Tyrosine is an amino acid used by the body to produce certain adrenal stress hormones and chemical messengers in the nervous system (neurotransmitters). Animal research shows that brain levels of these substances decline with stress, and that giving animals tyrosine supplements reverses this decline and improves various tests of performance in stressed animals.³⁹ In a controlled study, a protein drink containing 10 grams per day of tyrosine was more effective than a carbohydrate drink for improving mental performance scores in a group of cadets taking a stressful six-day combat training course.⁴⁰ A double-blind trial in humans found that one-time administration of 150 mg of tyrosine per 2.2 pounds of body weight helped prevent a decline in mental performance for about three hours during a night of sleep deprivation.⁴¹ Single administrations of tyrosine (100 to 150 mg per 2.2 pounds of body weight) have also helped preserve mental performance during physically stressful conditions such as noise or extreme cold in several controlled studies.^42,43,44,45

Animal studies have demonstrated protective effects of rhodiola extracts against physical stresses.^50,51,52 A double-blind study of healthcare workers experiencing the stress of night duty found that taking 170 mg per day of a standardized rhodiola extract prevented some of the decline in a set of mental performance measures during the first two weeks. However, when this regimen was repeated after a two-week period of not taking the extract, rhodiola did not provide protection from mental performance decline.⁵³ In another double-blind study, 100 mg per day of the same extract was given to medical students during a stressful exam period. Those taking the extract reported a better sense of general well-being, and performed better on tests of mental and psychomotor performance.⁵⁴ A third double-blind study of military cadets performing a 24-hour duty showed that 370 to 555 mg of rhodiola extract per day significantly reduced mental fatigue, as measured by several performance tasks.⁵⁵ Another double-blind trial confirmed the effectiveness of rhodiola for the treatment of stress-related fatigue.⁵⁶

Animal studies suggest that supplementing with vitamin C can reduce blood levels of stress-related hormones and other measures of stress.^57,58,59,60 Controlled studies of athletes have shown that vitamin C supplementation (1,000 to 1,500 mg per day) can reduce stress hormone levels after intense exercise.^61,62 Surgery patients given 2,000 mg per day of vitamin C during the week before and after surgery had a more rapid return to normal of several stress-related hormones compared with patients not given vitamin C.⁶³ In a double-blind trial, young adults took 3,000 mg per day of vitamin C for two weeks, then were given a psychological stress test involving public speaking and mental arithmetic.⁶⁴ Compared with a placebo group, those taking vitamin C rated themselves less stressed, scored better on an anxiety questionnaire, had smaller elevations of blood pressure, and returned sooner to lower levels of an adrenal stress hormone following the stress test.

The herbs discussed here are considered members of a controversial category known as adaptogens, which are thought to increase the body's resistance to stress, and to generally enhance physical and mental functioning.^65,66 Many animal studies have shown that various herbal adaptogens have protective effects against physically stressful experiences,^67,68 but whether these findings are relevant to human stress experiences is debatable.

Animal studies support the idea that Asian ginseng is an adaptogen.⁶⁹ Some studies have suggested that Asian ginseng can enhance feelings of well-being in elderly people with age-associated memory impairment,⁷⁰ nurses working night shifts,⁷¹ or people with diabetes.⁷² In a double-blind trial, people taking a daily combination of a multivitamin-mineral supplement (MVM) with 40 mg of ginseng extract (standardized for 4% ginsenosides) for 12 weeks reported greater improvements in quality of life measured with a questionnaire compared with a group taking only MVM.⁷³ The same MVM-ginseng combination was tested in a double-blind study of night-shift healthcare workers.⁷⁴ Compared with a placebo group, the group receiving the MVM-ginseng combination improved on one out of four measures of mental performance, one out of three measures of mood (increased calmness, but no change in alertness or contentment), and a measure of reported fatigue. However, in another double-blind study, healthy adults given 200 or 400 mg per day of a standardized extract of Asian ginseng (equivalent to 1,000 or 2,000 mg of ginseng root) showed no significant improvement in any of several measures of psychological well-being after two months.⁷⁵

Animal and human studies suggest that deficiencies of omega-3 fatty acids may contribute to behaviors associated with unhealthy responses to stress.^76,77 A double-blind study of students with a low dietary intake of DHA (docosahexaenoic acid, an omega-3 fatty acid) reported that taking 1.5 to 1.8 grams of DHA per day for three months prevented an increase in aggressiveness in these students during a stressful final exam period.⁷⁸ This group of researchers reported in another double-blind study that 1.5 grams per day of DHA given to medical students during a stressful exam period resulted in changes in some, though not all, blood measurements indicating improved responses to stress.⁷⁹

The herbs discussed here are considered members of a controversial category known as adaptogens, which are thought to increase the body's resistance to stress, and to generally enhance physical and mental functioning.^80,81 Many animal studies have shown that various herbal adaptogens have protective effects against physically stressful experiences,^82,83 but whether these findings are relevant to human stress experiences is debatable.

