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12 Best Adaptogens for Every Symptom of Stress

By: Bulletproof Staff
December 30, 2015

12 Best Adaptogens for Every Symptom of Stress

In India and China, soldiers have used adaptogens for centuries to handle the stress of combat, recover faster, and increase their energy. Today, you can use adaptogens for – you guessed it – their adaptogenic properties: they help your body adapt to biological and psychological stress by making it easier for you to balance your hormonal systems. What does that mean, exactly? Adaptogens help you cope with common symptoms of living in the modern world, including fatigue, impotence, and infertility. In other words, adaptogens make you more resilient in all facets of life, giving you energy, focus, strength and a better overall mood.

Even though these adaptogenic herbs have worked for thousands of years, scientific research is only beginning to reveal to the West the potential that adaptogens have to upgrade your stress response and energy levels.

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What are adaptogens?

Adaptogens are unique plants or herbs that support your adrenal system. They help balance your hormones, so you can manage your stress response on a day to day basis. They adapt to what your body needs and have the ability to regulate your system up or down depending on the need in the moment.

How do adaptogens work?

Think of it like this. If you’ve ever driven a sports car, when you step on the gas, it very quickly moves forward, and when you let off, it slows down quickly. In contrast, in your grandmother’s car, you can pin the accelerator to the floor, but you have to wait two seconds for the car to lurch forward. When you release the gas, it kind of coasts.

Your adrenals are the same way. You want them to make stress hormones quickly when needed, then to stop making the hormones as soon as you’re done. That’s what adaptogens do – they make your adrenals react more quickly, so you spend less time and energy making stress hormones.

This article will walk you through 12 adaptogens I’ve used for more than a decade, and dig into some of that research to help you decide which adaptogenic herbs are best for you. You don’t have to take all of these, or any of them for that matter. Different adaptogens work for different people. That’s why we have functional medicine docs, Ayurveda, herbalists, and even shamanic practitioners who work with herbs.

Ashwagandha

adaptogenic herbs ashwagandhaAshwagandha, one of the most common adaptogens, translates to ‘smell of horse,’ — it is used in Ayurvedic practices for all kinds of things, most notably for reducing stress. (Remember that stress comes from exercise, diet, infection, fear of stuff, and even your mother-in-law…and your body doesn’t care about the source.)

Related: Ashwagandha’s Benefits for Stress, Anxiety and Immunity

Benefits of ashwagandha

Decreases anxiety and stress: Several human studies show that ashwagandha decreases anxiety, stress, c-reactive protein and cortisol.[9, 10, 11] The decrease in cortisol is worth talking about, especially when you compare the effects of ashwagandha to those of other stress-reducing supplements. Studies show ashwagandha decreased stress 14.5-27.9% in healthy but stressed people.[9] (note: if you check email or Facebook, at least part of your body is stressed…you’re human.)

Ashwagandha may also be effective when used synergistically with alcohol to reduce stress and anxiety, although I think you’re better off skipping the alcohol or at least choosing a clean one and mitigating its harmful effects when you’re stressed.

Improves memory: Another cool thing about ashwagandha is that it shows promise in improving memory formation. This could be important in research for treating Alzheimer’s patients.[13] More large human studies are needed to show how and why this adaptogen might be effective, but there is research to suggest that ashwagandha could reverse the effects of neurological toxins associated with neurodegenerative diseases.[14, 15]

How to use ashwaghanda

You can use ashwagandha as a powder or in supplement form. You can also get creative in the kitchen and try out some adaptogenic recipes, like a stress-reducing drink or snack.
• Powder – 3 to 6 grams of powder per day
• Supplement – 1 capsule 2-3 times per day (found in Bulletproof Zen Mode)
Adaptogenic Bulletproof Chocolate recipe
Adaptogenic Turmeric Latte recipe

Ashwagandha is best for

  • reducing stress and anxiety
  • decreasing c-reactive protein levels
  • lowering the stress-hormone cortisol
  • improving memory formation
  • aiding with neurodegenerative diseases

I’ve taken this adaptogen daily for years, particularly because of the memory formation and neurological toxin effects. Reducing exposure neurological toxins (like Ochratoxin A, the most common coffee mold neurotoxin) can improve performance, and I feel the difference.

