Our Sources

Every recommendation in our quiz is grounded in peer-reviewed research, clinical guidelines, and information from leading health organizations. Below you'll find the evidence behind each supplement we recommend, organized by supplement and the specific claims we make.

How We Build Our Recommendations

Our quiz recommendation engine scores supplements based on your age, wellness goals, diet, activity level, and specific health concerns. Each scoring rule is informed by the research listed below. We prioritize sources from the NIH, Mayo Clinic, and peer-reviewed journals indexed on PubMed. We do not make diagnostic claims — our recommendations are informational and should complement, not replace, advice from your healthcare provider.

Looking for specific research citations? Each of our articles now includes inline citations linked directly to peer-reviewed sources. Visit our blog articles to see the research behind each recommendation.

Vitamin D3

Recommended for: bone health, immune support, mood regulation, sedentary lifestyles, ages 45+, and plant-based diets.

  1. NIH Office of Dietary Supplements. "Vitamin D — Fact Sheet for Health Professionals."
    Establishes recommended daily intakes, deficiency prevalence, and the role of vitamin D in calcium absorption and bone health.
    ods.od.nih.gov
  2. Holick MF. "Vitamin D deficiency." New England Journal of Medicine. 2007;357(3):266-281.
    Landmark review establishing widespread vitamin D deficiency and its effects on bone density, immune function, and chronic disease risk.
    PubMed 17634462
  3. Anglin RE, et al. "Vitamin D deficiency and depression in adults: systematic review and meta-analysis." British Journal of Psychiatry. 2013;202:100-107.
    Meta-analysis linking low vitamin D levels to increased risk of depression, supporting our mood-related recommendation.
    PubMed 23377209

Magnesium Glycinate

Recommended for: sleep and stress support, mood regulation, active lifestyles, ages 35+, and hormonal balance.

  1. NIH Office of Dietary Supplements. "Magnesium — Fact Sheet for Health Professionals."
    Documents magnesium's role in 300+ enzymatic reactions, recommended intakes, and common deficiency in women.
    ods.od.nih.gov
  2. Abbasi B, et al. "The effect of magnesium supplementation on primary insomnia in elderly." Journal of Research in Medical Sciences. 2012;17(12):1161-1169.
    Double-blind RCT showing magnesium improved sleep quality, sleep time, and serum melatonin levels.
    PubMed 23853635
  3. Boyle NB, et al. "The Effects of Magnesium Supplementation on Subjective Anxiety and Stress — A Systematic Review." Nutrients. 2017;9(5):429.
    Systematic review finding that magnesium supplementation may have a beneficial effect on subjective anxiety.
    PubMed 28445426
  4. Zhang Y, et al. "Can Magnesium Enhance Exercise Performance?" Nutrients. 2017;9(9):946.
    Review supporting higher magnesium needs in physically active individuals due to increased losses through sweat and urine.
    PubMed 28846654

Omega-3 Fish Oil

Recommended for: inflammation and joint pain, brain fog, cardiovascular health, sedentary lifestyles, plant-based diets, and ages 55+.

  1. NIH Office of Dietary Supplements. "Omega-3 Fatty Acids — Fact Sheet for Health Professionals."
    Comprehensive review of omega-3 roles in cardiovascular, neurological, and inflammatory health.
    ods.od.nih.gov
  2. Goldberg RJ, Katz J. "A meta-analysis of the analgesic effects of omega-3 polyunsaturated fatty acid supplementation for inflammatory joint pain." Pain. 2007;129(1-2):210-223.
    Meta-analysis demonstrating omega-3 supplementation reduces joint pain intensity and NSAID consumption.
    PubMed 17335973
  3. Yurko-Mauro K, et al. "Beneficial effects of docosahexaenoic acid on cognition in age-related cognitive decline." Alzheimer's & Dementia. 2010;6(6):456-464.
    RCT showing DHA supplementation improved memory and learning in adults with mild cognitive complaints.
    PubMed 20434961
  4. Sanders TA. "DHA status of vegetarians." Prostaglandins, Leukotrienes and Essential Fatty Acids. 2009;81(2-3):137-141.
    Documents significantly lower DHA levels in vegetarians and vegans, supporting our diet-based recommendation.
    PubMed 19500961

Collagen Peptides

Recommended for: skin and hair goals, joint comfort, active lifestyles, and ages 35+.

  1. Bolke L, et al. "A Collagen Supplement Improves Skin Hydration, Elasticity, Roughness, and Density." Nutrients. 2019;11(10):2494.
    RCT demonstrating oral collagen supplementation improved multiple skin parameters after 12 weeks.
    PubMed 31627309
  2. Clark KL, et al. "24-Week study on the use of collagen hydrolysate as a dietary supplement in athletes with activity-related joint pain." Current Medical Research and Opinion. 2008;24(5):1485-1496.
    Study showing collagen supplementation reduced joint pain in physically active individuals.
    PubMed 18416885
  3. Shuster S, et al. "The influence of age and sex on skin thickness, skin collagen and density." British Journal of Dermatology. 1975;93(6):639-643.
    Foundational research showing collagen density declines with age, supporting our age-based scoring.
    PubMed 1220811

Iron + Vitamin B12

Recommended for: energy goals, fatigue concerns, vegetarian and vegan diets, and ages 18–34.

