The green Mediterranean diet: principles and research

The green Mediterranean diet adds specific polyphenol-rich foods to a Mediterranean eating pattern while reducing red and processed meat. In DIRECT PLUS, this approach produced favorable changes in some fat deposits and metabolic markers. Many findings come from separate analyses of the same trial, however, rather than independent replications. They do not yet demonstrate protection against dementia or heart attacks.

How the green Mediterranean diet works in the body

The version studied combined a calorie-reduced Mediterranean diet with walnuts, green tea, Mankai duckweed and less red and processed meat. Polyphenols and changes in the gut microbiome are possible explanations for its effects. Because this was a combined intervention, the contribution of each component cannot be separated with confidence.

DIRECT PLUS assigned 294 adults with abdominal obesity or abnormal blood lipids to three groups; 88% were men. Both Mediterranean groups received 28 g of walnuts daily, supplying an estimated 440 mg of polyphenols. The green group also received 3–4 cups of green tea and 100 g of frozen Mankai duckweed as a shake, together providing about 800 mg of additional polyphenols. All groups received physical-activity guidance. Matching the energy targets of the two Mediterranean groups did not mean that individual plant compounds were tested in isolation. Study

In experimental studies, polyphenols can influence cellular signaling and microbial metabolites. The dietary trial found associations between consumption of particular foods, metabolites and health measurements. It did not directly show that individual Mankai compounds suppress neuroinflammation or improve insulin action in humans.

Effects on metabolism, hormones and body composition

After 18 months, visceral fat fell by 14.1% in the green group, compared with 6.0% on the conventional Mediterranean diet and 4.2% with general dietary guidance. Body weight fell by 3.9% in the green group. The frequently cited 6.2 kg weight loss, by contrast, comes from the six-month analysis. Visceral fat is associated with a less favorable metabolic risk profile. 18-month analysis Six-month analysis

Insulin sensitivity and glucose regulation

At six months, HOMA-IR fell more in the green group than in the general dietary-guidance group. HOMA-IR is an indirect research measure of insulin resistance. The findings are consistent with a more favorable metabolic profile, but cannot be attributed specifically to fewer branched-chain amino acids, individual polyphenols or Mankai alone. Study

Lipid metabolism and cardiovascular markers

The six-month analysis reported improvements in LDL cholesterol, diastolic blood pressure and HOMA-IR, among other measures. The greater LDL reduction was demonstrated against the general dietary-guidance group. This does not show that ApoB and LDL particle count changed the most, or that the diet has already been shown to prevent cardiovascular events. Study

Liver fat and metabolic dysfunction

Liver fat fell by a relative 38.9% in the green group, compared with 19.6% in the conventional Mediterranean group. The difference remained after statistical adjustment for weight loss. This is an encouraging finding for people with similar starting conditions, but it demonstrates neither a direct effect of individual polyphenols nor long-term protection against cirrhosis. Study

Brain structure and neuroprotection

Among participants aged 50 and older, both Mediterranean groups showed more favorable changes in selected MRI markers than the general dietary-guidance group, with the best values in the green group. Across the full study population, not every brain marker showed a clear difference between groups. The study examined structural changes, not the prevention of dementia or a definite improvement in memory. Study

Which components might explain the green diet’s stronger effects?

The amount and variety of polyphenols

The walnuts, tea and Mankai provided to the green group supplied an estimated 1,240 mg of polyphenols a day in total. That describes the study foods, not a clinically established daily target. Different plants contain different compounds. A supplement therefore cannot automatically be equated with the diet that was studied.

Less red and processed meat

The green group was asked to restrict red and processed meat more strongly and replace some animal protein with plant sources. The trial did not separately test whether less meat, more plant compounds or their combination explained the results. TMAO and other possible mechanisms remain research questions, not proof that complete meat avoidance produces the strongest effects.

Changes in the gut microbiome

The trial found changes in microbial composition that were associated with metabolic changes. Higher concentrations of some metabolites also correlated with more favorable MRI measurements. These associations do not demonstrate that particular bacteria labeled “good” caused the effects. Liver-fat study Brain MRI

Protein quality and amino-acid profile

Mankai was an additional source of plant protein in the trial. In everyday eating, getting enough total protein and essential amino acids remains important. The study does not prove that a lower proportion of branched-chain amino acids alone improves insulin action, or that switching to Mankai reliably preserves muscle mass.