Astragalus

adaptogenic herbs astragalusAstragalus is a fundamental adaptogenic herb used in Traditional Chinese Medicine and is primarily used for longevity, to fight inflammation, and for kidney support. It can also reduce levels of c-reactive protein, one of the inflammation markers that you can drive down with the Bulletproof Diet. Astragalus has 126 useful components, mostly flavonoids, saponins and polysaccharides.[31]

Benefits of astragalus

Lengthens telomeres (and lifespan): Astragalus is particularly interesting in that it’s the only natural substance that contains cycloastragenol, a molecule that can lengthen telomeres by activating telomerase production by 2-3x.[32, 33] Telomeres are structures on the end of chromosomes that, the shorter they become, the closer that cell is to dying. By lengthening telomeres, you could essentially delay cell death and slow down aging. The length of your telomeres is related to your lifespan, which is why protecting your telomeres may be key to aging gracefully.

You may have heard of TA-65. This is the branded and patented form of cycloastragenol. While studies do show that this substance is effective in increasing telomerase activity, but many of those studies were also conducted by the manufacturer of TA-65. It doesn’t make them irrelevant, it’s just something to keep in mind.

For the last two years, I’ve been taking up to 200 mg/day of cycloastragenol, which takes about 100 pounds of astragalus to make. It’s freaking expensive, so I stopped. Really hoping my telomeres are grateful, and wishing I’d measured them beforehand. My telomere measuring kit is on its way.

Boosts immune system: Astragalus also has immune-boosting properties and can activate T-cells even more than echinacea.[34]

How to use astragalus

You can use Astragalus as an adaptogenic supplement or in root form for cooking, teas, or tinctures.
• Supplement – 2 to 3 (500 milligrams) capsules per day
• Tea/Decoction – 3 to 6 grams of dried root per 12 ounces of water, up to three times a day
• Tincture – 2 to 4 millimeters per day

Astragalus is best for

  • reducing inflammatory-causing c-reactive protein
  • possible longevity effects
  • lengthening your telomeres
  • boosting your immune system

You should probably take astragalus to live longer because of inflammation and immunity, but don’t count on it to lengthen your telomeres unless you are willing to forgo buying a car to get cycloastragenol. (Seriously…that stuff starts at a couple hundred dollars a month and ranges up to thousands; I was fortunate to get some samples.)

Bacopa monnieri

adaptogenic herbs bacopa monnieriBacopa monnieri is a creeping marsh plant that is traditionally used as a nootropic (cognitive enhancer), for longevity, and as an adaptogen to help with anxiety and depression. It’s possible that the improved cognition is likely a result of the reduced anxiety. Bacopa is an effective adaptogen and can help you cope with stressful situations and decrease stress in all regions of the brain.[25] It’s also an antioxidant.

Benefits of bacopa monnieri

Enhances memory and recall: There’s some solid research on its effects on memory and can reliably improve memory in both healthy people and those experiencing cognitive decline. Studies show improvements in verbal learning, memory acquisition and delayed recall.[26] Other studies showed an increase in retention of new information, likely from a decrease in forgetting (as opposed to an increase in rate of learning).[26, 27] Bacopa promotes communication between neurons by increasing the growth rate of nerve endings.

Reduces stress: The evidence for Bacopa as a stress-reducer (and adaptogen), is solid. Research shows it reduces the effects of physiological stress, especially when taken in advance.[28]

This adaptogen does take time to work so you likely won’t see immediate results when you start taking it. It is also fat-soluble, so you can take it the traditional way, with ghee, or with your Bulletproof Coffee.

