CHAPTER EIGHT
Micronutrients
Indra was a twenty-five-year-old journalist who came to me to treat a persistent case of anxiety and exhaustion. Like many of us during the COVID-19 pandemic, Indra had gotten in the habit of staying indoors, spending most of her time on a laptop doing research and writing articles in her apartment. She kept active by following a home exercise plan on an app, so she wasn’t entirely sedentary, but even after she was vaccinated and the worst of the pandemic had passed, she was finding herself anxious about the possibility of exercising outdoors. Furthermore, she had started to become increasingly fatigued to the point that it was interfering with her ability to meet deadlines. The specter of missed deadlines sparked more anxiety, as did the possibility that her freelance connections would dry up. It had all left Indra feeling like a shell of herself. At first, she attributed her symptoms to professional burnout, but as they worsened, she came to see me to evaluate possible dietary concerns.
As I took a detailed dietary history, I noticed that, unlike many of my patients, Indra did not have any obviously unhealthy components in her diet. In fact, she was extremely conscious about what she ate, having shifted to a fully plant-based diet while restaurants were closed during the pandemic. The balance and quantity of the macronutrients she was consuming were aligned with what I would suggest to a woman with her age and lifestyle. That made me realize that solving the problem might mean thinking smaller.
Several of Indra’s symptoms raised concerns about deficiencies in vitamins and minerals. A combination of staying largely indoors, the cloudy Boston-area climate, and Indra’s skin tone meant that a vitamin D deficiency could be a factor. A plant-based diet can also make it difficult to ensure proper levels of iron and vitamin B12. I also wondered if her lack of vitality could be connected to low vitamin C—which can exacerbate low iron, since vitamin C helps with iron absorption.
We did a round of testing to check these parameters, and they all came back showing my hunches were correct: Indra was low on vitamins B12, C, and D and was suffering from a case of iron-deficiency anemia. For iron and B12, we turned to supplements to ensure she could get proper levels of them without consuming animal products, but I also recommended that she prioritize eating spinach and other leafy greens, up to 5 servings daily. She started to make a large mixed green salad every day and added vitamin C–packed red peppers, zests of lemon rind, and a squeeze of fresh lemon juice as her dressing. She ate kiwi a few times a week as dessert, another great source of vitamin C. For vitamin D, I encouraged her to spend at least ten minutes daily in the sun as the weather warmed, and I helped her incorporate sun-exposed mushrooms into her diet—keeping an eye on whether the glutamates in mushrooms worsened her anxiety, which they did not—and identify plant milks fortified with vitamin D without large amounts of added sugar.
Within a few weeks, Indra’s anxiety eased and she started to feel energetic again. It took a few months to get her vitamin D levels up, but everything else normalized quickly. As her worry subsided and her vitality returned, she felt comfortable getting outdoors more often, practicing meditation again, and reactivating her gym membership, all of which helped her regain a fire for her work life.
It’s incredible that substances found in such tiny amounts can have such a huge impact on health, but micronutrients are essential for proper functioning of enzymes, hormones, immunity, metabolism, and a wide variety of other biological processes throughout the body.1 Furthermore, they play important roles in the brain, particularly in ensuring proper synthesis and release of neurotransmitters. Given what we know about how tightly intertwined these systems are, it becomes clearer why micronutrient deficits are a flashpoint for anxiety.
HOW MUCH DO I NEED?
As we explore micronutrients, we’ll emphasize getting enough of various vitamins and minerals. But what is enough? That answer is quite variable, depending on the micronutrient in question as well as your gender, life stage, and other special circumstances. Men and women often have different micronutrient needs, as do younger and older people. Special subsets such as pregnant or lactating mothers often have their own unique requirements.
As you probably know, various health organizations publish guidelines to cover all these different cases. In this book, we’ll use the dietary reference intakes, published by the Food and Nutrition Board of the National Academies of Science, Engineering, and Medicine. The key measure is the recommended dietary allowance (RDA) of different micronutrients, which provides a baseline for how much of each micronutrient the average person in each gender and age group needs to consume for optimal health. Complete information about RDAs can be found online at the National Institutes of Health Office of Dietary Supplements web page (https://ods.od.nih.gov/factsheets/list-all/).
