The Fertility Diet

Although there are many old wives’ tales about the effects of certain foods on fertility, little scientific research has investigated whether specific dietary factors really play a role.

However, a number of publications by a research group at the Department of Nutrition of the Harvard School of Public Health in Boston, USA, have revealed that certain dietary factors may well influence female fertility.

Harvard studies
A team of researchers, led by Dr Jorge Chavarro, studied female ovulatory disorders in a group of more than 17000 premenopausal women without a history of infertility, for a period of eight years. They found that certain dietary habits increased the chances of conceiving.

It's important to keep in mind that the women included in these studies didn't have any defined infertility disorders (for example, polycystic ovary syndrome), and that these studies didn't research male infertility.

The basic results of the Harvard studies (Chavarro et al, 2007A) indicated that the following dietary patterns helped women fall pregnant:

• Diets rich in monounsaturated fats and low in trans-fats.
• Higher intakes of plant protein, rather than animal protein (Chavarro et al, 2008B).
• Higher intakes of carbohydrates with a low glycaemic index (GI) (Chavarro et al, 2007C).
• Use of high-fat, rather than low-fat milk and dairy products (Chavarro et al, 2007B).
• Use of multivitamin and B vitamin (especially folic acid) supplements (Chavarro et al, 2008A).
• Higher intake of iron, particularly from plant sources and iron supplements (Chavarro et al, 2006).

Chavarro and his team have dubbed this combination of foods the ‘Fertility Diet’.

What does this mean?
To translate these research findings into dietary guidelines, one can basically say that a woman who wants to fall pregnant should follow a diet that's rich in monounsaturated fats, plant protein, low-GI carbohydrates, and high-fat milk and dairy products, and take iron and B-complex supplements.

To help you put together your fertility diet, let’s consider which foods supply the above-mentioned nutrients:

Monounsaturated fats
Monounsaturated fats are mainly found in plant oils derived from olives and canola. Check in the supermarket for canola or olive oil and margarine made from these oils. Olives and avocados (including avocado oil) are also excellent sources of these ‘good’ fats. Eat at least 1-2 portions a day.

Trans-fats, which need to be avoided, are found in processed foods such as hard margarine, snack foods, pies, cakes, tarts and any other food that's made with processed fats. Not only will you potentially boost your chance of falling pregnant if you avoid trans-fats, but this will also help you to stay healthy and keep your weight in check.

Plant protein
The best sources of plant protein are legumes, which include dry, cooked beans, peas, lentils and soya products (soya mince or milk, and tofu). Try to include at least one serving of these foods a day.

Legumes contain plant protein, dietary fibre, vitamins and minerals (including iron – see below), and they have a low GI. In addition, they're less expensive than animal proteins and have the advantage that they're low in fat and don’t contain any cholesterol.

Carbohydrates with a low GI
These include:

• Hi-fibre bran cereals
• Maximize cereal
• Wholewheat Pronutro
• Low-GI muesli
• Provita
• Low-GI or seed bread or any other bread that contains plenty of whole barley, rye, wheat, buckwheat, seeds, nuts or dried fruit, oat bran, barley, crushed or pearled wheat, and bulgur
• All types of pasta
• Cooked and cooled maize meal
• Wild, long-grain and brown rice
• Whole corn (tinned, frozen or on the cob)
• All fresh and dried deciduous fruit (apricots, cherries, peaches, nectarines, plums, pears and apples)
• All berries
• All citrus fruits
• Fruit juices (e.g. apple or pear)
• Sweet potato
• Green peas and beans
• Most other vegetables

Low-GI carbohydrates help to control your blood-sugar and insulin levels and may prevent the onset of insulin resistance, metabolic syndrome and even type 2 diabetes, all of which can interfere with falling pregnant and/or complicate pregnancy.

Have at least three servings of low-GI starches and five servings of low-GI fruit and vegetables a day.

High-fat dairy products
The finding that the use of high-fat, instead of low-fat or fat-free, dairy products was associated with an improved chance of falling pregnant was startling to say the least (Chavarro et al, 2007B). Additional research will have to clarify why low-fat and fat-free dairy products don't have a positive effect on falling pregnant.

Foods that fall into this category are full-cream milk, yoghurt made with full-cream milk, cream cheese and all other cheeses.

Three servings of dairy products a day should provide all the necessary calcium that adult women need.

Multivitamins and B complex
The finding that women who took multivitamins or B-complex supplements three to five times a week were more likely to fall pregnant (Chavarro et al, 2008A) will also require further research in view of a recent report that the intake of vitamin supplements that contain beta-carotene, and vitamins A and E can increase mortality (death) significantly (see Are Vitamin Supplements Fatal?).

Chavarro and his coworkers (2008A) did mention that folic acid (one of the B vitamins) and the use of vitamin B complex appeared to make the greatest contribution to fertility.

It's therefore probably safe to say that women who are trying to fall pregnant can use vitamin B-complex supplements that contain folic acid three times a week.

Iron from food and supplements
The subjects in the Harvard studies who took iron supplements or obtained most of their iron intake from plant sources (legumes, spinach, dried fruit, iron-fortified breakfast cereals and breads) were more likely to fall pregnant than those who didn't take supplements (Chavarro et al, 2006).

It's plausible that adult women in the childbearing years will benefit from taking iron supplements because a lack of iron has been identified as one of the most common deficiencies in this population group.

But this doesn't mean that you should start taking iron supplements at random. Rather ask your doctor to do a blood test to determine if you are iron deficient (due to blood loss via menstruation or poor dietary intake) and if you are, let the doctor prescribe a suitable supplement. Products such as Ferofolic will supply you with iron and folic acid at the same time.

Go the Mediterranean route
The one thing that springs to mind when one looks at these recommendations for the ‘Fertility Diet’ is that it's very similar to the Mediterranean Diet. The latter diet includes plenty of olive oil, olives, low-GI starches like pasta, vegetables, fruits and legumes, fish, and full-fat milk, yoghurt and cheeses, but only small servings of meat and few processed foods.

If you're trying to fall pregnant, you may well benefit by applying the principles of the ‘Fertility Diet’ or by switching over to the Mediterranean Diet, which will probably keep your partner healthy as well.

(Dr I.V. van Heerden, registered dietician)

References:
(Chavarro JE et al (2006). Iron intake & risk of ovulatory infertility. Obstet Gynecol, 106(5):1145-52; Chavarro JE et al (2007A). Diet & lifestyle in the prevention of ovulatory disorder infertility. Obstet Gynecol, 110(5):1050-8; Chavarro JE et al (2007B). A prospective study of dairy foods & anovulatory infertility. Hum Reprod, 22(5)1340-7; Chavarro JE et al (2007C). A prospective study of dietary carbohydrate quantity & quality in relation to risk of ovulatory infertility. Eur J Clin, Nutr, Sept 19; Chavarro JE et al (2008A). Use of multivitamins, intake of B vitamins, and risks of ovulatory disorder infertility. Fertil Steril, 89(3):668-76; Chavarro JE et al (2008B). Protein intake and ovulatory infertility. Am J Obstet Gynecol, 198(2):210.21-7)