Protects against oxidative stress: You may have heard that Bacopa contains mercury and that’s probably because a crop in the past did. This isn’t a common occurrence and, on top of that, Bacopa is actually protective against the oxidative and adverse effects of metals on the brain, mostly iron and aluminum, but also mercury.[29, 30]

How to use bacopa

Bacopa is generally found as a supplement, powder, or extract. You can also make tea or add it to a pesto:

Bacopa is best for

  • reducing anxiety and stress
  • relieving symptoms of depression
  • improving cognition
  • reducing free radicals
  • boosting memory
  • protecting against toxic metal overload

This is a potent adaptogenic herb, one I use often and really like. I’m sad to see that many supplement marketing companies include small amounts of it in their formulas for cognitive enhancement, but they don’t include enough to actually work. Some of the most famous nootropics do this, and it sucks. When I use it, I take about 600mg per day. That won’t fit in over-hyped nootropic “stacks” capsules, so they put in decorative amounts.

Chaga

adaptogenic herbs chaga mushroomChaga mushrooms can be found growing in the forest on birch trees resembling a large clump of dirt. But the benefits of this fungus are astounding. Those who live in Russia and Siberia have used this adaptogenic mushroom for thousands of years. Known as a folk medicine in the past, it is now being recognized in research and has shown its power in supporting cellular health. While mushrooms are not part of the Bulletproof Diet, well-sourced, high-quality medicinal mushrooms do serve a purpose as supplement. You shouldn’t, however, eat mushrooms as part of your meal plan.

Benefits of chaga

Suppresses tumor growth: Chaga is rich in antioxidants and has shown to support apoptosis (cell death). A study performed on mice in 2016 showed that using an extract of Chaga reduced tumor size by 60%. It also showed a decrease in temperature after implantation of the tumor. The decreased temperature could explain the reason Chaga suppresses cancer growth by regulating energy metabolism.[1] Multiple studies performed on mice have shown that Chaga suppresses tumor growth in liver cancer,[2] lung cancer and breast cancer.[3] [4][5] It can even support the immune system during chemotherapy.[6]

Reduces blood sugar levels: Many mice studies have observed a positive effect of Chaga on diabetes. Not only does Chaga lower blood glucose levels, but also cholesterol and triglycerides. [7][8][9]

Prevents DNA damage: Stress causes a substantial amount of harm to the body leading to many different diseases. Chaga has been shown to reduce oxidative stress by almost 55%. Not only is it believed to support digestive issues, it could be a beneficial supplement to reduce oxidative stress in general.[10]

How to use chaga

You can use Chaga in many ways from teas and supplements to tinctures.

  • Tea – It is best to stick to pre-made teas unless you want to spend a lot of time preparing the mushroom to make tea.
  • Tincture – You can make a tincture, but it will need to soak for about six months, so trying one already made may be the better option.
  • Supplement – Take as directed on package. Typically, 1/2 to 1 teaspoon per day.

Chaga is best for

  • Supporting cancer cell apoptosis
  • Lowering blood glucose levels
  • Reducing oxidative stress
  • Boosting your immune system

Cordyceps

adaptogenic herbs cordycepsCordyceps is a rare combination of caterpillar and fungus found in Sikkim, India used in traditional Chinese and Tibetan medicine to promote longevity. Folk healers use this adaptogen to treat 21 different ailments including cancer, colds, low libido, and low energy.[11]

Benefits of Cordyceps

Combats fatigue: A two-week study used mice to observe the effects of Cordyceps on fatigue. The results showed that Cordyceps increased energy and reduced oxidative stress compared to the mice who did not receive it. It also supported the balance of energy and hormone levels.[12]

Enhances memory: Cordyceps was shown to reverse memory loss and improve memory by supporting the nerve growth. It promoted growth of the neuron pathways, which is crucial for memory development and neuroplasticity and regeneration. This could be part of the puzzle for treatment of Alzheimer’s, Parkinson’s and other neurodegenerative diseases.[13]

Boosts exercise performance: A study observing 20 healthy individuals aged 50-75 years showed that endurance and breathing thresholds both increased significantly after 12 weeks of taking Cordyceps as an adaptogenic supplement. This suggests supplementation improves exercise performance in healthy older subjects (and may be beneficial for younger athletes as well)[14].

