Are We What Our Mothers Eat?

What happens in the womb does not stay in the womb. What a mum eats - or doesn’t eat - during pregnancy can affect her child for life, from taste preferences to obesity, mental health and social issues. But how significant is the influence of a mother's diet on the well-being of her child? And what is a ‘healthy’ diet during pregnancy?

Alcohol, raw fish or meat, undercooked eggs, unpasteurised cheeses, unwashed produce, and too much caffeine. Most of us know what to avoid during pregnancy (and beyond).

Being pregnant during a pandemic with no social happenings made it easy for me to stay away from the wine. As a vegetarian with a tendency towards veganism, the sushi and steak tartare weren’t a problem either.

Still, I felt the pressure not to harm this creature inside me: opportunities for irresponsible behaviour were lurking in every corner. I remember the look on my partner’s face when he saw me eating an unwashed strawberry. I cooked my occasional egg for 15 minutes to not burden our child with deafness, schizophrenia or mental disability.¹

Nowadays, there is a big focus on what you shouldn’t eat or drink during pregnancy and what the effects could be in the short term.

These are, of course, real risks. But as professor Tessa Roseboom writes in her book The first 1,000 days: “There should be a more considerable emphasis on the importance of eating a healthy and varied diet for the long term health of the child”.²

The impact of maternal undernutrition

“You are what your mother ate” is the concise summary Roseboom, Director of Amsterdam Reproduction & Development and Professor of Early Development and Health at the Amsterdam UMC, gave when she presented her PhD research in 2000.³ The study she worked on was one of the first inklings of the importance of prenatal nutrition, and the lasting effects maternal malnutrition has on the child.

For her PhD, she assessed the effect of prenatal exposure to maternal malnutrition on coronary heart disease in people born around the Dutch famine, 1944-45. This famine, known in the Netherlands as the Hongerwinter (literal translation: hunger winter), took place in the German-occupied Netherlands, especially in the densely populated western provinces, during the winter and spring of 1944-45, near the end of World War II.⁴

Roseboom studied over 700 babies born between November 1943 and February 1947.⁵ Their birth records were preserved for decades in the attic of a hospital and were so surprisingly accurate that fifty years later, she could trace almost all babies from them. Nowhere in the world is hunger so well documented as in those records.⁶

She found that fifty years later, the men and women studied appeared less healthy than their peers. Cardiovascular diseases were more common, as well as diabetes, breast cancer and depression.⁷ According to the research, the basis for these diseases has already been laid in the womb. The study states: “The effects are great: people conceived during the famine appear to have had a heart attack twice as often in adulthood and even breast cancer four times more often.”⁸

The children weren’t only less healthy but also had smaller brains. Therefore, they were less able to participate in the labour market later in life because their mothers had fewer building blocks during pregnancy to pass on to their children via the placenta.⁹ Poorer health, more mental health problems, premature death and an economic disadvantage. This was seemingly the fate of those born to malnourished mothers.¹⁰

These findings sparked a slew of research on the impact of maternal undernutrition. This first evidence that malnutrition during pregnancy has lasting consequences for the child's future health and generations after has had huge implications on the importance of combating malnutrition worldwide.¹¹

From a deprivation of calories to an excess

Today, we are fortunate that undernutrition isn’t a problem for most pregnant women in Europe. However, we now have the opposite problem: a study of 15 - 44-year-olds showed the prevalence of maternal obesity in Europe varies from 7 to 25% and seems strongly related to social and educational inequalities.¹²

As a result of this shift, research in nutrition and pregnancy is now focused on the effects of overfeeding. Recent research done by obesity researcher Nicole Avena and colleagues (albeit mostly in rats) has found that an in-utero diet high in fat or sugar can lead to the child growing up obese. Avena decided to prove the womb’s influence by placing baby rats that were born to mothers fed on high-sugar and high-fat diets with rats on healthy diets – to breastfeed and raise them. She found that the adopted rats still grew up having changes in the brain and craved high-sugar and high-fat foods. However, if a child trains to improve their self-restraint and is brought up to recognise their satiety signals, this mitigates the effects that might have occurred from in-utero exposure.¹³

Other animal studies have shown that a caloric excess in the maternal diet can also have a long-lasting impact on the risk of developing mental health disorders, impaired social behaviours, lower cognitive abilities and increased response to stress.¹⁴

Jaap Seidell, Professor of Nutrition and Health at Free University Amsterdam, emphasises that childhood obesity starts even before conception. “The degree of overweight of the mother and the father is predictive of a later weight problem of the child. That is partly an indication of the genetic predisposition of the child. Still, research shows that when overweight mothers lose a lot of weight before becoming pregnant, the risk of being overweight in the child decreases.”

