By Sarah LoBisco, ND
Why Are We Talking About Essential Oils?
Dr. Fitzgerald recently asked me to write a case study with essential oils. Many practitioners are aware of essential oils’ potent antimicrobial power and are comfortable using them in treating dysbiosis or acute infections. This is for good reason.
Essential oils are well studied for their ability to kill off various microbes. Many in vitro and vivo studies, as well as some small clinical trials, indicate that essential oils are effective against resistant microorganisms.1-13 Furthermore, specific chemotypes (variations in predominant constituents) of oregano and its active constituent, carvacrol, have been found not only to have activity against various pathogens, 14-15 but also to inhibit new biofilm formations in-vivo. (However, carvacrol was not effective in breaking down pre-formed biofilms.)15
Although the mechanisms behind the action of how essential oils inhibit bacteria is still not fully understood, several studies have attributed their actions to their generating irreversible damage to the membrane of the critters’ cells. This leads the bacteria to “leak out its contents” and die. Other proposed mechanisms, among many, include inhibition of toxin-producing enzymes, protein degeneration, and interference with cellular respiration and electron flow. Furthermore, they have been shown to have antifungal and antiviral properties. 1,2 Perhaps, their strong action is in part related to their many constituents and the synergism among them.
A 2014 study of essential oils in The Open Microbiology Journal explained:
It has also been postulated that the function of the main components is regulated by other minor molecules which help in potentiating synergistic effect . It is likely that several components in essential oils play a role in characterizing the fragrance, the density, the texture, the color, ability in cell penetration, lipophilicity, fixation on cell walls, and most importantly the bioavailability. Considering that a vast range of different groups of chemical compounds are present in one essential oil, it is most likely that antibacterial activities cannot be attributed to one specific mechanism or component; and hence, there may be several targets in a cell which result in the potentiating influence. Thus, it is more meaningful and rational to study the whole essential oil rather than some of its components as to whether the concept of synergism truly exists between the components in essential oils .10
Due to the fact that essentials oils are secondary metabolites with immune modulating effects, I believe that they do not have the same negative impact on the beneficial microflora as synthetic antibiotics. In fact, a 2012 review article provided support that essential oils can work in synergism with probiotics to have “complementary antimicrobial effects with practically no side effects.” 15
Furthermore, essential oils can do so much more than kill off infections.
Essential Oils Actions
As mentioned above, essential oils are plant secondary metabolites that are essential for the plant’s survival. They are the aromatic and volatile compounds found within shrubs, flowers, trees, roots, bushes, resins, and seeds.
There are two different ways to look at an essential oils’ mechanisms of actions. The narrow view describes its effects based on the oil’s individual constituents; the broader view encompasses the impact of the oils on our biochemistry, physiology, and psychology.
I go into greater detail about this here; in summary:
1. Biochemical (pharmacological): the interactions essential oils and their constituents have with receptors for hormones and enzymes in our bodies.
2. Physiological: the action essential oils have on specific biological functions.
3. Psychological: According to The Therapeutic Benefits of Essential Oils, Nutrition, Well-Being, and Health, the “olfactory area of the brain (limbic system) undergoes an action triggered by the essential oil molecules and then, chemical and neurotransmitter messengers provide changes in the mental and emotional behavior of the person (Buchbauer, 1993; Johnson, 2011; Shibamoto et al, 2010).”
Usually, a psychological action also has a physiological or biochemical impact on the body. For example, hormonal support could be provided by a calming emotion from inhalation, affecting stress hormones or enzymes, a direct result of phytoestrogens modulating estrogen levels.
One small study with 22 menopausal women in their 50s examined changes in neurotransmitter concentrations, cortisol, and thyroid stimulating hormone in relationship to inhalation of clary sage oil. The researchers found that inhalation of this oil decreased cortisol, increased 5-hydroxytryptamine (the monoamine, serotonin), and had a calming effect.
In another randomized study of sixty-three healthy postmenopausal women, researchers found that inhalation of oil of neroli had positive effects on menopausal symptoms, stress, and estrogen levels.
Now that you have a little background on essential oils, let’s review a functional medicine case using essential oils.
