By Michaela Carrick, BSc Human Nutrition
What is PCOS?
Polycystic ovary syndrome (PCOS) is an endocrine (hormone) condition affecting women which can present with a diverse range of symptoms with varying severity. Women with PCOS commonly experience irregular periods, fertility problems, excess hair growth (usually on the face, chest, back, or bottom), hair thinning or loss, acne, insulin resistance, depression, and excess weight gain.
PCOS is estimated to affect roughly one in every ten women in the UK. The cause of PCOS is not yet fully understood, but it appears to result from both genetic and environmental risk factors. This leads to abnormal hormone levels in the body. For example, many women with PCOS have insulin resistance, meaning their cells become less sensitive to the actions of insulin, the hormone that controls blood sugar levels. This causes the body to make extra insulin. In turn, the high insulin levels cause the ovaries to make too much testosterone, disturbing the menstrual cycle.
How can diet affect PCOS?
There is no known cure for PCOS, but diet and lifestyle changes may help manage symptoms. Maintaining a healthy body weight, eating a balanced diet, and exercising regularly may benefit women with PCOS.
Weight loss
Weight loss is the primary lifestyle change used to manage PCOS symptoms in women who are overweight or obese (1). Regardless of the type of diet used to lose weight, achieving a healthy weight can improve symptoms of PCOS by making periods more regular, normalising hormone levels, improving insulin sensitivity, lowering cholesterol, and improving self-esteem and quality of life (2).
Carbohydrates
Choosing the right type of carbohydrate foods can help to manage PCOS symptoms. The best choices are low glycaemic index (GI) carbohydrates. The GI measures how quickly a food containing carbohydrates increases blood sugar after eating. High GI foods raise blood sugar quickly, while low GI foods raise blood sugar more slowly and gradually. High blood sugar triggers the release of more insulin, which can worsen symptoms of PCOS by causing changes in levels of testosterone and other hormones.
High GI foods include:
Sweets and desserts
Fizzy drinks
White bread
White rice
Potatoes
Lower GI foods include:
Some fruit like blueberries, blackberries, grapefruits, and apples
Peas, beans, and lentils
Wholegrains like porridge oats
Low-fat dairy
Nuts and seeds
Research has shown that insulin sensitivity improves more when a low GI diet is used to achieve weight loss compared to weight loss achieved through general healthy eating (3).
Here are some tips to try when eating a lower-GI diet:
- Fill half your plate with fruit or vegetables. Serve main meals with salad or roasted vegetables, and add fruit to breakfasts and desserts.
- Choose brown or whole-grain bread, rice, pasta, and breakfast cereals. The fibre in these foods slows down the rise in blood sugar after eating.
- Choose diet or sugar-free fizzy drinks or stick to water. Limit fruit juice and try to eat the actual fruit instead whenever possible.
- Add a source of protein to most meals. For example, try poached eggs and avocado on brown bread for breakfast, a grilled chicken salad for lunch, or chickpea curry with brown rice for supper.
- Try not to skip meals. Planning your meals for the week in advance, saving leftovers, or preparing meals the night before may help save you time.
Saturated fat
Saturated fats are found in meat, dairy, and baked goods. These fats can increase inflammation and disrupt insulin signalling, worsening insulin resistance and other symptoms of PCOS (4). You may see improvements in PCOS symptoms by reducing saturated fats in your diet and replacing them with healthier mono- or polyunsaturated fats.
Foods high in mono- and polyunsaturated fats include:
Vegetable oils
Olives
Oily fish like salmon, mackerel, and sardines
Nuts and seeds
Avocados
The Mediterranean Diet
The Mediterranean diet is high in healthy fats, low GI carbohydrates, fibre, vitamins, and antioxidants. The diet can help with weight loss and has anti-inflammatory effects. Women with PCOS who adhere to a Mediterranean style diet have been reported to have less severe PCOS symptoms (5). The benefits are likely due to a decrease in inflammation, an increase in insulin sensitivity, and a reduction in testosterone and other hormones involved in PCOS.
Supplements
Many women with PCOS report taking nutritional or herbal supplements (6). While a few very small studies reported improved PCOS symptoms in women supplemented with omega-3, chromium, cinnamon, and myo-inositol, larger controlled trials are needed before any recommendations can be made. However, vitamin D supplementation is often recommended as women with PCOS may be at higher risk of vitamin D deficiency (7).
The management of PCOS will vary according to a woman’s overall goals. Additional dietary and nutritional factors will be considered depending on whether a woman plans to conceive, lose weight, or manage specific PCOS symptoms. Because of this, it is essential to speak to a healthcare professional about your individual goals and needs.
References
1. Royal College of Obstetricians and Gynaecologists (2014) Long-term consequences of polycystic ovary syndrome. Green-top Guideline No.33.
2. Moran LJ, Ko H, Misso M, Marsh K, Noakes M, Talbot M, Frearson M, Thondan M, Stepto N, Teede HJ (2013) Dietary composition in the treatment of polycystic ovary syndrome: a systematic review to inform evidence-based guidelines. Journal of the Academy of Nutrition and Dietetics, 113(4), 520-45.
3. Marsh K, Steinbeck KS, Atkinson FS et al. (2010) Effect of a low glycaemic index compared with a conventional on polycystic ovary syndrome. American Journal of Clinical Nutrition, 92, 83-92.
4. Galgani JE, Uauy RD, Aguirre CA et al. (2008) Effect of the dietary fat quality on insulin sensitivity. British Journal of Nutrition, 100, 471-479.
5. Barrea L, Arnone A, Annunziata G et al. (2019) Adherence to the Mediterranean Diet, Dietary Patterns and Body Composition in Women with Polycystic Ovary Syndrome (PCOS). Nutrients, 11(10):2278.
6. Jeanes Y, Barr S, Smith K, Hart KH (2009) Dietary management of women with polycystic ovary syndrome in the United Kingdom: the role of dietitians. Journal of Human Nutrition and Diet, 22, 551-558.
7. He C, Lin Z, Robb SW et al. (2015) Serum vitamin D levels and polycystic ovary syndrome: a systematic review and meta-analysis. Nutrients, 7, 4555-4577.
