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Beta-carotene is the most widely known of the carotenoids, which are the natural pigments of plants which provide the orange, yellow and red hues you see in carrots, chilli, paprika, pumpkin and apricots.
Alpha-carotene and Beta-carotene are called pro-vitamin A carotenoids because they can be converted to active vitamin A once in the body.
Around 50 of the 600 carotenoids are able to be converted in this way but Beta-carotene is the largest and best studied.
Beta-carotene (written in technical books as ß-carotene) was once thought only useful as a vitamin A or Retinol precursor. Now, however, it has been under study for its role as an antioxidant in the prevention of cancers but the results haven’t been positive.
What does Beta-carotene do in the body?
Beta-carotene is a powerful antioxidant (it is the ‘A’ in the ‘ACE’ vitamins sold as antioxidant supplements) and functions to:
- Inactivate free radicals that would otherwise damage cell membranes, DNA and protein structures in the tissues.
- Inhibit the early stages of tumour (cancer) development.
These benefits have been reported but only for Beta-carotene consumed from food. Foods rich in Beta-carotene seem to have a positive association with decreasing the risk of heart disease as well as of mouth and lung cancers.
However, as supplements, the studies have not been convincing - research shows that supplements of Beta-carotene increased the likelihood of bladder, lung, stomach and prostate cancer. Supplementation appears harmful to health.
Two large scale prospective randomized studies on high-risk cigarette smokers were:
- The Alpha-tocopherol, ß-carotene (ATBC) cancer prevention study
- The ß-carotene and Retinol efficacy trial (CARET)
And found that Beta-carotene supplementation indeed increased the rate of lung cancer in the group.
This has been backed up by other studies that showed the general incidence of cancer in asbestos workers and smokers who took the supplement increased.
How much Beta-carotene do I need?
There is no Recommended Dietary Intake for Beta-carotene as there is for other vitamins. Around 5 or 6 mg a day is suggested for adults (US).
Safe upper limit for Beta-carotene
25 mg a day is the safe upper limit for adults.
My top 20 best food sources
Beta-carotene is found naturally as the orange and/or yellow pigments in vegetables, fruits, oils (red palm oil, corn oil) and whole grains. It is also in dark-green vegetables such as silverbeet but the colour is ‘masked’ by the green of the chlorophyll.
Here are my top 20 richest food sources of Beta-carotene by weight per 100g or 3 ½ oz in descending order:
- Carrot juice
- Basil, sage and rosemary, dried
- Chilli, dried
- Seaweed such as nori, dried
- Sun-dried tomato
- Apricots, dried and fresh
- Liver, cooked
Source: AUSNUT 2011-12.
Processing of foods such as cutting it up or juicing or cooking when you break up the intact cell structure greatly improves the availability and absorption of Beta-carotene from foods.
Carotenoids are used as natural colours in food products e.g. additive code 160a is Beta-carotene while 160c is paprika oleoresins.
Deficiency signs of Beta-carotene
There are few signs of deficiency. Most comes from observational studies that reported that low levels of Beta-carotene were associated with heart problems, stroke and certain cancers such as cancer of the lung, prostate and cervix.
Overdose of Beta-carotene
Too much Beta-carotene turns the skin and the whites of the eyes a yellow-orange colour. This rarely happens from food but can occur if you drink too much carrot juice or an excess of dried carrots or other carotene-rich extracts. Or if you overdose on Beta-carotene supplements.
My father used to tell the story of how his skin turned orange during the privations of World War II in Poland where he overdid a home-made coffee powder substitute made from dried carrots, dried parsnip, chicory and other root vegetables. Obviously regular coffee was unavailable so this was the next best thing. But it came at a price!
It is unsightly but harmless and will gradually disappear once you cease taking the excess.