Does Protein Make You Smarter? What the Research Shows for IQ

Eating more protein does not make you smarter if you already get enough, and most adults in wealthy countries do. The strong evidence comes from the other end of the scale: babies who suffered severe protein-energy malnutrition scored about one standard deviation (roughly 15 IQ points) lower as adults, and a randomized protein-and-energy supplement in Guatemala raised adult reasoning scores by about a quarter of a standard deviation.

This page covers what those childhood malnutrition studies found, what happens when well-fed adults eat extra protein or take amino acid supplements, and what the large diet cohorts can and cannot tell us. It describes research and is not medical or dietary advice.

Protein supplies the amino acids the body uses to build tissue, including the enzymes and neurotransmitters in the brain. That fact sits behind much of the "protein for brainpower" marketing. The relevant question is whether people are short of it.

In the United States, they mostly are not. Berryman and colleagues analyzed national dietary survey data from 2001 to 2014 for almost 58,000 people. Average protein intake ranged from about 55 grams a day in toddlers to 88 grams a day in adults aged 19 to 30, and average intake relative to body weight was above the estimated requirement in every age, sex and ethnic group they examined. The main exceptions were small minorities, such as about 11% of adolescent girls and 13% of Black men aged 71 or older, whose intake fell below the average requirement.

This matters for interpreting every study below. A nutrient tends to affect thinking when someone is deficient in it. Adding more on top of an adequate diet is a different experiment, and it usually produces much smaller effects, if any. For the wider picture of what food can and cannot do, see our overview of whether diet or nutrition affects IQ.

The clearest link between protein and intelligence comes from children who did not get enough food in their first years of life.

• The Barbados Nutrition Study: Researchers led by Janina Galler have followed Barbadian children who were hospitalized for moderate to severe protein-energy malnutrition in their first year of life, then rehabilitated, along with a healthy comparison group. Waber and colleagues tested 77 of the previously malnourished adults and 59 controls at an average age of about 38. After adjusting for childhood socioeconomic factors, the malnourished group scored about one standard deviation lower on IQ, a gap that had been stable from adolescence through midlife. IQ scores below 70 were about nine times more common in the malnourished group, even though their physical growth had fully recovered.

• The Guatemala atole trial: From 1969 to 1977, the Institute of Nutrition of Central America and Panama offered two villages a drink called "atole" (163 kcal and 11.5 grams of protein per cup) and two villages a drink called "fresco" (59 kcal and no protein). Pollitt and colleagues found that adolescents and young adults from the atole villages scored higher on tests of knowledge, numeracy, reading and vocabulary. Maluccio and colleagues followed the participants into adulthood. Exposure to atole from birth to age three raised scores on Raven's Progressive Matrices, a nonverbal reasoning test, by about a quarter of a standard deviation. That is roughly 4 points if put on the IQ scale (0.25 × 15), and women in the atole villages completed about 1.2 more grades of school.

• The long view: When the Guatemalan participants were retested at ages 40 to 57, Ramírez-Luzuriaga and colleagues found positive but inconsistent associations between early supplementation and executive function.

Neither study isolates protein. Children in Barbados were short of food in general, and atole supplied nearly three times the calories of fresco along with its protein. The Guatemalan trial randomized only four villages, so village-level differences could also play a part. The Barbados study was not randomized at all, and families whose babies became malnourished differed in other ways that adjustment may not fully capture.

There is also a history lesson here. In the 1950s and 1960s, international agencies believed the world faced a "protein gap", and they promoted high-protein foods for poor children. In 1974 the nutritionist Donald McLaren called this "the great protein fiasco", arguing that most malnourished children lacked enough food overall. Later work largely bore him out. Severe early malnutrition clearly harms cognitive development, but protein alone has rarely been the missing ingredient.

The trials in healthy and older adults are few, and most are small and short.