While RDAs are valuable, in my clinical experience, I’ve learned that they are only a starting point. I always remind my patients that when adjusting micronutrient intake to fight anxiety, it’s better to test levels and monitor anxiety symptoms as dietary changes are made, rather than exclusively adhering to RDAs.
NUTRIENT ABSORPTION
Another wrinkle in getting proper levels of micronutrients is that it’s not just about how much you eat; it’s about how much you absorb. Eating large amounts of vitamins and minerals doesn’t really matter if your body is simply passing them through with other waste. Often, absorption decreases as you eat more of a given micronutrient—your body’s natural way of regulating vitamin and mineral levels once your needs are met. But there may be other obstacles, including so-called antinutrients, specific compounds that hamper micronutrient absorption. For example, whole grains are a great source of many vitamins and minerals, but they also contain substances called phytates (or phytic acid), which can bind to minerals like calcium, iron, magnesium, and zinc in your gut. If the nutrients are bound by phytates, your gut can’t absorb them. Phytates are also found in amaranth, legumes, nuts, and seeds. Similar effects occur with tannins in tea, coffee, and legumes, lectins and saponins in legumes and grains, oxalates in spinach and Swiss chard, and glucosinolates in vegetables like broccoli and Brussels sprouts.2
Types of Antinutrients
| Antinutrient | Food Sources | Interferes with |
|---|---|---|
| Glucosinolates | Cruciferous vegetables: broccoli, Brussels sprouts, cabbage, cauliflower, kale | Absorption of iodine |
| Lectins | Legumes (beans, chickpeas, lentils), whole grains | Absorption of calcium, iron, and zinc |
| Oxalates | Leafy greens (especially spinach and Swiss chard), tea, beans, nuts, beets | Absorption of calcium |
| Phytates | Whole grains, seeds, legumes, nuts | Absorption of iron, zinc, magnesium, and calcium |
| Saponins | Whole grains, legumes | Absorption of vitamins A and E |
| Tannins | Tea, coffee, legumes | Absorption of iron |
It’s worth noting that antinutrients aren’t harmful substances outside of potentially hampering mineral absorption, and you certainly shouldn’t avoid foods that contain them, since cruciferous vegetables, whole grains, and legumes are some of the most powerful antianxiety foods you can eat. Even these antinutrient compounds are helpful to your body in various ways. For instance, phytates have been shown to be beneficial for lowering cholesterol and regulating blood sugar,3 and in chapter 9 we’ll learn about the antianxiety properties of the glucosinolates in cruciferous vegetables.
Antinutrients are a concern only if you’re having trouble with a deficiency of specific vitamins and minerals. If that is the case, the problem can usually be worked around by planning out your meals and eating food in different combinations, for instance, avoiding phytate-rich grains in meals otherwise rich in minerals. Many food preparations, such as soaking, sprouting, or boiling, can also reduce antinutrient content.4
FORTIFIED AND ENRICHED FOODS
In the mid-twentieth century, when processed and packaged foods were rising to prominence, food scientists began to understand that processing techniques often rob food of its micronutrient value. For example, processing whole wheat into white flour reduces not only fiber but B vitamins and iron. To combat this, many producers add these micronutrients back in after processing to create “enriched” flour, enhancing the nutritional content. The Food and Drug Administration oversees this process and delineates guidelines for how much of each micronutrient should be added back into processed foods.
Historically, there has been evidence that fortification has helped deter certain conditions that stem from micronutrient deficiency.5 But adding back nutrients doesn’t make processed foods healthy. Given the wide variety of unprocessed food available today, I discourage getting micronutrients through fortified foods, particularly grains, for several reasons. While some nutrients are added back through the enrichment process, not all of them are—for instance, processors might add B vitamins and iron back to flour, but they are not adding fiber, zinc, or magnesium, all of which are also valuable. Perhaps even more important, the kinds of processed foods that are likely to be fortified do not lead to healthy eating patterns, and we have already learned that bad fats and added sugars can increase anxiety. As crucial as vitamins are, adding them to sugary breakfast cereal or packaged snacks does not make those foods less likely to worsen your risk of anxiety.
There are times when fortified foods can be useful, such as the fortified nut milks that Indra used to help increase her vitamin D levels. But in most cases, focusing on whole, unprocessed foods will ensure you are getting full, natural nutrition out of what you eat and will steer you away from eating unhealthy foods.