Why the same diet produces different results in different people

Age and metabolic health at the start

The brain-structure findings were most apparent in participants aged 50 and older. This is an age-related observation within the trial, not a general threshold below which the diet cannot work. Improved insulin sensitivity was associated with more favorable MRI changes, but this cannot reliably predict an individual’s response before they begin.

The makeup of the gut microbiome

People do not all produce the same metabolites from plant compounds. In a separate study of 100 healthy adults, urolithin A was detectable at baseline in 12%; after pomegranate juice, a larger proportion produced it. This is not a general population estimate, and it does not establish who will benefit from walnuts or the green Mediterranean diet. Study

APOE genotype and neuroprotection

In the brain analysis, 15.7% of participants carried the APOE-ε4 allele. Failing to detect a difference by genotype does not establish equal effects in all groups, particularly with a limited sample. The accompanying review describes possible relationships between diet and cognitive decline in APOE-ε4 carriers, but does not offer a reliable personal prediction for this diet. Review

Everyday practicality and food quality

The trial supplied walnuts, green tea and Mankai free of charge and monitored lunch consumption in a closed workplace setting. How consistently people can follow the diet outside that setting will vary. The composition of green tea also varies: catechin content depends on the product and preparation. Walnut storage can affect polyphenols as compounds change during oxidation. Mankai’s availability differs by region. Other leafy greens fit a Mediterranean diet too, but an equivalent effect to the study product has not been established.

Connecting biomarkers with long-term metabolic health

The trial suggests that changes in fat distribution and metabolism can be informative beyond the number on the scale. These markers are not, however, a direct measurement of future life expectancy.

HOMA-IR and fasting insulin were studied as research markers. Improvements may indicate a more favorable metabolic profile. They are not a routine test package everyone needs in order to follow Mediterranean eating principles.

LDL cholesterol and other blood lipids can be monitored when there is a relevant medical question. The studies discussed here do not establish a specific effect on ApoB or Lp(a) that would justify additional testing for everyone.

Inflammation markers were also examined. These lab values can fluctuate for many reasons; a change does not, on its own, show that the diet prevents brain inflammation or future disease.

Liver blood tests may be part of follow-up for established fatty liver disease. Normal or falling enzyme levels do not reliably exclude significant liver disease. Liver-fat loss measured by imaging must be distinguished from evidence of improved liver function or prevention of cirrhosis.

Imaging measures such as the hippocampal occupancy score and lateral ventricle volume are related to cognitive trajectories. They are not routinely measured in clinical practice for this purpose. The green Mediterranean diet’s effects on these structural markers suggest potential for supporting cognitive health over the longer term, while longer follow-up is needed to establish functional benefits.

Appropriate follow-up depends on existing conditions and treatment. Healthy people do not need regular brain MRIs or an extensive metabolic panel to eat more vegetables, nuts and legumes.

Frequently asked questions

How does the green Mediterranean diet differ from the usual Mediterranean diet?

Both Mediterranean groups in the trial received walnuts. Only the green group received additional tea and Mankai and was asked to reduce red and processed meat more strongly. The estimated additional 800 mg of polyphenols came from tea and Mankai. Researchers studied a package that included physical activity, not an isolated polyphenol dose.

Can I follow a green Mediterranean diet without Mankai duckweed?

You can follow the general idea of a plant-rich Mediterranean diet without Mankai, using leafy greens, legumes, nuts and suitable protein sources. These foods do not need to reproduce Mankai’s chemical composition. Whether a particular substitute produces the same trial results has not been tested.

How much green tea do I need to drink for metabolic benefits?

The trial specified 3–4 cups of green tea a day. That is a study amount, not a necessary minimum dose for a health benefit. Catechin and caffeine content vary with the product and preparation. The trial does not support switching to concentrated extracts or seeking the highest possible dose.

Can the green Mediterranean diet help without weight loss?

Some differences, particularly in liver fat, remained after statistical adjustment for weight loss. This suggests that the composition of the diet may play a role. It does not prove that all observed benefits occur independently of weight loss or calorie restriction.

