Essential Minerals Phosphorous, Magnesium, Potassium and Chloride

As a London personal trainer, in addition to training my clients face to face, I also offer a package of 2 weeks nutrition coaching for just £100.00. I’ll analyse your eating habits, review your completed questionnaire, and advise you on how to improve your nutrition to help you achieve your health and fitness goals.

A key part of healthy eating is to get enough micro-nutrients,  namely vitamins and minerals. Here are three of the major minerals:


Phosphorus is the second most abundant mineral in the human body. The most abundant is calcium. An average 60kg (132lbs) person has 600g of phosphorous in their body, primarily in the bones, teeth, and cell membranes.

Phosphorous works closely with calcium for bone structure, and these two minerals are ‘co-dependent’ for bone health. Without phosphorous, you cannot absorb calcium, or repair broken bones, or use the B vitamins, or produce a whole range of hormones.

That’s not all. Phosphorous is also key to one of your energy systems, the creatine phosphate system, one of the anaerobic energy systems. It is also needed for the metabolism of fats.

What if your diet is deficient in this mineral? Phosphorous deficiency causes weak bones (which can lead to osteoporosis), and weak and painful muscles. It can be caused by excess sucrose in the diet, as sucrose is an anti-nutrient, cannibalizing phosphorous in order to metabolise it. Lack of vitamin D can also cause phosphorous deficiency. Alcoholism can also cause deficiency in this vital mineral. Vegetarians and vegans need to eat a lot of foods containing phosphorous to ensure adequate intake.

Medications containing aluminium hydroxide can inhibit phosphorous absorption. It is not uncommon for medication to have adverse effects on your ability to absorb certain vitamins and minerals.

Excess phosphorous is simply processed by the kidneys and excreted in urine. There are no toxic effects, at worst you get diarrhoea, and your ability to absorb other minerals such as magnesium and zinc may be impaired.

Foods rich in phosphorus include: meat, oily fish, eggs, milk, cottage cheese. Vegetable sources are less easily absorbed, and include beans, pulses, nuts, and wholemeal brown bread.

Recommended daily intake: 800 – 1,500mg (children 500mg).


This major mineral is vital to activate the body’s main source of energy in the cells: ATP (adenosine triphosphate). Magnesium also works with calcium for muscle contraction and relaxation.

Over 300 enzymes require magnesium in order to function. That makes magnesium a pretty big deal! Magnesium is also needed to generate nerve impulses. For healthy teeth and bones, magnesium is needed to enable calcium to perform its structural role, ie the absorption of calcium into the bones to strengthen them.

Magnesium is also one of the 4 electrolytes (the other 3 being potassium, sodium, chloride). Electrolytes are minerals which regulate fluid levels between the bloodstream and all the cells of the body, and an imbalance can be life-threatening. Correct blood volume and blood concentration has profound effects on your health. Electrolytes also enable nerve impulses to transmit around the body. When dissolved in water, the electrolytes conduct electricity.

Magnesium depletion is mainly caused by sweating. What makes magnesium unique among the electrolytes is that athletes lose it in sweat at the same rate as the average adult. In the case of the other three electrolytes, the body adapts to physical exercise and is increasingly able to conserve chloride, potassium, and sodium during exercise that causes sweating.

Of the 6 major minerals, magnesium is present in the smallest amount, roughly 30g in a typical 60kg adult. Over half of it is in your bones. The rest is in your muscles, heart, liver, and only 1% is in your bloodstream.

Magnesium deficiency causes lack of appetite, muscle weakness, fatigue, irregular heartbeat, and high blood pressure. Extreme dietary deficiency causes the body to release some magnesium from the bones to help the muscles, heart and liver to function effectively.

How can you become deficient in magnesium? Alcoholism, poorly controlled diabetes, and chronic vomiting/diarrhoea/sweating can all cause deficiency.

Foods rich in magnesium include: pumpkin seeds (the best source), and all green leafy veg (high concentration of chlorophyll molecules), also cashew nuts, almonds, beans and pulses, porridge oats, whole grains. Magnesium oil can be administered for people who are deficient, by way of ‘trans-dermal’ therapy: sprayed onto feet/backs of knees and rubbed in. Bathing in Epsom salts (magnesium sulphate) also boosts absorption of magnesium through the skin. You can buy Epsom salts cheaply at Boots the Chemist.

There is more magnesium in hard tap water, and some evidence that deaths from heart-attacks is lower in hard water areas, as magnesium enables the body to moderate heart spasms during heart-attacks.

High-intensity modern farming methods has depleted the magnesium levels in the soil, so  food grown in these conditions has less than half the magnesium as it did 100 years ago. This is a particular problem in China, where agricultural land is severely depleted in magnesium and other minerals.

(Magnesium should not be confused with manganese, which is a separate mineral. Manganese is found in spinach and oats, and manganese deficiency can lead to joint problems.)


Potassium helps regulate your blood sugar levels, and is one of the electrolytes (which regulate your fluid levels). One of the richest sources of potassium is bananas (which is also a good source of the soluble fibre pectin). If you’re playing sports on a hot day and sweating a lot, a banana break is a great idea to restore your potassium levels.


This major mineral is one of the 4 electrolytes, vital for fluid balance and nerve transmission (see above for full explanation).

Other functions include enabling absorption of potassium (which promotes muscle-contractions), formation of gastric juices (hydrochloric acid), removal of toxins, hormone production.

A typical 60kg person contains 90g of chloride, and recommended daily intake is 100mg.

Food sources: table salt (sodium chloride), abundant in processed and junk foods, also in sea-food and salt-water fish.

Deficiency: It’s rare in the world to have chronic deficiencies, but in countries with famine, children suffer stunted growth, mental apathy, and muscle cramps. Acute deficiency can occur during severe diarrhoea, vomiting, and sweating, resulting in muscle spasms/cramps, physical weakness and mental confusion.

Excessive chloride in the diet causes high blood pressure and excess fluid retention. I had a personal training client in east London with very high blood pressure. When I analysed his diet, he explained that he ate a lot of salty crisps. After a month of eating no crisps, and not adding salt to his food (another of his bad habits!) his blood pressure was back within healthy range.

Dominic Londesborough is a personal trainer in London and author of the blog.