The European Food Safety Authority (39) and the U.S. Food and Nutrition Board (1) have decided that the existing evidence is insufficient to establish a recommended dietary allowance (RDA) or adequate intake (AI) for beta-carotene and other carotenoids.
In most European countries, the recommended intake is based on the assumption that 4.8 mg beta-carotene is needed to meet the requirement of 800 micrograms vitamin A (conversion factor 6). The IOM, the Institute of Medicine in USA, applies a conversion factor of 12 for beta-carotene and 24 for other carotenoids such as beta-cryptoxanthin (1). For very complex matrices (i.e. spinach, kale), human studies have revealed even higher conversion factor for beta-carotene such as 1:21 for a fruit/vegetable mix or 1:26 for vegetables (69).
From epidemiological studies it can be concluded that a plasma level of 0.4 micromole/liter beta-carotene should be aimed at in order to benefit from the preventive health potential. This can be achieved with 2–4 mg/day(40).
Consumption of foods rich in beta-carotene is recommended by scientific and government organizations such as the U.S. National Cancer Institute (NCI) and the U.S. Department of Agriculture (USDA); these dietary guidelines recommend a dietary intake of 3 mg to 6 mg beta-carotene/day, which is associated with a lower risk of chronic diseases.
In response to two clinical studies observing an increased risk of lung cancer in heavy smokers taking long-term high doses (5 to10 times the recommended dose) of beta-carotene (see Safety) the German food industry introduced voluntarily a self-restriction for beverages (max. 2 mg beta-carotene/100 ml) and food supplements (max. 4.8 mg/day). It is advised that food supplements with daily doses above 4.8 mg beta-carotene are not suitable for heavy smokers or that they should only be used for a limited period of time.
Authored by Dr Peter Engel in 2010, reviewed and revised by Dr. Adrian Wyss on 03.10.17.