How to use cordyceps

Cordyceps can be added to soups and stews or taken in supplement or powder form.

  • Add 1/2 ounce of this adaptogen to your favorite Bone Broth Recipe
  • Supplement – follow directions on package

Cordyceps is best for

  • Combating fatigue
  • Enhancing memory
  • Supporting brain function
  • Fighting free radical damage
  • Increasing endurance and exercise performance

Holy basil (Tulsi/Ocimum sanctum)

adaptogenic herbs holy basilHoly basil, or Tulsi, is an herb used in Ayurvedic medicine and is traditionally used as an adaptogen, aphrodisiac, and liver supporter. It’s also used for longevity!

Benefits of holy basil

Protects liver: Studies show that this herb can be an effective liver protector, and is especially potent when paired with milk thistle, another liver supporter.[16]

Lowers stress and anxiety: Other practices include using holy basil as a stress reducer, antioxidant, and anti-anxiety supplement.[17, 18, 19, 20]

Increases muscle mass: Holy basil is high in ursolic acid, a compound also found in apple peels, that may affect body composition by increasing muscle mass and decreasing body fat, although there’s not enough solid evidence out there yet showing this really works.[21, 22] (I’ve used other forms of ursolic acid for body composition too…an interesting idea, but I couldn’t tell if it worked in my very short and not well controlled n=1 experiment.)

Boosts libido: Holy basil is also known to be both an anti-fertility agent and libido enhancer, so this could be a fun herb for couples not ready to conceive. Holy basil is one of the only aphrodisiac and testosterone boosting-supplements, while also being reducing fertility in men, and researchers aren’t entirely sure why. Some animal studies suggest that it could also be tied to its high ursolic acid content.[23, 24] The ursolic acid could prevent spermatogenesis.

How to use holy basil

You can use Holy Basil as a garnish on your dishes, add it to your water, or make a tea. You can also purchase a powder or supplement form.

Holy basil is best for

  • Reducing stress and anxiety
  • Supporting your liver
  • Lowering inflammation
  • Building muscle mass and lowering body fat
  • Lowering men’s fertility*
  • Boosting your (or your partner’s) libido

*I love the anti-inflammatory effects of holy basil, but I have some concern that anything that reduces fertility is often harmful to the rest of your cells too. Your swimmers (or eggs) are great signs of how healthy your system is. But I use it whenever I’m inflamed because it works.

Maca

adaptogenic herbs macaMaca is a Peruvian root that grows in the Andes and is becoming known for its abilities to support sex drive and boost fertility, which can go down in times of stress.

Benefits of maca

Boosts libido: In multiple studies with men and women, Maca has been shown to increase libido and the desire for sex. From antidepressant-induced sexual dysfunction to erectile dysfunction, Maca can boost the libido and get you in the mood.[15][16] [17][18][19][20]

Increases fertility: Maca has also been shown to increase fertility in both men and women. For men, Maca improves sperm count and motility (their ability to move through the woman’s reproductive system). For women, Maca encourages overall hormone balance, which can support regulation of the woman’s cycle.[21][22]https://www.ncbi.nlm.nih.gov/pubmed/11753476

How to use maca

Adding Maca powder to your Bulletproof Coffee or morning smoothie is a great way to make it a daily habit. You can also take this adaptogen in supplement form.

Maca is best for

  • Boosting libido
  • Increasing fertility
  • Balancing hormones

Mucuna pruriens

adaptogenic herbs mucuna pruriens l dopa beanMucuna pruriens, also known as the dopa bean, has a high content of L-dopa which is a precursor to the neurotransmitter dopamine. This adaptogen is known for its ability to boost your mood, lower stress, improve mood, reduce anxiety, and help you focus. Some people with ADHD find it works as well as Adderall at keeping them calm and productive.

