Vitamin D deficiency, an important indicator of proliferative diabetic retinopathy

Pubblicato il

Wednesday, 11 December 2019

Argomento

Retina

The diabetic retinopathy (RD) is a severe ocular pathology that can affect people suffering from diabetes.

Diabetes Mellitus

Diabetes Mellitus (DM) is now a true global emergency, characterised by an exponential growth in prevalence rates. In Italy, it has risen from 2.4 million in 1980 to 4.3 million in 2014 (ARNO Observatory data 2015). The main causes of this phenomenon include the ageing of the population and the progressive increase in the incidence of obesity and other metabolic dysfunctions.

Complications and quality of life

Diabetes Mellitus is a systemic disease that has a major impact on the quality of life of those affected due to the serious complications that affect countless body districts, first and foremost the visual system - along with the kidneys, peripheral nervous system and cardiovascular system.

The most important and frequent ocular complication of Diabetes Mellitus, both type 1 and type 2, is Diabetic Retinopathy (DR).

The conditions associated with an earlier onset and faster progression of Diabetic Retinopathy are the duration of DM, hyperglycaemia and the possible presence of other cardiovascular risk factors such as hypertension and hypercholesterolaemia.

Diabetic Retinopathy

Diabetic Retinopathy is the most important and frequent ocular complication of diabetes mellitus . It is the leading cause of legal blindness in adults of working age and is also the fifth leading cause of preventable blindness and moderate-to-severe visual impairment.

On average, between 30% and 50% of the diabetic population develop a form of Diabetic Retinopathy of varying severity, and in about one in ten patients more severe changes develop, including Diabetic Macular Oedema (EMD).

EMD is one of the most serious manifestations of Diabetic Retinopathy, as it can impair central vision if not adequately treated. The frequency of occurrence of EMD increases with the duration and degree of severity of diabetes: in fact, among patients who have had diabetes mellitus for more than 20 years, approximately 30% develop EMD.

Prevalence and outlook

It is estimated that DR afflicts 93 million people worldwide and that, in approximately 18% of cases, it occurs in its more advanced form, the proliferating diabetic retinopathy (PDR, Proliferative Diabetic Retinopathy) which, if not treated properly, can lead to blindness.

As diabetes continues to spread, even the RD which can be associated with it is set to become more and more frequentTherefore, it is necessary for scientific research to continue investigating this disease in order to better understand the mechanisms of its onset, so as to develop systems that enable earlier diagnoses e more effective treatments.

Diabetic Proliferative Retinopathy

Proliferative or advanced diabetic retinopathy (PDR) is the most serious type because it coincides with the abnormal growth of new blood vessels damaging the retina. Neovases are also stimulated by the formation of ischaemic areas in the retina.

RD and vitamin D

It has already been known for several years that people with DR show lower levels of vitamin D in their blood than healthy subjectssuggesting that deficiency of this vitamin may play a role in the development of the disease.

Vitamin D

According to some studies, in fact, the low concentration of vitamin D in the blood alters the mechanisms of insulin production, the hormone responsible for blood glucose control, and poor glycaemic control which in turn leads to a increased risk of developing DR.

The vitamin DMoreover, when it is present in normal quantitieshelps to counteract the onset and progression of DR by exerting a dual protective effect on the retinaanti-inflammatory and anti-angiogenic.

Anti-inflammatory action

The strong anti-inflammatory action exerted by vitamin D, in fact, prevents damage leading to degeneration of the retinal pigment epithelium, a crucial component for the proper functioning of the retina.

Anti-angiognetic action

Vitamin D has anti-angiogenic propertiesi.e. it is able to counteract the proliferation of new blood vessels. The latter function is particularly important in the prevention of DR, since the altered vascularisation of the retina is one of the main features of the disease.

Vitamin D as a biomarker for proliferative diabetic retinopathy (PDR)

Several scientific studies have shown that Vitamin D deficiency in the blood is associated with the most severe forms of RD. Recently published research also stated that a vitamin D concentration in the blood below 18.6 ng/mL may indicate the presence of the most advanced form of RD, the proliferating diabetic retinopathy (PDR)which is currently diagnosed through the use of technologies that allow certain parts of the eye to be observed, such as colour photography of the ocular fundus.

According to this study, subjecting people with DR to a vitamin D assay performed on a blood sample would represent a simple and effective method for early detection of patients with the most severe form of the disease.

