September 23, 2025, 10:54 am | Read time: 6 minutes
Men eat too much meat–and that should change! This premise was the basis of a recent study conducted over six weeks with 102 healthy men aged 21 to 61. It showed the positive effects of replacing part of their meat consumption with legumes.
Excessive consumption of red and processed meat (such as sausage or ham) is linked to an increased risk of cardiovascular diseases, certain cancers, and obesity.12 At the same time, many people do not consume enough health-promoting fiber–found in legumes, for example. The Planetary Health Diet, considered healthy and climate-friendly, recommends reducing meat consumption in favor of more plant-based protein sources like peas and beans. According to the diet’s guidelines, only 200 grams of meat per week is recommended.3
This prompted researchers from Finland to design their study. Since men tend to consume too much meat and too few legumes, they focused on them as the study group. The goal: to find out how a meat-reduced and legume-based diet affects the body.4
BeanMan Study
The BeanMan Study was a randomized controlled trial (RCT) with two groups over six weeks. A total of 102 healthy men aged 21 to 61 (average age was 38) participated. Participants were randomly divided into two groups:
- The Meat Group: Each person received 760 grams of red and processed meat weekly, accounting for 25 percent of their protein intake from meat.
- The Legume Group: Each person received 200 grams of meat weekly (the maximum of the Planetary Health Diet) and additional legume products with a protein content equivalent to 560 grams of meat. Here, 25 percent of the protein intake was divided into 5 percent from meat and 20 percent from legumes.
All participants otherwise adhered to their usual diet, except for the amounts of meat and legumes. The legume products were based on fava beans and peas and were delivered as frozen meals, spreads, or soups. Recipes were also provided. Consumption was documented through food logs and an app. Blood and urine samples, as well as body measurements, were taken at the beginning and end. Compliance was very high: Only one to two percent of the study foods were not consumed.
How Legumes Affected Men’s Nutrient Intake
In fact, the researchers were able to demonstrate a number of changes in the men in the Legume Group after just six weeks. The shift from meat to peas and beans had several positive effects on body and nutrient values.
Positive Effects
- In the Legume Group, total cholesterol in the blood decreased by an average of 0.25 mmol/l, and LDL (“bad cholesterol”) by 0.19 mmol/l. In the Meat Group, both values increased slightly.
- Fiber intake increased significantly in the Legume Group, and the proportion of healthy unsaturated fatty acids was higher in these participants than in the comparison group, while the intake of saturated fatty acids decreased.
- Additionally, the Legume Group lost an average of one kilogram over the six weeks, and their BMI decreased significantly. In contrast, the Meat Group showed little change in weight.
- There was no significant difference between the two study groups in blood sugar, insulin, or HOMA index (the latter is used to estimate insulin resistance).
Negative Effects
Other nutrient values were slightly negatively affected by the reduction of meat in favor of more legumes among the men studied.
This included vitamin B12 intake, which was 2.4 µg/d lower in the Legume Group, and the blood level of the sensitive vitamin B12 marker holoTC also decreased. Sixteen percent of participants fell below the threshold for a suboptimal status (compared to two percent in the Meat Group).
An also not optimal effect was observed in the iron level. Although the Legume Group consumed more iron, the ferritin level (stored iron) decreased slightly, but not to a deficiency level.
Iodine intake was similar in both groups, but urinary excretion was slightly lower in the Legume Group–indicating a somewhat reduced iodine availability.
Measurable Changes in a Short Time
The study’s biggest finding: Even a moderate reduction of meat to 200 grams per week–combined with increased legume consumption–can lead to measurable health improvements after just six weeks: from weight loss to better cholesterol levels to a healthier distribution of fatty acids. This is particularly relevant for men who currently consume significantly more meat than recommended–and were therefore the focus of the study.
At the same time, it also shows that the supply of certain micronutrients–especially vitamin B12–becomes critical with decreasing meat intake. Although vitamin B12 intake in this study remained above the recommended minimum, early signs of deficiency in the blood were already visible in some participants. Long-term effects on iodine and iron should not be underestimated either. It is surprising how quickly these nutrient changes appeared, less so that they occurred in general. It is known that people who eat (almost) no meat should pay attention to these nutrient values. However, there are a number of plant-based foods that can provide these nutrients–including special iodized salt.
Practically, this means that partially replacing meat with legumes is indeed advisable from a health perspective–as long as the selection of foods also ensures adequate supply of critical nutrients. For certain population groups (such as older adults or women with increased iron needs), monitoring could be particularly important.
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Study Assessment and Possible Limitations
The BeanMan Study impresses with its careful study design. Controlled randomized studies are the gold standard of research and have high validity. The high participation of the subjects is also a plus: No participant dropped out, and the dietary plans were very well adhered to. Particularly strong is the comprehensive evaluation–including biomarkers, urine analyses, and detailed food data.
As with most research, there are points in the BeanMan Study that limit the validity or generalizability of the results to all people. The participants were above-average healthy, highly educated, and health-conscious. Their eating habits–such as possibly already high fiber consumption–deviate from the population average. The study duration of only six weeks allows only statements about short-term effects. Long-term consequences–such as for vitamin B12 or iron–cannot be fully captured. The number of only 102 men also limits the validity. Further research should substantiate the effects in the male body–even then, similar health effects in women or children cannot be assumed.
Overall, however, the study provides a valuable contribution to the discussion on sustainable nutrition and shows that moderate meat reduction is both healthily feasible and nutritionally justifiable–at least in the short term.
Conclusion
Partially replacing meat with legumes–as recommended in the Planetary Health Diet–can lower cholesterol, reduce weight, and improve overall nutrition in healthy men after just six weeks. At the same time, critical nutrients like iron, iodine, and vitamin B12 remain in the sufficient range–though with trends that should be observed in the long term. For many men, consuming 200 to 350 grams of meat per week could be a realistic, healthy, and sustainable goal.