There is a lot that we can do from a nutritional perspective to help with insulin resistance. Improving insulin sensitivity can reduce the risk of and help the management of conditions such as diabetes or PCOS.
Obviously, diet and exercise play a massive role. Both of those things are more important than supplements.
Just because those things are more important though, does not mean we should just ignore supplements. There can still be additional benefits of supplements if used well.
This post aims to cover those benefits from an evidence-based perspective. It will also cover how and when to use them.
It would be unnecessary to take all these supplements at once. Picking and choosing the ones that fit the best for your specific situation makes sense.
Inositol
Inositol is one of the most underrated options for improving insulin sensitivity.
Research on post-menopausal women has indicated a dramatic decrease in insulin resistance.
There is a wealth of research supporting it for PCOS. Similarly for diabetes.
To be more specific in terms of the effect size, one study measured the insulin response to an oral glucose tolerance test. Consumption of 1200mg of di-chiro-inositol per day for 8 weeks led to a 62% decrease in the amount of insulin required.
Dosage and How to Take:
The simplified approach that works well is to take 2-4g of myo-inositol per day.
Research indicates that taking a combined supplement with both di-chiro and myo-inositol likely works better. It is a little bit more expensive to do this though.
In that case, a supplement containing 2000mg myo-inositol and 50mg di-chiro inositol works well.
Resveratrol
Resveratrol does not have as consistent evidence as other options on this list for being beneficial for insulin sensitivity. It is still a promising option though.
A 6 month randomised controlled trial on those who were overweight but did not have diabetes found that resveratrol did not seem to change insulin resistance, although HbA1c dropped a little bit.
This lines up with the body of research indicating that there are improvements in insulin sensitivity in those with Type 2 Diabetes, but not in those without.
A 2017 systematic review of 9 randomized controlled trials found that fasting blood glucose levels and insulin levels improved to a statistically significant degree. The effect size was not massive though.
Doses of >100mg/day provided a more significant difference in outcomes than doses <100mg/day.
The proposed mechanism is that resveratrol increases Sirt1 activation and improves AMP-activated protein kinase. This theoretically both reduces insulin resistance and increases insulin secretion.
Dosage and How to Take?
~200mg per day is the recommended dosage.
Although resveratrol is found in food, it is quite difficult to get this amount through food.
There are many other reasons to follow a polyphenol-rich diet. For resveratrol in particular though, supplementation would be the best move.
Based on the research, resveratrol is one of the lower priority recommendations on this list.
Magnesium
At a minimum, magnesium deficiency increases insulin resistance. Intracellular magnesium is involved in important processes for insulin receptors.
Low magnesium impairs insulin’s action directly and plays a role in inflammation that might further reduce insulin sensitivity.
If a blood test identifies magnesium deficiency, addressing this through food or supplements is beneficial.
What about those who are not deficient though?
A 2016 systematic review found that taking magnesium supplements for >4 months significantly improved insulin sensitivity in both those with and without diabetes. Taking it for shorter durations did not show a statistically significant effect.
On average, magnesium supplementation helps.
The average person typically does not consume enough magnesium in their diet. From what I have seen, most people consume less than the RDI.
My interpretation of the research is that:
- People who are deficient will get a lot of benefits from supplementing magnesium.
- People who are not deficient but have a sub-optimal intake of magnesium will still get some benefit from supplementing magnesium.
- People who have a high intake of magnesium in their diet will likely not get many benefits from magnesium supplementation.
Dosage and How to Take:
In supplement form: ~300mg magnesium per day. There are many different types. Keeping it simple, magnesium citrate is a good option due to it having good absorption. But that does not mean that no other options are equally good.
In food form: Aiming to reach the RDI (320mg for women and 420mg for men) is a good starting point. Most people fall short of this, so there is likely room for some easy wins here.
Omega-3’s
Adding omega-3 polyunsaturated fatty acids does not seem to improve insulin sensitivity on average in those without any characteristics of metabolic syndrome. It does in those who have at least one characteristic, on average.
This is not overly surprising. As you can see from the definition below, people with characteristics of metabolic syndrome are also far more likely to be insulin resistant as well.
The proposed mechanism is that omega-3’s counteract insulin resistance development by modulating mitochondrial bioenergetics and endoplasmic reticulum stress.
On average the effect of omega-3’s is not massive and not super consistent either.
My interpretation of the research is that if people have low baseline intakes of omega 3’s they likely get more benefit from supplementing it than those with good baseline intakes.
This is also supported by research indicating that those with a higher omega-3 index have improved insulin sensitivity.
Dosage and How to Take:
In supplemental form: 1-3g of fish oil or krill oil per day.
In food form: Having fish 2-3x per week, with at least one of those times being a fatty fish such as salmon.
For plant-based individuals: Omega-3 for those who are plant based is a longer topic, so I encourage reading this post covering it in detail.
Zinc
Zinc deficiency is clearly associated with insulin resistance.
Research on PCOS and zinc supplementation has been promising. Women with PCOS on average have lower zinc levels than those without. And this research has identified that supplementing with ~50mg of zinc per day has the potential to help improve a lot of symptoms.
Higher zinc intake has been associated with lower rates of developing type 2 diabetes as well.