Now, All About Ella…
Ella, a beautiful 50-year-old female, 5 foot 8 inches, BMI 20.5, arrived at my office a few years ago. She had been recently diagnosed with Lyme disease due to the presence of “the Lyme rash” ((erythema migrans (EM)) on the inside of her right thigh and lower back. This was despite her EIA (enzyme immunoassay) and Western Blot being negative. (I discuss the issues with Lyme testing here.) She had had symptoms of fever, chills, and debilitating fatigue that she “couldn’t shake for a week or so”prior to her visit to the ER. She was prescribed doxycycline 100 mg twice a day. Although she felt initial improvement in fatigue, she did not finish the prescription, feeling uncomfortable being on an antibiotic for 20 days. An itchy rash had also developed under her breasts and in the right axilla, which she was currently treating with steroids. She reported it was finally “getting better and barely visible now.”
Ella was concerned as she felt fatigue worsen, and she wanted a more natural approach for the symptoms. Her major goals were to make sure the Lyme disease was not returning, to balance her hormones, to implement healthier lifestyle choices, to get relief from fatigue, and to optimize brain support. She did not have a primary care provider and was managing her symptoms by acute care visits.
Medical history included hypoglycemic symptoms (she was known for getting light-headed from skipping meals and feeling better after eating), HSV, chronic urinary tract infections which started in her twenties, and chronic constipation that began with abuse of laxatives while bulimic in her college years.
In order to have a bowel movement daily, she took 3-6 capsules a day of an herbal product that contained the following in unspecified doses:
Chamomile (Matricaria recutita) flower extract, Cascara sagrada (Frangula purshiana) bark, Psyllium (Plantago ovata) seed, barberry (Berberis vulgaris) bark, burdock (Arctium lappa) root, Fennel (Foeniculum vulgare) seed, garlic (Allium sativum) bulb, Echinacea (E. purpurea) root, Bentonite, Diatomaceous earth, Ginger (Zingiber officinale) root, apple pectin, licorice (Glycyrrhiza glabra) root, cayenne (Capsicum annuum) fruit, tarragon (Artemisia dracunculus) leaf, ginger (Zingiber officinale) root, tangerine (citrus reticulata) rind, rosemary (Rosmarinus officinalis CT cineol) leaf, anise (Pimpinella anisum) seed, peppermint (Mentha piperita) leaf, mugwort (Artemisia vulgaris) leaf/root, German chamomile (Matricaria recutita) flower, gelatin, alcohol and water.
She brought with her a grocery bag full of supplements that included thyroid and adrenal formulations, multivitamins, minerals, iodine, several B complexes, fish oil, and various herbal preparations. She was not sure if any of them were helpful and wasn’t consistent with any of them, except the “herbal laxative.”
Ella also had a history of alcohol abuse but had been sober for 16 years. She reported dry, thinning hair that was worsening. Menses were beginning to get more irregular and heavier in the past few years, and she started to have hot flashes. She had never had issues with her period before, except some minor cramps on occasion.
Ella was born vaginally and did not have the benefit of breast feeding longer than three months. She was the youngest of seven children and her childhood was stressful. Her father was an alcoholic and her family struggled financially. She also noted that her childhood house could have contained lead paint and mold. Both her parents and older siblings smoked. She had a 3-pack year history of smoking in in her twenties, stopping prior to the birth of her son.
Ella remembered falling out of a tree when she was 7 years old and losing consciousness. She was brought to the emergency room but does not remember being assessed for a concussion or having any follow-up.
Ella continued to have an excessive amount of psychological stress. This included caring for her physically-challenged son who was born with a rare “chromosomal abnormality” when Ella was 32 years old. He was in and out of the hospital for various procedures and surgeries. Her ex-husband was still very present for his son, and they had an amicable friendship based around him.
Ella recently suffered the death of a long-term boyfriend and best friend. She was currently in a relationship with someone not in alignment with her values, exposing herself to unhealthy foods, cigarette smoke, mold, and emotional strain when she was with him. Her diet was mostly organic foods when at home but included sugar and “unhealthy things” at her boyfriend’s home. She was drinking copious amounts of coffee with synthetic creamer — “pots of it a day.”
Besides the debilitating fatigue, brain fog, and low mood, Ella’s hot flashes were particularly bothersome, and they appeared “out of nowhere.” Ella tended to be very “stoic”; when asked for her ratings of pain and fatigue, she reported both at a 5, as she could “push” herself through it. She slept only 5-6 hours, due to her demanding schedule, and awoke unrefreshed.
Family history was significant for heart disease, asbestosis, depression, hypertension and hyperlipidemia. Her father died of congestive heart failure at 84 and mother, from a pulmonary embolism at 83. Siblings had histories of hepatitis C, Hashimoto’s thyroiditis and hyperlipidemia.