How long does it take to see results?

The analyses discussed here examined outcomes at six and 18 months, among other time points. They do not provide a reliable individual timetable for changes within a few weeks. An eating pattern you can sustain is more useful than expecting particular lab or MRI results quickly.

Do I have to give up meat?

The green version strongly restricted red and processed meat and replaced some animal protein with plants. The trial does not show that complete avoidance alone explains its results. You can draw on its approach by emphasizing vegetables, legumes, whole grains and nuts, while choosing the rest of your protein sources to suit your needs.

Which biomarkers improve the most?

The trial found more favorable results in selected fat deposits and metabolic markers. A particularly notable finding was the relative liver-fat reduction of 38.9%, compared with 19.6% in the conventional Mediterranean group. Not every marker improved equally, or clearly more than in every comparison group. Study

How can I put the diet into practice without Mankai duckweed?

Other leafy greens, legumes, nuts and whole grains can form a plant-rich Mediterranean diet. There is no evidence, however, that walnuts and tea alone were the two decisive components. You do not need to calculate a daily polyphenol total of 1,240 mg; whether a replacement plan is equivalent to the trial protocol remains an open question.

Sources and bibliography from the original article

• Zelicha H, Kloting N, Kaplan A, Yaskolka Meir A, Rinott E, Tsaban G, Chassidim Y, Bluher M, Ceglarek U, Isermann B, Stumvoll M, Quayson RN, von Bergen M, Engelmann B, Rolle-Kampczyk UE, Haange SB, Tuohy KM, Diotallevi C, Shelef I, … Shai I (2022). The effect of high-polyphenol Mediterranean diet on visceral adiposity: the DIRECT PLUS randomized controlled trial. BMC medicine, 20(1), 327. https://doi.org/10.1186/s12916-022-02525-8 Source

• Yaskolka Meir A, Rinott E, Tsaban G, Zelicha H, Kaplan A, Rosen P, Shelef I, Youngster I, Shalev A, Blüher M, Ceglarek U, Stumvoll M, Tuohy K, Diotallevi C, Vrhovsek U, Hu F, Stampfer M, Shai I (2021). Effect of green-Mediterranean diet on intrahepatic fat: the DIRECT PLUS randomised controlled trial. Gut, 70(11), 2085-2095. https://doi.org/10.1136/gutjnl-2020-323106 Source

• Kaplan A, Zelicha H, Yaskolka Meir A, Rinott E, Tsaban G, Levakov G, Prager O, Salti M, Yovell Y, Ofer J, Huhn S, Beyer F, Witte V, Villringer A, Meiran N, B Emesh T, Kovacs P, von Bergen M, Ceglarek U, … Shai I (2022). The effect of a high-polyphenol Mediterranean diet (Green-MED) combined with physical activity on age-related brain atrophy: the Dietary Intervention Randomized Controlled Trial Polyphenols Unprocessed Study (DIRECT PLUS). The American journal of clinical nutrition, 115(5), 1270-1281. https://doi.org/10.1093/ajcn/nqac001 Source

• Singh A, D’Amico D, Andreux PA, Dunngalvin G, Kern T, Blanco-Bose W, Auwerx J, Aebischer P, Rinsch C (2022). Direct supplementation with Urolithin A overcomes limitations of dietary exposure and gut microbiome variability in healthy adults to achieve consistent levels across the population. European journal of clinical nutrition, 76(2), 297-308. https://doi.org/10.1038/s41430-021-00950-1 Source

• Fote GM, Geller NR, Reyes-Ortiz AM, Thompson LM, Steffan JS, Grill JD (2021). A Scoping Review of Dietary Factors Conferring Risk or Protection for Cognitive Decline in APOE ε4 Carriers. The journal of nutrition, health & aging, 25(10), 1167-1178. https://doi.org/10.1007/s12603-021-1705-4 Source

Origin and editorial review

Translated and adapted for Nutrient Desk from the original article. Promotional membership, newsletter and laboratory offers have been removed. The bibliography is retained in its original form so the sources can be identified accurately. Figures and source attributions were checked within the documented editorial scope. Remaining limitations are recorded in the evidence report. Clinical review remains pending.