Animal research has reported antistress effects of Eleutherococcus senticosus (also known as Siberian ginseng),⁸⁴ and Russian research not available in the English language reportedly describes human studies showing similar effects in humans.^80,86 A double-blind study of healthy elderly people reported that those who took 60 drops per day of a eleuthero liquid extract (concentration not specified) scored higher in some quality-of-life measures after four weeks, but not after eight weeks, compared with a group taking a placebo.⁸⁷ Athletes experiencing the stress of training who took an eleuthero extract equivalent to 4 grams per day had no changes in their blood levels of an adrenal stress hormone after six weeks.⁸⁸ More research is needed to clarify the value of eleuthero for treating stress.

When asked why they are taking nutritional supplements, combating stress is one of the most common reasons given by people.^88,89,90 Despite this popular attitude, human research on the effects of supplements on stress is sparse and conflicting.⁹¹ While there are animal studies and preliminary human reports suggesting that many vitamins are important for protecting the body from the consequences of physical stresses such as surgery,⁹² evidence supporting the use of vitamins to combat everyday stress is somewhat limited.

Several studies have evaluated a daily supplement of vitamin B1 (15 mg), vitamin B2 (15 mg), vitamin B3 (50 mg), vitamin B6 (10 mg), vitamin B12 (10 mcg), vitamin C (500 mg), pantothenic acid (23 mg), folic acid (400 mcg), biotin (150 mcg), calcium (100 mg), magnesium (100 mg), and zinc (10 mg) for combating stress effects. People participating in preliminary trials of this combination have reported some benefits that relate to the effects of chronic stress, including improved concentration, better mood, and less fatigue.^93,94,95 A small double-blind study of this combination reported no significant psychological benefits relating to stress.⁹⁶ However, in a larger double-blind trial with healthy young men, this supplement resulted in significantly less anxiety and perceived stress according to some measurements after one month, though other stress-related symptoms did not improve.⁹⁷ Another large, double-blind study of people experiencing high stress levels found this combination significantly helpful after one month according to several measures of anxiety, well-being, and psychological stress.⁹⁸

In a year-long double-blind trial, a one-a-day type multivitamin-mineral supplement was no better than a supplement containing only vitamin B2, calcium, and magnesium for improving mental or physical measures of quality of life in a group of healthy adults.⁹⁹

Stress is understood to have a detrimental effect on the balance of intestinal bacteria,^100,101 but whether probiotic supplements improve the ability to handle stress is unknown. In a six-month preliminary trial, a multivitamin-mineral (MVM) supplement that also contained a blend of Lactobacillus acidophilus, Bifidobacterium bifidum, and Bifidobacterium longum was effective for improving scores on a stress questionnaire.¹⁰² However, this improvement could have been a placebo effect or could have been due to the MVM component. Controlled research comparing MVM supplements with and without added probiotics is necessary to determine whether probiotics are helpful for treating stress.

The herbs discussed here are considered members of a controversial category known as adaptogens, which are thought to increase the body's resistance to stress, and to generally enhance physical and mental functioning.^103,104 Many animal studies have shown that various herbal adaptogens have protective effects against physically stressful experiences,^105,106 but whether these findings are relevant to human stress experiences is not always clear.

Animal studies have suggested that ashwagandha may be helpful for reducing the effects of stress,^107,108,109 including chronic psychological stress.¹¹⁰ In a double-blind study of people experiencing chronic stress, supplementation with 300 mg per day of a concentrated ashwaganda extract for 60 days significantly decreased perceived stress, compared with a placebo.¹¹¹

An herbal formula from the Ayurvedic medicine tradition, containing extracts of ashwagandha, asparagus, pueraria, argyreia, dioscorea, mucuna, and piper, has been studied as an aid to coping with the stress of military combat. A double-blind study found that soldiers performed similarly in a set of mental and psychological tests after an eight-day combat mission whether they were given two capsules daily (exact content not revealed) of this formula or a placebo.¹¹² This suggests there was no real benefit of the herbal formula under these conditions.

The herbs discussed here are considered members of a controversial category known as adaptogens, which are thought to increase the body's resistance to stress, and to generally enhance physical and mental functioning.^113,114 Many animal studies have shown that various herbal adaptogens have protective effects against physically stressful experiences,^115,116 but whether these findings are relevant to human stress experiences is debatable.

Animal studies have shown that maca can reduce the negative effects of stress; however, whether maca is effective in humans is unknown.¹¹⁷

Stress is understood to have a detrimental effect on the balance of intestinal bacteria,^118,119 but whether probiotic supplements improve the ability to handle stress is unknown. In a six-month preliminary trial, a multivitamin-mineral (MVM) supplement that also contained a blend of Lactobacillus acidophilus, Bifidobacterium bifidum, and Bifidobacterium longum was effective for improving scores on a stress questionnaire.¹²⁰ However, this improvement could have been a placebo effect or could have been due to the MVM component. Controlled research comparing MVM supplements with and without added probiotics is necessary to determine whether probiotics are helpful for treating stress.