Muscle Cramps – Magnesium or Potassium?

Muscle Cramps – Magnesium or Potassium?

One of the major causes of cramping is lack of proper hydration from the get go – not drinking enough water period!  Also, nutritional deficiencies play a major role here – if you are not getting enough magnesium in your diet of which it is now predicted that 65% of Americans are deficient in magnesium, the Diva of Nutrients.  Potassium is usually not a nutrient deficient issue because we hold potassium inside the cells but if we get dehydrated, we lose potassium as we sweat and the body’s need for hydration increases.

Therefore cramping is usually an issue with electrolytes imbalances most notably magnesium and potassium.  It is also a side effect of some medications like tamoxifen (common breast cancer drug) which causes a reduced blood flow to the muscles leading to cramping.


Should you eat bananas to replace potassium?  Many professional athletes are seen eating a bananas on breaks
between tennis games but I have noticed that professionals have switched to sports drinks that have been specially designed and developed for them.  Why?  Most likely because bananas can give you a rush of blood sugar that is followed by a blood sugar crash – an athlete’s worse nightmare.   In addition, sports drinks with the right balance of electrolytes, vitamins and specially designed carbohydrates sources are more readily absorbed and will maintain even blood sugar levels.


For the weekend athlete or even someone who plays tennis 2-3 times a week, I usually do not recommend eating bananas to restore potassium levels to prevent cramping.  This is a for a couple of reasons – first most of us are actually deficient in magnesium and it can cause a blood sugar crash especially if we have blood sugar control issues.   On top of that – it can lead to weight gain as it can promote imbalances in fat metabolism hormones.


Potassium or Magnesium Deficiency? Which Is It?

When and where cramps occur – calf, toes – will tell you what mineral you are deficient in.

  • Ever get cramp in your calf right when you are warming up and just started exercising – that is magnesium deficiency.
  • Cramping during the end of exercise or right after exercise, is usually caused by a potassium deficiency.
  • Toe Cramps or leg cramps at night – Magnesium Deficiency


Magnesium is the usual cause of these cramps and can easily be resolved if you take a magnesium supplement. Or, make sure you are properly hydrated and eat foods rich in magnesium – green leafy vegetables and nuts are both great sources. Want to learn more about magnesium and why the average American is deficient in this important minerals, see my blog on magnesium.

Should You Supplement with Potassium & Magnesium?
First supplementing with potassium is usually not recommended unless it is low dosage say in a multiple/mineral supplement or in a sports drink.

Why? Because too much potassium can be lethal as it can disturb the electrical rhythm of the heart.

It is also very readily absorb as every cell in the body need potassium so you will see a respond to even low dosage potassium say in a sports drink in relieving cramps.

Magnesium on the other hand – you can supplement in the important mineral, just be very careful with the type of magnesium as too much can lead to diarrhea. If you are not working with a

Nutrition Tip:  Potatoes are actually one of foods that is high in potassium; banana fall way behind compared to potatoes.

qualified nutritionist – it is safe to supplement with this mineral in sports drinks, like this one, that contain this mineral. Or, keep this supplement on hand for night time cramping as it is slowly absorbed and less likely to have negative side effects.

Unless you are working with a nutritionist or registered dietitian, I would not recommend going over 300 mg. per day of magnesium.  In addition, make sure that you are getting enough of the other minerals like calcium, otherwise mineral imbalances can occur.