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Pregnancy Apr 24, 2020
8 Minutes

Fish, alcohol, caffeine during pregnancy? We take a look at the latest evidence…

We are firm believers that it is never too early to lay the foundations for long term health in a child. Preconception and Pregnancy is an excellent opportunity and for most women a positive pregnancy test leads to the question: what is ok to eat? What is not? As with most things these days, there is a huge amount of opinion and ‘noise’ on this subject. Particularly when it comes to fish. Fish has Omega 3 Polyunsaturated fatty acids (good), but it is also a well documented source of Mercury (bad) and other assorted potential nasties. As usual, we want to bypass opinions and just go straight to the evidence/latest science. We’re also going to take a look at the latest on Caffeine, Alcohol and a few other common question marks. Plus, what some research suggests could be very positive contributors to long term health if you get enough during pregnancy. 

The controversy over fish: what you need to know: 

Fish can be a source of Mercury (aka Methylmercury) which has well researched negative impacts on brain and metabolic health. Click here for more. However, it is also the major dietary source of omega 3 long chain polyunsaturated fatty acids (click here for more). These have shown powerful anti inflammatory effects. Click here for more as to why that is so crucial particularly for pregnancy and early development. Most people are also told to avoid shellfish and sushi while pregnant.

No wonder we’re confused! Here is what the latest research suggests… 

A research paper published in the highly respected JAMA journal took a look at the links between fish consumption during pregnancy, mercury levels in the mother and the outcome that had on inflammatory markers. It then looked at a child’s longer term disposition to factors like weight gain (adiposity), high cholesterol and insulin resistance. All which can predispose a person  to heart disease over the long term. (1)

Spoiler alert: actually the benefits of moderate fish intake appear to outweigh potential negatives: 

The study looked at three categories: low fish intake (1 portion or less per week), moderate (1-3 portions) and high intake (3+ portions). It measured mercury levels in the blood of the mother and looked at levels of key inflammatory cytokines in the blood. Why are inflammatory cytokines are important and what are they?!

Chronic low levels of inflammation is not what we want at any time but especially not during pregnancy: 

Cytokines sound complicated but in brief they are signals to the body’s immune system. Good and crucial when needed. The trouble is when we have too many for too long. That can damage other cells and tissue. Click here to read more if you fancy. 

Chronic inflammation has been linked to all sorts of things from trouble with implantation during conception, to insulin resistance, to development of allergies and autoimmune conditions and at the more extreme end brain development challenges and preterm birth. (2)

Fish 1-3x per week had positive long term effects on a child: 

The study showed a net benefit when it came to inflammation from moderate intake vs low and longer term it revealed a benefit to a child’s metabolic profile. Specifically regarding waist circumference, lower HDL cholesterol and improved insulin resistance.

However, not too much, not too little…. 

Goldilocks as always. The research showed that high levels had the opposite effect. As a reminder: high = more than 3x per week. Another important consideration is that not all fish is created equally. Going lower down the food chain is always a good idea as Mercury bioaccumulates. That means if a small fish is eaten by a larger fish that larger fish will have the small fish’s mercury plus its own. Here is a chart to help you (source: FDA):


What about shellfish? 

This is best avoided during pregnancy, principally as there is higher risk of food poisoning which is something you want to avoid at all times. Particularly if you are pregnant.

Avoiding food poisoning: 

Is the main reason why it is recommended that pregnant women stay away from things like:

Raw and cooked meat plus hams and salamis.

Cetrain dairy products (including eggs unless cooked thoroughly) and particularly raw unpasteurised milk and soft cheeses that could have been made with raw milk (a source of Listeria which is something you really want to avoid).

Preprepared foods: like pasta and rice salads, sandwiches and bagged salad.

Rice and pasta that is not cooked/heated thoroughly.

The key is fresh food that is heated thoroughly (minimum over 60 degrees).

Caffeine: are the guidelines too liberal? 

This is another area of debate. The European guidelines (European Food Safety Authority) say no more than 2x cups of coffee a day (approx 200mg) and according to the WHO it is 3x cups (approx 300mg). However, recent research (3) emphasises the point that it really is better to avoid as much as possible and  that current guidelines could in fact be too liberal. Remember: caffeine is not just in coffee. Click here to read more. See chart below for a hint where you can find it.


Alcohol: the party poopers… 

Once again – a bit of a grey area. Is one glass ok now and again? Is it not? The most recent comprehensive research (4) suggests once again even a glass could be too much and the evidence really does support total avoidance if you can. Particularly when it comes to all important birthweight and neurodevelopment. Click here for more. 

Now onto the good stuff: positives that can help build the foundations for health: 

What about if you’re vegan/plant-based and you do not want to consume fish? The good news is that Algae (specifically Spirulina and Chlorella) are both excellent sources of plant-based Omega 3. Click here for more. 

