Adopting a Mediterranean diet -- with high intakes of fruits and veggies, nuts and legumes -- during IVF treatment would offer a single straightforward approach to improve outcomes compared to that of a Western diet, according to a study.

Adjuvant therapies to help infertile women conceive by IVF -- especially those whose treatments have been unsuccessful in the past -- are now a common feature both before and during the treatment cycle.

The study, published in the journal Reproductive Biomedicine Online, found evidence from studies of nine commonly used nutritional supplements to be inconsistent and not always of good quality.

Professor Roger Hart, University of Western Australia and City Fertility, Perth, Australia, explained that the extent to which nutritional supplements are used in IVF is largely unknown.

"Nutritional supplements are usually not prescribed but bought online or over-the-counter. They're self-medicated and solid data on usage is impossible to determine. Our information is largely anecdotal but it's quite clear from online IVF discussion forums that they are widely used and of great public interest," he added.

The study found evidence of much stronger favour for a Mediterranean diet, showing benefits in both embryo development and pregnancy outcome (even from a six-week intervention program).

Professor Hart explained that the common features of these favourable diets were those with high intakes of fruits and vegetables, whole grains, legumes, nuts, fish, and monounsaturated or polyunsaturated oils, but with a limited intake of highly processed foods.

"These diets are high in B-vitamins, antioxidants, omega-3 poly-unsaturated fatty acids and fibre, and are low in saturated fat, sugar and sodium," he said.

Omega-3 fatty acids, often taken as combined preparations, are the most studied dietary fatty acids in the IVF literature largely, said Hart, because of their perceived benefits in general health and reproduction.

The evidence suggests that omega-3 fatty acids "may be beneficial" in improving IVF clinical outcomes and embryo quality.

The team also analysed nutritional supplements such as dehydroepiandrosterone (DHEA), melatonin, co-enzyme Q10 (CoQ1O), carnitine, selenium, Vitamin D, myo-inositol, Omega-3, Chinese herbs and several diets (as well as weight loss).

Many were reviewed as adjuvants for poor response to previous IVF treatment, of which DHEA and COQ10 appeared in studies to have more benefit than control therapies.

Similarly, there was some evidence of benefit from melatonin, but it remains unclear which patient groups might benefit, and at which dose.

Based on the study, Hart advised that a simple nutritional approach to assist conception via IVF would be the adoption of a Mediterranean diet. The use of COQ-10 and DHEA before starting IVF may be a useful adjunct for women who had a previously poor response to ovarian stimulation, while supplementation with omega-3 free fatty acids may indeed improve some clinical and embryological outcomes.