Ella’s nutritional symptom questionnaire revealed high need of support for her HPA axis, liver, thyroid and digestion. Her brain checklist was showing imbalances in her deep limbic region (score of 25). Specifically, she struggled with frequent low mood, low energy, sleep changes, and problems with focus. Her other scores were within normal limits.
Her fingernails were brittle with leukonycia (white spots) on her first and third digits. Her waist-to-hip ratio was 0.7. Blood pressure was “always low.”
Ella did not have any current bloodwork. Because I am not a PCP in New York, I suggested she find a primary care doctor and obtain the following blood work: a lipid panel (NMR), celiac serology and genes; homocysteine; thyroid and sex hormones including progesterone, estrogens, testosterone, TSH, FT3, FT4, RT3, TT3, TT4; antibodies: thyroid (TgAb, TPO), ANA, RF, CCP, and an organic acids profile with amino acids. We were not able to obtain all the labs, but had a good start (see below).
Because Ella had been using essential oils prior to our consultation, I immediately suggested she start cold air diffusing a blend of Clove (Syzygium aromaticum) bud oil, Lemon (Citrus limon) peel oil, Cinnamon (Cinnamomum verum) bark oil, Eucalyptus (Eucalyptus radiata) leaf oil, and Rosemary (Rosmarinus officinalis) leaf oil daily, 4 hours on and 2 hours off. This regimen was to combat mold at home and cigarette smoke at her boyfriend’s house she was subjected to. I explained to her that chronic exposure to toxins and mold would further deplete her immune system and may be interfering with achieving remission from the Lyme disease and other challenges. (I discuss this in detail here.) She was open to hearing about mold remediation in her home, as she did feel intuitively it was an issue. Furthermore, we discussed other mediation and lifestyle factors she could implement until we spoke again after her labs were done, which included a gradual reduction in coffee and replacement with green tea.
We also discussed implementing gargling a few times a day in order to develop vagal tone for digestion stimulation. I suggested starting a mild exercise regime of short bursts as tolerated. This could also assist with mitochondrial support in the brain, given history of brain trauma and current brain fog and fatigue. She agreed.
Our long discussion about self-care and stress modulation focused on improving sleep -– 6-7 hours a night were needed to assist in balancing immune response, hormones, and blood sugar. The importance of not letting blood sugar dip and its relationship to hot flashes (adrenaline surges), compromising her hormonal axis, was emphasized. I provided her with a list of various snacks to have handy.
When Ella returned to discuss her labs, she had experienced mild improvement. She was “feeling better overall.” She wasn’t consistent with the exercise but was walking and trying to do some burst intervals. She was slowly making progress with sleep and felt some energy improvement, especially when diffusing the essential oils. Ella also was slowly weaning off coffee and saw she was “addicted to it.” She noticed a mild improvement in hot flashes, not “soaking through things as much.”
Functional Medicine Matrix (populated using baseline assessment and pertinent baseline laboratory results):
Assimilation (gut/lungs/skin): constipation; hypoglycemia: sugar and gluten consumption with elevated thyroid antibodies; fungal rash and steroids; history of bulimia; dysbiosis (high indican and very high tricarballylate on organic acid panel); breast fed x 3 months and Caro Syrup x 6 months; dry skin
Defense and Repair (immune/inflammation): Hashimoto thyroiditis (TgAb 1782 (
Communication (endocrine): Hashimoto’s, low FT4 (0.71); Blood sugar dysregulation with possible beta cell dysfunction (Fasting glucose 87, A1C 5.7, insulin
Transportation (cardiovascular/lymphatics): hypercholestemia (224) (LDL 115, Tg 65, HDL 96, Tg/HDL 0.68); low blood pressure (poor profusion); FMH: Heart disease, pulmonary embolism, hypertension, hyperlipidemia
Energy (mitochondrial health): Fatigue; brain fog; low mood; compromised cellular energy (high suberate and succinate); (oxidative stress biomarkers, B vitamins, and essential amino acids were normal); low blood pressure (poor profusion and oxygen delivery)
Biotransformation and Elimination: exposure to lead, mold, cigarette smoke, alcohol abuse history, nutrient deficiencies (oxidative stress markers within normal limits (on essential oils))
I believed Ella was showing dysregulation of various nodes due to the effect of Lyme on multiple systems. I thought Lyme was a trigger and mediator to Hashimoto’s disease due to an underlying predisposition to autoimmune imbalance. Furthermore, her poor lifestyle patterns, stress, and food choices contributed to dysbiosis and compromised cellular energy. We discussed that improved health would be a process assisted by continuing above suggestions. Our priority was to decrease the stressors of infections, inflammation, and lifestyle patterns on her immune system.
