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Nutrients & Compounds in Foods

Nutrients and compounds in functional foods: fiber, beta-glucan, resistant starch, polyphenols, carotenoids, omega-3, plant sterols, soy isoflavones and nitrate, with evidence.

Content last updated . This page has not been medically reviewed.

Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.

Food results are often credited to a single compound. Trials of the compound, the food and the supplement are different studies.

CompoundIn which foodsWhat the sources show
Soluble fiber, beta-glucanOats, barleyAt 3 g or more a day, oat beta-glucan lowered LDL by 0.25 mmol/L in a meta-analysis; FDA allows a claim for oats and barley. [1][2] See Oats, Barley.
Fiber for constipationMany plant foods; trials mostly of supplementsFiber supplementation improved stool frequency and consistency; psyllium, doses over 10 g a day and at least 4 weeks looked best, with more flatulence. [3] This is a supplement review, not food.
Resistant starchCooled starchy foods, legumes, some grainsTypes 1 and 2 lowered after-meal blood glucose in people with type 2 diabetes in a review of 36 trials; supplementation lowered total and LDL cholesterol modestly (-7.33 and -3.40 mg/dL). [4][5]
PolyphenolsBerries, cocoa, tea, citrusWild blueberry powder improved vascular function in older adults; hesperidin in orange juice might not affect lipids or blood pressure. [6][7] Polyphenol content does not guarantee effect.
CarotenoidsTomato (lycopene), leafy greens and avocado (lutein)Observational links only for tomato and prostate cancer; avocado raised macular pigment in a small trial. [8][9]
Omega-3Oily fish (EPA, DHA); walnuts, flax, chia (ALA)Fish associations are observational. Fish-oil capsules are a separate supplement topic. [10]
Plant sterols and stanolsAdded to spreads and drinksMeta-analysis of 124 studies: 0.6 to 3.3 g a day lowered LDL 6% to 12%; FDA claim 1.3 g sterol esters (3.4 g stanol esters). [11][12]
Soy isoflavones, soy proteinSoy foodsSoy protein 25 g a day lowered LDL 4.76 mg/dL; isoflavones small effect on menopause symptoms. [13][14]
NitrateBeetroot, leafy greensBeet juice lowered systolic pressure 5.31 mmHg in hypertension (low certainty); another review found no effect in hypertensive adults. [15][16]

What this does not mean

A compound's effect in a trial does not tell you that a food containing it has the same effect, or that a supplement of it is safe. For nutrient values of specific foods see FoodData Central. [17]

Frequently asked questions

Is fiber from food the same as a fiber supplement?

We did not find a source comparing them directly. The constipation review studied supplements. [3]

References

  1. Whitehead A et al. Cholesterol-lowering effects of oat β-glucan: a meta-analysis of randomized controlled trials. Am J Clin Nutr 2014. PMID 25411276.
  2. U.S. Government. 21 CFR 101.81: Health claims: soluble fiber from certain foods and risk of coronary heart disease. Electronic Code of Federal Regulations, read 2026-10-22.
  3. van der Schoot A et al. The Effect of Fiber Supplementation on Chronic Constipation in Adults: An Updated Systematic Review and Meta-Analysis of Randomized Controlled Trials. Am J Clin Nutr 2022. PMID 35816465.
  4. Pugh JE et al. A comparison of the effects of resistant starch types on glycemic response in individuals with type 2 diabetes or prediabetes: A systematic review and meta-analysis. Front Nutr 2023. PMID 37051127.
  5. Yuan HC et al. Meta-analysis indicates that resistant starch lowers serum total cholesterol and low-density cholesterol. Nutr Res 2018. PMID 29914662.
  6. Wood E et al. Wild blueberry (poly)phenols can improve vascular function and cognitive performance in healthy older individuals: a double-blind randomized controlled trial. Am J Clin Nutr 2023. PMID 36972800.
  7. Mohammadi M et al. Hesperidin, a major flavonoid in orange juice, might not affect lipid profile and blood pressure: A systematic review and meta-analysis of randomized controlled clinical trials. Phytother Res 2019. PMID 30632207.
  8. Xu X et al. Tomato consumption and prostate cancer risk: a systematic review and meta-analysis. Sci Rep 2016. PMID 27841367.
  9. Scott TM et al. Avocado Consumption Increases Macular Pigment Density in Older Adults: A Randomized, Controlled Trial. Nutrients 2017. PMID 28832514.
  10. Krittanawong C et al. Fish Consumption and Cardiovascular Health: A Systematic Review. Am J Med 2021. PMID 33444594.
  11. Ras RT et al. LDL-cholesterol-lowering effect of plant sterols and stanols across different dose ranges: a meta-analysis of randomised controlled studies. Br J Nutr 2014. PMID 24780090.
  12. U.S. Government. 21 CFR 101.83: Health claims: plant sterol/stanol esters and risk of coronary heart disease. Electronic Code of Federal Regulations, read 2026-10-22.
  13. Blanco Mejia S et al. A Meta-Analysis of 46 Studies Identified by the FDA Demonstrates that Soy Protein Decreases Circulating LDL and Total Cholesterol Concentrations in Adults. J Nutr 2019. PMID 31006811.
  14. Luan H et al. Effects of soy isoflavones on menopausal symptoms in perimenopausal women: a systematic review and meta-analysis. PeerJ 2025. PMID 40718787.
  15. Grönroos R et al. Effects of beetroot juice on blood pressure in hypertension according to European Society of Hypertension Guidelines: A systematic review and meta-analysis. Nutr Metab Cardiovasc Dis 2024. PMID 39069465.
  16. Zhang Y et al. Regulatory effect of dietary nitrate on blood pressure: a meta-analysis of randomized controlled trials. Food Funct 2023. PMID 36740972.
  17. U.S. Department of Agriculture. FoodData Central. Nutrient values for specific foods; we link to it rather than copying numbers.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.