Dr Karan Rajan

The Mediterranean diet does indeed have the strongest and most consistent evidence of all diets when it comes to longevity, cardiovascular disease and cognitive health. However, claiming it produces "the best outcomes in terms of general and metabolic health" goes beyond what the research actually demonstrates: the evidence centres on cardiovascular disease, mortality and brain health, and comes largely from observational studies in which cause and effect cannot be fully separated. The claim also gives the impression that this diet wins on every health front, whereas for specific outcomes such as metabolic health the comparison with other dietary patterns has been less thoroughly investigated.

Multiple responses indicate that LDL plays a role in cardiovascular risk, but the full picture, including triglycerides, HDL and lipoprotein(a), determines that risk. The claim points in the right direction: elevated LDL is associated with a higher risk of cardiovascular disease. However, it goes slightly too far by singling out LDL alone, because other lipid factors each play an independent role. Moreover, the claim makes no distinction between mildly and substantially elevated LDL, whereas the overall risk profile is what determines how concerning a particular value actually is.

There are promising signals that GLP-1 receptor agonists may have beneficial effects on the brain, but a statistically significant reduction in dementia risk has not yet been demonstrated in randomised trials. The available evidence comes from early and small-scale research, and it is too soon to act on it. The direction of the claim is plausible, but the certainty implied by 'statistically significant' is not currently supported.

Multiple reviews consistently show that 1.2 to 1.6 grams of protein per kilogram of body weight per day is well supported for maintaining muscle mass in people who do strength training. The claim is therefore correct in terms of the range. However, it goes somewhat beyond what the evidence shows: the studies support this amount primarily for maintaining muscle mass, and maximizing muscle growth is a stronger claim than what the research actually demonstrates. Moreover, protein alone is considerably less effective; the combination with strength training is a prerequisite that the claim does not mention.

Several large population studies consistently show that eating more fibre is associated with a lower risk of colorectal cancer, and that association is well supported by biological explanations. The direction of the claim is therefore correct. However, the specific figure of a 10% reduction in risk per 10 grams of additional fibre per day cannot be firmly established on the basis of available research, and the precise amount of 10 grams as a threshold value is equally unsupported. The claim is therefore more specific than the evidence justifies.

Several studies suggest that older adults need more protein than the standard guideline of 0.8 grams per kilogram per day, due to a reduced sensitivity to protein. For healthy older adults, 1.0 to 1.2 grams per kilogram per day is a reasonably well-supported lower threshold for counteracting age-related muscle loss. The evidence for this is of moderate strength, but the direction is consistent. Combining this with strength training makes the effect considerably greater.

Research consistently shows that regular exercise is linked to a lower risk of colorectal cancer, and that falls within a broader range of 10 to 42 percent risk reduction across multiple types of cancer. The specific figure of 29 percent for colorectal cancer is not firmly established in the available evidence, so the direction is correct but that precise percentage cannot be substantiated. The protective effect of physical activity on bowel health is biologically well explained, in part through a beneficial effect on the gut microbiome.