I also suggested she really “boost her immune and detoxification system” by increasing phytonutrient dense foods and eating a “rainbow of vegetables.” Due to the connection between Hashimoto’s and gluten sensitivity, and dysbiosis increasing the risk for intestinal permeability, I suggested she avoid gluten. I also explained that she may want to avoid dairy and sugar. (The state of New York does not allow for IgG panels, and she was not willing to do a full elimination at this time).
For the dysbiosis, Lyme and infectious history, I suggested she take three drops of oregano oil and lemon essential oil by mouth in a veggie cap 3 times a day for 20 days. This would be rotated throughout the months with other highly antimicrobial oils (thyme, rosemary, clove and various blends) to assist with antioxidant support, infectious agents, and anti-inflammatory support. I suggested she take S. boulardii because of mold exposure and to support immune response and intestinal integrity. We also added a multi-strain probiotic to be started a few weeks after being on the essential oils and S. boulardii alone.
We supported her mitochondrial health nutritionally with coQ10 200 mg, B vitamins and carnitine, as Ella did not eat a lot of meat. I suggested she balance her hormones and blood sugar with a high protein smoothie in the morning, consisting of greens, 1 tbsp. olive oil, 2 tsp. flax seeds, berries, and coconut milk for brain support.
She was given digestion enzymes with HCL to assist with pancreatic dysfunction and assimilation; the laxative she had used was replaced with a formulary blend of the following:
L-Glutamine 1.5 g, N-Acetyl Glucosamine 1.0 g, Citrus Pectin 1.0 g, Deglycyrrhizinated Licorice (DGL) (Glycyrrhiza glabra)(root) 400 mg, Aloe Vera Extract (Aloe barbadensis)(leaf) 300 mg, Slippery Elm (Ulmus fulva)(bark) 200 mg, Mucin 200 mg, Marshmallow (Althaea officinalis)(root) 100 mg. Chamomile (Matricaria chamomilla)(flower) 100 mg, Okra Extract (Abelmoschus esculentus)(fruit) 100 mg, Cat’s Claw (Uncaria tomentosa)(bark) 100 mg, Methylsulfonylmethane (MSM) 100 mg, Quercetin 100 mg, Prune Powder 100 mg, Zinc Carnosine 75 mg.
She was also asked to take a combination of magnesium citrate and glycinate to “bowel tolerance.” This would assist with blood sugar, calming, and immune support.
We also included Rhodiola rosea to take in the morning for mitochondrial imbalances and fatigue. Although we were not able to obtain salivary cortisol, her DHEA-S was low normal and serum cortisol was high, indicating that she probably wasn’t yet in stage three adrenal exhaustion.
High dose EPA/DHA (for inflammation, estrogen dominance, triglycerides and lipids, joint pain, brain support, cardiovascular health) was also suggested, and we added vitamin D for bone support, immune and hormonal health, and minerals for hormonal and thyroid support (selenium 100mg).
Ella did not want to go on thyroid medication. She was “very sensitive” to medication and wanted to see what we could do naturally first. I did explain that with a TSH that high– the risk of damaging the thyroid existed. Her PCP was willing to monitor TSH.
I suggested a combination of essential oils that included, in a base of sesame seed oil, spearmint (Mentha spicata), sage (Salvia officinalis), geranium (Pelargonium graveolens), myrtle (Myrtus communis), nutmeg (Myristica fragrans) and German chamomile (Matriciaria recutita) for thyroid and hormonal support. She was also asked to use lavender by inhalation and by being rubbed on the back of her neck 3x a day. (Essential oils are able to modulate hormones through direct receptor stimulation and biochemical balances.) We also added l-tyrosine for thyroid production. Finally, I suggested chlorophyll for detoxification.
Over the next few years, Ella was determined to get better. Energy and sleep improved, and she had only occasional back pain when lifting her son. Her mood brightened; hot flashes occurred only if she ate gluten or skipped meals. She no longer struggled with chronic urinary infections and rarely was sick, though had yeast infections if ate too much sugar. She practiced stress management and was happily out of her “dysfunctional relationship — taking good care of herself.”
