How Not to Die

  Indeed, major depression can be a life-threatening ailment.

  Good mental health isn’t “merely the absence of disease,” though. Just because you’re not depressed doesn’t necessarily mean you’re happy. There are twenty times more studies published on health and depression than there are on health and happiness.5 In recent years, however, the field of “positive psychology” has emerged, focusing on the relationship between optimal mental and physical health.

  Growing evidence indicates that positive psychological wellbeing is associated with reduced risk of physical illness, but which came first? Are people healthier because they’re happy, or are people just happier because they’re healthy?

  Prospective studies that follow individuals over time have found that people starting out happier do indeed end up healthier. An analysis of seventy such studies on mortality concluded that “positive psychological well-being has a favorable effect on survival in both healthy and diseased populations.”6 Those who are happier appear to live longer.

  Not so fast, though. While positive mental states may be associated with less stress and more resilience to infection, positive well-being might also be accompanied by a healthy lifestyle. In general, people who feel satisfied appear to smoke less, exercise more, and eat healthier.7 So is being happier just a marker of good health and not a cause of it? To find out, researchers set out to make people sick.

  Scientists at Carnegie Mellon University took hundreds of individuals—some happy, some unhappy—and paid them $800 (£500) each to be allowed to drip the common cold virus into their noses. Even if someone with a cold sneezes right into your face and the virus gets into your nose, you won’t get sick automatically, because your immune system may be able to fight it off. So the study question was: Whose immune system would be better at fighting off a common virus—those in the group initially rated as happy, relaxed, or those in the group who were anxious, hostile, and depressed?

  About one in three of the negative-emotion individuals failed to successfully fight off the virus and came down with a cold. But only one in five of the happy individuals became sick, even after the researchers took into account such factors as subjects’ sleep patterns, exercise habits, and stress levels.8 In a subsequent study, the researchers even exposed subjects (who had also been paid) to the influenza virus, a more serious infection. Once again, increased positive emotions were associated with decreased verified illness rates.9 Happier people, it seems, are less likely to get sick.

  So mental health does appear to play a part in physical health. That’s why it’s crucial that the food you eat support both your mind and your body. As you’ll see, common foods from leafy green vegetables to your basic garden-variety tomato may positively affect your brain chemistry and help ward off depression. In fact, even simply smelling a common spice may improve your emotional state.

  But avoiding the blues is not just about eating your greens. There are also components in certain foods that may increase the risk of depression, such as arachidonic acid, an inflammation-promoting compound found mostly in chicken and eggs in the diet that is blamed for potentially impairing mood by inflaming the brain.

  Arachidonic Acid

  Studies on the emotional health and mood states of those eating plant-based diets suggest that eating less meat isn’t just good for us physically; it’s good for us emotionally too. Researchers employed two psychological tests, the Profile of Mood States (POMS) and the Depression and Anxiety Stress Scale (DASS). POMS measures levels of depression, anger, hostility, fatigue, and confusion. The DASS gauges other negative mood states as well, including hopelessness, lack of interest, anhedonia (lack of pleasure), agitation, irritability, and impatience with other people. Subjects eating plant-based diets appeared to experience significantly fewer negative emotions than omnivores. Those eating better also reported feeling more “vigor.”10

  The researchers offered two explanations for their findings. First, people eating better diets may be happier because they’re healthier.11 Those eating plant-based diets don’t just have lower rates of many of the leading killer diseases but also appear to have lower rates of such annoying ills as hemorrhoids, varicose veins, and ulcers; fewer surgeries; fewer hospitalizations; and only about half the odds of being on drugs, including tranquilizers, aspirin, insulin, blood pressure pills, pain medications, antacids, laxatives, or sleeping pills.12 (Being able to avoid doctor visits and health insurance hassles would make anyone less irritable, stressed, and depressed!)

  The researchers also suggested a more direct explanation for their results: Maybe the proinflammatory compound arachidonic acid found in animal products can “adversely impact mental health via a cascade of neuroinflammation.”13 The body metabolizes arachidonic acid into an array of inflammatory chemicals. In fact, that’s how anti-inflammatory drugs like aspirin and ibuprofen work to relieve pain and swelling—by blocking the conversion of arachidonic acid into these inflammatory end products. Maybe the mental health of omnivores was being comparatively compromised by inflammation in their brains.

  Inflammation isn’t always bad, of course. When the area around a splinter gets all red, hot, and swollen, it’s a sign that the body is using arachidonic acid to mount an inflammatory response to help fight off infection. But your body already makes all the arachidonic acid you need, so you don’t need to take in any more via your diet.14 In this way, arachidonic acid resembles cholesterol, another essential component that the body makes all on its own: When you add excess amounts through diet, it may upset your system’s internal balance.15 In this particular case, the researchers suspected arachidonic acid intake might impair the body’s emotional state. There is data suggesting that people with higher levels of arachidonic acid in their blood may end up at significantly higher risk of suicide and episodes of major depression.16

  The top-five sources of arachidonic acid in the American diet are chicken, eggs, beef, pork, and fish, although chicken and eggs alone contribute more than the other top sources combined.17 Just a single egg’s worth of arachidonic acid a day may significantly raise arachidonic acid levels in the blood.18 Overall, omnivores appear to consume about nine times more arachidonic acid than those eating plant-based diets.19

