><\/p>\n

    What\u2019s more, as counterintuitive as it may seem, studies tell us that people who drink diet sodas are more likely to gain weight<\/a>. In one study<\/a>, participants who started out at a normal weight and drank 21 diet sodas per week were twice as likely to be overweight or obese eight years later as their non-diet-soda-drinking peers. While the exact reason for this is unclear, it seems plausible that there could be a microbiome connection.<\/p>\n

    Unhealthy Fats<\/h3>\n

    The types and concentrations of microbes in your gut, and therefore the function of your intestinal barrier, are heavily influenced<\/a> by the amount and composition of fat in your diet. In particular, there\u2019s an association between long-chain saturated fatty acids<\/a> (found in vegetable oils along with dairy and other animal products), dysbiosis, and impaired intestinal barrier function.<\/strong>\u00a0This can lead to metabolic endotoxemia, a condition in which certain toxins leak into your bloodstream from your gut, leading to an inflammatory response<\/a> in the immune system.<\/p>\n

    And there\u2019s a well-documented association between inflammation and depression<\/a>.<\/p>\n

    Artificial Additives and Preservatives<\/h3>\n
    \"Man
    iStock.com\/chabybucko<\/figcaption><\/figure>\n

    Artificial additives and preservatives also can cause damage to the gut microbiome.<\/p>\n

    A 2019 study found<\/a> that two additives \u2014 sodium sulfite and polysorbate 80 \u2014 strongly inhibited the growth of a beneficial gut bacterium called Faecalibacterium prausnitzii<\/i>.<\/p>\n

    Carrageenan<\/a>, often added to ultra-processed foods as an emulsifier or thickening agent, can also disrupt the intestinal barrier, leading to inflammation.<\/strong><\/p>\n

    Evidence Linking Ultra-Processed Foods and Depression<\/h2>\n

    We\u2019ve already identified several key mechanisms by which ultra-processed foods can trigger effects in the body that are associated with depression. If this were a detective novel, the crusty private eye would tell the client, \u201cThis is all circumstantial. A jury would laugh it out of court.\u201d<\/p>\n

    Over the past few years, however, research has turned up convincing evidence for a strong link between ultra-processed foods and depression.<\/p>\n

    A 2022 meta-analysis of 17 published observational studies of almost 400,000 people found<\/a> that people who ate more ultra-processed foods were more likely to experience symptoms of depression. And the results appeared to be cumulative; eating a lot of these foods over time increased the risk of developing depression later on.<\/strong><\/p>\n

    Three papers published in 2023 replicated these findings. One looked at 14 years of data from over 30,000 adult women participating in the Nurses Health Study II. The researchers found<\/a> that participants who consumed the most ultra-processed food had a 50% higher risk of serious depression than those who consumed the least. Artificial sweeteners and artificially sweetened beverages were highlighted as having the greatest contribution to depression.<\/p>\n

    A study using data from the Korea National Health and Nutrition Examination Survey also found<\/a> that eating a lot of ultra-processed food was linked to a higher incidence of depression, especially in women. Data from almost 10,000 women showed that those who ate the most ultra-processed foods were 50% more likely to have depression.<\/p>\n

    Another study recruited 152 adults to see how their diets, mental health, and brain structures were connected. The researchers found<\/a> that when people ate a lot of ultra-processed foods, parts of their brains shrunk \u2014 specifically, the posterior cingulate cortex and the left amygdala, regions dedicated to maintaining a sense of self and enabling emotional regulation.<\/strong> Not surprisingly, the people who ate the most processed food also suffered from an increased risk of depression.<\/p>\n

    Foods and Nutrients That Help Fight Depression<\/h2>\n

    Now that we have a good sense of what foods and ingredients are linked to depression, let\u2019s look at nutrients that can reduce dysbiosis, inflammation, and other biochemical processes associated with depression. You might think of these substances as natural antidepressants<\/a>.<\/p>\n

    Fiber<\/h3>\n
    \"Healthy
    iStock.com\/marilyna<\/figcaption><\/figure>\n

    When it comes to your mood, fiber is fabulous. Low fiber intake is a risk factor for depression,<\/a> and getting enough fiber is crucial for maintaining a healthy gut and central nervous system.<\/p>\n

    A 2021 study found<\/a> that women who consumed the most fiber were 37% less likely to have depression than those who consumed the least. And a 2021 meta-analysis of four studies totaling almost 100,000 participants found<\/a> that for both men and women, the odds of depression dropped by 26% in those who were consuming the most fiber.<\/strong><\/p>\n

    Find out more about fiber and why it\u2019s good for you<\/a>.<\/p>\n

    Antioxidants<\/h3>\n

    Another potential dietary approach to depression (both for treatment and prevention) is to make sure you get enough antioxidants in your diet. One class of antioxidants, polyphenols, is being studied<\/a> for its potential to manage or prevent depression by reducing oxidative stress and inflammation while modulating the gut microbiota.<\/strong><\/p>\n

    A 2021 meta-analysis of seven studies found<\/a> that the higher people\u2019s dietary total antioxidant capacity (dTAC) scores, the lower their chances of experiencing depression. Based on prior research, the paper\u2019s authors identified specific antioxidants that are known to be related to mental health, including polyphenols, beta-carotene, and vitamins A and C.<\/p>\n

    Here are some of our articles that go into more depth about the wonderful world of antioxidants:<\/p>\n