TL;DR: In adults aged 60 and older, eight weeks on either a pulse-protein diet or a lean-pork-protein diet built to match the Dietary Guidelines for Americans improved blood-sugar and lipid markers, while the pulse version lowered the visceral-to-total-fat ratio more and raised ferritin more.

A direct test of protein source inside a healthy eating pattern

The question was whether the main protein food matters when the rest of the diet already meets national guidance.

According to Clinical Nutrition ESPEN, investigators created two versions of a high-quality eating pattern aligned with the Dietary Guidelines for Americans, known as the DGA.

One version centered on pulses, called the pulse-protein diet or PPD. The other centered on meat, called the meat-protein diet or MPD.

Both versions were designed to study cardiometabolic and iron-related measures described as relevant to aging in later life, according to the Nutrition Evidence Database summary of the work.

The background idea was that eating patterns built around pulses supply relatively little methionine, and limits on that amino acid have been connected in prior work with better metabolic health and longer life, according to Clinical Nutrition ESPEN.

The investigators therefore compared the pulse-protein and meat-protein approaches head to head, rather than comparing a healthy diet with an ordinary diet.

The report identifies the project as Protein-Distinct Macronutrient-Equivalent Diet 1, or PRODMED1.

The authors are listed as Bruna O de Vargas, Saba Vaezi, Lee Weidauer, Wade M Sanders and Moul Dey.

Their affiliations are given as the School of Health and Human Sciences at South Dakota State University in Brookings and the CLASS Laboratory in the Department of Epidemiology at the University of Michigan School of Public Health in Ann Arbor.

Funding is listed as coming from the National Institute of Food and Agriculture.

The paper appeared in Clinical Nutrition ESPEN with publication dating of May 19, 2026.

How the two feeding periods were constructed

Each participant was asked to follow both diets in turn.

According to the Nutrition Evidence Database, participants consumed the meat-protein diet and the pulse-protein diet for eight weeks each.

The two eight-week feeding periods were separated by a washout interval of at least two weeks, according to Clinical Nutrition ESPEN.

The daily amount of the featured protein food was specified. The meat-protein diet supplied 162 grams per day of lean pork, while the pulse-protein diet supplied 331.6 grams per day of pulses, according to the Nutrition Evidence Database.

Those featured foods were not small additions. They supplied at least 45% of total dietary protein in each period, according to Clinical Nutrition ESPEN.

The two menus were built to be equivalent in overall energy, macronutrients and total iron.

They were intentionally different in heme iron and methionine, according to the Nutrition Evidence Database.

That design let researchers separate the effect of protein source from differences in calories, major nutrients or total iron intake.

The analysis used robust linear mixed-effects models with adjustment for covariates, according to Clinical Nutrition ESPEN.

Who completed the crossover

The trial enrolled Midwestern adults aged 60 years or older.

Forty-seven people finished both feeding periods, according to the Nutrition Evidence Database.

Seventy-two percent of those completing the trial were women.

The mean age was 69.2 years with a standard deviation of 6.6 years, according to the Nutrition Evidence Database.

Mean body mass index at entry was 28.6 kilograms per square meter with a standard deviation of 5.4, according to the same summary.

The crossover structure meant that the same older adults experienced both the lean-pork period and the pulse period, with a washout between them.

What improved no matter which protein was emphasized

The prespecified primary outcomes were ferritin, fasting blood glucose and trimethylamine N-oxide, known as TMAO.

Secondary outcomes included inflammation, body composition, lipid-related cardiovascular-risk markers and circulating biogenic amines, according to Clinical Nutrition ESPEN.

Across both diet periods, markers of glucose and lipid metabolism improved, with the exception of high-density lipoprotein, according to the Nutrition Evidence Database.

Each of those improvements reached the p-less-than-0.05 threshold within diets, with no significant difference between diets, according to the same source.

In other words, the pulse-protein and meat-protein versions produced similar changes in those blood-sugar and lipid measures.

Inflammation measured by C-reactive protein, or CRP, also fell during both diets, according to Clinical Nutrition ESPEN.

The decline in CRP reached p-less-than-or-equal-to-0.001 in both groups, again with no significant difference between diets, according to the Nutrition Evidence Database.

Total fat mass and visceral fat mass declined during the trial, according to Clinical Nutrition ESPEN.

Those declines reached p-less-than-0.0001, with no significant difference between diets for the absolute losses, according to the Nutrition Evidence Database.

The authors concluded that high-quality diets aligned with the Dietary Guidelines for Americans improved cardiovascular risk factors regardless of the primary protein source, according to Clinical Nutrition ESPEN.

They interpreted that pattern as underlining the importance of overall dietary-matrix quality, rather than protein source alone.

Where the pulse period showed an extra change

Two between-diet differences favored the pulse-protein period.

