Which diet label wins?

In 200,000 adults followed for over two decades, a plant-based diet heavy in refined grains, potatoes, and sweetened drinks carried 32% higher coronary heart disease risk, while one built on whole grains, vegetables, nuts, and legumes carried 25% lower risk. Both count as "plant-based" [4]. The same split runs through every camp: the pattern name tells you what someone excludes, not what they actually eat.

Across 86 cross-sectional and 10 prospective studies, vegetarians had about 25% lower death from ischemic heart disease and 8% lower cancer incidence, but no significant advantage in all-cause mortality [1]. The sharpest test is EPIC-Oxford, which recruited health-conscious meat eaters as the comparison group: there, vegetarians and omnivores died at the same rate [2].

In the Adventist Health Study-2, following 73,000 adults, pesco-vegetarians had the lowest all-cause mortality of any group: 19% below omnivores, ahead of vegans at 15% and lacto-ovo vegetarians at 9% [5]. A mostly-plant diet plus fish also describes the traditional diets of most of the longest-lived populations studied.

Vegans did well on mortality in Adventist data [5], but the diet has documented failure modes. B12 exists only in animal foods and fortified products, and deficiency rates among unsupplemented vegans are high in every population studied [7]. In EPIC-Oxford, vegans had 43% more total fractures and more than double the hip-fracture rate, largely tracking low calcium and protein intake [3].

The omnivore average in cohort studies is dragged down by its processed tail. Remove that tail and omnivores match the plant camps: EPIC-Oxford's health-conscious meat eaters equalled vegetarians [2], and in the PREDIMED trial a Mediterranean diet including fish, poultry, and dairy cut major cardiovascular events by about 30% against a low-fat control [9].

Processed meat is classified as a Group 1 carcinogen, with each daily 50g portion (roughly two slices of bacon) linked to 18% higher colorectal cancer risk [6]. In pooled US cohorts, higher processed meat intake was associated with more cardiovascular disease and earlier death [10]. Unprocessed red meat carries a smaller signal; processed is the clear problem.

There are no cohort or trial data following all-meat eaters for years; the best available is a self-selected survey reporting short-term satisfaction, with no mortality follow-up [11]. The nearest studied pattern is an animal-based low-carb diet, and in 25 years of follow-up it was associated with higher all-cause mortality, while the plant-based low-carb version was associated with lower [8]. An all-meat diet also removes fiber entirely, and every 8g of daily fiber tracks with 5 to 27% lower mortality and disease risk [12].

Modeling of the global cohort data puts the biggest life-expectancy gains not in avoiding meat but in adding foods: legumes, whole grains, and nuts top the list, worth up to 10 years if the shift starts in early adulthood [13]. Every one of those foods is available to every camp; the camps differ mainly in how easy they make the additions.