Minerals are chemical elements required by organisms to perform vital functions. Plants absorb these minerals from the soil, and when these are later consumed by animals they are stored within its flesh. Upon consuming animal products, plants or indeed water, humans can ingest all of the minerals they require.
Minerals can be broadly separated into macrominerals and trace minerals, called so because the macrominerals are required in large amounts and the trace minerals in far smaller amounts. We will start with the macrominerals.
Magnesium
The human body at birth contains around 760mg of magnesium, rising to around 5g at 4-5 months of age and 25g in adulthood. 30-40% of this is found in muscles and soft tissue, 1% in extracellular fluid and the rest being found in bones.
Soft tissue magnesium is a coenzyme involved in energy metabolism, protein, DNA and RNA synthesis and is used in the transfer of electrical signals around the body. It’s also important for maintaining cell membrane integrity and has a role maintaining potassium and calcium levels in cells (which are used to transfer information and perform numerous functions including muscle contractions and motor unit innervation). Because of this, magnesium can be considered vital for maximal exercise performance.
Deficiency can result in muscular weakness, lethargy, nausea, unwanted weight loss and sleep issues. On top of this, hyperirritability, muscle spasms/cramp and even cardiac arrhythmia can result from prolonged deficiency. In the short-term, magnesium loss is associated with poor exercise recovery. Maintaining healthy magnesium levels is associated with a protective effect against both depression and ADHD.
Undergoing repeated strenuous exertion, especially in the heat, can make us very susceptible to these problems if we don’t pay attention to what we eat, as magnesium can be lost in sweat.
Serum magnesium levels have also been positively related to maximal muscle contraction ability, since the reactions involving the build-up and the breakdown of ATP, ADP, and creatine phosphate are Mg dependent. The effect of magnesium levels on the high-energy phosphates have been repeatedly investigated in the quadriceps muscles in states of varying hypomagnesaemia in man, and a significant lowering of contraction ability/force generation has been found, as compared with normal, non-magnesemic controls in men.
A WHO report recommended that magnesium intake could be considered as a function of mg per kilogram of bodyweight, or as a recommendation of mg per calorie consumed. They did contest, however, that recommendations at present are based potentially upon some amount of estimation.
What is noteworthy is that in theory magnesium absorption is well controlled and therefore toxicity is unlikely, though due to reduced absorption with high intakes, diarrhoea can ensue.
The WHO Recommendation is 4mg per kilogram for males and females, dropping to 3.5mg per kilogram after age 65. Due to magnesium’s functions within exercise, athletes have been known to supplement it at higher doses but a lot more evidence is needed before it could be concluded that high-dose magnesium supplementation has any benefit to exercise performance.
However, magnesium is one of the most common deficiencies in the Western World, and a 200-400mg supplement of magnesium (there are many forms, but citrate is one of the most effective) is not a bad idea for those most at risk of deficiency, including those on restricted calorie intakes and athletes. As always, though, before using supplementation consider whether deficiency is actually likely, we will discuss how to do this at the end of this module.
Potassium and sodium
Potassium accounts for around 0.2% of the weight of a human body, and its ions are present in a huge amount of proteins and enzymes used for normal function. Potassium performs a colossal amount of functions, but the key reason you need to be aware of it is because of its impact on total body water homeostasis. Potassium is present in green leafy vegetables, and is also found in large amounts in low sodium salt alternatives.
Sodium is most commonly consumed in table salt (sodium chloride). Much like potassium it is one of the prime minerals relevant to health and nutrition, and although it has been commonly demonised for causing high blood pressure, this needs to be taken into context with a few different factors.
In nerve cell membranes, a ‘sodium/potassium pump’ transports 3 sodium ions outside of the cell and 2 potassium ions back in. Ions carry an electrical charge, and this exchange leads to a disparity between the charge inside and outside of the cell. This creates what is known as an ‘action potential’ and is the main way which nerves are able to communicate.
As mentioned, though, the key reason you need to consider sodium and potassium in an applicable sense is because of their role in body water level management. This will be explained in far greater detail in the module on hydration, but for now consider that the recommended intake for potassium is 3.5g, and the recommended upper limit for sodium consumption is 2.4g per day. Though a maximum intake of sodium is given, this should NOT be taken as meaning that less is better or that the ideal amount is zero or as little as possible. Both of these minerals are crucial for survival.
Like we mentioned, however, this will be covered in detail when we talk about hydration.
Chlorine
Chlorine is crucial for the production of the hydrochloric acid which plays a role in stomach digestion. Aside from this, it’s a key player in cellular functions including allowing things to cross the cell membrane. The recommended daily intake is 3.4g which will be consumed almost entirely from sodium chloride (table salt).
Calcium
Calcium is probably best known for its role as a component of bones, though it is also vital for heart function, digestive health and the contraction/relaxation of muscles. On top of this an adequate calcium intake is needed for the proper function of blood cells. Deficiency in calcium can lead to cramping and muscle spasms as well as bone weakness. The Recommended daily intake for calcium is 1000mg, though the upper limit of 2500mg should not be exceeded as this can cause constipation and impair iron and zinc absorption.
The majority of calcium you consume will be via dairy, though calcium can be consumed from vegetable products such as broccoli and kale. It’s worthy of note that many vegetable sources of calcium contain oxalic acid which can block calcium absorption, though, and as such a vegan client may wish to look at tofu or fortified milk alternatives.
Phosphorus
The final macromineral is phosphorus, which is a component of bones just like calcium but on top of that it is used to make phosphate, which is a critical part of DNA, ATP and other molecules. Generally, the majority of phosphorus you consume will be via protein-containing animal products such as meat, poultry, fish and dairy. Plant based phosphorus is harder to absorb, so again this is a mineral which vegans may need to be aware of. Phosphorus RNI is 550mg/day.