In its risk assessment VKM suggested the limit of four milligrams a day, but specified these health concerns did not apply to beta-carotene obtained through fruit and vegetables.
No EU-wide safe upper limit has been set for beta-carotene, while national risk-assessment bodies have previously tried to establish indicative or temporary upper guidance levels.
It said insufficient data meant neither it, these national bodies nor the European Food Safety Authority (EFSA) had been able to establish a firm tolerable upper intake level for the precursor of retinol vitamin A.
Nonetheless it concluded: “VKM is of the opinion that because beta-carotene may increase the risk of lung-cancer in smokers, there is a theoretical risk that beta-carotene may increase the risk of adverse health effects in all people with chronic inflammatory conditions in the lungs. Such groups include asthmatics and [chronic obstructive pulmonary disease] COPD-patients who, in addition to smokers, should be discouraged from taking beta-carotene supplements.”
The authority considered whether beta-carotene should be regulated separately from retinol compounds.
Cancer risk concern
The report said a number of studies pointed to different mechanisms through which this health risk may occur, including activities related to the protein cytochrome P450, altered retinoid signalling or to a pro-oxidant affect.
This has not yet been pinned down, largely because of the lack of a good animal model within which to study the phenomena.
A global picture
Only 3% supplemented in Norway
As part of the assessment it calculated average beta-carotene intakes for different groups in Norway.
For two-year-olds this mean was put at 1521 µg a day, while for adults 2423 µg a day and in the 95th percentile 6859 µg a day.
While the report suggested only around 3% of adults used beta-carotene supplements, this may have been under-reported in the food survey by those unknowingly consuming beta-carotene through tanning pills.
Such supplements, which capitalise on beta-carotene's skin yellowing effect at high doses, contain 3-9 mg of beta-carotene per daily dose. “At the 9 mg dosage, the producer promises a deep and lasting brown glow to the skin, especially for people with a fair complexion,” VKM said.
The assessment can be found here in English.