Understanding what you should and shouldn’t be eating if you want to get pregnant is a subject rife with old wives’ tales and, sadly, opportunism from marketing teams trying to sell products and diet plans. However, pre-pregnancy nutrition invariably is an area best addressed by a combination of scientific understanding and common sense.
In 2009 Harvard Health Publishing reported on the largest ever scientific review of the role of nutrition in conception and fertility. The Nurses Health Study drew on eight years of research and the experience of nearly 20,000 women, and offered the most definitive evidence-based pre-pregnancy nutrition recommendations published so far. The good news is that the findings of this and various other studies* are both easy to digest and easy to apply.
The ideal foods for women who are trying to conceive
All of the foodstuffs recommended by the study were chosen for their role in either preventing or undoing ovulatory infertility (infertility caused by ovulation problems). This means that adherence to the diet will be effective in around one in four cases and that the diet will have no impact on cases of infertility caused by physical impairments – for example blocked fallopian tubes.
However, given that the diet effectively constitutes a well-rounded food plan, it is likely to be suitable for all but those individuals with the most specific health and dietary needs.
Pre-pregnancy nutrition – foods to avoid
Trans fats: these are unfortunately a fact of the Western diet. However, by avoiding processed foods, baked goods, fried food, shortening (a type of hard vegetable fat used in baking) and margarine, you can quickly eliminate trans fats from your diet.
Refined carbohydrates: refined carbohydrates (also called simple carbohydrates) include sugars and grains that have been stripped of their fibre and nutrients. Avoid white flour, white bread, white pasta, pizza dough and many breakfast cereals.
Sugar: sugar is known to reduce fertility. This does not mean that you should deny yourself the odd sweet treat, only that you should look to reduce consumption of sugary drinks and sweets.
Skimmed milk and low fat dairy products: fat-containing products have been maligned for a long time. However, research has found that full-fat dairy products are associated with reduced risk of ovulatory infertility; low-fat dairy products were associated with a higher risk.
Caffeine: there are mixed messages regarding the influence of coffee and tea on fertility and conception. However, there is no definitive evidence of either a negative or positive impact. That said, too much caffeine during pregnancy can be harmful, so pre-pregnancy may be a good time to reduce your consumption.
Fast foods: most fast foods (think burgers, fried chicken, etc.) tend to be highly processed and generally contain large amounts of most of the above.
A word of caution: these “avoid” foods may reduce fertility and the chances of conception but they should never be consumed as a substitute for contraception.
Foods you should eat if you are trying to conceive
The Nurses Health Study recommends all of the following foodstuffs as part of a balanced and varied diet for conception:
Unsaturated vegetable oils. Both monounsaturated and polyunsaturated fats aid fertility by reducing inflammation and effectively regulating blood sugar levels. Good sources include olive oil, sunflower oil, peanut oil and flax oil. Cold water fish, avocados, seeds and nuts are other good sources.
Vegetable protein: studies have found that replacing a serving of meat protein each day in favour of a plant-based alternative – e.g. lentils, beans, peas, nuts, soybeans or tofu – may increase ovulatory function and the chances of successful conception. This does not mean that it is necessary to forgo animal-based protein altogether, only that regular consumption of plant-based alternatives may be beneficial.
Unrefined carbohydrates: fibre-rich carbohydrates such as whole grains, vegetables, fresh unprocessed fruit, and beans and pulses or legumes (chickpeas, lentils,) can help control blood sugar and inflammation and thereby increase the chances of successful conception.
Full fat dairy: not only are full-fat milk, yoghurt and cheese tastier than low-fat alternatives, they are also associated with enhanced ovulatory function.
Vegetables: ensure you get plenty of iron and folate from green leafy vegetables and enjoy the broader health benefits provided by vegetables such as sweet potato, pumpkin, tomatoes, and beetroot.
Oily fish: women who are hoping to conceive should follow the general popular guideline of one portion of oily fish per week. Oily fish such as sardines, salmon and mackerel contain omega-3 long-chain fatty acids, which play an important role in general health and may have a positive impact on a woman’s chances of conceiving.
A word on weight
Being either underweight or overweight is likely to reduce your chances of conception. As such, aim for a body mass index (BMI) of between 20 and 25. This is best achieved through a combination of regular suitable exercise (too much may have a negative impact, particularly if you are underweight) and a healthy diet that largely consists of the foods listed above. Crash diets are unlikely to be in the interests of either your long-term health or your chances of successful conception.
In summary
The take home message really is quite simple: if you are trying to conceive, you should eat a balanced and healthy diet comprised of whole grains, full fat dairy, fresh fruit and veg, and healthy protein sources including plant-based proteins.
In addition, it may be beneficial to take a daily prenatal vitamin and to aim for a healthy body mass index.