Major review challenges the idea that cutting saturated fat extends life for most

A major review published in the Annals of Internal Medicine found that cutting saturated fat did not reduce the risk of death for most adults over five years. The analysis pooled data from 17 trials, involving more than 66,000 participants, across studies lasting at least two years and comparing reduced saturated fat with various nutrient replacements such as polyunsaturated fats.

While lowering saturated fat did lead to significant reductions in total cholesterol and LDL cholesterol, the cholesterol changes did not consistently translate into fewer heart attacks or deaths among those at low baseline cardiovascular risk over the five-year span. Among individuals at higher baseline risk, researchers said reducing saturated fat probably conferred benefits for all-cause mortality and for non-fatal heart attack and stroke when fats were replaced with polyunsaturated fats rather than simply reduced. The authors added that more research is needed to understand the impact of replacing saturated fat with protein rather than carbohydrates to reflect modern diets more accurately.

Experts outside the study cautioned against assuming the findings should immediately shift national dietary guidelines. The analysis did not examine outcomes beyond five years, which limits how the results map onto long-term heart-disease risk models. Not all saturated fats act the same in the body, and the source matters: saturated fat from red and processed meat may have different effects from that found in fermented dairy products. Nutrition researchers urged a focus on foods and dietary patterns rather than nutrients alone when interpreting the findings.

Professor Nita Forouhi of the University of Cambridge, who was not involved in the study, said it would be premature to change existing dietary recommendations that aim to keep saturated fat below 10 percent of total energy intake. She noted that the analysis did not capture longer-term outcomes and that the effects may differ by food source. Professor Tom Sanders of King’s College London said population-wide dietary advice is designed to lower average cholesterol levels because this slows the progression of cardiovascular disease, a strategy that has coincided with a notable decline in LDL cholesterol over decades.

UK health guidance continues to emphasize replacing saturated fats with unsaturated fats and to limit saturated fat intake to below 10 percent of daily energy, with practical limits such as about 30 grams per day for men and 20 grams per day for women in many cases. The NHS also highlights the value of weekly oily fish, which provides heart-healthy omega-3 fats.

In a separate line of research summarized in the notes, volunteers consuming diets high in saturated fats showed adverse changes in health markers compared with those who ate similar calories from healthier fats such as nuts, salmon, and mackerel. Total and LDL cholesterol rose by around 10 percent in the saturated-fat group, while liver fat increased by roughly 20 percent; in contrast, those who consumed polyunsaturated fats saw LDL drop about 10 percent and improvements in energy reserves tied to heart health. These findings reinforce that the health effects of fats depend on their overall dietary context and the foods they come from, not merely the amount of saturated fat alone.

Overall, experts say the new synthesis underscores the complexity of nutrition science and the importance of dietary patterns. While cutting saturated fat can lower cholesterol in many people, its impact on mortality and major cardiovascular events may depend on baseline risk, the foods replaced, and the broader diet.