The importance of a healthy diet for proper functioning of the brain is increasingly being recognized. Week in, week out studies appear recommending a high intake of certain foods in order to achieve optimal brain function and prevent brain diseases. Although it is definitely no punishment for the most of us to increase our chocolate consumption to boost brain function, the most important period during which nutrition affects our brain may already be behind us.
Nutrition affects the brain throughout life, but it is potentially most important during the critical prenatal period, during which the lion’s share of our brain development takes place. During the time we spend in the womb, our brains undergo dramatic changes. The fetal nervous system from which the brain and spinal cord progress is one of the first systems to develop. Its foundations are laid down during the very first days of pregnancy. At the end of pregnancy, the brain has grown exponentially and is capable of learning and forming memories. It is actually not very hard to imagine that to lay a good foundation for the brain it is of utmost importance to receive the best building blocks through proper nutrition of the mother.
A very dramatic illustration of the consequences of not receiving adequate nutrition was shown in a study from the seventies in which Zena Stein and colleagues investigated the effects of prenatal exposure to the Dutch famine on the development of babies. The Dutch ‘Hungerwinter’ was a period of severe famine that struck the Western part of the Netherlands at the end of World War II. There was so little food available that even pregnant women suffered from severe undernutrition. Stein and her colleagues found that babies that had been exposed to the famine during the first trimester of pregnancy had increased rates of birth defects of the central nervous system.
The babies who were born around the time of the Dutch famine are currently about 70 years old. In Amsterdam, we have been following a cohort of people who were all born around the time of the famine from the age of 50 onwards and investigated their health during four waves of research. In each of these studies we compared people who had been exposed to the famine during early, mid-, or late pregnancy to people who had been unexposed to the famine during pregnancy. At age 50, the men and women who had been exposed to the famine in early gestation were shown to more often have heart disease accompanied by risk factors for heart disease such as increased cholesterol levels and obesity. At age 63 years, it also appeared that sadly the women who had been exposed to the famine early gestation, had died more often than their contemporaries.
Instigated by the research of the late David Barker and his colleagues who showed that low birth weight as a marker of a poor (nutritional) fetal environment was associated with an increased risk for heart disease and type 2 diabetes, we initially focused our studies in the Dutch famine birth cohort on cardio-metabolic health. At age 58 years, the participants of the cohort underwent a cardiovascular stress testing procedure and as a part of the procedure they performed a so called Stroop task. In this task, you have to name the color of the ink in which a color name is written. Doing this requires selective attention. People who had been exposed to the famine in early gestation, performed much worse on this task. As selective attention is a cognitively ability that is one of the first to deteriorate with increasing age and performance on a computerized Stroop task has been shown to be a predictor for development of Alzheimer’s Disease, we suspected that those who had been exposed to famine in early gestation may not only be at increased risk for cardio-metabolic disease but may also be at higher risk for accelerated ageing of the brain.
To investigate this further, we studied a subsample of our cohort by performing MRI scans of their brains. The first analyses of these scans showed that the intracranial volume and total brain volume in men exposed to famine in early gestation was smaller than the volumes in the control group. We did not find this difference in women, which may be due to the fact that we have studied a relatively healthy sample of exposed women as the more unhealthy women may have already died.
When we adjusted our analyses on total brain volume for the differences in intracranial volume, the effects of famine exposure on brain volume disappeared. This means that the effect of famine exposure seems to apply to intracranial volume predominantly. Intracranial volume is presumed to be a measure of the maximum size that the brain has reached during lifespan. While brain volume tends to decrease with age, intracranial volume tends to stay the same, although recent studies have cast doubt over this assumption. It is therefore difficult to say whether the smaller brains in the exposed men have been smaller from the start or have become smaller with increasing age. Smaller brain size attained in childhood has been shown to be associated with the development of Alzheimer’s Disease which makes us wonder whether prenatal exposure to undernutrition also increases the risk for Alzheimer’s Disease.
In general, we think that it is striking that the effect of a period of undernutrition in early life is still visible in the brain after almost 70 years. It underscores the vital impact that nutrition in early life has on the brain and may have for the rest of your life.
Featured image credit: Pregnancy by Greyerbaby. CC0 Public Domain via Pixabay.