Her labs showed significant improvement:
Thyroid: TSH 3.983, FT4 0.77, T3 2.7, FT3 1.4, TgAb 443, TPO 25
Lipid: Tg 67, HDL 86, LDL 109, CHOL/HDL 2.4, TC/Trig 3.4, HDL/TC 0.41, Tg/HDL 0.78, TC 208
GFR and creatinine were within normal limits and she was “less lightheaded all the time” (better profusion).
However, HbA1c was 5.8 H. We discussed that we might need to do more work around her toxic exposure. Vitamin D was still low but increasing. I increased her oil support blend and kept everything else the same.
At next contact she was doing well; having her thyroid monitored by PCP who was “very pleased with her progress!”
Recently Ella reported that her TSH was elevated to a 5.43 and her HbA1c was 5.7. She still had “high antibodies.” She reported that she was no longer doing as well managing her blood sugar; however, her energy was still good and she “felt great.” After getting her “back on track,” and discussing the importance of exercise and blood sugar, and continuing to take her essential oils and supplements, Ella continues to improve. “I don’t know what I would’ve done without this support; I didn’t realize how bad I felt till I felt better,” she reported recently. We are currently awaiting her thyroid and HbA1c levels.
Summary & The Hidden Effects of Emotional Healing for Ella
We know that essential oils are powerful microbe inhibitors. We also know that aroma itself is connected to our emotions. Olfaction has direct neural pathways to emotional processing centers in the brain. These include the amygdala, hippocampus, and orbitofrontal cortex (OFO). The context and our past history impact the reaction we have to odors.17-22 Still, inhaling an essential oil does more than have a functional neurological response which is to activate the olfactory receptors to stimulate the parahippocampus..23 They are also more than an alternative to synthetic antibiotics.
I believe that Ella’s results were so powerful because of the synergism of the essential oils use within the functional medicine model. Essential oils have psychological, biochemical, and physiological effects. They can modulate stress, emotions, inflammation, cortisol, neurotransmitter pathways, and infections. The potential of one bottle of oil goes well beyond manipulating or even supporting a biochemical pathway with a single nutrient or herb. It is true synergy and encompasses everything functional medicine stands for.
1. Essential Oils and Future Antibiotics: New Weapons against Emerging ‘Superbugs’? J Anc Dis Prev Rem. 2013;1: 105. doi:10.4172/2329-8731.1000105
2. Djilani, A & Dicko, A. The Therapeutic Benefits of Essential Oils, Nutrition, Well- Being and Health. Dr. Jaouad Bouayed ed. 2012; 165-166.
3. Yap PS, Lim SH, Hu CP, Yiap BC. Combination of essential oils and antibiotics reduce antibiotic resistance in plasmid-conferred multidrug resistant bacteria. Phytomedicine. June 2013;15;20(8-9):710-3. doi: 10.1016/j.phymed.2013.02.013.
4. Sue Chao S, Young G, Oberg, C, Nakoka K. Inhibition of methicillin-resistant Staphylococcus aureus (MRSA) by essential oils. Flavour and Fragrance Journal. 2008; 23: 444-449. DOI: 10.1002/ffj.1904
5. Nelson, J. Selection of resistance to the essential oil of Melaleuca alternifolia in Staphylococcus aureus. J. Antimicrob Chemother. 2000; 45 (4): 549-550. doi: 10.1093/jac/45.4.549
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7. Becerril R, Nerín C, Gómez-Lus R. Evaluation of bacterial resistance to essential oils and antibiotics after exposure to oregano and cinnamon essential oils. Foodborne Pathog Dis. 2012; 9(8):699-705. doi: 10.1089/fpd.2011.1097. Epub 2012 Jul 24
8. Halcón L, Milkus K.Staphylococcus aureus and wounds: a review of tea tree oil as a promising antimicrobial. Am J Infect Control. November 2004;32(7):402-8.
9. Edmondson M1, Newall N, Carville K, Smith J, Riley TV, Carson CF. Uncontrolled, open-label, pilot study of tea tree (Melaleuca alternifolia) oil solution in the decolonisation of methicillin-resistant Staphylococcus aureus positive wounds and its influence on wound healing. Int Wound J. August 2011;8(4):375-84. doi: 10.1111/j.1742-481X.2011.00801.x. Epub 2011 May 12.
10. Yap PSX, Yiap BC, Ping HC, Lim SHE. Essential Oils, A New Horizon in Combating Bacterial Antibiotic Resistance. The Open Microbiology Journal. 2014;8:6-14. doi:10.2174/1874285801408010006.