Seidell explains: “The weight itself, therefore, influences the growth and development of the child. When the mother gains a lot of weight during pregnancy, it increases the risk of having an overweight child, especially if the mother is already overweight during the pregnancy”.¹⁵

Infographic by Indigo Price and Cait Mack

Taste preference

Eating too little or too much does seem to have a long-term impact on the baby, but what about taste preference? Does what the mother eats during pregnancy also affect the child’s taste buds in a way that pre-programs a preference for a healthy and varied diet or for having a sweet tooth instead?

The parent’s job to teach their offspring to eat begins well before the fight to get toddlers to eat their veggies. Not only do parents pass on the genes that define taste receptors, but research suggests that what mothers eat while pregnant and breastfeeding might affect their child’s taste preferences later in life.

Researchers have shown that the mother’s diet can flavour the amniotic fluid (that surrounds the fetus in the womb). At about 10 to 12 weeks gestation, a fetus starts to swallow hundreds of millilitres of this fluid a day. The sense of taste and smell is well-developed by 21 weeks. So, the changing flavours of the amniotic fluid caused by the mum’s diet are likely detected by the baby and may help program the baby’s flavour preferences.

Researchers have tested the maternal diet/offspring taste theory in controlled experiments by giving mothers particular foods and testing the babies' reactions to these foods. In one study, 12 pregnant women ate foods containing aniseed, and 12 did not. After birth, babies were given anise-flavoured syrup.Those who were exposed to aniseed before birth responded more positively than those who were not exposed. The same has been shown with carrots.

Although these outcomes are surprising, it’s worth recognising that these studies in the field are done with small groups, so the accuracy of conclusions is to be taken with a pinch of salt. In fact, the scientific consensus on how a mum’s diet influences her baby’s taste is not yet completely clear. Nor is the length by which this influence is believed to last into a child’s life. As we age, additional factors (cultural, social, economic) also impact our taste and diet, and the further removed you are from the exposure, the harder it is to study.¹⁶

So, what is a healthy diet during pregnancy?

Of course, it’s not just food during pregnancy that has a significant influence on the health and well-being of a baby later in life. The overall environment (stress, love, attention, infections, stimulation) in utero and the first years of life influence how our genes express themselves and determine our susceptibility to disease and stress.¹⁷ But if we focus on a mum’s diet, and you want to know what to focus on instead of what to avoid, the World Health Organisation (WHO) has three simple rules for you:

Try to eat a variety of foods such as green and orange vegetables, milk, meat, poultry, fish, beans, nuts, whole grains and fruit
Take supplements, like folic acid and iron, as advised by a health worker
Make sure food is safe and clean

You can of course zoom in further to learn more about the specific essential nutrients, how much you need in what trimester and what food sources they provide them (find sources below). But it’s good to remember it’s essentially the same as for everyone else, but in bigger quantities - specifically folic acid and iron are very important for the healthy development of the baby.¹⁸

In a society that sometimes seems designed to make people fat, the responsibility to eat healthy and varied shouldn’t be all put on the pregnant mother. Our food environment plays a significant role in how easy or hard it is to make healthy choices. These wholesome choices should be the most accessible choices for everyone, and women (and men) should get rigorous support in making lifestyle changes.

Our son Ezra just turned 1. It’s hard to say if my diet during pregnancy influenced him in the long run. Being a privileged consumer, who did her best to eat a varied, healthy diet, gave him probably relatively good building blocks. So far, he eats most things we put in front of him, and he seems to share the cravings I had for potatoes in all their forms.

Additional reading on nutrition for pregnant women

WHO published an updated booklet on the topic in 2001.
The Mayo Clinic, a nonprofit American academic medical centre, focuses on the essential nutrients you should prioritise during pregnancy and the food sources that provide them - based on US Department of Agriculture data.
Nicole M. Avena's book, ‘What to Eat When You're Pregnant - A Week-by-Week Guide to Support Your Health and Your Baby's Development'.
Nutritional information in your language provided by your national nutrition centre

Illustrations by Indigo Price