VITAMINS
The major goal of my work with Indra was to restore her vitality. It’s no coincidence that “vitality” and “vitamin” share the same root word—the Latin “vita,” which means life. Vitamins are organic compounds that are required for life. They are essential nutrients, meaning they can’t be made by your body and therefore must come from dietary sources.
Humans require thirteen vitamins: four fat-soluble vitamins, A, D, E, K; and nine water-soluble vitamins, vitamin C and the eight B vitamins—thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7), folate (B9), and cobalamin (B12).
Fat-soluble vitamins are absorbed along with fats you eat, and excess amounts can be stored inside your liver and fatty tissues for months, keeping them available for later use. Excess water-soluble vitamins are flushed out of your system as you drink and urinate; they cannot be stored, meaning you require a daily supply to remain healthy.
The entire range of vitamins can influence anxiety, but I will focus on the most important for brain health: vitamins B, C, D, and E.
B Vitamins
The B vitamins can feel a little tricky to grasp since there are so many of them, each with both a name and a number. They were discovered and named during a flurry of vitamin research in the early twentieth century, and they were numbered in the order that they were officially recognized. The gaps in the numbering are a quirk of the definition of the word “vitamin” itself. There is a compound, adenine, that was discovered between B3 and B5. It would have become vitamin B4, but further research determined that adenine can be synthesized within the body. Therefore, it doesn’t count as a vitamin, and its number is skipped. The same is true of the compounds that would make up vitamins B8, B10, and B11.
B vitamins play a significant role in maintaining healthy brain function, helping to provide energy and synthesize chemicals like the key neurotransmitters dopamine and serotonin, which can cause anxiety when disrupted.6 B vitamins have also been shown to keep your brain young deeper into your life, improving cognition and discouraging degenerative brain conditions like dementia.7
The body of research on the role of different B vitamins in anxiety is not huge, but there are signs that nearly all of them are important. One cross-sectional population-based study showed that a moderate to high intake of B1, B3, B5, and B7 leads to lower levels of anxiety.8 Another randomized controlled study found that high doses of B6 and B12 showed some promise for reducing anxiety and depression.9 Yet another study found that adults over sixty who were in the lowest 20 percent of levels of B2, B6, and B9 were more likely to be depressed, and those deficient in B6 had increased anxiety.10
While some studies and reviews have not been quite as definitive,11 I believe that B vitamins should be on the radar of anyone suffering from anxiety, especially since most of them are plentiful in otherwise nutritious food that shouldn’t be difficult to add to your diet.
Foods that contain B vitamins: The B vitamins often appear together in many foods, like whole grains, leafy greens, nuts, seeds, meat, poultry, and fish.12
Vitamin B1 (thiamin) is found in lean pork and beef (especially liver), wheat germ and whole grains, eggs, fish, legumes, and nuts. Thiamin is very sensitive to food preparation, including grain processing, soaking, and even high-heat cooking. Because of this, thiamin is often added back into processed foods, but it’s always better to get it from unprocessed, whole sources.
Vitamin B2 (riboflavin) is found in dairy (though reduced-fat dairy has lower riboflavin content), fatty fish, and certain fruits and vegetables, especially dark green vegetables. Many processed grains are also fortified with B2, but I prefer to focus on unprocessed sources.
Vitamin B3 (niacin) is found in beef, pork, poultry, fish, nuts, legumes, and grains. Forms of niacin found in animal products (and those used to fortify processed grains) are easier for your body to process, so it may be a bit harder to ensure proper niacin levels in those on a plant-based diet. You may also want to discuss a supplement with your doctor.
Vitamin B5 (pantothenic acid) is found in beef, poultry, mushrooms, avocados, nuts, seeds, milk, yogurt, potatoes, eggs, brown rice, oats, and broccoli.
Vitamin B6 (pyridoxine) is found in meat, fish, nuts, beans, grains, fruits, and vegetables. It is also heavily featured in many multivitamins and added as a supplement to a variety of processed foods.
Vitamin B7 (biotin) is found in beef liver, pork, eggs, salmon, avocados, sweet potatoes, and nuts. Biotin is often marketed as a supplement to treat hair loss and promote healthy skin and nails.
