Nutrition and PCOS – The Food Medic

This article was written by registered dietitian Maeve Hanan

Unfortunately, those with PCOS are targeted with a lot of confusing and often conflicting nutrition advice. This article will explore the evidence-based nutritional management of PCOS. 

What is PCOS?

Polycystic ovary syndrome (PCOS) is a hormonal disorder which is thought to affect roughly one in ten women (1). 

PCOS can be diagnosed by a doctor when at least 2 of the following 3 features are present (2): 

• Irregular ovulation and periods
• Excess androgens – these are sex hormones (including testosterone) that are vital for male sexual development. They are also found in females, although usually in lower levels. Androgens may increase the chances of acne, thinning hair on the head or more facial or body hair
• Polycystic ovaries – when the ovaries are enlarged and contain follicles (fluid-filled sacs) around the eggs

For some people, PCOS can be linked with insulin resistance. This means that insulin no longer allows glucose from the blood to enter the cells properly, which can lead to higher blood glucose levels. There’s also a link between PCOS and inflammation, although the mechanism behind this isn’t entirely clear. 

For these reasons, PCOS can be linked with a higher risk of certain medical conditions including fertility issues, type 2 diabetes and heart disease (3).  

Therefore, a number of medical and lifestyle factors can impact the management of PCOS. Let’s take a look at nutrition specifically.

Carbohydrates and PCOS

Many people with PCOS will have been recommended a low-carb diet at some point. Lower carbohydrate diets have been linked with improvements in PCOS markers such as testosterone, insulin, and cholesterol levels and a lower weight (3, 4).  But it’s important to highlight that not all studies in this area have found this to be the case. Furthermore, a lot of the studies that have found a benefit didn’t actually look at diets that were significantly lower in carbohydrates. For example, the definition of low-carb in much of the research looking at these studies was < 45% total energy intake from carbohydrate – which isn’t far from the usual recommendation for the general public of 50% (4). This is why low-carb diets aren’t recommended in evidence-based guidelines for PCOS such as this fact sheet from the British Dietetic Association.

It’s also important to consider whether a low-carb works on an individual basis in terms of lifestyle, food preference, appetite, energy levels, relationship with food etc. For example, a recent study looked at the effects of a ketogenic Mediterranean diet on 24 women with PCOS and while some positive outcomes were found at the end of the 12-week study, only 14 women completed the study (5).

However, the type of carbohydrate-based foods can make a difference for those with PCOS due to what is called the glycemic index (GI). GI is a way of ranking the effect of food in terms of how quickly they spike blood glucose levels —  high GI means a fast rise in blood glucose whereas low GI means a low rise. 

A low glycaemic index (GI) diet has been linked with reducing insulin resistance, improving hormone levels and regulating periods in those with PCOS (6, 7).  

A low GI diet can usually be achieved by consuming less refined carbohydrate foods (like sugary food and drinks, white bread, white rice etc.) and more complex carbohydrates like wholegrains and higher fibre options. However, a number of factors like cooking method and ripeness can impact GI. For more information about the low GI diet, check out this factsheet.

Carbohydrate cravings are commonly reported in women with PCOS. This may be related to a number of factors such as changes in blood glucose levels, food guilt or restriction. Eating in a satisfying way, with regular meals that contain low GI carbohydrates, protein, fruit/vegetables and fats quite evenly spaced out over the day may help with this. Some people may also benefit from support for their relationship with food if struggling with binge or emotional eating. 

Meal patterns

As mentioned above, eating regular balanced meals and snacks during the day is important for managing blood glucose levels and reducing the risk of binge eating (which is common in those with PCOS). This is also a good nutritional strategy in general.

In terms of meal size, one study found that eating most calories at breakfast, followed by lunch then dinner, improved fertility, insulin and hormone levels in women with PCOS (8). 

Although this is only one study, other research has found health benefits related to eating bigger meals earlier in the day, such as improved insulin levels and reduced inflammation (9). This is thought to be related to syncing up our meals with our body clock (which is also known as our ‘circadian rhythm’). ‘Night owls’ with PCOS have also been seen to be less likely to consume a Mediterranean-style diet (10). 

Anti-inflammatory diets

Healthy eating is encouraged for those with PCOS in order to improve symptoms and reduce the risk of heart disease and diabetes (11). Due to the link between PCOS and inflammation, anti-inflammatory patterns of eating may be particularly beneficial (12).

The Mediterranean diet is known for its anti-inflammatory properties, and is associated with a lower risk of a number of chronic diseases. This way of eating is based on consuming a good intake of fruit, vegetables, grains, nuts, olive oil and fish.  

Currently, there aren’t many studies that have looked at the impact of this diet on PCOS. However, a study from 2020 found that following the Mediterranean diet or the similar DASH diet led to improvements in PCOS outcomes (13). Another study found that those with PCOS may be less likely to consume a Mediterranean-style diet (14). 

Some research has also supported specific parts of anti-inflammatory diets when it comes to PCOS. For example, a good intake of fibre and opting for unsaturated fats like flaxseed oil and omega-3 and a lower intake of saturated fat have been linked with benefits (15, 16).  

What about weight loss?

PCOS isn’t caused by a higher weight, but carrying more fat around the abdomen in particular is associated with worsened insulin resistance which can have a knock on impact on higher levels of androgens. 5-10% weight loss in those who have a higher weight has also been linked with improvements in PCOS (17). 

However, people of all sizes can have PCOS and this condition makes it more difficult to lose weight due to hormonal and metabolic changes – and maintaining weight loss in the long term is already notoriously difficult without adding PCOS into the mix (18, 19).  

When considering a weight loss diet it’s always important to weigh up the pros and cons on an individual level. Possible risks include worsened: self-esteem, mental health, body image, disordered eating, weight cycling and reduced health behaviours (20). 

This is particularly important in the context of PCOS where the risk of mental health issues, disordered eating and binge eating are already higher (21, 22, 23). Stress can also have a big impact on insulin resistance and hence PCOS symptoms, so if a weight loss diet feels stressful this may not be a good idea (24). 

There are also many lifestyle and medical changes that can improve PCOS, without focusing on weight loss. So if you are unsure about whether this is a good idea for you, you can seek information and support from your medical team, and potentially a health professional who specialises in non-diet or weight-inclusive approaches as well.  

Summary:

The evidence-based nutritional management of PCOS involves consuming a balanced and varied diet that prioritises a regular meal pattern, low GI carbohydrates and anti-inflammatory foods (like those found on the Mediterranean diet).

Watch this space for an upcoming article about nutritional supplements for PCOS.

References:

1. NHS Website (2019) “PCOS” [accessed September 2022 via: https://www.nhs.uk/conditions/polycystic-ovary-syndrome-pcos/
2. Rotterdam ESHRE/ASRM‐Sponsored PCOS Consensus Workshop Group. (2004). Revised 2003 consensus on diagnostic criteria and long‐term health risks related to polycystic ovary syndrome (PCOS). Human reproduction, 19(1), 41-47. [accessed September 2022 via: https://pubmed.ncbi.nlm.nih.gov/14688154/]
3. Peigné, M., & Dewailly, D. (2014, September). Long term complications of polycystic ovary syndrome (PCOS). In Annales d’endocrinologie (Vol. 75, No. 4, pp. 194-199). Elsevier Masson. [accessed September 2022 via: https://pubmed.ncbi.nlm.nih.gov/25156132]
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5. https://pubmed.ncbi.nlm.nih.gov/32103756/
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Nutrition and PCOS was last modified: September 9th, 2022 by Maeve Hanan