After an intensive training weekend on immuno-inflammatory disorders, I can’t help but share a focus on vitamin D — which should really be called Hormone D, since it acts as a true hormone. It is well known for its role in rickets and calcium fixation in bones. But it plays a role in many other areas; let’s look at these in detail:

Bones & muscles: It is involved in the fixation of calcium in bone, in intestinal calcium absorption, and in the renal reabsorption of calcium and phosphorus. It improves muscle fibre quality, thereby contributing to muscular strength, reducing the risk of falls, and having an anti-atrophic effect. Don’t forget vitamin K either in this chapter — it helps prepare the framework: when you repaint a chassis, you sand it first, otherwise the paint won’t hold… Vitamin K is produced by the microbiome of a healthy gut and is found in cabbages and fermented foods such as natto and miso. I’ll describe below how to eat natto, which can be off-putting at first glance.

At the immune level, you’ve no doubt heard about it over recent years: it helps in the differentiation and multiplication of white blood cells (via telomerase); it has an anti-inflammatory effect (blocks COX, regulates Th1, and raises Treg — thereby modulating allergies and preventing autoimmune diseases including type 1 diabetes and multiple sclerosis among others); and it produces anti-microbial peptides, beta-defensins, which act as real co-antibiotics. Its anti-inflammatory role can be applied to all domains of human health, as we know that chronic inflammation underlies civilisation diseases.

It is also protective against cancers because it prevents loss of contact inhibition and inhibits a specific protein (beta-catenin) activated in 50% of tumours. This preventive action against cancer is vital: it can reduce breast cancer risk by 50% in women if levels are above 45 ng/ml, and all hormone-dependent cancers are concerned (with slightly different figures for levels and risk factors). Colon cancer could be prevented with an 80% reduction in risk factor if levels approach 70 ng/ml. (Combined study compilation by Dr Résimont.) Obviously, hygiene must also be taken into account — it is a cancer largely conditioned by environment and lifestyle.

At the cardiovascular level, it has an anti-hypertensive effect (via the angiotensin system), protects vascular cells, and prevents calcium deposits in the arteries (again with its partner vitamin K).

In all our cells, it also plays a role alongside vitamin A in the quality of cellular receptors (thyroid hormone receptors, insulin receptors…). It is therefore vital in all hormonal functions. For this reason, it is known among gynaecologists for its action in fertility.

The icing on the cake: through its activity in supporting telomerase — the enzyme that protects against the shortening of our chromosomes — it has an anti-ageing effect.

But what quantity and how to take it?

The RDA in Belgium is 800 IU, which is shamefully underestimated. Because the minimum needed is 70 IU/kg of body weight. The amount of vitamin D to take must be determined after a blood test to estimate the deficiency to be corrected, and a precise correction protocol should be followed. The toxicity threshold is 150–160 ng/ml, so it is impossible for a well-monitored person to reach such levels.

If you live in Sicily or southern Spain, grow strawberries, and stroll around in swimwear without sunscreen, then you may synthesise enough vitamin D. But needless to say, sunscreens have another crucial role to play, and most of us don’t live that lifestyle…

In Belgium, supplementation is essential to achieve optimal levels.

Vitamin D should be taken in the evening, with a fatty meal. If you forget one day, take a double dose the next day. What form to take? If possible as pearls or drops — ideally daily (best option) or, for practical reasons, once a week (7 times the daily dose).

Natto

It looks like little eggs surrounded by slime, and smells like Herve cheese. Appetising, you might say? In Japan, it is used as a condiment, alone or with rice. Well prepared with grain mustard and soy sauce, it can be delicious — you can find it in Japanese grocery stores and freeze it. I include it in the autumn workshops ☺