Vitamin B9 (folate) is found in liver, seafood, eggs, whole grains, dark leafy vegetables, fresh fruit, beans, peanuts, and sunflower seeds. Folate is particularly important to pregnant women to reduce the risk of certain birth defects, so in 1998, the Food and Drug Administration began requiring manufacturers to fortify enriched grains with it. Most people should be able to get enough folate through normal dietary sources, but it’s recommended that pregnant women also take a folic acid supplement.
Vitamin B12 (cobalamin) is found in animal products like meat, eggs, and dairy. Because of this, it can be a challenge for those on plant-based diets. B12 can also be difficult to absorb; it relies on a protein called an intrinsic factor to be properly processed in the gut. The B12 in supplements is formulated in a way to make it easier to absorb, so it may make sense to consider that route.
Vitamin C
Vitamin C might be the best-known vitamin, due to the popular idea (first championed by famous chemist Linus Pauling) that large doses of it help prevent the common cold and other seasonal diseases. While this association isn’t totally backed up by science—a prominent review showed that colds were no less likely in study participants who took extra vitamin C, though symptoms weren’t quite as severe and didn’t last quite as long13—there’s no doubt that vitamin C contributes to overall immune function and assists with a variety of metabolic processes. A severe deficit of vitamin C famously leads to the hemorrhagic disease scurvy, which causes bleeding gums and poor wound healing.
Vitamin C is active in the brain, particularly as an antioxidant, protecting the brain against oxidative stress caused by dangerous free radicals.14 Like the B vitamins, vitamin C also plays a significant role in neurotransmitter synthesis and regulation, particularly concerning dopamine.15
Studies have shown that vitamin C promotes mental vitality, reducing fatigue and improving mood.16 Other studies have explored how the antioxidant properties of vitamin C can help ease the burden of stress-related diseases like anxiety and depression.17 A double-blind randomized controlled trial also found that vitamin C supplementation directly reduced anxiety levels.18
Foods that contain vitamin C: Citrus fruits are a great source of vitamin C, but surprisingly, higher amounts are found in kiwi and red bell peppers. It’s also found in berries, tomatoes, potatoes, and green leafy vegetables. Vitamin C can be destroyed by high heat and leached off into cooking liquids during boiling or simmering. Therefore, it’s better to use quicker cooking methods like stir-frying and blanching, or, better yet, to eat ripe vitamin C–rich fruits and vegetables raw.19
Vitamin D
Vitamin D is best known as the “sunshine vitamin,” and indeed, it’s the only vitamin that our bodies can synthesize on their own, through a reaction in our skin when exposed to UV rays from the sun. However, as we saw with Indra, skin color, climate, latitude, sunscreen usage, and an indoor-focused lifestyle can all be obstacles to healthy levels of vitamin D. As a result, an estimated 77 percent of Americans are vitamin D deficient.20 That means everyone should be trying to get as much vitamin D as possible from every source, especially through the food you eat. Since the best sources of vitamin D are fish, meat, and dairy, those who are on a plant-based diet will want to consider a supplement, which you should discuss with your doctor.
Vitamin D performs many important functions throughout your body, helping to build strong bones by allowing the body to absorb calcium (which we’ll talk about later in the chapter), reducing inflammation, and boosting immune function. In the brain, vitamin D has been shown to be neuroprotective, protecting against cognitive decline.21 As with other vitamins, vitamin D is involved with neurotransmitter production and regulation and has an effect on glutamine, norepinephrine, dopamine, and serotonin.22
Vitamin D has been shown to reduce negative emotions brought on by depression and anxiety,23 and lower levels of vitamin D have been shown to correlate with both conditions.24 Increasing vitamin D levels in patients who are deficient has been shown to reduce anxiety.25 In another study, GAD patients who were given vitamin D supplements showed improved symptoms compared to controls.26
Vitamin D is most effective at fighting anxiety in those who are already extremely deficient in vitamin D,27 but given how common vitamin D deficiency is in our society, I feel strongly that anyone suffering from anxiety should make a conscious effort to eat as much vitamin D as possible, or consider the possibility of a supplement.28
Foods that contain vitamin D: Your body’s ability to make its own vitamin D from sun exposure complicates pinpointing exactly how much of it you need to take in through dietary sources. But given its importance, I think everyone should get as much as possible from food. The best food sources of vitamin D are fatty fish, liver, eggs, and certain sun-exposed mushrooms. Many foods are also fortified with vitamin D, including grains and dairy. Cod liver oil is a great source of vitamin D. Vitamin D is also available in other supplements, which are worth discussing with your doctor if you feel like you’re at risk of vitamin D deficiency due to lack of sun exposure.