• Young men on a very high-protein diet: Jakobsen and colleagues randomized 23 healthy men aged 19 to 31 to their usual protein intake (1.5 grams per kilogram of body weight) or double that (3.0 g/kg) for three weeks, with all food provided. The high-protein group improved its reaction time. Reaction time is a speed measure, and the trial did not test reasoning or IQ.

• Frail older adults: Van der Zwaluw and colleagues gave 65 frail or pre-frail older adults (average age 79) a drink with 15 grams of protein or a placebo drink twice a day for 24 weeks. Reaction time improved more in the protein group (68 milliseconds versus 18), but protein had no effect on memory, attention, working memory, processing speed or executive function.

• Tyrosine supplements: Tyrosine is an amino acid the brain uses to make dopamine and noradrenaline. In a review published in Military Medicine, Attipoe and colleagues assessed 10 randomized trials and 4 controlled trials. They found that the evidence was insufficient for confident recommendations, though every included study of cognitive performance under stressful conditions found some benefit. These are short-term effects under strain, measured on specific tasks.

The observational reviews point the same way. Coelho-Júnior and colleagues pooled nine cross-sectional studies of 4,929 older adults and found no significant association between protein intake and global cognitive function. An earlier review by Koh and colleagues judged the evidence linking protein intake to cognition in healthy older people as weak. If you eat eggs partly for their protein, our page on eggs and IQ covers the separate story of choline.

The biggest studies of protein and thinking come from long-running cohorts of American health professionals.

Yeh and colleagues followed 49,493 women in the Nurses' Health Study and 27,842 men in the Health Professionals Follow-up Study with diet questionnaires repeated over about two decades. People who got more of their calories from protein, in place of carbohydrate, were less likely to report "subjective cognitive decline" later in life. Replacing 5% of energy from carbohydrate with protein was linked to 11% lower odds (odds ratio 0.89). The association was stronger for plant protein (0.74), and beans and legumes were among the protein foods linked to lower odds.

Ardisson Korat and colleagues studied 48,762 women from the same cohort who were under 60 in 1984. Higher protein intake in midlife, especially plant protein, was associated with higher odds of "healthy aging", a combined outcome that required freedom from 11 major chronic diseases, good mental health, and no impairment in cognitive or physical function.

These results deserve caution. Subjective cognitive decline is a questionnaire about memory complaints, not a test score and not IQ. Diet was self-reported. People who eat more beans and fish and less processed meat also tend to differ in exercise, income, smoking and overall health, and statistical adjustment never removes every difference. A cohort of nurses and health professionals is also more educated than the general population, which limits how far the results apply.

Not if you already eat enough, which most adults in wealthy countries do. Severe protein-energy malnutrition in infancy is linked to IQ scores about 15 points lower in adulthood, so adequate early nutrition matters.

Small trials found faster reaction times with extra protein, but no gains on memory, reasoning or IQ. No trial has shown that a high-protein diet raises intelligence in healthy adults.

There is no evidence that they raise IQ. Tyrosine may help performance on some tasks under acute stress, but the evidence is limited and the effects are short-lived.

Severe malnutrition in the first years of life is associated with lasting IQ deficits. Those children usually lacked food energy and many nutrients, so the effect cannot be pinned on protein alone.

Large cohort studies link plant protein with fewer memory complaints and healthier aging. They are observational, so they cannot show that plant protein itself caused the difference. Anyone worried about their memory should talk to a doctor.

Protein is essential, and going without enough food in infancy can cost a child many IQ points for life. For people who already eat a normal diet, eating extra protein or taking amino acid pills has not been shown to raise intelligence. The best evidence shows modest gains in reaction speed and associations in diet cohorts that may reflect healthier lifestyles. If you want an accurate measure of your reasoning ability, take a full-length online IQ test.

