What’s new on the vitamin front?
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Vitamins were first discovered at the beginning of the twentieth century. At that time, states of complete deficiency were described, like scurvy, a fatal haemorrhage effect observed in sailors when they went without fresh fruit and vegetables for a long time (and thus vitamin C). Vitamins were subsequently described as follows: nutrients that are essential for life and which must be included in the human diet.
Today, we very rarely see extreme vitamin deficiencies anymore in the world, and especially not in the West. However, researchers have been continually uncovering evidence of the actions vitamins have on the body, which were hitherto unknown.
What’s new with vitamin A?
Reputed to be essential for vision, an extreme deficiency in vitamin A can even lead to blindness. Vitamin A is also known as the growth vitamin, and we now know that it regulates the expression of more than 500 genes, playing a part in cellular differentiation and renewal. These tasks are part of vitamin A’s overall contribution to the functioning of the immune system: it can stimulate the production of antibodies and lymphocytes (white blood cells).
On the other hand, an excess of vitamin A could encourage the onset of osteoporosis, the demineralisation of bones accelerated by the menopause in women. There would appear to be a thin line between an essential supply of this vitamin, and a potentially toxic overdose.
In practice: vitamin A in animals, otherwise known as retinol, can be found in offal (liver, kidneys etc.), oily fish (mackerel, herring, salmon and sardines), eggs, butter and cheese. You can also consume it in the form of beta-carotene in fruit and veg, the pigment in carrots, apricots, yellow peaches and melons.
What’s new with vitamin D?
Essential for healthy bones, vitamin D increases the assimilation of calcium into the body and facilitates the fixing of calcium onto the bones. Getting enough vitamin D prevents rickets in young children, and is prescribed together with calcium for elderly people suffering from osteoporosis. By identifying its importance for bones, researchers have been able to identify vitamin D’s other qualities.
Vitamin D contributes to muscle tone, reducing the risk of falls for the elderly. And could equally protect against some diseases; like cancer of the rectum, colon cancer and breast cancer, as well as cardio-vascular diseases leading to high blood pressure. Finally, it bolsters immunity: it has been noted that populations with low vitamin D intake between the ages of 15 and 20 will demonstrate higher numbers of immune system disorders (when the organism makes antibodies which attack its own cells), such as type 1 diabetes, multiple sclerosis or rheumatoid polyarthritis.
In practice: vitamin D can be mainly found in oily fish, offal, eggs, butter and cheese. In spring and summer, the body produces vitamin D itself if it's exposed to the sun.
What’s new with vitamin K?
With its anti-haemorrhage effect, vitamin K activates blood clotting and also stops you from bleeding for too long if you cut yourself. Anticoagulant medicines, prescribed to prevent thrombosis in cardiac patients, are in fact made out of an anti-vitamin K. But it is now known that if you restrict your intake of vitamin K too much during such medical treatment, you could end up becoming deficient and weakening your bones.
In practice: vitamin K can be found in green vegetables (spinach, broccoli, green salad, cabbage etc.), rapeseed oil and soya and matured cheese. A varied diet will supply more than the necessary amount. For individuals taking anti-coagulant medication, a sufficient and regular supply of vitamin K is advised (the dose of the anti-coagulant prescribed matches this).
Some recommended daily vitamin allowances to increase soon
Recommended daily allowances (RDA) of different nutrients are re-evaluated regularly, keeping up with the evolution of scientific knowledge. For vitamins, as well as avoiding deficiencies, it is about preventing different degenerative illnesses, such as cardio-vascular disease and cancer. The recommendations concerning vitamins D and C should thus be reviewed and increased.
A new RDA for Vitamin D?
The RDA for vitamin D, currently 5 mg (equivalent to 200 IU or international units), has been fixed for populations benefiting from moderate exposure to the sun in warm seasons. This is insufficient for those who are less exposed to the sun (especially young children and the elderly). Furthermore, pigmented skin or very aged skin are factors that limit the production of vitamin D. Finally, additional effects of vitamin D have been observed in higher doses than those known to have an effect on bones.
While it is possible to reach 5 mg per day by eating oily fish twice a week, it is not obvious how to further increase the amount of vitamin D you get through diet, however varied it is. On top of this, right now most people in colder, less sunny climates, are lacking in vitamin D and researchers are debating as to whether medicinal supplements should be offered or not. What must be determined is for whom these supplements should be recommended and what dosage to advise.
A new RDA for Vitamin C?
The RDA for vitamin C is currently 110 mg per day, or 130 mg for smokers. Vitamin C participates in the immune system’s defences and facilitates the assimilation of iron extracted from vegetables. It counts as an antioxidant, nutrients which protect the body and guard against premature aging.
For the best protection against cancer, heart disease and eye disorders, the optimal intake of vitamin C is 200 mg. This level is possible to achieve if you get your recommended “5 a day” when it comes to fruit and vegetables, concentrating on citrus fruit, strawberries, kiwis, cabbage, spinach and peppers.
Vitamin C is however fragile, but some good kitchen habits help preserve this nutrient better. Keep vegetables in the refrigerator and eat them within 2 to 5 days, peel them or mash them at the last moment, cook them in a steamer for just the right amount of time and no more, and avoid reheating vegetables more the once.
Keep in mind: More and more studies are putting us on our guard: yes to a balanced diet, but no to dietary supplements, which can sometimes lead to far too much of a good thing, thus morphing into rather not a good thing!
Source: Nutrition conference, Pasteur Institute, Paris June 2011
Florence Daine
More information:
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Getting and preserving vitamins
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