Vitamin E
Vitamin E is particularly important to your immune function. Like vitamin C, vitamin E is a powerful antioxidant that binds to harmful free radicals, protecting your cells from oxidative stress. These antioxidant properties are particularly important in the brain, where oxidative stress is especially dangerous, increasing in severity as we age. Sure enough, high levels of vitamin E have been firmly associated with better cognitive performance in older people, and it has been studied as a possible treatment for Alzheimer’s disease.29
Animal studies have also suggested that vitamin E deficiency can lead to anxiety.30 Though one review of human studies came up a bit mixed,31 vitamin E has been shown to alleviate chronic inflammation and improve metabolic disorders like metabolic syndrome, both of which we know are connected to anxiety.32
Foods that contain vitamin E: The richest sources of vitamin E are vegetable oils like sunflower, safflower, soybean, palm, and peanut oil. Unfortunately, as we covered in chapter 7, these omega-6 PUFA–rich oils aren’t healthy to consume in large quantities, so it’s important to look to other sources. Vitamin E can also be found in almonds, peanuts, hazelnuts, and leafy greens.
MINERALS
I once had a friend whose new puppy was adorable in every way, except that he was entirely too keen on eating rocks, constantly on the hunt for gravel to put in his mouth. My friend was diligent about not letting the pup swallow them, and a bit exasperated that she was constantly on her knees, prying another pebble out of her beloved pet’s mouth. I tried to console her that even though he was going about it the wrong way, he had the right idea: we all eat rocks, if in extremely tiny quantities. And these essential dietary minerals are crucial to good health.
The National Institutes of Health identifies fifteen minerals that are key to health, but we will focus on the five that are most tightly tied to anxiety: calcium, iron, magnesium, manganese, and zinc. We’ll review them in alphabetical order.
Calcium
Calcium is the most abundant mineral in the body. It makes up a large proportion of your bones and teeth, providing their rigidity. There is also a small amount of calcium in your blood and tissues, which helps with the functioning of your blood vessels, muscles, nerves, and hormones. Calcium is involved in several aspects of brain function, including the synthesis and release of neurotransmitters like serotonin.
A 2022 study of 1,233 American college students33 and a 2020 study of college students in Jordan34 found that higher calcium intake was correlated with lower stress, positive mood, and reduced anxiety. Low calcium intake has also been associated with poor sleep quality, which has been found to correlate with anxiety.35
Foods that contain calcium: The best sources of calcium are dairy products like milk, yogurt, and cheese. Of course, many people are lactose intolerant and cannot consume dairy, or they avoid it because they follow a plant-based diet. Luckily, there are plenty of other sources of calcium, including nuts, seeds, peas, beans, and fish. Consider that in the United States and Western Europe, well over half of most people’s calcium intake is from dairy, but in China, only around 7 percent comes from dairy, with most of it coming from vegetables and legumes.
Iron
Iron is one of the best-known dietary minerals for good reason: iron deficiency is the most common nutritional deficiency in the world. The resulting condition, iron deficiency anemia, is a serious health threat, particularly to women and children.
The classic role of iron in your body is in your blood, where iron-rich hemoglobin allows your red blood cells to carry oxygen throughout your tissue. But iron also plays an important role in the brain. Iron deficiency in pregnant mothers can lead to a premature birth and low birth weight, both of which can result in long-term complications. Iron is also a key to healthy neurotransmitter metabolism, with iron levels playing a role in the availability of neurotransmitters like serotonin and dopamine, as well as affecting levels of GABA.36
Human and animal studies have linked iron deficiency with anxiety, among other psychiatric disorders, particularly in infants, children, and adolescents.37 Iron deficiency early in life can continue to cause trouble in the brain for many years, long after iron levels return to a healthy level, so it’s particularly important to make sure that infants and children get the recommended amount of iron.38
It’s worth noting that some animal studies have shown that a surplus of iron in the brain can cause anxiety symptoms.39 While this is a consideration when taking iron supplements (working with a doctor to monitor this is key), it’s hard to consume that much iron from dietary sources—another example of why it’s preferable to get nutrients from food sources rather than supplements.
