Polycystic Ovarian Syndrome

Polycystic ovary syndrome (PCOS) is caused by a slight excess of androgens (male sex hormones). These extra hormones can cause irregular periods, skin changes, polycystic ovaries, and infertility. They can also change body fat patterns and reduce insulin sensitivity. This leads to rising blood sugars and sometimes diabetes. PCOS affects an estimated 5 million women of reproductive age in the U.S.¹ Lifestyle changes, especially those that lead to weight loss, are the first line of therapy and can improve multiple symptoms.

Weight Loss

A meta-analysis of diet studies found that weight loss improved PCOS symptoms in overweight women regardless of diet composition.² One randomized controlled trial found that losing as little as 5-10% of weight results in resumption of menses and decrease in blood androgen levels.³ A plant-based diet has proven to be effective for weight loss and maintaining a healthy body weight–read more about the research on our Weight Loss page.

Insulin Resistance

A low-fat, plant-based diet causes weight loss and reduces insulin resistance, which affects many women with PCOS. Studies show that eating a diet high in fatty foods can cause fat particles to build up inside our cells.⁴ These fat particles interfere with insulin’s ability to move sugar out of the bloodstream and into cells. Instead of powering our cells, the glucose remains in the bloodstream, eventually leading to diabetes. A plant-based diet is low in fat, which reverses that accumulation of fat inside the cells, and allows insulin to function properly resulting in improved glycemic control.^5,6 Avoid fried foods, foods high in saturated fats such as meats, dairy products, and eggs, and high glycemic index foods (see below).

Limit or avoid high glycemic index foods such as flour, white bread, some varieties of breakfast cereals, and rice to improve insulin sensitivity. Instead, focus on low glycemic index foods, such as beans, peas, lentils, pasta, pumpernickel bread, bulgar, parboiled rice, barley, and oats. Diets rich in these foods can lead to improvements in blood glucose control.⁷

Inflammation

Diets high in fruits, vegetables, whole grains, and legumes reduce oxidative stress and inflammation.⁸ A systematic review and meta-analysis found that markers of inflammation are altered in women with PCOS, independent of obesity.⁹ Oxidative stress impairs glucose uptake in muscle and adipose tissue in humans. In contrast, animal products and processed foods should be minimized or avoided. These foods contain cholesterol oxidation products and lipid peroxides that increase both oxidative stress and inflammation.¹⁰

Key Nutrients

One of the key nutrients in a diet that emphasizes whole grain intake, legumes, and nuts in place of refined carbohydrates is inositol, which is a type of sugar. In clinical trials, inositol has been shown to improve insulin action, decrease androgen levels, and improve ovulatory function in both lean and obese women with PCOS.^11-13

Chromium is an essential mineral found to improve insulin sensitivity, lower the risk for developing type 2 diabetes, and increase the chances of ovulation in women with PCOS.^14-17 A dietary supplement may be helpful for women with PCOS. Talk to your doctor to see if supplementation is right for you.

Fiber is an important nutrient for weight loss and improving insulin resistance, which are the targets for improving PCOS symptoms. In a study with 57 overweight or obese women with PCOS, the strongest predictor of weight loss was increased fiber intake.¹⁸ Aim for 40 grams of fiber daily.

Omega-3 supplementation has been shown to decrease inflammation, reduce insulin sensitivity, and improve cholesterol, which indirectly benefits treating women with PCOS.¹⁹ However, more studies need to be done to determine dosage and length of supplementation. Women with PCOS can focus on including omega-3 rich foods such as ground flaxseed, chia seeds, walnuts, hempseed, and soybeans.

Soy protein appears to be beneficial for women with PCOS. One randomized clinical trial compared the effects replacing 35% of daily protein from animal sources with soy protein and found that women who ate the soy protein reduced their BMI, fasting blood sugar, testosterone levels, and triglyceride levels.²⁰

Advanced glycation end products (AGEs) are highly reactive molecules that promote insulin resistance and chronic inflammation, both of which are key features in PCOS. Dietary AGEs also appear to cause ovarian dysfunction in PCOS.²¹ Eating a low fat, plant-based diet has been shown to reduce dietary AGEs by 73%, according to research published by the Physicians Committee in 2024.²²