Tomato paste: Barcelona trial links daily intake to sharper attention and memory

A daily serving of concentrated tomato paste, eaten for three months, went hand in hand with better scores on attention tests and on recalling which names belong to which faces, according to a randomised clinical trial carried out by researchers at the University of Barcelona and published in the journal Antioxidants. The volunteers were healthy adults in midlife.

The improvements were small. The team also measured a borderline increase in a protein tied to brain cell growth. In a handful of participants who were scanned, the way certain brain networks communicate appeared to change. The authors suggest a single everyday food might help support thinking skills in middle age.

Why tomatoes

Plant-rich eating patterns such as the Mediterranean diet are often associated with a brain that ages better and with fewer cases of declining mental function. The tomato, a central ingredient of that diet, is people’s main food source of lycopene. This pigment is a carotenoid, part of a group of fat-soluble plant compounds responsible for the bright shades of many fruits and vegetables.

Of all carotenoids in food, lycopene stands out for neutralising unstable oxygen molecules, and it can cross the blood-brain barrier. Inside the brain it is believed to reduce inflammation and oxidative stress. Researchers also think it helps regulate brain-derived neurotrophic factor (BDNF), a protein that keeps existing neurons alive and encourages new ones to grow.

Human trials testing tomatoes on cognition have been rare. Most focused on older people and blended tomato extracts or lycopene with vitamins, herbs or berries, so the source of any benefit could not be pinned down.

42 volunteers completed the study

The research team, including Ricardo López-Solís, Marina Corrado and Rosa M. Lamuela-Raventós, recruited 47 non-smokers living around Barcelona, all aged 40 to 55, free of chronic disease and of cognitive impairment. Of these, 42 saw the trial through. Average age was about 47, women made up two-thirds of the sample, and nearly 93 percent had higher or postgraduate education.

Every participant followed both diets in turn, each lasting three months, with a one-month washout in between. During the tomato period, they added commercial paste containing nothing but tomatoes and salt to their meals each day, cooked or raw. The dose depended on weight, 0.5 grams per kilogram, averaging some 35 grams a day, or roughly two tablespoons, with 38.4 milligrams of lycopene.

For the control period, the menu excluded lycopene-rich foods: tomatoes, along with watermelon, papaya, pink grapefruit and guava, plus anything made from them. Participants received a booklet of paired recipes so the rest of their eating stayed similar. Food questionnaires and activity trackers worn on the wrist kept watch on diet, sleep, physical activity and body composition.

Blood tests and cognitive tasks

At the beginning and end of each period, fasting blood was drawn to measure lycopene and BDNF. Volunteers completed three standard tests. In one, they scanned rows of letters against the clock, marking only target letters, a measure of selective attention and how quickly they process visual information. Another asked them to recall 12 face-name pairs after 15 minutes, and a card-sorting game assessed executive function. Fourteen participants also had resting-state functional MRI scans.

Calories, sleep and exercise stayed unchanged throughout. In the control period, blood lycopene held steady at an average of 0.40 micromoles per litre. With the paste, it more than doubled from a starting level of 0.32. Using a lycopene threshold, the team concluded that 14 participants did not stick fully to the diet during one phase or both.