Foods that contain iron: Meat is the best source of iron, since it has high levels in the form of hemoglobin, which is easy for our bodies to absorb. Liver is the most iron-rich cut of meat, but if you don’t have a taste for organ meat, beef has the highest iron content, followed by pork. Chicken and fish also contain iron, though at slightly lower levels.
As we saw with Indra, iron can be a bit trickier to get on a plant-based diet. Plants offer many sources of iron, including leafy greens like spinach and chard, whole grains, nuts, and berries. Unfortunately, the iron in plant-based foods is harder for our bodies to absorb, so even if you’re eating generous amounts of plant-based sources of iron, you may still have an iron deficiency. Complicating matters further, antinutrients and other chemicals in dairy and soy products can inhibit iron absorption. Luckily, there are some nutrients, like vitamin C, that do promote iron absorption.
Given the difficulties of getting enough iron in a plant-based diet, I often recommend that my vegetarian patients (particularly women of childbearing age) take an iron supplement, as I did with Indra. Since iron supplements can cause some side effects—especially upset stomach—it’s best to consult with your doctor to determine the proper dosage.
Magnesium
Magnesium is active throughout your body, facilitating more than three types of enzymatic action that help you build strong bones, create energy, and regulate blood sugar and blood pressure. Its role in metabolism explains why magnesium deficiency is often associated with conditions like type 2 diabetes.40 Magnesium can be a bit tough to measure, since most of it is tied up in your bones and cells rather than floating freely in the blood where it can be easily tested. Still, researchers estimate that magnesium deficiency is quite widespread, with up to 60 percent of Americans not consuming enough.41
In the brain, magnesium assists with myelination (the formation and maintenance of the junctions between nerve cells called synapses) and with regulation of neurotransmitters like glutamate and serotonin.42 Research on magnesium’s role in mood disorders was originally focused on depression, and a variety of studies have shown that low magnesium levels can lead to depression and that supplementation can improve symptoms.43 There is also evidence that magnesium levels affect the stress response and that stress can actually deplete magnesium in your body.44 A systematic review of the effects of magnesium on anxiety found that about half the relevant studies showed that magnesium improved anxiety symptoms.45 Even though results are somewhat mixed, given magnesium’s significance in so many anxiety-adjacent conditions, I strongly recommend ensuring that you eat enough magnesium-rich foods.
Foods that contain magnesium: Magnesium is found primarily in whole grains, legumes, nuts, and dark chocolate. Vegetables, fruit, meats, and fish also have magnesium, though at lower levels.
The importance of eating whole grains for their anxiety benefit is particularly crucial with regard to magnesium. Refining and processing grains drastically reduces magnesium levels, with white flour and rice having approximately 80 percent less magnesium than whole wheat flour and brown rice.46
Manganese
Manganese also plays a role in many of the body’s enzymatic actions, assisting with bone formation, metabolism, and antioxidant processes. Magnesium and manganese have more in common than just their names—their properties are so similar that many enzymes can function using either one, though there are roles that are unique to manganese.47
Unlike magnesium, manganese deficiency is extremely rare, and in fact, the greater concern is overexposure. An overabundance of manganese in the brain has been associated with neurological disorders similar to Parkinson’s disease48 as well as increased anxiety in both animal and human studies.49 Despite this association, manganese overexposure tends to be associated with environmental factors, like working in manganese-rich environments, and it’s doubtful that you would get too much manganese from a normal diet. Still, that’s another illustration of the potential danger of getting too much of certain micronutrients from supplements.
Foods that contain manganese: Manganese is primarily found in whole grains, rice, and nuts. Dark chocolate, tea, mussels, clams, legumes, fruit, leafy vegetables (spinach), seeds (flax, sesame, pumpkin, sunflower, and pine nuts), and spices (chili powder, cloves, and saffron) are also rich in manganese.
Zinc
Zinc is another mineral that is active throughout the body, assisting with enzymatic activity and enhancing the immune system—you may recognize zinc as an additive in some over-the-counter cold remedies.