  The study showing improved moods and emotional states in those eating plant-based diets was a cross-sectional study, meaning it was a snapshot in time. What if people who start out mentally healthier go on to eat healthier, too, and not the other way around? To show cause and effect, researchers would have to perform an interventional study, the gold standard of nutritional science: Gather subjects, change their diets, and see what happens. The same research team did just that. They took men and women who ate meat at least once a day and took away their eggs and chicken, along with other meats, to see what would happen to their moods. Within just two weeks, the study subjects experienced a significant improvement in measures of their mood states.20 The researchers concluded: “Perhaps eating less meat can help protect mood in omnivores, particularly important in those susceptible to affective disorders [such as depression].”21

  Given these results, another research team decided to put a healthy diet to the test in a workplace setting, where healthy bodies and minds could potentially translate into improved productivity—and elevate the mood of shareholders as well. A group of overweight and diabetic employees at a major insurance company was encouraged to follow a whole-food, plant-based diet, cutting out all meat, eggs, dairy, oil, and junk foods. There was no portion-size restriction, no calorie counting, and no carb tracking, and participants were explicitly told not to change their exercise habits. Meals were not provided, but the company cafeteria did start offering such daily options as bean burritos and lentil and minestrone soups. A control group of employees received no dietary advice.22

  Despite the dietary restrictions, over the course of about five months, the plant-eating group reported greater diet satisfaction than the control group. How well did they do? The plant-based group experienced i
mproved digestion, increased energy, and better sleep, as well as significant improvement in their physical functioning, general health, vitality, and mental health. No surprise, then, that they showed measurable improvements in work productivity too.23

  Based on this success, a much larger study of plant-based nutrition was conducted at ten corporate locations across the country from San Diego, California, to Macon, Georgia. The same resounding success was reported, showing improvements not only in subjects’ body weight, blood sugar levels, and ability to control cholesterol24 but also in their emotional states, including depression, anxiety, fatigue, sense of well-being, and daily functioning.25

  Fighting the Blues with Greens

  Here’s a statistic you probably haven’t heard: Higher consumption of vegetables may cut the odds of developing depression by as much as 62 percent.26 A review in the journal Nutritional Neuroscience concluded that, in general, eating lots of fruits and veggies may present “a non-invasive, natural, and inexpensive therapeutic means to support a healthy brain.”27

  But how, exactly?

  The traditional explanation of how depression works, known as the monoamine theory, proposes that the condition arises out of a chemical imbalance in the brain. The billions of nerves in your brain communicate with each other using chemicals called neurotransmitters. Your nerve cells don’t physically touch one another. Instead, they manufacture and deploy neurotransmitters to bridge the gap between them. The levels of an important class of neurotransmitters called monoamines, which includes serotonin and dopamine, are controlled by an enzyme called monoamine oxidase (known as MAO) that breaks down any excess monoamines. People who are depressed appear to have elevated levels of this enzyme in their brains.28 Thus, the theory goes, depression is caused by abnormally low levels of monoamine neurotransmitters due to elevated levels of the neurotransmitter-munching enzyme.

  Antidepressant medications were developed to try to boost the levels of neurotransmitters to offset their accelerated breakdown. But if the excess MAO is responsible for depression, why not just develop a drug that blocks this enzyme? Such drugs do exist, but they have serious risks—not the least of which is the dreaded “cheese effect,” in which eating certain foods (such as certain cheeses, cured meats, and fermented foods) while on the drug can potentially cause fatal brain hemorrhaging.29

  If only there were a way to tamp down the monoamine oxidase enzyme safely. Well, it turns out that many plant foods, including apples, berries, grapes, onions, and green tea, contain phytonutrients that appear to naturally inhibit the MAO, as do such spices as cloves, oregano, cinnamon, and nutmeg.30 This may help explain why those eating plant-rich diets have lower rates of depression.31

  Even on a day-to-day basis, studies have shown that the more fruits and vegetables you eat, the happier, calmer, and more energetic you may feel that day—and this positivity can spill over into the next day. For your diet to have a meaningful psychological impact, though, you may need to consume approximately seven servings of fruits or eight servings of vegetables each day.32

  Seeds and Serotonin

  Although some plant foods contain significant amounts of serotonin,33 the so-called happiness hormone, serotonin can’t cross the blood-brain barrier. This means that dietary sources of serotonin can’t make it into the brain, but the building block of serotonin, an amino acid called tryptophan, can get from your mouth to your blood to your brain. Tryptophan depletion experiments in the 1970s showed that people given specially concocted tryptophan-deficient diets suffered from irritability, anger, and depression.34 So if you give people extra tryptophan, will they feel better?

