Quick Summary tl;dr
In the initial weeks of starting your low carb or ketogenic diet, you may experience symptoms of the ‘keto-flu’. This could be due to a lack or loss of magnesium in the body. Ensuring you get a good source of magnesium rich foods in your diet is extremely important.
If you are unable to eat any of these foods or cannot eat enough, then looking to supplement will be of added benefit.
What is Magnesium and Why is it Needed in the Body?
Magnesium is the fourth most abundant mineral in the body and is needed for several important functions including:
- Maintaining normal muscle and nerve function
- Keeping a healthy immune system
- Maintaining normal heart rhythm
- Building strong bones ( 1)
It is involved in over 300 different biochemical reactions in the body and is also needed to help generate and use ATP, the main unit of energy in the body’s cells ( 2).
An adult body contains around 25 g of magnesium, with around 50% to 60% being present in bones and the rest in soft tissue, red blood cells and serum ( 3).
Normal Ranges and the Recommended Daily Intake
Only 1% of magnesium is found in the blood serum and red blood cells ( 3). The most common way for magnesium levels to be tested in the body is through the serum. Since this only accounts for 1% of where it is stored, it may not give a true representation of its status in the body. Likewise, if serum magnesium levels drop, then stores from the bone will be used to top this up ( 4).
The reference nutrient intake for magnesium does vary slightly for males and females but a range of 300-400 mg/day is recommended (5).
Symptoms of Low Magnesium Levels
Normal serum magnesium levels range between 0.75 mmol/L and 0.95 mmol/L ( 4). Hypomagnesemia, or low magnesium, is defined as having a serum magnesium level of <0.75 mmol/L.
The levels of magnesium in the body are closely regulated by the kidneys. The serum magnesium concentration is primarily controlled by its excretion in the urine.
Low levels of magnesium in the body can results in symptoms including:
- Muscle spasms
- Heart palpitations
- Low Blood pressure
- Sleep problems
- Muscle cramps
Diseases Linked to Magnesium Deficiency
Epidemiological evidence has also shown that many diabetics can often suffer from a deficiency in magnesium. Other long-term health conditions like cardiovascular disease and depression has also been linked to low magnesium levels ( 6).
Low Levels of Magnesium and "Keto-Flu"
Within the first few weeks of starting a low carbohydrate or ketogenic diet, you may notice certain symptoms of the “keto flu”. There are many reasons for this happening but some of the symptoms may be due to a loss in magnesium.
In the first few weeks of a low carbohydrate diet, you can lose a lot more water from the body. As glycogen is stored in the body as one-part glycogen and three parts water, it means that more water is dumped through the kidneys. Since magnesium levels are controlled through the kidneys, this can then inadvertently cause a drop-in serum magnesium levels.
Top 7 Magnesium Rich Foods
To help combat any loss in magnesium and help alleviate symptoms, below is an overview of how to get magnesium into your diet.
1. Nuts and Seeds
Nuts and seeds are a great source of fats and can contribute a small amount of protein to a low carbohydrate diet. They also have a great mineral content to them.
Nuts that are especially higher in magnesium are almonds and cashew nuts. A 28 g serving (roughly 1 oz or a handful) provides 76 mg from almonds (18% RDA) and 83 mg (21 %) from cashew nuts ( 7).
As with nuts, seeds also have a great nutritional profile. In particularly they have a significantly high fibre content meaning their carb count can be pretty low using the net carb counting method.
Hemp seeds are by far the best source as they provide 170 mg (43% RDA) per 28 g (1 oz), followed by pumpkin seeds at 168 mg (41% RDA), and sunflower seeds at 92 mg (23% RDA) ( 7).
For more information: Nuts & Seeds on a Ketogenic Diet.
Healthy recipes using nuts & needs:
2. Dark Leafy Greens
All leafy greens including spinach, kale, chard and collard greens are all packed with nutrients including magnesium. A 5-oz (144 g) serving provides 110-130 mg magnesium (25-30% RDA).
As well as being high in magnesium, spinach is also a great source of vitamin A, C, K and iron. Adding this leafy green and others into your daily food intake will make sure you hit many of your vital vitamins and minerals needed, especially magnesium ( 7).
Healthy recipes using leafy greens:
3. Fatty Fish
As well as being an excellent protein source and being one of the only few food sources of vitamin D, certain cuts of fatty fish also provide other key nutrients including that of magnesium.
The major sources of fish that have a higher magnesium content include that of mackerel, sardines, salmon, sea bream and halibut. Depending on the type of fish, a 5-oz (142 g) serving provides up to 110 mg (28% RDA) of magnesium ( 7).
Healthy recipes using fatty fish:
4. Dark Chocolate (above 70% cocoa)
Dark chocolate and cacao powder not only provide several health benefits, it is also a great source of magnesium. A 28 g (1 oz) servings of dark chocolate provides up to 65 mg (16% RDA) of magnesium ( 7).
Although one bar would contribute significantly to your magnesium intake for the day, it can also add considerably to your overall carbohydrate intake. Consuming around 1-2 squares per day will still offer a significant amount of magnesium to your diet.
Healthy recipes using dark chocolate and cacao:
Avocados are mostly known for being packed with the heart-healthy monounsaturated fats. They make a great staple fat source within a low carbohydrate and ketogenic lifestyle, especially for vegetarians.
One 150 g (5.3 oz) avocado provides 44 mg (11 % RDA) of magnesium ( 7). Many people are often concerned about the carbohydrate content of them. However, most of the carb source is that of fibre and so it has a relatively low net carb content.
Healthy recipes using avocados:
6. Bone Broth
One recommendation that is made to anyone starting a low carbohydrate and particularly that of a ketogenic diet, is to incorporate some form of bone broth.
Bone broth is made by simmering the bones and connective tissue of animals (it's easy to make your own bone broth).
The mineral content is extremely high in just having one cup a day and can significantly help with the symptoms of the keto flu. Unfortunately, the exact content of magnesium in a standard recipe is a little harder to calculate as it is dependent on the type of animal used and the parts of the animal used.
7. Mineral Rich Water
As well as coming from our food, magnesium can also be found in mineral rich water. If you are struggling to get any of the food sources above in, then try adding in one glass or small bottle of mineral water.
As well as helping to replenish any water loss that can happen in the first couple of weeks with a low carb diet, it will also contribute to your magnesium intake for the day.
Commercial waters can vary considerably so do be sure to check the labelling to see how much magnesium is contained within them.
Other Sources of Magnesium
Other good sources of magnesium include crab meat, okra, coconut milk, chicken, zucchini, beef, turkey, liver, wild game, tuna and white fish.
For some people, trying to hit the RDA for magnesium may still be a bit of a struggle. Or some people may be experiencing severe symptoms of the keto flu. For both groups, looking at supplementing with magnesium could help significantly.
Best forms of supplementation include magnesium:
Click here for a Complete Guide to Magnesium Supplementation
The upper limit of magnesium supplementation is 350 mg per day (8).
One of the side effects or uses of magnesium supplements is to help with constipation. This means that if you take too much, it can cause diarrhoea and/or bloating in some people.
These symptoms are more common with the oxide and chloride options due to the lower absorption rates (9). Citrate is also commonly used as a laxative treatment.
Magnesium glycinate and malate has less of an impact on the gut and would be recommended if diarrhoea occurs with taking any of the others.
Milk of magnesia can also be taken, especially if you are experiencing high amounts of cramps or constipation. The magnesium quantity of this is generally way above the RDA, but due to it being in liquid form, the bowels often excrete any excess.
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