Vitamin D needs are different for each of us. This is because vitamin D is a fat-soluble vitamin, that is to say soluble in fat. After ingestion it is therefore distributed throughout the body. Its metabolism is therefore directly proportional to body volume and to our total weight. In recent years, researchers have developed several simple and rapid calculations that allow us to accurately calculate the vitamin D requirement for each of us. But before I explain this to you in detail, it's important to understand the history of vitamin D requirements.
Random needs ...
Initially, the French health authority (ANSES) recommended a 200 IU intake of vitamin D3 per day for good health since 2001. This is a low dose, which can be obtained by eating only 50 g of salmon. Any supplementation would therefore be unnecessary. However, this same agency fixed this recommended intake to 480 IU per day in 1992. And, even more surprising, the National Academy of Medicine affirmed in 2012 that the daily vitamin D requirements had to be reassessed and changed to 1000 IU per day, that is to say 5 times more than those recommended by ANSES (1). At the same time, the Institut National de Veille Sanitaire (INVS) carried out a test by measuring the level of vitamin D in the blood of French people. Result: the level was insufficient in more than 80% of cases(2). How can we explain such inconsistencies? To find out, we must look to the original work of researchers who are actively working on vitamin D.
The vitamin D revolution
In the 1970s, a few teams of researchers worked on vitamin D in the laboratory: they observed its effects on different types of cells. In these experiments, the researchers found that an infusion of vitamin D into animal colon cancer cells causes apoptosis, which is the cell death of cells, including cancer cells, which in turn cures cancer.
Very intrigued by this work, two researchers from the University of San Diego (United States), brothers Frank and Cedric Garland, wondered in 1980 whether the sun played a role in the prevention of cancer. The idea was surprising, even ludicrous, for the time, because it was also during this period that the first public health messages urged people to limit their sun exposure to prevent skin cancer.
Their first study was to map colon cancer mortality in the United States. And the results were clear: less people die from this cancer in the sunny regions of the south and west than in the big cities drowned by pollution and the north-eastern regions, despite a higher consumption of green vegetables, the protective effect of which was already known.
In 1991, Thierry Souccar, editor-in-chief of the LaNutrition.fr news site, met the two researchers. Cédric Garland explained: “This intriguing study was a trigger for us, but also for other researchers. Around us, opinions about the sun have started to change, and research on vitamin D has taken off. This vitamin was not only good for the bones, but also for immunity.”. »
A few years later, the Garland brothers extend the observation to breast cancer: the risk of death after 50 is inversely proportional to the intensity of sunlight. Thus, residents of Phoenix (southwest) and Honolulu (Hawaii) have half the risk of dying from such cancer as residents of New York or Boston (northeast of the country). In the former USSR, the rate of breast cancer triples between the southern and northern regions.
The two researchers were then called in by the United States Navy to refine knowledge about malignant melanoma (the most serious skin cancer) which is the second leading type of cancer in the United States Navy, after testicular cancer. Cedric Garland told Thierry Souccar: “To tell the truth, this did not surprise anyone, since sailors are generally very exposed to ultraviolet radiation and he said to himself that all melanomas are due to the sun. With Frank, we started from scratch. We went through the statistical records of the Naval Health Services and something surprising even to us came to light that had not been noted before." The one thing is that melanoma certainly affects the sailors who work on decks daily, but even more so those who rarely see the sun. The most affected by melanoma were the submariners and the least affected were the sailors whose job led them to be exposed regularly, but not excessively to the sun. The two brothers are already premeditatively announcing that “short, but regular periods of sun exposure have a protective effect, while too much or too little exposure increases the risk of skin cancer” Greeted with amazement when it was published in 1990, this study opened up new perspectives for the two brothers and sparked a surge in research on this vitamin.