  1. NIH Office of Dietary Supplements. "Iron — Fact Sheet for Health Professionals."
    Documents iron requirements for menstruating women (18 mg/day) and higher deficiency risk in younger women.
    ods.od.nih.gov
  2. NIH Office of Dietary Supplements. "Vitamin B12 — Fact Sheet for Health Professionals."
    Establishes B12 deficiency risk in plant-based diets and its role in energy metabolism and red blood cell formation.
    ods.od.nih.gov
  3. Pawlak R, et al. "How prevalent is vitamin B12 deficiency among vegetarians?" Nutrition Reviews. 2013;71(2):110-117.
    Systematic review finding high B12 deficiency rates in vegetarians (up to 86.5% in some populations), supporting our diet-based scoring.
    PubMed 23356638
  4. Houston BL, et al. "Efficacy of iron supplementation on fatigue and physical capacity in non-anaemic iron-deficient adults." Transfusion. 2018;58(6):1504-1511.
    Systematic review showing iron supplementation reduces fatigue even in non-anemic women with low ferritin.
    PubMed 29624699

Calcium + Vitamin K2

Recommended for: bone and joint health, ages 45+, and menopause-related bone density concerns.

  1. NIH Office of Dietary Supplements. "Calcium — Fact Sheet for Health Professionals."
    Recommends 1,200 mg daily for women over 50 and details the relationship between calcium, estrogen, and bone loss.
    ods.od.nih.gov
  2. Knapen MH, et al. "Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women." Osteoporosis International. 2013;24(9):2499-2507.
    RCT demonstrating vitamin K2 (MK-7) reduced age-related bone mineral density decline in postmenopausal women.
    PubMed 23525894
  3. Geleijnse JM, et al. "Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease." The Journal of Nutrition. 2004;134(11):3100-3105.
    Population study showing K2 intake was inversely associated with cardiovascular calcification, supporting the calcium + K2 pairing.
    PubMed 15514282

Ashwagandha (KSM-66)

Recommended for: stress and sleep goals, hormonal balance, mood concerns, and ages 45–54.

  1. Chandrasekhar K, et al. "A prospective, randomized double-blind, placebo-controlled study of safety and efficacy of a high-concentration full-spectrum extract of ashwagandha root." Indian Journal of Psychological Medicine. 2012;34(3):255-262.
    RCT showing ashwagandha significantly reduced serum cortisol levels and stress assessment scores versus placebo.
    PubMed 23439798
  2. Langade D, et al. "Efficacy and Safety of Ashwagandha Root Extract in Insomnia and Anxiety." Cureus. 2019;11(9):e5797.
    Double-blind RCT showing ashwagandha root extract improved sleep quality and reduced sleep onset latency.
    PubMed 31728244
  3. Lopresti AL, et al. "An investigation into the stress-relieving and pharmacological actions of an ashwagandha extract." Medicine. 2019;98(37):e17186.
    RCT demonstrating ashwagandha reduced cortisol, improved sleep, and decreased stress and anxiety in stressed adults.
    PubMed 31517876

Women's Probiotic

Recommended for: digestive concerns, immune support, and ages 65+.

  1. Hempel S, et al. "Probiotics for the prevention and treatment of antibiotic-associated diarrhea: a systematic review and meta-analysis." JAMA. 2012;307(18):1959-1969.
    Large meta-analysis supporting the efficacy of probiotics for digestive health.
    PubMed 22570464
  2. Reid G, et al. "Oral use of Lactobacillus rhamnosus GR-1 and L. fermentum RC-14 significantly alters vaginal flora." FEMS Immunology & Medical Microbiology. 2003;35(2):131-134.
    Clinical trial demonstrating specific probiotic strains can restore healthy vaginal flora in women.
    PubMed 12628548
  3. Yan F, Polk DB. "Probiotics and immune health." Current Opinion in Gastroenterology. 2011;27(6):496-501.
    Review of probiotic mechanisms in modulating immune responses, supporting our immunity-related recommendation.
    PubMed 21897224

Vitamin C

Recommended for: immune support, skin and hair goals, and ages 18–24.

  1. NIH Office of Dietary Supplements. "Vitamin C — Fact Sheet for Health Professionals."
    Documents vitamin C's roles in immune defense, collagen synthesis, and antioxidant protection.
    ods.od.nih.gov
  2. Hemilä H, Chalker E. "Vitamin C for preventing and treating the common cold." Cochrane Database of Systematic Reviews. 2013;(1):CD000980.
    Large Cochrane review finding regular vitamin C supplementation reduces cold duration and severity.
    PubMed 23440782
  3. Pullar JM, et al. "The Roles of Vitamin C in Skin Health." Nutrients. 2017;9(8):866.
    Review of vitamin C's essential role in collagen synthesis and photoprotection, supporting our skin-health recommendation.
    PubMed 28805671

CoQ10 (Ubiquinol)

Recommended for: energy goals, fatigue concerns, active lifestyles, and ages 45+.

  1. Hernández-Camacho JD, et al. "Coenzyme Q10 Supplementation in Aging and Disease." Frontiers in Physiology. 2018;9:44.
    Review documenting age-related decline in CoQ10 levels and the rationale for supplementation in older adults.
    PubMed 29459830
  2. Rosenfeldt FL, et al. "Coenzyme Q10 in the treatment of hypertension: a meta-analysis of the clinical trials." Journal of Human Hypertension. 2007;21(4):297-306.
    Meta-analysis showing CoQ10 supplementation may support healthy blood pressure, relevant to cardiovascular health.
    PubMed 17287847
  3. Mizuno K, et al. "Antifatigue effects of coenzyme Q10 during physical fatigue." Nutrition. 2008;24(4):293-299.
    Study demonstrating CoQ10 reduced physical fatigue and improved exercise tolerance, supporting our energy and activity-based scoring.
    PubMed 18272335

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