The Maasai and Kikuyu study shows a whole-food meat diet beats a whole-food plant diet
The study compared two specific 1920s diets, not 'plant-based' against 'meat-based' in general. The Kikuyu ate a narrow, cereal-heavy diet short on calcium, with no B12 source, and the authors themselves blamed specific gaps that a planned plant diet fills today. Two groups that differ in food, land, disease and way of life cannot show what diet alone does.
Theory has to answer to observation. Here were two neighbouring, closely related peoples eating mostly whole foods: one largely on grains and plants, the other on milk, meat and blood. The meat-eaters were taller, heavier, stronger and had far less anaemia, tooth decay and bone deformity. It is not a trial, but it covered thousands of people, and a result that large should make us question confident claims that plant diets are just as good.
The study is Orr and Gilks' 1931 report for the Medical Research Council, and it does not compare what the claim says it compares. The Kikuyu diet it describes was mostly maize, millet and sweet potato. It was monotonous, low in calcium, and had no reliable source of B12, because B12 supplements and fortified foods did not exist. That is not a model of a modern whole-food plant-based diet, which is built around pulses, soya, varied grains, greens, nuts and seeds, with B12 supplemented. The authors did not conclude that meat was the missing ingredient. They pointed to specific deficiencies, calcium above all, and suggested fixing them. The passage notes that Kikuyu women, who ate more leafy greens, did better than Kikuyu men. That points the same way: the problem was what was missing from a narrow diet, not the absence of animals.
The design also cannot isolate diet. These were two peoples with different economies, workloads, terrain, food security and exposure to disease, observed in colonial Kenya almost a century ago. The speaker concedes that nothing was controlled. Height, strength, anaemia and tooth decay all respond to total calories, parasites, infection and childhood food supply, as well as to what the food is. Pairing two populations and attributing every difference to meat is the step the data cannot support.
The question has also been studied far more directly since. Large cohorts of people eating well-planned vegan and vegetarian diets in high-income countries do not show the pattern of deficiency the Kikuyu did. The major dietetic associations judge such diets adequate at every life stage. A single comparison from the 1920s does not outweigh that.
It is fair to take one lesson from it. A plant diet that is narrow, short on calories and missing key nutrients will harm people. That is an argument for planning, which nobody disputes. It is not evidence that eating animals is necessary.
Treating two things as comparable when the differences that matter to the argument are large.
How it applies here: Treats the 1920s Kikuyu diet, a narrow cereal diet low in calcium with no B12 source, as though it stood for 'a whole food plant-based diet' in general. The differences between that diet and a planned modern one are exactly the ones the study's authors blamed for the poor outcomes.
Drawing a general conclusion from a sample too small or too unrepresentative to support it.
How it applies here: Draws a general conclusion about plant versus meat diets from one uncontrolled comparison of two populations. Those populations also differed in environment, way of life, food security and disease exposure, so the sample cannot isolate diet.