Related: Mucuna Pruriens: The Mood-Boosting Productivity Pill You’ve Been Looking For

Benefits of mucuna pruriens

Lowers stress and anxiety: Dopamine is essential for mood, and when you don’t have enough, you can struggle with stress and anxiety. While you don’t want to take too much Mucuna, adding some to your diet can be effective at calming the nervous system and reducing anxiety, stress and even depression.[23][24][25][26]

Increases fertility and libido: While reducing stress, Mucuna has been shown to improve semen quality in infertile men. After three months of taking a daily dose of Mucuna, 120 men showed a decrease in stress and increase in sperm count.[27]

Boosts productivity and focus: Taking Mucuna can give you that extra focus to get things done. L-dopa, the main compound found in Mucuna, has been studied for its ability to increase focus and learning in adults. One study in adults ages 21-28 showed it increased reaction time, while another showed lasting memory recall of new words.[28][29]

How to use mucuna

Mucuna is best used in supplement form with dosage between 100-200mg per day. You can also add mucuna to your Bulletproof Coffee.

Mucuna is best for

  • Increasing dopamine
  • Lowering stress
  • Boosting mood
  • Improving fertility
  • Enhancing memory and focus

Panax ginseng

best adaptogenic herbs for stressPanax ginseng is probably the most well-known adaptogen. Traditional Chinese Medicine has used ginseng for a wide variety of treatments, especially in preventative practices and as a performance enhancer and immune booster. You may have also heard that it enhances libido, although that aspect is way over-marketed.

There are more than a dozen forms of panax ginseng. Only five of them are used medicinally, and two very popular ones are Korean red ginseng and white ginseng. There’s science to back up claims about this root that resembles two legs of a human.

Benefits of panax ginseng

Improves brain power and focus: Studies show that ginseng is effective when used to improve cognition and focus.[1] The improvement in cognition is most likely a result of a decrease in fatigue (kind of like coffee). In studies where individuals were not already experiencing fatigue, they did not see an increase in cognition.

Increases sense of well-being: There’s conflicting evidence when it comes to using ginseng as a mood-booster, with ginseng having the same effects on mood as the placebo.[7] Other studies, however, do show that in healthy people, ginseng does have a mood-boosting effect and can increase calm and improve memory and performance.[8]

Boosts libido and sexual performance: Research shows that taking panax ginseng improves the quality of erections in men suffering from erectile dysfunction [2, 3, 4]. It also stimulates sexual behavior (e.g. friskiness) in animal studies.[30] Other research in post-menopausal women found that Korean red ginseng improved their sexual arousal.[31]

Lowers blood sugar: There’s also some evidence that ginseng can lower blood glucose levels, although it doesn’t appear to have any effect on people that don’t have an existing condition like diabetes or hypertension, for example.[5, 6] Large human studies are lacking though and there’s conflicting results in the studies that do exist.

How to use panax ginseng

You can take Panax Ginseng as a supplement or add it to your teas. You can also use it as a root.

Ginseng is best for

  • Decreasing fatigue
  • Balances blood glucose levels
  • Boosting libido and sexual arousal
  • Improving erectile dysfunction
  • Boosting your mood

One annoying thing is that most studies don’t use the same forms or the same preparations of ginseng, so it’s hard to know if you’re getting the right stuff, or even if there’s anything besides sawdust in your capsules. Real ginseng is expensive and fake stuff is all over the place. I’ve used panax ginseng occasionally as an energy booster but not daily most of the time.

Reishi

Reishi mushroom has been used for over 2,000 years in China with documented scripts of their many benefits. From boosting the immune system and reducing blood sugar to supporting the liver and fighting cancer, this mushroom is one to keep on hand, assuming you’re using high-quality, medicinal-grade mushrooms — and not taking it every day.[32] Mushrooms are OK as medicine, but not something to eat in your diet.

