Raspberries: small effects, one real kitchen rule

The research on raspberries is modest, and most of it is short. A 2024 meta-analysis of 9 randomised trials found that raspberries lowered one inflammation marker, TNF-alpha, by 3.07 pg/mL. TNF-alpha is a lab marker, and these trials did not measure illness. Fasting glucose, HbA1c, CRP and IL-6 did not move. The insulin results were mixed: one insulin measure rose by 1.89 µU/mL, and the other did not change. In one trial, 59 adults with overweight or abdominal obesity and slightly raised insulin or triglycerides ate 280 g of frozen raspberries a day for 8 weeks, and their insulin, glucose, inflammation markers and blood pressure stayed where they were. Before you read further, check what people actually ate, because several studies here did not test the fruit in your basket. The blood pressure evidence pooled raspberry powder with other berry products, and the analysis did not report a separate significant effect for raspberry. The pregnancy trials used raspberry leaf extract. The absorption work in men with prostate cancer used a black raspberry confection and a nectar. The clearest practical finding has nothing to do with nutrients. Imported frozen raspberries have carried norovirus, and the team that investigated one outbreak advises heating them before you eat them.

The numbers, per 100 g

What your body absorbs

• After 4 weeks of 1 cup of red raspberries a day, 35 adults had more gut-made polyphenol metabolites such as urolithins, and people with prediabetes started lower. — 35 adults (25 with prediabetes and insulin resistance, 10 healthy), 4-week periods (n = 35) Evidence B source
  Urolithins, phenyl-gamma-valerolactones and phenolic acids rose after 4 weeks; 123 metabolites measured
• In men with prostate cancer eating 10 or 20 g of black raspberry products daily for 4 weeks, a chewable confection yielded more urolithin A than a nectar, with large person-to-person differences. — Men with localised prostate cancer, a control group and four intervention groups, n = 8 per group, 4 weeks before surgery Evidence C source
  Dose-dependent urinary urolithins; higher urolithin A and DMEA with confection

What cooking and storage change

• In a 2013 Oslo norovirus outbreak, people who ate mousse made with unheated imported frozen raspberries had 3.4 times the risk of illness, and investigators advise heating imported frozen berries. — 147 conference participants, 74 cases (n = 147) Evidence C source
  ARR 3.4 (95% CI 1.4-8.2) for raspberry mousse

What it does to your health

• Eating 280 g of frozen raspberries a day for 8 weeks did not change insulin, glucose, inflammation markers or blood pressure in 59 adults with overweight or abdominal obesity and slightly raised insulin or triglycerides. — 59 adults with overweight or abdominal obesity and mild hyperinsulinaemia or hypertriglyceridaemia (n = 59) Evidence B source
  No significant change in insulin, glucose, inflammatory markers, blood pressure
• A 2024 meta-analysis of 9 RCTs found raspberries lowered TNF-alpha by 3.07 pg/mL but did not change fasting glucose, HbA1c, CRP or IL-6. — Adults in 9 randomised trials (12 arms) (n = 9 trials) Evidence A source
  TNF-alpha WMD -3.07 pg/mL (95% CI -5.17 to -0.97); one insulin measure +1.89 uU/mL while insulin is also listed as unchanged; no effect on fasting glucose, HbA1c, HOMA-IR, CRP, IL-6

Safety, limits and interactions

• In the 1996 Florida outbreak, eating raspberries, traced to Guatemala, was linked to cyclosporiasis with a matched odds ratio of 31.9, with a very wide confidence interval. — 86 laboratory-confirmed cases matched with up to 4 controls, plus 9 clusters (n = 86) Evidence C source
  Matched OR 31.9 (95% CI 7.4 to 138.2); vehicle traced to Guatemala

What people believe that the data does not support

• Adding raspberries to pancakes did not lower the blood glucose response (54.7 vs 41.8 for a control with similar sugar, a difference that was not statistically significant), which did not support the idea that berries blunt starch spikes. — Healthy volunteers tested on 7 occasions Evidence C source
  Glycaemic response raspberry 54.7 vs control 41.8, no significant difference

Who this works differently for

• In obese adults with type 2 diabetes, a raspberry meal lowered blood glucose at 2 and 4 hours, and 4 weeks of daily raspberries lowered IL-6 and TNF-alpha, with no change in fasting glucose or lipids. — Obese adults with type 2 diabetes, acute test days then two 4-week periods Evidence B source
  Lower postprandial glucose at 2 and 4 h; lower IL-6 and hsTNF-alpha after 4 weeks; fasting glucose, lipids, CRP unchanged
• In adults with prediabetes, 125 g of red raspberries daily for 4 weeks cut LDL cholesterol by 7.2% and hepatic insulin resistance by 30.1% from baseline. — 26 adults with prediabetes and insulin resistance plus 10 healthy controls, two 4-week periods (n = 36) Evidence B source
  LDL -7.2%, total cholesterol -4.9%, hepatic IR -30.1% versus baseline
• Among 354 pregnant Australian women using complementary medicines, raspberry leaf was the most popular herb. — 354 pregnant Australian women who already used complementary medicines (out of 810 pregnant or breastfeeding respondents) (n = 354) Evidence C source
  Raspberry leaf top herb in pregnancy

