The figures are dramatic, as 15 million people worldwide suffer from heart failure, and health insurance company spending focuses on diagnosis, therapy or prevention of chronic heart failure (CHF). Even so, the prognosis is poor: every second patient – no matter whether they are young or old – dies within the first five years after the disease has been diagnosed. Scientists from the University of Bonn, in co-operation with the Bad Oeynhausen Heart Centre, have now been studying the causes of cardiac failure. They have detected ‘clear indications’ that vitamin D deficiency contributes to the emergence of the disease. They have now published their findings in the Journal of the American College of Cardiology (vol. 41, no. 1, 2003, pp.105-112).
In heart failure the vena cava muscle is weakened to such an extent that the heart can no longer pump sufficient quantities of blood through the body. Consequently, adequate blood supply to organs and muscles is not guaranteed. Patients become tired after the slightest exertion, their pulse rate soars, they cannot get enough oxygen. Because of the poor circulation the kidneys cease to function properly and can no longer dehydrate the body adequately. The result is hydropexis in the tissues, what are known as edemas. The heart reacts by releasing the hormone ANP, which promotes fluid elimination. A high blood level of ANP is thus a reliable indicator of cardiac failure – and this is true even in early stages, when the disease hardly shows any symptoms.
For several years now it has been known that Vitamin D in cell cultures slows down the production of the ‘dehydration’ hormone ANP. Chicks with Vitamin D deficiency develop heart failure, which disappears again as soon as Vitamin D is added to their feed. And in the cardiac muscle cells of rats scientists have been able to detect a large number of receptors for Vitamin D. Thus it made sense to assume that the substance found in eels, salmon and herring might also be relevant for human CHF symptomatology.
The German university lecturer Dr. Armin Zittermann and his PhD candidate Stefanie Schulze Schleithoff of the Bonn Institute of Nutrition have been looking into this theory in co-operation with the Bad Oeynhausen Heart Centre. A total of 54 CHF patients and 34 healthy persons as a control group took part in this study, which is the first of its kind worldwide. The two scientists determined the concentration of two different Vitamin D metabolites in the blood of the study participants: in patients with CHF vitamin D blood levels were up to 50% lower than in the control group.
The ANP level, by contrast, had increased to more than twice the normal level in the CHF patients. There was a correlation between the degree of disease severity and the extent of the vitamin D deficiency. “All these data are clear indications that an insufficient supply of Vitamin D can be important in the emergence of chronic heart failure,” Dr. Zittermann said. The two researchers are currently carrying out a follow-up study in which they give the CHF patients vitamin D and check whether their condition improves.
Vitamin D plays an important role in regulating the calcium concentration in the body – for example, by improving the absorption of calcium from the intestine. However, it also appears to be able to influence the calcium ‘transfer’ in the cardiac cells. So that the muscle can contract, the calcium concentration has to be briefly boosted. For this purpose, the heart taps into a calcium reserve within the cell which it then fills up again by means of little ‘pumps’ during the relaxation phase. Vitamin D seems to influence the activity of these mini-pumps. However, if they do not work properly, the myocardium cannot contract completely.
Human beings make their Vitamin D themselves. “75% to 90% is derived from UVB irradiation in the skin. We absorb the rest via our food,” Dr. Zittermann added. At least under normal conditions. People who are stuck behind their desks in an office and mainly spend their spare time sitting in front of the TV or PC do not produce enough vitamin D. And in the winter months the intensity of UVB irradiation is insufficient – at least in northern latitudes. “In industrial countries vitamin D deficiency is a common phenomenon,” is how Dr. Zittermann summarises the problem. Especially as people get older: over time we lose our ability to synthesise this valuable substance ourselves – an 80-year-old only produces a quarter of the amount a 20-year-old does from the same UVB irradiation. “Interestingly, almost all senior citizens suffer from at least moderate CHF.” At present the possibility cannot be excluded that the disease itself contributes to the low vitamin D level, thereby producing a vicious circle – patients with heart disease, after all, are only rarely exposed to the sun due to their few outdoor activities.
The two scientists do not advise stepping up sunbathing activities. “UV radiation is simply too dangerous for that,” Dr. Zittermann explained. “Apart from that, the link between low vitamin D status and heart failure still needs to be conclusively proved.’ Nevertheless, regular intake of food rich in vitamin D would do no harm. However, the substance is only present in substantial amounts in fish – two to three meals a week involving fish are recommended.