Fitness and well-being: The 5 essential vitamins

Fitness and well-being: The 5 essential vitamins

• Vitamin D: immunity superstar

Gone are the days when it was only related to bone health! Acting like a hormone, vitamin D has been shown to be effective on the prevention of numerous diseases (cardiovascular, cognitive, etc.) and its central role in immunity was confirmed at the start of the Covid epidemic. The majority of immune cells have receptors for this vitamin capable of increasing its effectiveness and therefore reducing the severity and duration of infections. But here it is: more than 90% of vitamin D being synthesized by the skin under the effect of UVB rays from the sun, in winter (but not only), it is sorely lacking. And food doesn’t provide much…

Where to find it naturally?
Essentially in cod liver oil which provides 10,000 IU/100g of the 1000 to 4000 IU recommended per day. Then in the oily fish (herring, sardines, anchovies, mackerel…), which on average peak at 400 IU/100g.

What about supplementation?

It is almost essential for everyone: 8 out of 10 French people are deficient in vitamin D, even in sunny areas.

A blood test makes it possible to specify the needs which, in the event of a severe deficiency (immunocompromised, over 50 years old, vegan, alcohol consumer, etc.), can exceed 5000 IU/d.

In all cases, it is vitamin D3 (animal or vegetable origin) that should be favored, similar to that produced naturally and more effective than D2 (UV-exposed yeast). One ampoule per quarter is not always enough and depending on the case, the doctor may prescribe a daily intake in the form of drops until June.

The risk of vitamin D overdose is non-existent with food and the sun! And very low in supplementation. However, because in excess, it can lead to the precipitation of calcium crystals on the vessels, joints, taking vitamin D is contraindicated in case of hypercalcemia and kidney stones due to this excess of calcium in the blood. To be clarified by a urologist.

• Vitamin C: simply vital!

Anti-fatigue, anti-infectious, anti-inflammatory and powerful antioxidant, the vitamin C is a key player in immunity due to its ability to stimulate white blood cells and the production of antibodies. The problem: water-soluble, it cannot be stored in the body. Rapidly eliminated via the urine, it therefore requires a permanent supply.

Where to find it naturally?
Especially in red fruits, citrus (orangelemons), exotic fruits (kiwi, mango…), certain vegetables (peppers red, cabbage…), herbs (parsley, chervil) and algae. As this vitamin is very sensitive to light, air and heat, always favor seasonal vegetables to be eaten immediately, raw or quickly steamed.

What about supplementation?

Even if 2 to 3 portions per day of plants can cover the daily needs, with the changes of season, it is better to take a 21-day cure of vitamin C as a preventive measure to strengthen your immune defences.

Forget the classic supplements that spin illico in the urine. Opt for those with prolonged action (AP) diffused for 6 to 8 hours. Combined with natural citrus bioflavonoids (colored fruit pigments), up to 60mg/tablet, they increase the absorption of vitamin C. As a cure, in the event of an ENT or respiratory infection, the dose of vitamin C can be 2g/day in 4 doses.


Contrary to popular belief, vitamin C even taken at night does not interfere with sleep! Thanks to its anti-stress action, it can even promote it. In the event of excess (more than 2g/day), it can also however promote slight transient digestive disorders (cramps, diarrhoea) and sometimes increase the risk of kidney stones and aggravate hemochromatosis (excess iron in the blood).

Read also> Are you lacking in vitamin C?

• Vitamin E: to breathe better

Antioxidant, it has shown its immunomodulatory effects, particularly on respiratory infections. In older people, studies show that it compensates for the loss of immunity due to age and improves the response to the flu vaccine.

Where to find it naturally?

Especially in the hwheat germ oil, oil and sunflower seeds (to consume with moderation because very rich in omega-6but not in good omega-3), almonds, walnuts, avocado, fish and their eggs.

Also Read > Diet Memo: Omega 3 and Omega 6, What’s the Difference?

What about supplementation?

A balanced diet providing enough vitamin E, it is often not necessary. Except on medical advice if deficiency established by blood test.


Avoid the synthetic version (stamped dl-alpha-tocopherol or just Vitamin E) extracted from petrochemicals, obviously much cheaper than the natural version.

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• Vitamin A: barrier function

A deficiency of this vitamin which includes beta-carotene (provitamin A) and retinol is correlated with an increased risk of respiratory infection. It intervenes in fact in the production of antibodies but first in the proper functioning of the first natural barriers of the body: skin, mucous membranes, intestine, respiratory tract.

Where to find it naturally?

In yellow-orange plants (carrot, pumpkin, pumpkin, sweet potato… but also spinach) which provide beta-carotene and animal livers (veal, poultry, cod) which provide retinol.
Read also> Dietary: these plants with colored pigments that heal!

What about supplementation?

It may be necessary, after blood testing, if the conversion of beta-carotene into retinol is hindered by digestive disorders, a lack of magnesium, iron or heavy alcohol consumption.


An excess of vitamin A is no more desirable than a deficiency. In smokers, beta-carotene capsules taken to promote tanning have been shown to increase the risk of lung cancer.

• B vitamins: ministers of defense

They are 8 in total, all involved in energy metabolism and therefore important for immunity. In particular the B1, B2 B3, B6, B9 and B12. Special mention to B6, both necessary for the assimilation of magnesium and the improvement of immune function.

Where to find it naturally?

Vitamin B6 is very present in whole grains, legumes, oilseeds, flax seeds, poultry, meat, fish, bananas.

What about supplementation

It is to be decided by the doctor on a case-by-case basis after a blood test. Vegetarians are often supplemented with B12, which is only present in animal products. And brewer’s yeast (live or revivable) rich in other B group vitamins and minerals can be indicated for a balanced and natural overall intake.


Some excess B vitamins can cause problems. This is the case of vitamin B9, taken in its synthetic form (folic acid).

Our Experts

Dr Marc Perezgeneral practitioner, specialist in sports medicine, osteopath, phytotherapist, author of the Guide to star food supplements and Viruses will not pass by me (ed. Eyrolles, 2019 and 2020) and Veronique Liessedietitian, nutritionist and trainer, author of Le Grand Livre de l’alimentation “special immunity” with Alix Lefief-Delcourt, (ed. Leduc).


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