The research directly on zinc supplementation and insulin resistance is relatively weak though. There appears to be a small non-significant improvement on average.
My interpretation of the research is that you should definitely avoid low zinc intake. If you have a good intake already, it is unlikely supplementation will provide much more benefit.
Dosage and How to Take:
In supplemental form: 30-50mg per day. This is only recommended if zinc status is sub-optimal and unlikely to be solved through food.
In food form: 14mg per day and 8mg per day for men and women respectively. A list of zinc-rich foods for context can be found here.
Berberine
Berberine is a compound that can be extracted from certain plants. It has long been used in Chinese traditional medicine.
Some people might become sceptical when they hear “Chinese traditional medicine.” But there is consistent evidence indicating that berberine can reduce blood glucose levels and HbA1c in those with Type 2 Diabetes.
More research is needed. The results look promising so far though.
One study found that fasting insulin levels were reduced by 28.1%. In that same study, a scale measuring insulin sensitivity found a 44.7% improvement.
Dosage and How to Take:
Most studies showing benefits use 1-1.5g of berberine per day.
To optimise outcomes, 500mg consumed 3x per day prior to meals seems to be the most common recommendation. This is because the half-life is only a few hours long.
Chromium
On average, those with Type 2 Diabetes have lower chromium levels in their blood than those without.
Supplementation with chromium picolinate has been demonstrated to improve insulin sensitivity.
A meta-analysis on chromium supplementation in PCOS found reductions in insulin and free testosterone.
Dosage and How to Take:
The recommended dosage is 200-1300µg daily of chromium picolinate.
Apple Cider Vinegar
I have written elsewhere about how the science does not support apple cider vinegar helping with many of the things it is claimed to help.
One thing it does seem to help with is the management of blood glucose levels.
When consumed prior to a high-carb meal, vinegar has been shown to improve insulin sensitivity by 19-34%.
It is not specifically the apple cider vinegar, but more the acetic acid content. This makes up ~5-6% of apple cider vinegar.
The proposed mechanism is delayed gastric emptying. Insulin levels do not need to rise as high to get the job done and bring blood glucose levels back within range.
Dosage and How to Take:
10-30ml of apple cider vinegar is an appropriate dosage for this outcome.
There are concerns that undiluted apple cider vinegar can damage teeth enamel and the oesophagus. Due to these concerns, it makes sense to dilute this dosage with water.
Cinnamon
There is relatively strong evidence that cinnamon helps with blood glucose control.
A meta-analysis that included a total of 6 clinical trials and 435 patients showed a small consistent improvement in HbA1c levels and fasting blood glucose.
This is great news for anybody looking to reduce their blood glucose levels.
The mechanism for how it improves insulin sensitivity is debated. The current consensus is that sensitivity is increased at insulin receptors, while also increasing the number of receptors available, amongst other things.
Dosage and How to Take:
Research has involved dosages of 500mg to 6g per day, in either powder or liquid form.
Taking 1-6g per day is a protocol that commonly shows benefits, with minimal downside. This could be consumed in powder form (ideally added to food), or as part of a supplement.
One study even found that between those dosages, there is no significant difference in outcomes.
Having it around the time of food makes sense, although it is unclear whether that makes it more effective.
Vitamin D
Vitamin D has so many benefits beyond just insulin sensitivity.
A large percentage of the population is deficient in vitamin D too.
Another large percentage of the population also has what could be defined as sub-optimal levels of vitamin D, even while within the healthy range.
Since we get vitamin D from the sun and there are a lot of factors that go into how much we need it is complex to give exact numbers. My rough estimation is that ~30% of the population is deficient and another ~30% have sub-optimal levels.
Since the benefits of supplementation typically are based on baseline levels, this means >50% of people likely could benefit from increasing their vitamin D levels.
There is also evidence that those with insulin resistance often have lower vitamin D levels.
This is always a tricky topic to interpret in isolation though. Vitamin D status is influenced by sun exposure.
Without context, this could be interpreted as “those with insulin resistance likely spend less time in the sun.”
Fortunately, there is consistent evidence that vitamin D supplementation improves insulin sensitivity. As mentioned though, the benefit is likely not to be seen in those who already have good blood levels.
Dosage and How to Take:
In supplement form: 1000IU per day is the standard dosage. Unfortunately, this might not be enough for some people. The best approach is to get regular blood tests and monitor your levels over time. The best dosage is the amount that is required to get you to the top half of the healthy range on a blood test.
From the sun: The standard recommendation is 10 minutes per day in summer and 30 minutes per day during winter.
This also needs to be individualised. People with darker skin need significantly more time in the sun to optimise vitamin D levels.
Obviously, this time in the sun must be balanced with skin cancer risk.
If spending longer than the recommended amount of time in the sun, it makes sense to use sunscreen (even though this blocks further vitamin D absorption).
Practical Summary
As you can tell, there are a lot of options for improving insulin sensitivity.
A lot of these options are quite effective too. They could improve the management of certain conditions such as type 2 diabetes or PCOS.
Some of these supplements could be used alongside medication, or they could potentially reduce the need for medication in certain cases.
A food-first approach is preferred. It makes a lot of sense to emphasise improving your diet if relevant. It is also helpful to know that strategic supplementation could provide additional benefits under some circumstances too though.