  That’s the theory. However, in the 1980s, certain tryptophan supplements created a debacle, causing a rash of deaths.35 But if tryptophan is an amino acid and if proteins are made out of amino acids, why can’t you just give people high-protein meals to boost their serotonin levels by delivering extra tryptophan to the brain? It’s been tried, and it’s failed,36 likely because other amino acids in protein-rich foods crowd out the tryptophan for access to the brain. However, carbohydrate ingestion does the opposite: It helps shunt many nontryptophan amino acids out from the bloodstream and into the muscles, allowing tryptophan greater access into the brain. For example, having a carb-rich breakfast like waffles and orange juice resulted in higher tryptophan levels in those studied than did a protein-rich breakfast of turkey, eggs, and cheese.37

  This principle may explain why women suffering from premenstrual syndrome (PMS) sometimes crave carbohydrate-rich food. Consumption of even a single carb-rich, protein-poor meal has been shown to improve depression, tension, anger, confusion, sadness, fatigue, alertness, and calmness scores among women with PMS.38 In a yearlong study, about one hundred men and women were randomly assigned to eat either a low-carb or high-carb diet. By the end of the year, the subjects eating the high-carb diets experienced significantly less depression, hostility, and mood disturbance than those in the low-carb group. This result is consistent with studies finding better moods and less anxiety among populations eating diets higher in carbohydrates and lower in fats and protein.39

  Carbohydrates may facilitate tryptophan transport into the brain, but you would still need a dietary source. Ideally, it would have a high tryptophan-to-protein ratio to facilitate brain access.40 Such seeds as sesame, sunflower, or pumpkin may fit the bill. Indeed, a double-blind, placebo-controlled trial of butternut squash seeds for social anxiety disorder reported a significant improvement in an objective measurement in anxiety within an hour of consumption.41 All of these factors may contribute to the comprehensive improvement in mood one may achieve after just a few weeks on a plant-based diet.42

  Saffron

  The earliest recorded medical use of a spice appears to be more than 3,600 years ago, when saffron was evidently first used for healing.43 A few thousand years later, scientists finally put saffron to the test in a head-to-head trial against the antidepressant drug Prozac for the treatment of clinical depression. Both the spice and the drug worked equally well in reducing depression symptoms.44 As you can see in the box here, this may not be saying much, but at the very least, the saffron was safer in terms of side effects. For example, 20 percent of people in the Prozac group suffered sexual dysfunction, a common occurrence with many antidepressant medications, whereas no one in the saffron group did.

  However, saffron may be one of those rare cases in which the natural remedy is more expensive than the drug. Saffron is the world’s most expensive spice. It is harvested from crocus flowers, specifically the dried stigmas (the threadlike tips inside the flower), which are ground up to make the spice. You need more than fifty thousand crocuses—enough to cover a football field—to produce just a single pound of saffron.45

  A Prozac-equivalent dose of saffron may cost more than twice as much as the drug, but a subsequent study found that even just smelling saffron appeared to have psychological benefits. Though researchers diluted the spice so much that the study subjects couldn’t detect its odor, they still noted a significant drop in stress hormones measured in women who sniffed the saffron for twenty minutes compared with those who spent twenty minutes smelling a placebo, along with significant improvement in the women’s symptoms of anxiety.46

  So if you’re feeling anxious, perhaps wake up and smell the saffron.

  Coffee and Aspartame

  Speaking of waking up to pleasant aromas, a cup of coffee may be doing more for the brain than making it feel less groggy in the morning. Researchers from Harvard University looked at data from three large-scale cohort studies of more than two hundred thousand American men and women. They found that people who drank two or more cups of coffee daily appeared to have about only half the suicide risk compared to non-coffee drinkers.47 What about drinking more than four cups a day? A Kaiser Permanente study of more than one hundred thousand people found that suicide risk seemed to continue to drop with increases in coffee dose. People who drank more than six cups a day were 80 percent less likel
y to commit suicide,48 though drinking eight or more cups a day has been associated with increased suicide risk.49

  What you put in your coffee may also make a difference. The NIH-AARP study, which followed hundreds of thousands of Americans for a decade, found that frequent consumption of sweetened beverages may increase the risk of depression among older adults. Indeed, adding sugar to coffee may negate many of its positive effects on mood, and adding the artificial sweetener aspartame (found in Equal and NutraSweet) or saccharine (in Sweet’n Low) was associated with an increased risk of depression.50

  The controversy surrounding the neurological effects of aspartame began in the 1980s.51 At first, concern was limited to those with preexisting mental illness. An early study at Case Western Reserve University was halted prematurely for safety reasons because subjects with a history of depression appeared to be experiencing such severe reactions to the sweetener. The researchers concluded that “individuals with mood disorders are particularly sensitive to this artificial sweetener and its use in this population should be discouraged.”52

  Only recently were the neurobehavioral effects of aspartame investigated in a population free from mental illness. Healthy individuals were split into two groups—half were given a higher dose of aspartame (the equivalent of about three liters of Diet Coke’s worth) and the other half received a lower dose (a single liter of Diet Coke’s worth). Then the groups switched.53 Bear in mind that the higher-aspartame diet contained just half the acceptable daily intake of the stuff, as determined by the U.S. Food and Drug Administration.54 After only eight days on the higher-aspartame dose, participants exhibited more depression and irritability and performed worse on certain brain function tests.55 So not only may aspartame cause adverse mental effects in sensitive populations but it may also harm the general public at sufficient doses.