Zinc is prominent in your brain, performing several roles to promote optimal brain function, including spurring the growth of new neurons—particularly in anxiety hot spots like the hippocampus—and mediating inflammation and oxidation.50 Zinc is also crucial to the pituitary gland, a central component of the HPA-axis that helps control mood regulation, and zinc deficiency can result in a range of abnormal behaviors.51
Zinc has been found to be effective in treating certain types of depression and has also been shown to enhance the effects of antidepressant drugs in treatment-resistant patients.52 Studies have also shown that anxiety sufferers have lower levels of zinc than controls.53 Zinc deficiency was also correlated with both depression and anxiety in a study of female high school students54 and a study of adults age sixty and over,55 indicating that it is important in all stages of brain development.
Foods that contain zinc: The richest food sources of zinc are meat, fish, and seafood—oysters contain more zinc per serving than any other food. If fresh oysters are unavailable, canned oysters are an option. Eggs and dairy also contain zinc. Beans, nuts, and whole grains contain zinc, too, but it’s not as easy to absorb from plant sources due to their phytate content, as we discussed earlier in the chapter.
SMART SUPPLEMENTATION
When it comes to getting the correct level of micronutrients, I am always a proponent of food first. As long as you are eating a healthy diet full of whole foods, there is a good chance you won’t need to take a regimen of supplements. However, there are certainly times when dietary restrictions, interactions with other drugs, or differences in physiology can mean that diet alone doesn’t ensure sufficient levels of certain micronutrients. When such gaps occur in our nutrition, supplements can be an important part of lowering anxiety.
My golden rule for supplementation is “test, don’t guess.” Before beginning to take any supplement, have your doctor test your micronutrient levels. If you are low in any vitamins or minerals, first try to make up the deficit with food. If you don’t see the desired results on follow-up tests, consider a supplement. The most common micronutrient deficiencies I see in my clinic are found in the following table. Remember that RDAs can vary by gender, age, and a variety of other factors. The specifics can be found at the National Institutes of Health Office of Dietary Supplements web page (https://ods.od.nih.gov/factsheets/list-all/).
| Micronutrient | Who Should Test? | Tips |
|---|---|---|
| B complex vitamins | Those who follow a plant-based diet are at risk of low B complex levels, especially B12, since most food sources are of animal origin. | Supplements are available that cover the entire B complex. With your doctor’s help, decide whether to take a full B complex supplement or a specific B vitamin. Since B vitamins are water-soluble, the body excretes excess amounts in urine, so there is relatively low risk of overdoing it. However, excessively high doses of B vitamins can still be dangerous and can interact with certain medications, so talk to your doctor about risk factors. |
| Vitamin D | The chief risk factor for vitamin D deficiency is lack of sun exposure, particularly for those with darker skin tones. Vegetarians and vegans are also at risk, because dietary vitamin D sources are largely from seafood and fortified dairy. | Vitamin D is stored in body fat and can be toxic in excess.
Given interactions with vitamin D, magnesium, and calcium, I often recommend supplementing them together. |
| Magnesium | Magnesium is difficult to test, since the bulk of it is tied up in your bones, with only roughly 1 percent circulating in your blood. Discuss the possibilities for testing with your health practitioner. | There are several types of magnesium supplements, but for mental health I generally recommend magnesium bisglycinate or magnesium L-threonate.
Magnesium can interact with a range of prescription drugs, so talk to your doctor about risk factors. |
| Calcium | Calcium deficiency is most common in those who do not eat dairy. Women are more likely to suffer from calcium deficiency than men. | Calcium can interact with prescription medicines, including antibiotics and blood pressure medication, so talk to your doctor about risk factors. |
| Iron | Vegetarians and vegans are at heightened risk of iron deficiency because plant-based iron is more difficult for your body to absorb than the iron found in animal products. | Iron supplements are less easily tolerated than other supplements, so work with your doctor to find the correct formulation and dosage.
Vitamin C can increase iron absorption from plant-based dietary sources, but studies show that it is not necessary to pair a vitamin C supplement with an iron supplement.56 |
BIG THINGS COME IN SMALL PACKAGES
I could write an entire book on micronutrients’ role in mental health, so this is not an exhaustive review. For instance, there have been indications that vitamins A57 and K58 are also linked to anxiety, as are minerals like copper59 and selenium.60 But the key message is that even these tiny dietary components can have a massive effect on mental health and offer ways to calm your mind with food.
Vitamins and minerals aren’t the only compounds that can make a big difference in fighting anxiety. In the next chapter, we’ll learn about the world of bioactives, phytochemicals, and herbal supplements.