Vitamin A
TL;DR
something.
Fat soluble so take with food containing fat.
Retinol is vitamin A1.
The UK's NHS recommends 700 µg a day for men and 600 µg a day for women.
Found in cod liver oil. Based on UK recommendations two typical doses of cod liver oil will provide double your RDA of vitamin a.1 This may be an issue and if you supplement with cod liver oil and a multivitamin you should ensure you take a multivitamin that does not include vitamin a.
Avoid taking vitamins, minerals (such as calcium) and other supplements for 30-60 minutes after consuming coffee - it contains compounds (polyphenols) that limit the absorption of many micronutrients.
Something about bones.
Food Sources
Forms/Types
Quality
As with all supplements - buyer beware. It's quite common for supplements to be contaminated with a variety of impurities, often in the form of heavy metals, and/or contain far more or less of the ingredients stated on the label. There's no simple rule of thumb to avoid this, such as avoiding cheap or imported products; expensive or well-known brands produced in-country may be just as bad. Ideally you should take some time to find products (if you can) that;
- have been laboratory tested on behalf of the manufacturer by a reputable body or company that operates in your country or region (here's an example of a Peak Supps creatine supplement available on Amazon in the UK which has been tested by Eurofins: Creatine Monohydrate Powder 1Kg | Pure Micronised | Packaging May Vary - see pictures 3 & 4)
- in the UK & EU, are manufactured in facilities that meet the minimum standards of good manufacturing practice (GMP) in their production processes (for medicines).23 Facilities are inspected for compliance and manufacturers' product(s) must:
- be of consistent high quality
- be appropriate to their intended use
- meet the requirements of the marketing authorisation (MA) or product specification
Be wary of any manufacturers or brands making claims around these valid but irrelevant standards;
- HACCP: this standard relates to food safety which indicates that the seller is claiming their supplement is a food; whilst meeting this standard is worthwhile, GMP (detailed above) would be a more appropriate standard
- ISO22000: same as HACPP
- ISO9001: this standard is focussed on quality control management systems in the context of managing a business or organisation, not directly on the the quality of the products that business produces (although it may have a beneficial impact)
Dosage - How Much?
Deficiency - Too Little
Toxicity - Too Much
Caution required.