What is still unknown

• In a meta-analysis of 45 RCTs, a mixed group of berry products including raspberry powder lowered systolic pressure by 3.68 mmHg, and the analysis did not report a separate significant effect for raspberry. — Adults in 45 chronic (1 week or longer) randomised trials of berries, citrus and cherries (n = 45 trials) Evidence A source
  Pooled berries SBP -3.68 mmHg (95% CI -6.79 to -0.58); significance limited to cranberry and cherry juice
• A systematic review found only 3 RCTs on berries and gut bacteria, and 8-12 weeks of berries including raspberries did not change blood pressure or gut microbiota. — Adults in 3 randomised trials (n = 3 trials) Evidence A source
  No significant effect on blood pressure or gut microbiota
• A 2025 meta-analysis of 14 pregnancy trials found no benefit of raspberry leaf extract on preeclampsia outcomes. — Pregnant women in 14 randomised trials of six polyphenol products (n = 14 trials) Evidence A source
  No differences for raspberry leaf extract

The bottom line

If you have type 2 diabetes or prediabetes, the picture is a little more hopeful and still small. In obese adults with type 2 diabetes, a raspberry meal kept blood glucose lower at 2 and 4 hours afterwards, and 4 weeks of daily raspberries lowered IL-6 and TNF-alpha. Fasting glucose and blood fats did not change. IL-6 and TNF-alpha are lab markers, and that trial did not measure illness. In 26 adults with prediabetes, 125 g a day for 4 weeks lowered LDL cholesterol by 7.2 percent. That was measured against each person's own starting point, over 4 weeks, in a small crossover trial. It is a reason to want a bigger trial, and too thin to plan your diet around. Berries on a starchy meal are often said to blunt the sugar spike. In one small study, pancakes with raspberries were compared with control pancakes that had similar amounts of sugar. The glucose response was 54.7 with raspberries against 41.8 for the control, and that difference was not statistically significant. The study did not support the idea that berries blunt the spike. Your gut does work on raspberries. After a cup a day for 4 weeks, adults had more of the compounds gut bacteria make from raspberry polyphenols, such as urolithins, and people with prediabetes started with less of them. What that means for health is a separate question, and the answer so far is empty. The three trials that looked at berries and gut bacteria, over 8 to 12 weeks, found no change in the gut microbiota or in blood pressure. The one habit worth changing is about safety. In Florida in 1996, people who ate raspberries had 31.9 times the odds of cyclosporiasis, a parasitic gut infection, and the raspberries were traced to Guatemala. That was one outbreak, and the uncertainty around the number is very wide (7.4 to 138.2), so it does not show that imported raspberries as a whole are risky. In Oslo in 2013, a mousse made with unheated imported frozen raspberries carried 3.4 times the risk of norovirus illness. If you put imported frozen raspberries into something you will not cook, heat them first, as the Oslo investigators recommend. They recommend heat treatment, but our source does not say for how long or at what temperature. In an Australian survey of women who already used complementary medicines, raspberry leaf was the herb pregnant respondents used most. A 2025 meta-analysis of 14 pregnancy trials found no benefit of raspberry leaf extract on preeclampsia outcomes. That finding covers leaf extract and preeclampsia only, and says nothing about the fruit. We have no study on whether raspberry leaf is safe in pregnancy, so this page cannot tell you that it is. If you are pregnant and thinking about the leaf, ask your midwife or doctor. Two gaps are ours to admit. We have no study on raspberry allergy and none on raspberries and medicines, so this page cannot tell you whether either is a concern.