Benefits of reishi

adaptogenic herbs reishiBoosts the immune system: Reishi contains antioxidants which protect cells from oxidative damage. With this protection comes the ability to be more resilient and respond to threats properly.

Detoxes your system: A study of 300 one-day-old male broiler chickens fed a contaminated diet of aflatoxin (poisonous carcinogens produced by mold) showed that when Reishi was introduced to the diet, it counteracted the negative effects of the aflatoxin. This suggests that reishi is protective of the immune function and helps detox the system – especially useful when you’ve been exposed to allergens or toxins.[33] [34]

Fights cancer: Studies on different types of cancer show the possibilities of Reishi as an antitumor and cancer preventative. Human prostate cancer cell lines were used to observe the effect on prostate cancer. Results showed that the cells were sensitive to Reishi, causing a 45% to 55% decrease in cells.[35] A study of reishi on inflammatory breast cancer also showed anticancer properties with a reduced tumor growth and weight.[36]

How to use reishi

You can use Reishi as a tea, tincture, or supplement.

Reishi is best for

  • Boosting immunity
  • Supporting apoptoisis
  • Protecting the liver
  • Balancing blood sugar

Rhodiola Rosea

adaptogenic herbs rhodiola roseaLike other adaptogenic herbs, rhodiola rosea is known for helping your body adapt to stressful situations, by keeping fatigue and exhaustion at bay. Also known as arctic root or golden root, this potent root contains more than 140 active ingredients, the most bioactive ones being rosavin and salidroside.

Benefits of rhodiola rosea

Fights fatigue and exhaustion: Rhodiola is used in Traditional Chinese Medicine and is often used to promote vitality and immunity. Rhodiola can reduce fatigue and exhaustion in prolonged stressful situations and can also reduce c-reactive protein.[35, 36] (If you commute, you’re in prolonged stressful situations every day!)

Boosts cognition and performance: There’s also plenty of evidence to show that rhodiola will improve cognition, independent of fatigue-reduction. A study on the effects of rhodiola on physicians on night duty fatigue showed that the herb could improve performance by about 20%, regardless of fatigue levels.[37]

Improves mood and lowers depression: Rhodiola could also improve your mood and decrease the symptoms of depression.[38] Improvements in feelings of well-being might be, in part, caused by rhodiola’s effect on serotonin levels.[38]

How to use rhodiola

Like the others, this adaptogen is best taken as a supplement or tea.

Studies show that if you take rhodiola for longer periods of time, it helps even more.[36] There does appear to be a bell-curve response, so finding the right dose matters, and mega-dosing is counterproductive (and expensive!). It can also have a slightly stimulatory effect, so it might be better to take in the morning. Some people find it helpful when trying to go off of caffeine.

In the Bulletproof Coffee shop in Santa Monica, we will gladly blend this into your Bulletproof Coffee!

Rhodiola is best for

  • Reducing fatigue
  • Lowering c-reactive protein levels
  • Boosting your mood and sense of well-being
  • Improving cognition

Siberian Ginseng

adaptogenic herbs siberian ginsengTraditional healers have used Siberian ginseng (not to be confused with panax ginseng) to fight fatigue, maximize physical performance, and improve overall immunity and longevity. Research backs their practices.

Benefits of Siberian Ginseng

Improves endurance: Looking to up your endurance? In one study, Siberian ginseng increased subjects’ time to exhaustion by more than 500% [40].

Fights mental and physical fatigue: Other research shows that it can improve resistance to both cognitive and physical fatigue.[41, 42]

Boosts immune system: There’s also promising evidence that this adaptogen has immunity-boosting effects and can increase t-cell count.[44]

How to use Siberian ginseng

Siberian Ginseng is best used as a capsule or tincture.

