Discover what case-control studies say about plant-based diets.

This large, case-control study with 15,152 heart attack cases and 14,820 healthy controls from 52 countries found that several factors significantly affected the risk of heart attack. Smoking increased the risk by 187% (odds ratio [OR] 2.87), while eating fruits and vegetables daily lowered the risk by 30% (OR 0.70). Hypertension raised the risk by 91% (OR 1.91), diabetes by 137% (OR 2.37), and abdominal obesity by 12% for the highest vs. lowest tertile (OR 1.12). These findings highlight that smoking, inadequate fruit and vegetable consumption, and conditions like hypertension, diabetes, and obesity are major contributors to heart attack risk worldwide. PubMed

This case-control study examined the relationship between insulin resistance (IR) and two dietary patterns—vegetarian and non-vegetarian (Western) diets—among 202 normal weight adults (95 vegetarians and 107 non-vegetarians). The results showed that vegetarians had significantly lower glucose, insulin, and IR (HOMA) values compared to non-vegetarians. Specifically, glucose levels were 5.1% lower in vegetarians (4.47 vs. 4.71 mmol/l), insulin levels were 32.4% lower (4.96 vs. 7.32 mU/l), and IR values were 37.7% lower (0.99 vs. 1.59). Vegetarians consumed more whole grains, pulses, and foods from oat and barley, contributing to these lower IR values. The study suggests that a long-term vegetarian diet may provide age-independent protection against insulin resistance, potentially lowering the risk of metabolic syndrome, diabetes, and cardiovascular disease.. PubMed

This case-control study examined the relationship between plant-based diets and breast cancer (BC) risk in Iranian women . Researchers analyzed dietary patterns in 350 women with newly diagnosed BC and 700 healthy controls, assessing adherence to an overall plant-based diet (PDI), a healthy plant-based diet (hPDI), and an unhealthy plant-based diet (uPDI). A greater adherence to PDI was linked to a 67% lower risk of BC (OR 0.33, 95% CI 0.22-0.50), showing the strongest inverse association. Women with high adherence to hPDI had a 36% lower risk (OR 0.64, 95% CI 0.43-0.94), while those consuming more unhealthy plant-based foods (uPDI) had a 2.23 times greater BC risk (OR 2.23, 95% CI 1.48-3.36). These findings suggest that reducing animal foods alone may offer significant protection against breast cancer, but consuming low-quality (i.e. processed/junk food) plant-based foods increases BC risk. PubMed

A case-control study of 2,799 colorectal cancer patients and 2,799 matched controls in China found that adherence to a healthy plant-based diet (hPDI) was strongly linked to a lower risk of colorectal cancer. Those with the highest adherence to an overall plant-based diet (PDI) had a 21% lower risk, while those following a healthy plant-based diet had a 55% lower risk compared to those with the lowest adherence. In contrast, individuals consuming more unhealthy plant-based foods (uPDI) had a 45% higher risk of colorectal cancer. These findings suggest that while plant-based diets can reduce colorectal cancer risk, the quality of plant foods matters—whole, nutrient-dense plant foods are protective, while processed plant foods may increase risk. PubMed

A case-control study of 128 glioma patients and 256 hospital-based controls found that adherence to a healthy plant-based diet (hPDI) was linked to a significantly lower risk of glioma, a common type of brain tumor. Individuals with the highest adherence to an overall plant-based diet (PDI) had a 69% lower likelihood of glioma, while those following a healthy plant-based diet had a 71% lower risk compared to those with the lowest adherence. In contrast, a diet high in unhealthy plant-based foods (uPDI) was associated with a 2.85 times higher risk of glioma. These findings suggest that a diet rich in whole, healthy plant foods may help protect against glioma, while processed plant foods may increase risk. PubMed

This multi-center case-control study included 3,684 stroke patients and 3,684 matched controls from Nigeria and Ghana to examine the link between diet and stroke risk. Researchers found strong links between diet and stroke risk. Eating more vegetables was associated with a 55% lower stroke risk, while whole grains and fruit drinks lowered risk by 19%, and fruits by 15%. In contrast, consuming more poultry and organ meats increased stroke risk by 74%, red meat by 51%, and fried foods and sweetened drinks by 21%. These findings highlight the benefits of a plant-based diet for reducing stroke risk. PubMed

This case-control study conducted in Iran investigated the relationship between adherence to the EAT-Lancet Reference Diet (ELD) (a plant-based diet) and the risk and severity of premature coronary artery disease (PCAD). The ELD is a globally sustainable dietary pattern proposed by the EAT-Lancet Commission, which emphasizes plant-based foods such as vegetables, fruits, whole grains, and legumes, while limiting animal-based foods, processed foods, and sugar. The study involved 3,185 participants, including 2,033 cases with severe coronary artery disease and 1,152 healthy controls. Results showed that individuals in the highest quartile of adherence to the ELD had a 78% lower risk of severe PCAD(OR 0.29, 95% CI: 0.21–0.39). An inverse association was found between higher adherence to the ELD and lower risk and severity of PCAD, suggesting that a plant-based, sustainable diet could offer significant protection against heart disease. PubMed