The ratio of visceral fat to total fat fell more during the pulse-protein diet than during the meat-protein diet, according to the Nutrition Evidence Database.

That between-diet contrast reached p-less-than-0.05, even though the absolute losses of total and visceral fat did not differ significantly between diets.

Ferritin rose more during the pulse-protein diet than during the meat-protein diet, according to Clinical Nutrition ESPEN.

The reported mean increases were 15.7 nanograms per milliliter during the pulse-protein diet and 7.0 nanograms per milliliter during the meat-protein diet.

The between-diet comparison for ferritin reached p-equal-to-0.027, according to the Nutrition Evidence Database.

That result is notable because the menus were matched for total iron and differed in heme iron, with pulses generally supplying non-heme iron rather than the heme form found in meat.

The trial also found that the two diets produced distinct circulating biogenic-amine profiles, according to Clinical Nutrition ESPEN.

That overall profile difference reached p-equal-to-0.001, according to the Nutrition Evidence Database.

The authors concluded that the pulse-based diet conferred added benefits for the visceral-to-total-fat ratio and iron status, according to Clinical Nutrition ESPEN.

They described pulses as a feasible, nutrient-dense and effective dietary strategy with potential relevance for healthspan in aging populations.

What stayed the same

TMAO, one of the three primary outcomes, remained unchanged across the diets, according to the Nutrition Evidence Database.

That stability occurred while glucose and lipid markers improved and CRP declined.

HDL was the lipid-related exception singled out as not improving alongside the other glucose and lipid markers, according to Clinical Nutrition ESPEN.

The absence of a between-diet difference for glucose and lipid markers, CRP and absolute fat-mass losses means those benefits were shared rather than unique to either menu.

Why pulses are back in the protein conversation

Pulses are the dry edible seeds of legumes, a group that includes dry beans, lentils, chickpeas and dry peas, according to Tim McGreevy, CEO of USA Pulses, as reported by NPR.

McGreevy leads the trade group for the pulse-crop industry, according to NPR reporting published May 18, 2026.

NPR reported that one-half cup of cooked kidney, navy, cannellini or black beans supplies around 8 grams of protein.

NPR also reported that beans supply abundant fiber, a nutrient that many American adults under-consume.

A separate systematic review and dose-response meta-analysis published May 14, 2026 in the Journal of the American Heart Association examined whole dietary pulses and lipid targets across 38 trials with 2,095 participants.

That analysis reported a median trial length of six weeks and a median dose of 130 grams per day, with reductions in low-density-lipoprotein cholesterol, non-high-density-lipoprotein cholesterol and apolipoprotein B.

The PRODMED1 trial differs from that literature because it used a controlled feeding crossover in adults 60 and older, matched calories and macronutrients, and tracked iron, glycemic, fat-distribution and amine outcomes together.

NPR reported that the Trump administration updated the Dietary Guidelines for Americans in January and moved beans, peas and lentils from the vegetable category to the protein category.

More than 130 physicians had urged that change in a joint letter, saying it was long overdue and would help dispel the idea that plant proteins are incomplete or inadequate, according to NPR.

The 2025 Dietary Guidelines Advisory Committee had also recommended emphasizing beans, peas and lentils and reducing red and processed meat, according to NPR.

PRODMED1 did not test that policy shift directly, but it tested the nutritional question behind it: whether a guidelines-aligned pattern built around pulses can support cardiometabolic and iron measures in older adults as well as a guidelines-aligned pattern built around lean pork.

Reading the results for adults over 60

For an older adult, the central message is that overall pattern quality carried most of the measured benefit.

Both eight-week periods improved glucose and lipid markers except HDL, lowered CRP and reduced total and visceral fat, with no significant protein-source difference for those endpoints, according to the Nutrition Evidence Database.

The pulse-protein period added a larger improvement in the proportion of fat stored viscerally and a larger rise in ferritin, the iron-storage protein measured as a primary outcome.

The trial registration is listed as NCT05577858 on ClinicalTrials.gov, dated October 11, 2022, according to Clinical Nutrition ESPEN.

The trial was relatively small and short, with 47 completers and eight-week feeding periods separated by at least two weeks without the assigned diets.

The authors framed pulses as feasible and nutrient-dense within a DGA-aligned pattern, with potential relevance for promoting healthspan, rather than as a proven longevity treatment, according to Clinical Nutrition ESPEN.

For readers considering a change, the practical cue from the design is to keep energy, overall nutrients and guideline alignment steady while changing the leading protein contributor, rather than adding pulses on top of an unchanged diet.

Anyone managing iron deficiency, diabetes medication, lipid treatment or unintentional weight loss should discuss a protein switch with a clinician, because the trial reports group-level biomarker changes, not individualized treatment guidance.

Sources referenced