Even better it is a food and not a supplement (common misconception) and has a whole host of benefits during pregnancy including high protein, iron, B vitamins and iodine.

Definitely worth investigating and easily incorporated into smoothies and porridge if you’re not keen on the taste!

Fibre is where it’s at: 

We are not shy about the importance of good gut health during pregnancy and particularly in preparation for birth. Birth is the time where the foundations of a baby’s own microbiome are laid. Click here as to why this is so crucial for long term health, immunity and brain development. 

It is also something that comes from you. So ensuring you have enough diversity when it comes to whole fresh foods, a dose of probiotic foods (those that add good bacteria) and prebiotic foods (those that feed the existing bacteria we have) is crucial.

New research is suggesting that it could even help in the fight against autoimmunity. One study found that prebiotic fibrous food (that feed the bacteria we have) may actually help prevent autoimmune diseases developing in children (5). Specifically Coeliac disease. So getting enough is key. Click here for more. 

It will also help with pregnancy related constipation, as will a bit of movement and plenty of hydration!

What about probiotic supplements? 

As with all supplements, the trouble is lack of regulation. This means that between brands you can get highly variable strains, efficacy and therefore impact. As it stands currently, what we do know is that changing what you eat can be extremely powerful in terms of improving the microbiome. In fact, it can alter it in as little as 24hrs – click here for more. 

That being said, emerging research is also supportive of specific and targeted strains being used for specific purposes. In fact, research has linked Lactobacillus strains to reducing things like preterm birth. Click here for more.  

No harm discussing this with your doctor.

Other supplements while pregnant? 

Of course your doctor is the very first port of call when it comes to taking supplements at any time but particularly if you’re pregnant. The ideal is that your levels for key vitamins and minerals get tested regularly so you can see your own accurate individual picture. Click here for a reminder as to why this is important. 

However, Folate (the food based form of the synthetic Folic Acid) is absolutely crucial for helping to prevent neural tube defects. Folic Acid is what most people have heard of, however, some people have a genetic difference (MTHFR) which means they struggle to absorb this synthetic version. Which is why Folate is always a good option. Click here for more. 

All about the Vitamin D: 

When it comes to laying the foundations for long term immunity, recent research has shown that getting enough Vitamin D during pregnancy could be a powerful factor against some common issues we see more of today. Some recent research has linked getting enough during pregnancy to lower risk of infections in early childhood. Specifically ear, nose, throat and even skin infections and asthma. Click here for more. (6). Once again, immune issues and even challenges around brain development do seem to be on the rise more generally. There is also evidence linking low levels during pregnancy to ADHD. Click here.  Many of us are deficient so it is very much something that is worth checking with your doctor.

The others: 

For our top evidence-based supplements to consider for pregnancy. Click here. 

Bottom line: 

When you’re newly pregnant your natural instinct is to want to ‘do the right thing’ and to question everything you’re doing, eating and drinking. However, ultimately it is not rocket science. A Mediterranean based diet full of lots of whole fruits, veggies, high quality fish and healthy oils, nuts and seeds is a great start. We all want to avoid food poisoning, but it is definitely more important during pregnancy, so just be sensible. Moderation remains key and asking your doctor to test your all important vitamin and mineral levels is also a great start. Click here for our top evidence based supplements to discuss with your doctor. 

Next up: just relax and enjoy!


1) Stratakis N, Conti D, Borras E: Association of Fish Consumption and Mercury Exposure During Pregnancy with Metabolic Health and Inflammtory Biomarkers in Children. JAMA: Mar 2020. 

2) Elovitz MA, Brown AG, Byrd I: Intrauterine inflammation, insufficient to induce parturition, still evokes fetal and neonatal brain injury. International Journal of Developmental Neuroscience: the official journal of the INternational Society for Developmental Neuroscience: 2011 Oct: 29(6): 663-671

3) Lyngso J, Ramlau-Hansen CH: Association between coffee or caffeine consumption and fecundity and fertility: a systematic review and dose-dependent meta-analysis: Clinical Epidemiology: 2017: 9: 699-719

4) Mamluk L, Jones T, Donovan J: Evidence of detrimental effects of prenatal alcohol exposure on offspring birthweight and neurodevelopment from a systematic review of quasi-experimental studies: International Journal of Epidemiology: Jan 2020:

5) Stordal K: 52nd Annual Meeting of the European Society of Paediatric Gastroenterology Hepatology and Nutrition. June 2019.

6) Moukarzel S, Ozias M, Carlson S: Maternal Vitamin D status and infant infection: MDPI Nutrients: 2018 Feb: 10(2): 111


This article is for informational purposes only. This article is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment and should never be relied upon for specific medical advice. The information on this website has been developed following years of personal research and from referenced and sourced medical research. Before making any changes we strongly recommend you consult a healthcare professional before you begin.

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