In Part One I discussed some guidelines to help ensure that you are getting the best out of your supplements. Read on for more pointers.
There isn’t much point in taking a supplement in a form that your body cannot use. Mineral bioavailability simply refers to the proportion of a mineral that is actually absorbed into the blood to be used by the body.
A ‘bioavailable’ mineral must be soluble in the intestine so that it can be absorbed. Minerals should be bound to different compounds to aid their absorption. This binding, or ‘chelation’, helps the mineral to survive the acid environment of the stomach and pass through into the small intestine for absorption.
If the mineral is bound too tightly, or not tightly enough, it can be released at the wrong time. This is why the ‘form’ of the mineral is an important consideration.
Generally inorganic forms of minerals – carbonates, sulphates and oxides are not well absorbed. On the other hand, organic forms such as citrates, gluconates, aspartates and amino-acid chelates are more bioavailable.
Better quality minerals, i.e. those that are in a bioavailable, organic form do tend to be more expensive. However, cheaper supplements may be a false economy if they are poorly utilised by the body. Choosing a supplement becomes a case of weighing the cost of the supplement against its bioavailability. For example, in the New Optimum Nutrition Bible, Patrick Holford (1) explains that iron amino acid chelate is four times better absorbed than other forms, making it worth the additional cost.
Holford lists the most bioavailable forms of each mineral. All of the following forms are the most readily available to the body. In descending order (the very best first), he lists:
Calcium – amino acid chelate, ascorbate, citrate, gluconate, carbonate
Magnesium – amino acid chelate, ascorbate, citrate, gluconate, carbonate
Iron – amino acid chelate, ascorbate, citrate, gluconate, sulphate, oxide
Zinc – picolinate, amino acid chelate, ascorbate, citrate, gluconate, sulphate
Manganese – amino acid chelate, ascorbate, citrate, gluconate
Selenium – Selenocysteine or selenomethionine, sodium selenite
Chromium – Picolinate, polynicotinate, ascorbate, gluconate
Tablets or Capsules?
Deciding between capsules or tablets is often a personal preference. Those who find tablets difficult to swallow often favour easy-to-swallow capsules. Sensitive individuals also tend to prefer capsules which are more likely to be free from fillers or binders. On the other hand, tablets can be compressed meaning that a higher dosage can be delivered in a single pill. They also allow for ‘sustained-release’ formulas. This can be useful for water-soluble vitamins such as Vitamin C, where absorption is better when given as a steady release formula rather than in a single dose.
For very sensitive individuals or for the delivery of light-sensitive nutrients such as coenzyme Q-10, capsules are the best choice. There are of course advantages to both types of supplements, which are listed below.
|Superior protection against oxygen and light||Low cost|
|No need for fillers and binders||Allows for sustained-release formulas|
|Odorless and tasteless||Can fit more ingredients in through compression|
|Less gastrointestinal irritation||Can be notched to divide the dose|
The simplest way to be certain of the quality of a supplement is to check that it is GMP certified. Good Manufacturing Practice (GMP) is an assurance of quality of manufacture. While medical drugs are held to these strict standards, it is not currently a legal requirement for food supplements in the UK. However, most reputable supplement companies voluntarily submit their products to GMP certification. This compliance requires thorough record keeping, quality testing, and standards consistent with the manufacture of drugs.
1. Holford, P (2004) Patrick Holford’s New Optimum Nutrition Bible. London: Piatkus.