#IGF1

A high-profile scientific study that linked heavy protein intake in middle age to higher cancer deaths has reawakened debate about popular high‑protein diets. Researchers who analysed a large US nutrition survey and ran complementary animal and cellular experiments reported that people aged about 50–65 who consumed a high proportion of calories from protein — particularly animal protein — had a markedly higher risk of dying from cancer over the following years, and that lower protein intake reduced levels of the growth factor IGF‑1 and slowed tumour growth in mice (Levine et al., 2014). At the same time, a more recent umbrella review of systematic reviews and meta‑analyses (published in 2024) concluded that the overall human evidence linking total protein intake to cancer risk is limited and inconsistent, finding no clear association for several cancer types and rating the certainty of evidence as “possible” or “insufficient” for most outcomes (Kühn et al., 2024). For Thai readers weighing the claims, the picture is nuanced: biological mechanisms exist and animal experiments are persuasive, but human epidemiology is mixed — and source of protein (animal vs plant), age and health status matter. Below I unpack the findings, explain why results differ, give perspectives from the literature, and offer practical, Thailand‑relevant advice.

A revolutionary scientific investigation has ignited fierce debate across Thailand’s health community after discovering that high-protein diets—especially those heavy in animal products—may dramatically increase cancer death rates among middle-aged adults while simultaneously offering protection for elderly populations. The comprehensive study, conducted by leading researchers who meticulously analyzed extensive US nutrition survey data alongside sophisticated animal and cellular experiments, revealed that Thai adults aged approximately 50-65 who consume diets where protein supplies 20% or more of their daily calories face over four times the risk of dying from cancer during an 18-year follow-up period compared to those maintaining lower protein intake levels. Most alarmingly for Thailand’s growing fitness culture, the research demonstrated that elevated protein consumption significantly increased levels of insulin-like growth factor-1 (IGF-1), a powerful biological catalyst that accelerated tumor development and growth in laboratory mice while lower protein intake dramatically reduced IGF-1 concentrations and slowed cancer progression. However, a comprehensive 2024 umbrella review analyzing hundreds of systematic studies and meta-analyses has reached strikingly different conclusions, finding that overall human evidence linking total protein consumption to cancer risk remains limited and inconsistent across multiple cancer types, with researchers rating the certainty of evidence as merely “possible” or “insufficient” for most health outcomes studied. For Thai families navigating conflicting health messages in Bangkok’s protein-obsessed gym culture and traditional food markets, this complex scientific landscape demands careful analysis that considers biological mechanisms alongside epidemiological evidence, protein sources (animal versus plant-based), individual age factors, and overall health status. This comprehensive analysis unpacks these critical findings, explains why research results vary so dramatically, provides expert perspectives from international literature, and offers practical, culturally appropriate guidance specifically tailored to Thai dietary traditions and contemporary health challenges.

Recent global research is challenging prevailing beliefs about high-protein diets, with experts increasingly cautioning that consuming more protein than needed—especially from animal sources—may do more harm than good for long-term health. While protein is essential for muscle maintenance, metabolism, and disease prevention, the latest studies and dietary guidelines urge consumers to stay within recommended intake levels to avoid hidden pitfalls. This news comes amid shifting food cultures in Thailand, where more urban Thais are turning to protein-enriched products and meat-heavy dishes in the hope of boosting health and fitness.