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2. Waber, D. P., Bryce, C. P., Girard, J. M., Zichlin, M., Fitzmaurice, G. M., & Galler, J. R. (2014). Impaired IQ and academic skills in adults who experienced moderate to severe infantile malnutrition: A 40-year study. Nutritional Neuroscience, 17(2), 58-64. [doi.org/10.1179/1476830513Y.0000000061](. doi.org

3. Pollitt, E., Gorman, K. S., Engle, P. L., Martorell, R., & Rivera, J. (1993). Early supplementary feeding and cognition: Effects over two decades. Monographs of the Society for Research in Child Development, 58(7), 1-99. [doi.org/10.2307/1166162](. doi.org

4. Maluccio, J. A., Hoddinott, J., Behrman, J. R., Martorell, R., Quisumbing, A. R., & Stein, A. D. (2009). The impact of improving nutrition during early childhood on education among Guatemalan adults. The Economic Journal, 119(537), 734-763. [doi.org/10.1111/j.1468-0297.2009.02220.x](. doi.org

5. Ramírez-Luzuriaga, M. J., DiGirolamo, A. M., Martorell, R., Ramírez-Zea, M., Waford, R., & Stein, A. D. (2021). Influence of enhanced nutrition and psychosocial stimulation in early childhood on cognitive functioning and psychological well-being in Guatemalan adults. Social Science & Medicine, 275, 113810. [doi.org/10.1016/j.socscimed.2021.113810](. doi.org

6. McLaren, D. S. (1974). The great protein fiasco. The Lancet, 304(7872), 93-96. [doi.org/10.1016/S0140-6736(74)91649-3](. doi.org

7. Jakobsen, L. H., Kondrup, J., Zellner, M., Tetens, I., & Roth, E. (2011). Effect of a high protein meat diet on muscle and cognitive functions: A randomised controlled dietary intervention trial in healthy men. Clinical Nutrition, 30(3), 303-311. [doi.org/10.1016/j.clnu.2010.12.010](. doi.org

8. van der Zwaluw, N. L., van de Rest, O., Tieland, M., Adam, J. J., Hiddink, G. J., van Loon, L. J. C., & de Groot, L. C. P. G. M. (2014). The impact of protein supplementation on cognitive performance in frail elderly. European Journal of Nutrition, 53(3), 803-812. [doi.org/10.1007/s00394-013-0584-9](. doi.org

9. Attipoe, S., Zeno, S. A., Lee, C., Crawford, C., Khorsan, R., Walter, A. R., & Deuster, P. A. (2015). Tyrosine for mitigating stress and enhancing performance in healthy adult humans, a rapid evidence assessment of the literature. Military Medicine, 180(7), 754-765. [doi.org/10.7205/MILMED-D-14-00594](. doi.org

10. Coelho-Júnior, H. J., Calvani, R., Landi, F., Picca, A., & Marzetti, E. (2021). Protein intake and cognitive function in older adults: A systematic review and meta-analysis. Nutrition and Metabolic Insights, 14, 11786388211022373. [doi.org/10.1177/11786388211022373](. doi.org

11. Koh, F., Charlton, K., Walton, K., & McMahon, A. T. (2015). Role of dietary protein and thiamine intakes on cognitive function in healthy older people: A systematic review. Nutrients, 7(4), 2415-2439. [doi.org/10.3390/nu7042415](. doi.org

12. Yeh, T. S., Yuan, C., Ascherio, A., Rosner, B. A., Blacker, D., & Willett, W. C. (2022). Long-term dietary protein intake and subjective cognitive decline in US men and women. The American Journal of Clinical Nutrition, 115(1), 199-210. [doi.org/10.1093/ajcn/nqab236](. doi.org

13. Ardisson Korat, A. V., Shea, M. K., Jacques, P. F., Sebastiani, P., Wang, M., Eliassen, A. H., Willett, W. C., & Sun, Q. (2024). Dietary protein intake in midlife in relation to healthy aging: Results from the prospective Nurses' Health Study cohort. The American Journal of Clinical Nutrition, 119(2), 271-282. [doi.org/10.1016/j.ajcnut.2023.11.010](. doi.org

Hero image: Mixture of beans, peas and lentils, by Bean appreciator, CC0. Via Wikimedia Commons.