By integrating over 5,500 gut metagenomes from across the globe with biochemical and food composition databases, this team mapped how 775 dietary phytonutrients — flavonoids, isoflavones, polyphenols, carotenoids — are biotransformed by gut microbial enzymes. Approximately 70% of gut microbial enzymes are potentially involved in these transformations, and the activity varies enormously between individuals and across geographies. Machine learning models built on phytonutrient-modifying enzyme profiles could discriminate health status across multiple disease contexts.

Researchers at Weill Cornell Medicine identified a specific gene (bo-ansB) in Bacteroides ovatus that encodes an enzyme breaking down asparagine. When this gene is active, the bacterium consumes intestinal asparagine before it reaches the bloodstream, effectively starving tumors of a growth-promoting nutrient while simultaneously enabling stronger T-cell anticancer immunity.

Lactobacillus reuteri, a well-studied probiotic species, produces L-theanine — the same amino acid found in green tea associated with relaxation and cognitive focus. This microbially-produced L-theanine enhances the host’s ability to break down branched-chain amino acids (BCAAs), which are linked to insulin resistance and metabolic dysfunction when elevated.

This review synthesizes how microbial metabolites — short-chain fatty acids, bile acids, branched-chain amino acids, tryptophan catabolites, and imidazole propionate — mediate the effects of dietary, surgical, and pharmacological obesity interventions. It explains why identical weight management strategies produce different results in different individuals.

The gold-standard Cochrane review has weighed in: across 22 randomized controlled trials involving nearly 2,000 participants, intermittent fasting — including alternate-day fasting, periodic fasting, and time-restricted feeding — produced little to no clinically meaningful difference in weight loss or quality of life compared to conventional dietary advice.

When calorie intake was held constant, neither early (8 a.m.–4 p.m.) nor late (1 p.m.–9 p.m.) time-restricted eating improved insulin sensitivity, blood glucose, blood lipids, or inflammatory markers over two-week periods. However, late eating did shift circadian clocks by approximately 40 minutes. The researchers concluded that health benefits in prior TRE studies were likely attributable to unintended calorie reduction.

For the first time, the Dietary Guidelines for Americans explicitly name and discourage “highly processed foods,” moving beyond the vague language of previous editions. The guidelines emphasize minimally processed, nutrient-dense foods and specifically call out sugar-sweetened beverages and highly processed packaged products.

Three prominent physicians argue that the new guidelines still give undue prominence to meat, dairy, and saturated fat, contradicting the advisory committee’s own scientific report. They note that “poor diet — specifically a dietary pattern high in sodium, saturated fat, fried food, refined grains, animal protein, cholesterol, and added sugar — is the leading cause of death and disability in the US, surpassing tobacco and inactivity.”

Instead of trying to define all the characteristics of ultra-processed foods — a moving target that allows manufacturers to reformulate around classifications — the authors propose defining what ultra-processed foods are not. If a food product does not contain recognizable whole, minimally processed ingredients, treat it as ultra-processed.

Just three days of eating a refined, fiber-free diet impaired long-term emotional memory in aged (but not young) rats. The critical finding: this happened regardless of whether the diet was high in fat or sugar. The common factor was the absence of dietary fiber, which led to rapid depletion of butyrate — a short-chain fatty acid produced by gut bacteria from fiber — triggering mitochondrial dysfunction and neuroinflammation specifically in the amygdala’s microglia.

Higher intake of fiber, unsaturated fats, carotenoids, and key micronutrients (vitamins A and E, magnesium, potassium) was associated with better cognitive function and memory. Refined grains were negatively associated with cognitive performance. Taken together with the Butler et al. animal study above, the case for whole, fiber-rich, micronutrient-dense diets in aging populations is compelling.

In nearly 180,000 participants followed for over 12 years, higher adherence to the EAT-Lancet planetary health diet was consistently and inversely associated with chronic kidney disease risk across four different scoring methods (adjusted HR 0.91, 95% CI 0.88–0.94 using the Stubbendorff method).

This umbrella review — a review of reviews — synthesizes the strongest available evidence on the Mediterranean diet and cardiovascular outcomes. Fatal CVD risk reduction of 10–67% and non-fatal CVD risk reduction of 21–70% across multiple prior meta-analyses. The wide effect-size ranges reflect variation across study designs, but the direction of benefit is consistent and robust.