5 Foods to Avoid While Taking Metformin

Following my recent post about the pros and cons of taking the prescription drug metformin for the common condition of PCOS experienced by many females, I’ve had a few clients asking me more generally about metformin – and in particular I’ve been asked a few times whether there are any foods to avoid while taking metformin?

So today, let’s dig down and see which foods you would better off avoiding in order to get the maximum benefit whilst taking metformin.

What is Metformin?

Before we get into the foods to avoid while taking metformin, first of all – what exactly is metformin? Well, it’s a drug which is commonly prescribed in the form of oral tablets and is used to treat high blood glucose caused by type 2 diabetes. Common brand names include: Axpinet, Diagemet, Glucient, Glucophage, Glumetza and Metabet. Specifically, it works by reducing the amount of glucose produced by your liver, lowering the amount of glucose your body absorbs and increasing the blood-sugar lowering effect of insulin in your body.

The Importance of Diet & Lifestyle

Metformin can be a powerful intervention in treating the symptoms of type 2 diabetes and PCOS because it helps reduce the insulin resistance which leads to pre-diabetes and eventually to type 2 diabetes.  However, we know that lifestyle and dietary interventions can have a very significant impact on improving the underlying causes of insulin resistance.

My first-line recommendation to clients suffering from PCOS, pre-diabetes or type 2 diabetes is therefore to switch to a more ‘wholefood-centric’ diet – reducing ultra-processed foods as much as possible which can have a very significant impact, since these foods can harm your friendly gut-bacteria. In particular, ensuring your diet contains sufficient dietary fibre is crucial to improving the symptoms of type 2 diabetes. Similarly, introducing frequent bouts of short yet higher intensity forms of exercise can also have a huge benefit.

For more information on using diet and lifestyle to help get to the root cause of type-2 diabetes/ PCOS, have a look at my Enhanced Energy programme which has successfully helped many clients tackle the underlying issues causing their symptoms.

Foods to Avoid While Taking Metformin

In terms of diet, it’s clear that what you eat can have a huge impact on the effectiveness of metformin. In order to gain the most benefit from metformin, here are the 5 foods to avoid while taking metformin:

1. Added sugar

 High sugar foods will lead to large spikes in your blood sugar – making it much harder for metformin to do it’s job in lowering blood glucose. Stick instead to slower releasing, higher-fibre carbohydrates such as whole fruits, vegetables, beans and wholegrains such as whole oats and barley. Try to avoid desserts, sugary snacks and particularly sugar-sweetened beverages as much as you can! 

2. Refined carbs

 Here I’m referring to those ‘ultra-processed’ carbohydrates where all the fibre has been removed in the refining process – so think white flour, white rice – even mashed potato! Believe it or not, they are converted very quickly into glucose – and so have exactly the same effect as added sugar! Again, the solution here is to avoid highly-refined carbohydrates (eg white bread, white pasta, cakes) and choose wholefood / wholegrain alternatives such as brown rice, wholegrain barley, rye bread, oat cakes etc. The higher fibre content will ensure you have a steady and sustained release of glucose, as opposed to the big spikes that metformin will struggle to deal with. 

3. Alcohol

 Metformin has been shown to increase lactic acid in the blood after drinking alcohol – which in certain circumstances may lead to a condition called lactic acidosis – since both alcohol and metformin can independently increase lactate levels in your body. However, this is usually associated with higher amounts of alcohol consumption over more extended periods of time. Nevertheless, by cutting down on alcohol you will reduce the risk of increasing your lactic acid levels – whilst also reducing your risk of long-term chronic conditions such as many types of cancer. 

4. Grapefruit & Grapefruit Juice

 I know this one sounds a bit random, but grapefruit has been shown to promote the accumulation of metformin in the liver, which may “exacerbate lactic acidosis in diabetic patients taking metformin concurrently”. Do note though, that this study was only performed on non-diabetic rats, so it does need to be replicated in humans with type 2 diabetes. It’s worth bearing in mind though that grapefruit is known to interact with 85 different drugs, potentially making them more powerful by reducing the rate at which they are broken down in the stomach. 

5. Low Protein Breakfasts!

 This is more of a general meal-recommendation as opposed to an individual food – but it is one of the most important principles to bear in mind when trying to stabilise your blood sugar – and hence improve the effectiveness of metformin. Try to base your first meal of the day on high-protein foods such as eggs, Greek yogurt, kefir etc which will help stabilise your blood sugar for the rest of the morning. Even better when paired with higher fibre foods (as mentioned above) such as avocado, oats, berries, seeds etc. I recently saw the direct benefits of doing this with a client who was using a ‘continuous glucose monitor’ (CGM) which showed her how adding in these higher-protein wholefoods for breakfast really helped to stabilise her blood sugars throughout the entire morning.

The moral of the story – try to cut down on those sugary cereals and white bread/ pastries at breakfast and add in higher protein wholefoods such as eggs and natural yogurt!

Bonus: Karela

Karela (also called bitter gourd) is sometimes used to flavour curries such as bitter gourd masala – as well as being made into juices and teas. It has been known to lower blood sugar – so use it with caution when taking metformin to avoid the risk of your blood glucose falling too low

What Else Can You do to Improve the Effectiveness of Metformin?

Whilst metformin will certainly help improve the symptoms of poor blood-glucose control, and avoiding these 5 foods will certainly enhance the effectiveness of metformin, in my view the bigger picture is trying to get to the root of the issue and actually begin to tackle the underlying causes of poor blood sugar control.

We know that prediabetes, type 2 diabetes and PCOS are all closely related to insulin resistance – and the diet & lifestyle/ exercise interventions I recommend to clients are very much focussed on removing the underlying causes of insulin resistance – not just treating the symptoms.

So, the key is to not only bear in mind these foods to avoid while taking metformin, but to also begin switching to a predominantly natural wholefoods diet. In addition, introducing plenty of frequent but short bouts of high-intensity activity can have a significant impact on your type 2 diabetes/PCOS symptoms, as well as improving many other aspects of your health – with no side-effects!

Struggling to manage your metabolic health or balance your hormones? Just before I sign-off – if you’re tired of ‘generic’ advice and want a personalised, evidence-led approach, I just want to let you know that I offer premium 1-to-1 online coaching for busy professionals. Click here to learn more and book a Free 30-Minute Health Review. I’d love to hear from you!

Good luck!