Polycystic ovarian syndrome (PCOS) is the most common endocrine and metabolic disorder amongst women in Australia and New Zealand, affecting 5-10% of women and girls of reproductive age. PCOS is characterised by a cluster of symptoms relating to androgen excess and ovarian dysfunction, including hirsutism, acne, amenorrhea, enlarged bilateral polycystic ovaries and central adiposity. PCOS is also associated with an increased risk of gestational diabetes.
Insulin resistance is a significant risk factor for PCOS development. Elevated insulin concentrations act to promote androgen secretion from both the ovary and adrenal glands. This androgen excess promotes deposition of abdominal adipose tissue, which in turn secretes signaling molecules exacerbating insulin resistance and further promoting androgen production.
Women with PCOS are also more likely to have higher blood pressure and elevated blood lipid levels, placing them at increased risk for cardiovascular disease.
While there are many proposed mechanisms for the development of PCOS, the standard Western diet, high in fat and overall calories may contribute to PCOS etiology.
In isolation, high fat diets are well established mediators of insulin resistance.[7, 8] In a cohort study examining risk of sporadic anovulation in regularly menstruating women; risk of anovulation was associated with increases in testosterone concentrations and correlated with intake of total and polyunsaturated fats. In addition, in several cross-sectional studies, dietary fibre was inversely correlated with both PCOS, body fat and markers of glucose control. Low dietary fibre intake, combined with high fat intake characteristic of a Western diet is therefore likely to contribute to PCOS development in susceptible women.[10,11]
The nutrition prescription
Dietary modifications are recommended as a first-line therapy for the management of PCOS. Low fat, plant-based diets improve insulin sensitivity and beta cell function independent of changes to BMI. In addition to this, weight loss reduces the risk of progression to type two diabetes and other cardiometabolic risks.
High-fibre diets have been consistently shown to aid long-term weight management and in patients with PCOS, increased dietary fibre, along with reductions to trans fatty acid intake was the strongest predictor of reductions to BMI and improved glucose control.
Compared to a standard Western diet, a whole food plant-based (WFPB) diet is lower in fat and calories and higher in fibre, which helps in maintaining a healthy body weight over the long-term. A randomised, controlled pilot study found that participants following a WFPB diet were more successful in weight loss and managing PCOS symptoms than those following a non-vegan low-calorie diet. In addition, a recent review of dietary approaches to managing PCOS recommended that the focus be on a low-glycemic diet rich in whole grains, legumes, fruits and vegetables, thus aligning well with a whole-food plant based approach.
In addition to a beneficial effect on weight control, a whole food plant-based approach, naturally high in dietary fibre may help to increase sex-hormone binding globulins (SHBG), thus regulating bioavailability of androgens. SHBG has been shown to be an important predictor of PCOS risk and severity.
Medical supervision of diet change is essential
Shifting to a low fat plant-based diet can lead to rapid reductions in medication needs; patients on pharmaceutical agents for glycaemic control, hyperlipidemia or hypertension should be managed carefully.
There are a range of health benefits associated with a WFPB eating pattern, even for people who do not need to lose weight. The increased dietary fibre, antioxidants and polyphenols contained on a WFPB diet exert favourable effects on glucose control and cardiovascular risk profiles, independent of any weight loss. A WFPB diet is also generally lower in calories and total fat, and higher in fibre, so it can also help maintain normal hormone levels, a healthy weight into the future and prevent exacerbation of PCOS.
Maintaining a healthy weight is one of the most effective ways to manage PCOS. Other treatments include the combined oral contraceptive pill to manage menstrual irregularity, as well as pharmacological interventions to assist in pregnancy. The use of diabetic agents such as metformin can also be considered if there is a high risk of developing type 2 diabetes. All management strategies should be discussed with a medical practitioner.
 Australian Government, Department of Health. Polycystic ovarian syndrome (PCOS). Published September 1, 2020. Accessed October 9, 2020. https://www.healthdirect.gov.au/polycystic-ovarian-syndrome-pcos
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