4000-8000 IU of vitamin D per day
Following this work, in February 2011, Prof. Garland unveiled their conclusions to the general public in the international medical journal Anticancer Research “We have found that an adult must have 4000 to 8000 IU of vitamin D3 per day to keep blood levels of vitamin D and its active derivatives in the range that roughly halves the risk of several diseases - breast cancer, colon cancer, multiple sclerosis, type 1 diabetes” ». In other words, our vitamin D needs would be 20 to 40 times higher than the intakes recommended by the health authorities in France!
Prof. Garland continues: “I was surprised to find that the intakes needed to maintain vitamin D status in the protective zone are so high. Much higher than the dose of 400 IU / day that was needed to overcome rickets in the 20th century.”It would be easy to go from this to saying that the recommended daily intakes in France are dangerous for health. This is a conclusion that I’m going to make!
The study by these Californian researchers was conducted by following thousands of people who took vitamin D supplements at doses between 1,000 and 10,000 IU per day and whose blood levels were precisely examined. They explain in more detail that the prevention of chronic diseases requires a level between 40 and 60 ng / mL as a minimum.
« "Now that the results of this study are published, it will become commonplace for almost all adults to take 4,000 IU of vitamin D per day"says Prof Garland. “It is a dose well below 10,000 IU / d that is the lower threshold for the risk of hypervitaminosis D set by the US health authorities, and the benefits are considerable. People should discuss their vitamin D needs with their family doctor, if needed.". »
The French system really lacks common sense...
Professor Garland's message is clear. Yet the message was shared in February 2011 and in France nothing has changed. But is that really so shocking?
As early as March 2007, fifteen researchers, biochemists, doctors, epidemiologists and public health specialists denounced the daily adult intake of vitamin D in the northern hemisphere as “frustrating and regrettable” in an editorial published in the l’American Journal of Clinical Nutrition of March 2007 (an international scientific journal in nutrition) (4). Among the signatories were Prof Walter Willett of Harvard School of Public Health. These fifteen researchers believed that the time had come for doctors and patients to put pressure on health agencies, ministries and political decision-makers, so that people living above the 42nd parallel (latitude of the Pyrenees) take advantage of the health benefits of vitamin D. The signatories accused the health authorities and the public authorities of neglecting this situation, while studies outlining the health effects of an insufficient vitamin D intake have been piling up for years.
In France, the message was heard and relayed by Thierry Souccar, editor-in-chief of the LaNutrition.fr site but also a pioneer in nutrition in France. In his best-selling book Santé, mensonges et propagandeswhich you should still be able to get second-hand on the internet or at a good bookstore, he investigated and discovered that the calculation of the maximum safe dose for the vitamin D (fixed at 1000 IU per day) carried out by the Superior Council of Public Hygiene of France (CSHPF) was vitiated by a calculation error, and that the CSHPF should have retained the figure of… 10 000 IU. To believe that our health authorities really do suffer from a deficiency... in gray matter!
Calculation of vitamin D requirements based on your body weight
Vitamin D3 is found in small amounts in food, but it is also provided by exposure to the sun. The skin produces the vitamin under the influence of UV rays. This skin synthesis only takes place when the rays hitting the skin are UVB-type and with a wavelength between approximately 290 and 313 nm. These conditions are met in France only between the months of April and October. In addition, this synthesis is blocked by the use of sunscreens, by clothing or by air pollution. All this explains the massive deficits in the population. Simple exposure to the summer sun (shirtless) for 15 to 20 minutes is enough to produce up to 15,000 IU of vitamin D3, which is far more than you can get from food.
As early as 2011, I had informed my readers of the first pharmacokinetic studies on vitamin D in my first book, Nutrition de la ForceAlready at that time, researchers had developed a simple calculation to know your personal need for vitamin D according to your weight; they recommended a dose of 1000 IU per 15 kilograms of body weight; or about 4000 IU for an adult weighing 60 kilos.
In 2013, I published the results of more recent studies in my book Gluten, comment le blé moderne nous intoxique. This time, the researchers had refined their calculations: they now recommended a daily intake of around 75 IU per one kilogram of body weight, i.e., for an adult weighing 60 kilos, 60 x 75 = 4500 IU (5). Researchers also advise against exceeding a daily dose of 10,000 IU (6, 7).