Sources

1. rsp-04 · randomised crossover trial
   consumed 1 cup RRB (fresh weight equivalence) per day ... After 4-week RRB supplementation, several metabolite groups were significantly increased (p < 0.05), including urolithins, phenyl-γ-valerolactones, and phenolic acids. ... 4-week RRB supplementation significantly increased microbial metabolites that were lower in PreDM-IR group.
   Molecules, 2020 · checked 2026-09-23
2. rsp-11 · clinical trial
   (confection or nectar, 10 or 20 g dose; n = 8 per group) for 4 weeks prior to prostatectomy ... Men in the BRB confection groups have greater urinary excretion of the microbial urinary metabolites urolithin A and DMEA, suggesting that this food matrix provides greater colonic microflora exposure.
   Mol Nutr Food Res, 2020 · checked 2026-09-23
3. rsp-09 · cohort
   Risk of illness was higher in those who consumed raspberry mousse (aRR 3·4, 95% CI 1·4-8·2) ... We recommend heat-treatment of imported frozen berries before consumption.
   Epidemiol Infect, 2016 · checked 2026-09-23
4. rsp-02 · randomised controlled trial
   59 subjects with overweight or abdominal obesity and with slight hyperinsulinemia or hypertriglyceridemia were randomized to consume 280 g/day of frozen raspberries or to maintain their usual diet for 8 weeks. ... The intervention did not significantly affect plasma insulin, glucose, inflammatory marker concentrations, nor blood pressure.
   Nutrients, 2020 · checked 2026-09-23
5. rsp-05 · meta-analysis
   Raspberry consumption led to a significant increase in insulin concentrations (WMD: 1.89 μU/mL; 95%CI: 1.45, 2.34; P < 0.001) and a significant decrease in tumor necrosis factor-α (TNF-α) concentrations (WMD: −3.07 pg/mL; 95%CI: −5.17, −0.97; P = 0.004), compared with the control groups. Raspberry consumption did not have a significant effect on fasting blood glucose, insulin, hemoglobin A1C, glucose tolerance tests, homeostatic model assessment for insulin resistance, C-reactive protein, and interleukin-6 concentrations.
   Curr Dev Nutr, 2024 · checked 2026-09-23
6. rsp-08 · case-control
   In the case control study, eating raspberries was strongly associated with cyclosporiasis (matched odds ratio = 31.9; 95% confidence interval [CI] 7.4, 138.2). ... Guatemalan raspberries were the vehicle for the 1996 Florida cyclosporiasis outbreak.
   Public Health Rep, 1999 · checked 2026-09-23
7. rsp-10 · clinical trial
   Results showed that there were no differences in GR (blueberry 51·3 (SEM 5·7); raspberry 54·7 (SEM 5·6); blueberry control 43·9 (SEM 4·2); raspberry control 41·8 (SEM 6·4)), GR area under the curve or satiety index between any of the tests.
   Br J Nutr, 2011 · checked 2026-09-23
8. rsp-01 · randomised crossover trial
   The postprandial phase revealed significantly lower levels of serum glucose at 2 and 4 h postprandial after raspberry versus control phase. ... Four-week daily raspberry supplementation continued to show a significant lowering effects on IL-6 and hsTNF-α versus control phase (all p < 0.05) ... No effects were noted on fasting glucose and lipids, C-reactive protein and arterial elasticity.
   Ann Nutr Metab, 2019 · checked 2026-09-23
9. rsp-03 · randomised crossover trial
   consumed either RRB (125 g fresh equivalents) daily or RRB + 8g FOS daily, separated by a 4-week washout ... In PreDM-IR, RRB supplementation reduced hepatic-IR (-30.1% ± 14.6%; P = 0.04) and reduced plasma total and LDL cholesterol [-4.9% ± 1.8% (P = 0.04) and -7.2% ± 2.3% (P = 0.003), respectively] from baseline.
   J Nutr, 2022 · checked 2026-09-23
10. rsp-13 · cross-sectional
    A total of 810 completed surveys (354 pregnant and 456 breastfeeding women) were analysed. ... The most popular herbs were raspberry leaf, ginger, peppermint and chamomile (pregnant respondents)
    Health Expect, 2022 · checked 2026-09-23
11. rsp-06 · meta-analysis
    Berries including juice of barberry, cranberry, grape, pomegranate, powder of blueberry, grape, raspberry and freeze-dried strawberry significantly reduced SBP by 3.68 mmHg (95% CI - 6.79 to - 0.58; P = 0.02) ... No other significant improvements were observed for other specified fruits.
    Eur J Nutr, 2021 · checked 2026-09-23
12. rsp-07 · systematic review
    Ultimately three randomized clinical trials in humans met the eligibility criteria. ... Together the randomized clinical trials showed that berry consumption (Aronia berry, strawberries, raspberries, cloudberries and bilberries) for 8-12 weeks had no significant effect on both blood pressure and the gut microbiota.
    Nutrients, 2022 · checked 2026-09-23
13. rsp-12 · meta-analysis
    Fourteen trials investigating six candidates were included. ... No differences were observed for other outcomes or candidates (Salvia miltiorrhiza, Bryophyllum pinnatum , raspberry and cranberry extracts).
    BJOG, 2025 · checked 2026-09-23