Nutrition Foundations.

The PREDIMED trial (n=7,447) found about 30% fewer major cardiovascular events with a Mediterranean diet supplemented with extra-virgin olive oil or nuts than with a low-fat control diet.

As studied: the olive oil arm received about 1 liter of extra-virgin olive oil a week and the nut arm 30 g of mixed nuts a day, with dietary counseling in both arms. The trial did not test seed oils.

Graded B on its own record: a pooled analysis of 28 randomized trials of psyllium, at a median of about 10 g a day, found LDL-C Low-density lipoprotein cholesterol, the cholesterol fraction most closely tied to plaque in the arteries. about 0.33 mmol/L lower, with non-HDL cholesterol and apolipoprotein B also lower. LDL-C is a surrogate endpoint A lab value or measurement used in place of the outcome that matters, such as LDL cholesterol standing in for heart attacks. Moving a surrogate does not always move the outcome., and no psyllium trial has tested heart attacks or deaths, which is why the letter is B and not A.

Ratio figures such as 4:1 are widely published. No randomized trial cited on EBL tests a ratio, so this entry carries no letter. The trials that tested seed oils directly, summarized on the myths page, did not find that they raised inflammation.

The graded record covers muscle: pooled randomized trials in healthy adults found that higher protein intake increased lean body mass, and with resistance training, strength. The letter is for muscle mass and function. It is not a grade for glucose control.

In the 10-hour trial cited below, adults with metabolic syndrome lost weight and had lower blood pressure and atherogenic lipids. When a randomized trial compared an eating window with the same calorie cut without one, Liu et al. (N Engl J Med, 2022; PMID PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed. 35443107), weight loss did not differ, which is part of why the letter is C.

In a 6-month randomized trial, 47 overweight adults drank a liter a day of sugar-sweetened cola, milk, diet cola or water. Compared with the other three drinks, the sugared cola more than doubled liver fat and raised visceral fat and blood triglycerides. The trial measured stored fat and lipids, not glucose control, and it did not test refined carbohydrates in food. One small trial is not graded.

In a small randomized crossover A trial design in which each participant receives both the treatment and the comparison, one after the other, and serves as their own control. trial, 12 healthy adults took 400 mg of caffeine or a placebo An inactive substitute made to look like the real treatment, so participants cannot tell which one they received. at bedtime, 3 hours before or 6 hours before. Even at 6 hours, caffeine shortened sleep measured at home by more than an hour. One small trial is not graded, and it tested one dose, not a cutoff time.

A 2025 meta-analysis of sleep-laboratory studies in healthy adults found that alcohol reduced REM sleep, with larger effects at higher doses.

In a small randomized crossover trial, 20 healthy adults ate the same dinner at 6 p.m. or 10 p.m. and went to bed at 11 p.m. in a sleep laboratory. After the late dinner, overnight glucose ran higher and less dietary fat was burned. Sleep architecture did not differ. One small trial of a single meal is not graded, and it tested two dinner times, not a cutoff.

In an inpatient randomized trial, 20 adults ate an ultra-processed diet and an unprocessed diet for 2 weeks each, offered as much food as they wanted. On the ultra-processed diet they ate about 500 more calories a day and gained weight. Large cohort studies An observational study that follows a group of people over time and compares what happens to them. link ultra-processed food to higher mortality, but observational Research that watches what people already do rather than assigning a treatment. It can show that two things travel together, not that one causes the other. data does not carry a grade on EBL.

No trial on EBL tests polyphenol-rich foods themselves. The largest polyphenol trial tested a cocoa extract supplement: in COSMOS, 21,442 older adults took 500 mg of cocoa flavanols a day or a placebo for a median 3.6 years, and total cardiovascular events were not significantly lower. Cardiovascular deaths were lower, a secondary outcome. This entry carries no letter.

Diet comes first in EBL's method; supplements address the gaps diet does not close.