11. Yap PS1, Lim SH, Hu CP, Yiap BC. Combination of essential oils and antibiotics reduce antibiotic resistance in plasmid-conferred multidrug resistant bacteria. Phytomedicine. 2013 Jun 15;20(8-9):710-3. doi: 10.1016/j.phymed.2013.02.013. Epub 2013 Mar 26
12. Rosato A, Vitali C, De Laurentis N, Armenise D, Antonietta Milillo M. Antibacterial effect of some essential oils administered alone or in combination with Norfloxacin. Phytomedicine. 2007 Nov;14(11):727-32. Epub 2007 Feb 15.
13. Hongbin Si , Jinqiang Hu , Zhichang Liu , Zhen-ling Zeng Antibacterial effect of oregano essential oil alone and in combination with antibiotics against extended-spectrum B-lactamase-producing Escherichia coli. FEMS Immunology & Medical Microbiology. July 2008.
14. Origanum vulgare subsp. hirtum essential oil prevented biofilm formation and showed antibacterial activity against planktonic and sessile bacterial cells. J Food Prot. 2013 October; 76(10):1747-52.
15. The Natural Antimicrobial Carvacrol Inhibits Quorum Sensing in Chromobacterium violaceum and Reduces Bacterial Biofilm Formation at Sub-Lethal Concentrations. PLoS ONE. 2014;9(4):e93414. doi:10.1371/journal.pone.0093414.
16. Shpradeep, Karmaker S, Khare RS, Ojha S, Kundu K, Kundal S. Development of Probiotic Candidate in Combination with Essential Oils from Medicinal Plant and Their Effect on Enteric Pathogens: A Review
17. Krusemark EA, Novak LR, Gitelman DR, Li W. When the Sense of Smell Meets Emotion: Anxiety-State-Dependent Olfactory Processing and Neural Circuitry Adaptation. The Journal of Neuroscience. 2013;33(39):15324-15332. doi:10.1523/JNEUROSCI.1835-13.2013.
18. Kadohisa M. Effects of odor on emotion, with implications. Frontiers in Systems Neuroscience. 2013;7:66. doi:10.3389/fnsys.2013.00066.
19. Debiec, J, Sullivan, RM. Intergenerational transmission of emotional trauma through amygdala-dependent mother-to-infant transfer of specific fear. Proc Natl Acad Sci U S A. 2014 Jul 28. pii: 201316740.
20. Matsunaga M, Isowa T, Yamakawa K, Kawanishi Y, Tsuboi H, Kaneko H, et al. Psychological and physiological responses to odor-evoked autobiographic memory. Neuro Endocrinol Lett. 2011;32(6):774-80.
21. University of Wisconsin- Madison. Neuroanatomy. Olfactory Pathway and Limbic System. 903-913. Available at: http://www.neuroanatomy.wisc.edu/coursebook/neuro3%282%29.pdf
22. Savic I, Berglund H. Passive perception of odors and semantic circuits. Hum Brain Mapp. 2004 Apr;21(4):271-8.
23. Datis Kharrazian, DC, DHSc, MS. Advanced Case Assessment Skills for the Management of Energy Disorders. Institute for Functional Medicine. Energy Advanced Practice Module. Dallas 2015.
References for Case Study:
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• Abidov M, Crendal F, Grachev S, Seifulla R, Ziegenfuss T. Effect of extracts from Rhodiola rosea and Rhodiola crenulata (Crassulaceae) roots on ATP content in mitochondria of skeletal muscles. Bull Exp Biol Med. 2003 Dec;136(6):585-7.
• Jacob R, Nalini G, Chidambaranathan N. Neuroprotective effect of Rhodiola rosea Linn against MPTP induced cognitive impairment and oxidative stress. Annals of Neurosciences. 2013;20(2):47-51. doi:10.5214/ans.0972.7531.200204.
• Szajewska H, Mrukowicz J. Meta-analysis: non-pathogenic yeast Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea. Alimentary Pharmacology & Therapeutics. 2005; 22: 365–372. doi: 10.1111/j.1365-2036.2005.02624.x
• Efficacy of probiotics in prevention of acute diarrhoea: a meta-analysis of masked, randomised, placebo-controlled trials. Lancet Infectious Diseases. June 2006. 6(6): 374-382.
• Czerucka D, Piche T, Rampal P. Review article: yeast as probiotics –Saccharomyces boulardii. Alimentary Pharmacology & Therapeutics. 2007; 26: 767–778. doi: 10.1111/j.1365-2036.2007.03442.x