Regarding dosage for infants, researchers recommend a dose of 100 IU for every 1 kg of body weight, checking the child's weight change regularly (8). After that, that is, after the age of 2, it is appropriate to switch to the calculation intended for adults.
Finally, it should be noted that when breastfeeding, vitamin D supplementation for the infant is not essential, according to the researchers, if the mother consumes enough vitamin D because it passes into the milk. In this case, it is recommended that breastfeeding women increase their daily intake by around 2000 IU per day to meet the needs of their breastfed child if the child is not receiving supplementation (9).
Which dietary supplement should I buy?
First of all, it’s important to remember that supplementation based on highly dosed ampoules is not recommended (see the other articles on the blog on this subject) and that it is better to favor daily supplementation to mimic natural doses that we would otherwise obtain via exposure to the sun. Food supplements sold in the form of drops are therefore ideal since they allow a personalized daily intake: everyone can take the number of drops they really need. Of course, the dosage prescriptions indicated on the labels of these products are imposed by the French health authorities, which is why you will never find the same advice as given here.
In terms of food supplements in the form of drops, there are two types of vitamin D3 food supplements: supplements made from lanolin and those extracted from boreal lichen, the only plant to naturally contain vitamin D3 (in plant foods, there is no vitamin D3 but vitamin D2, which does not have the same beneficial effects as D3).
Lanolin is the fat contained in the wool of sheep. To make vitamin D, it is irradiated with UVB rays, the same process that takes place in our skin when exposed to the sun. It is therefore a natural source of vitamin D. In addition, the production of lanolin does not require killing an animal; the process is carried out after shearing.
Products made from the lichen are directly extracted. So, this is also a natural source of vitamin D, which is a good alternative for those who do not want to use animal products. But since the lichen is rarer, its manufacturing cost for professionals is about 16 times higher. Supplements made from lichen are therefore always more expensive than those based on lanolin; but the exact price obviously varies by brand.
References : (1) « Statut vitaminique, rôle extra osseux et besoins quotidiens en vitamine D – Rapport, conclusions et recommandations », Académie nationale de médecine, 29 mai 2012.
(2) Vernay M. et al. Vitamin D status in the French adult population: the French Nutrition and Health Survey (ENNS, 2006-2007). Usen, invs, Avril 2012.
(3) Garland CF. Vitamin D Supplement Doses and Serum 25-Hydroxyvitamin D in the Range Associated with Cancer Prevention. Anticancer Res Feb 21 2011.
(4) Vieth R. The urgent need to recommend an intake of vitamin D that is effective. American Journal of Clinical Nutrition 2007, 85(3) : 649-50.
(5) Drincic AT, Armas LA, Van Diest EE, Heaney RP. Volumetric dilution, rather than sequestration best explains the low vitamin D status of obesity. Obesity (Silver Spring). 2012 Jul;20(7):1444-8.
(6) Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. Am J Clin Nutr. 1999 May;69(5):842-56.
(7) Heaney RP. Vitamin D: criteria for safety and efficacy. Nutr Rev. 2008 Oct;66(10 Suppl 2):S178-81.
(8) Pludowski P, Socha P, Karczmarewicz E, Zagorecka E, Lukaszkiewicz J, Stolarczyk A, Piotrowska-Jastrzebska J, Kryskiewicz E, Lorenc RS, Socha J. Vitamin D supplementation and status in infants: a prospective cohort observational study. J Pediatr Gastroenterol Nutr. 2011 Jul;53(1):93-9.
(9) Hollis BW, Wagner CL, Howard CR, Ebeling M, Shary JR, Smith PG, Taylor SN, Morella K, Lawrence RA, Hulsey TC. Maternal Versus Infant Vitamin D Supplementation During Lactation: A Randomized Controlled Trial. Pediatrics. 2015 Oct;136(4):625-34.