An early detection of these individuals would make it possible to correctly plan the calendar of periodic checks to be performed to monitor the state of progression of the disease and the choice of best treatment strategies.

Vitamin D

The vitamin D is a fat-soluble molecule, present in the body and more specifically in the liver.

It is an essential vitamin for the immune system and bone tissue. Its function is related to the absorption of calcium, iron, magnesium, phosphates and zinc, minerals that are essential for healthy bones and teeth.

In nature, the body synthesises vitamin D through regular exposure to sunlightwhich enables the body to produce vitamin D1, D2, D3, D4 and D5.

During winter, one is necessarily less exposed to the sun's rays and, therefore, to ensure regular vitamin D synthesis, one can rely on specific food sources, which ensure an adequate intake of this valuable substance and enable the daily requirements.

Foods rich in vitamin D

The body produces vitamin D both through skin exposure to Uv-B rays (ultraviolet) radiation from the sun, and through diet and, therefore, the intake of certain foods, which are rich in this nutrient.

During the cold seasons, autumn and winter, daily habits tend to be more sedentary and homely. But, with the daily consumption of vitamin D foods, can make up for the lack of sun exposure that deprives us of this important vitamin.

Vitamin D: an indicator of diabetic retinopathy

Individuals who have more difficulty in attaining their daily vitamin D requirements must, instead, resort to taking specific food supplements, under the guidance and monitoring of the family doctor. Food supplementation is often the necessary solution for those suffering from obesity, and for some fragile individuals, such as infants, the elderly and those with intestinal diseases.

Foods may specifically contain vitamin D2 e vitamin D3which are called 'ergocalciferol' and 'cholecalciferol' respectively.

Here is a list of 11 foods that contain good amounts of vitamin D:

Mushrooms
Liver meat
Bovine liver
Cod liver oil
Butter
Fat cheeses
Mackerel
Tuna
Salmon
Oysters
Prawns

Of each of these foods, one must then identify the quantities that are advisable to consume, based on one's taste, body mass index and the nutritional characteristics of each food.

Vitamin D-rich foods are often of animal, rather than vegetable, origin. However, there are various options for a vegetarian diet rich in vitamin D, always paying attention to quantities, in order to follow a varied yet balanced diet.

In the plant source vitamin D mainly include the wild mushroomsand, to a lesser extent, vegetables with green leaves, such as spinach, chard and Swiss chard. Among the plant foods that contain a higher percentage of vitamin D, you can find porcini mushrooms, followed by morel, chanterelle, chanterelle and the meadow mushroom, which is the poorest in vitamin D: to give you a better idea, 100 g of porcini mushrooms contain 3.00 µg of vitamin D compared to 0.45 µg of meadow mushrooms. If you wanted to get your vitamin D exclusively from mushrooms, you would need 625 µg/day, however, as these are toxic and contaminated foods, excessive intake is not recommended and it is always better to opt for a varied diet.

Also the cocoa contains vitamin D2, which is mainly found in dark chocolate. Cocoa beans during drying in the sun assimilate this vitamin, which is so important for the health of our organism.

Vitamin D3, also known as "sunshine vitamin', comes mainly from animal source. Therefore, it can be assimilated not only through sun exposure, but also through foods such as liver meat and bovine liverdairy products and dairy productsas butter and fatty cheesesbut is also found in the yolk of eggs; in thecod liver oil; in fat fish such as mackerel, tuna, salmon, salmon trout, eel, swordfish, carp, sardines and herring; in the seafood such as oysters or prawns.

Among these foods thecod liver oil is the one with the highest level of vitamin D (approximately 210 µg per 100 g) but is not usually consumed except through supplements or using products such as algae oil or krill oil. As for fatty fish such as the salmonherring and blue fish, these contain 25 µg per 100 g.

Among the meats the liverwhich contains 0.5 µg per 100 g. With regard to dairy products, butter contains up to 0.75 µg per 100 g and fatty cheeses contain 0.5 µg, while egg yolks have 1.75 µg of vitamin D per 100 g.

The above confirms that, in general, vitamin D is more present in foods of animal origin. This may be a limitation for those who have alactose intolerance or who follow a vegan or vegetarian diet.

However, there are foods 'fortified' with vitamin D such as the waxesoatmeal, orange juice, as well as dried fruit rich in Omega 3including walnuts or almonds.

Bibliografia