• Capsule – 100-200mg twice per day or as directed
• Tincture – Use as directed on package

Siberian ginseng is best for

  • Fighting fatigue
  • Improving endurance in strenuous activity
  • Increasing cognitive and physical performance
  • Boosting your immune system

Consider adding adaptogens into your day, especially when you’re going to have a big day, or when you were out late partying or otherwise didn’t recover well the night before. There’s an argument for taking them every day, which is what I do. That’s why I created a special blend of adaptogens that is available only at the Bulletproof Coffee shop in Santa Monica. Take the time to look around online, and try single adaptogens so you know what works best for you!

Let me know how it works on Facebook…really interested in your results!

1] http://www.ncbi.nlm.nih.gov/pubmed/11895046

2] http://www.ncbi.nlm.nih.gov/pubmed/15982990

3] http://www.ncbi.nlm.nih.gov/pubmed/8750052

4] http://www.ncbi.nlm.nih.gov/pubmed/19234482

5] http://www.ncbi.nlm.nih.gov/pubmed/21619921

6] http://www.ncbi.nlm.nih.gov/pubmed/19017419

7] http://www.ncbi.nlm.nih.gov/pubmed/11424544

8] http://www.ncbi.nlm.nih.gov/pubmed/20737519

9] http://www.ncbi.nlm.nih.gov/pubmed/23439798

10] http://www.ncbi.nlm.nih.gov/pubmed/19718255

11] http://www.lifeforce.net/pdfs/withania_review.pdf

12] http://www.ncbi.nlm.nih.gov/pubmed/22208270

13] http://www.ncbi.nlm.nih.gov/pubmed/22208270

14] http://www.ncbi.nlm.nih.gov/pubmed/23340606

15] http://www.ncbi.nlm.nih.gov/pubmed/24012642

16] http://www.ncbi.nlm.nih.gov/pubmed/21731390

17] http://www.ncbi.nlm.nih.gov/pubmed/21619917

18] http://www.ncbi.nlm.nih.gov/pubmed/7275241

19] http://www.ncbi.nlm.nih.gov/pubmed/19253862

20] http://www.ncbi.nlm.nih.gov/pubmed/19253862

21] http://www.ncbi.nlm.nih.gov/pubmed/24614098

22] http://www.jbc.org/content/286/7/5546.abstract

23] http://www.ncbi.nlm.nih.gov/pubmed/15854639

24]http://onlinelibrary.wiley.com/doi/10.1002/(SICI)1099-1573(19980201)12:1%3C32::AID-PTR185%3E3.0.CO;2-4/abstract

25] http://www.ncbi.nlm.nih.gov/pubmed/12410544

26] http://www.ncbi.nlm.nih.gov/pubmed/20590480

27] http://www.ncbi.nlm.nih.gov/pubmed/12093601

28] http://www.ncbi.nlm.nih.gov/pubmed/12957224

29] http://www.ncbi.nlm.nih.gov/pubmed/21366957

30] http://www.ncbi.nlm.nih.gov/pubmed/22366895

31] http://www.ncbi.nlm.nih.gov/pubmed/15346617

32] http://www.ncbi.nlm.nih.gov/pubmed/20822369

33] http://www.ncbi.nlm.nih.gov/pubmed/21426483

34]http://www.ncbi.nlm.nih.gov/pubmed/17661330

35] rhttp://www.ncbi.nlm.nih.gov/pubmed/15514725

36] http://www.ncbi.nlm.nih.gov/pubmed/22228617

37] http://www.ncbi.nlm.nih.gov/pubmed/11081987

38] http://www.ncbi.nlm.nih.gov/pubmed/17990195

39] http://www.ncbi.nlm.nih.gov/pubmed/22921986

40] http://www.ncbi.nlm.nih.gov/pubmed/3749339

41] http://www.ncbi.nlm.nih.gov/pubmed/21793317

42] http://www.ncbi.nlm.nih.gov/pubmed/15207399

43] http://www.ncbi.nlm.nih.gov/pubmed/10641044