Too Many Vitamin Supplements Can Be Dangerous. The Dose Makes the Poison
Redaktion
Hardly any Central European needs additional vitamins, say scientists. Worse still: in certain cases, excessive intake can even endanger health.
Useless, pointless, superfluous but generally harmless: this is how health experts at the German Nutrition Society (DGE) assess food supplements. British researchers are even clearer and call them a waste of money. The scientific effectiveness of artificial vitamins and minerals has not been proven. Preparing fresh food is healthier than swallowing pills. But convenience and ignorance can also become dangerous. New scientific findings from clinical studies even show that taking vitamin and mineral tablets carries a risk of cancer.
Dangerous side effects
Preparations of fat-soluble vitamins in particular can endanger health. The fat-soluble vitamins include vitamins A, D, E and K. They are stored in the body, more precisely in the tissue, and therefore tend to accumulate if too much of them is taken in. An overdose can have a toxic effect. This is also described as an increased toxicity potential.
For example, a large analysis by Danish researchers at the Copenhagen Trial Unit (Bjelakovic et al., JAMA 2007) of 68 trials with around 230,000 participants found that additionally taken vitamin E can increase mortality by about 4 per cent, vitamin A by about 16 per cent and beta-carotene by about 7 per cent. Large trials from Finland (ATBC, 1994) and the USA (CARET, 1996) also showed that in smokers, additionally taken beta-carotene can even increase the risk of lung cancer instead of lowering it as hoped. However, this only applies to the artificially produced variant in pill form. A natural diet with carotenoid-rich vegetables has been shown to lower the risk of lung cancer, for everyone, including heavy smokers. Caution is also needed with minerals. Some studies suggest that calcium supplements may increase the risk of heart attack; however, the evidence is inconsistent.
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Vitamins from vegetables are as healthy as ever
The main sales argument is predominantly the threat of vitamin deficiency. But you should not fall for it. Unlike carbohydrates, fats or proteins, vitamins supply neither energy nor building material for the body. Rather, vitamins control or promote certain metabolic processes. The body therefore needs only very small amounts. Vitamin deficiency is very rare in Western societies – requirements can be met by a balanced diet. What matters is not the intake of individual substances, but the diet as a whole. Two thirds of what you eat should be plant foods. According to nutrition scientists, 250 grams of fruit and 400 grams of vegetables per day are enough for health. Most people can do without vitamin preparations. Supplementation only makes sense with certain diets, diseases or during pregnancy.
Another sales argument for vitamin preparations is that fruit and vegetables are low in vitamins because of incorrect preparation, long transport routes and storage or poor soil quality. But that is a misconception! Analyses of tomatoes have shown that today’s tomatoes contain roughly the same amount of vitamins and trace elements as 30 years ago. Even tinned tomatoes have at least 80 per cent of the vitamins of fresh tomatoes. Local fruits and fruit juices also fully cover the body’s needs. There is no need to buy overpriced exotic fruit juices. Some of today’s apple varieties even contain three times more vitamin C than earlier varieties. The numerous vitamins and plant compounds in apples are sometimes even able to reduce the growth of cancer cells. Artificial vitamin C, by contrast, cannot do this.
Vitamin preparations are not useful for older people either
A healthy diet is also crucial in old age. Vitamin preparations are not a useful food supplement for older people. Above all, supplementation with such preparations over many years should be avoided. People who regularly take vitamin pills are no better protected against heart disease, cancer and mental decline than others. British scientists observed 20,000 people aged between 40 and 80 for five years. Taking vitamins is not harmful to health, “but you might as well not bother”, said Professor Rory Collins of the University of Oxford (Heart Protection Study).
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One half were given tablets containing vitamin C, vitamin E and beta-carotene. The other half – the control group – received ineffective placebo tablets. The surprising result of the study: in both groups, the risk of developing heart disease, asthma or senile dementia and of suffering fractures was the same. An observational study by the Harvard T.H. Chan School of Public Health (Neurology, 2018) also found that men who drank a small glass of orange juice daily for around 20 years were considerably less likely to report declining memory in old age. However, cause and effect cannot be reliably inferred from such observational data. “Fresh” vitamins are therefore more effective than their artificial counterparts pressed into pills.
Older people, too, therefore take in enough vitamins with a balanced diet – with plenty of fresh fruit and vegetables. Five meals spread over the day are recommended. Only when appetite declines does the vitamin intake fall along with the reduced amount of food.
For whom is nutrient supplementation useful?
With a healthy and balanced diet, there is no need to fear a deficiency of vitamins and minerals, unless requirements are increased. This is the case in special life situations such as diets, certain diseases, in competitive athletes, during pregnancy or in children. In any case, the type, duration and level of dosage should be agreed with a doctor.
People at risk are those who, for a longer period, can or want to use only a restricted selection of foods. Vegans are particularly at risk of vitamin B12 deficiency. The supply of vitamin D, iron and iodine can be critical. With particularly strict diets (very restricted calorie intake), there may be a lack of iron, folic acid, vitamin B6 and zinc.
Smokers take in large amounts of free radicals with every inhalation. They have a 20% higher vitamin C requirement than non-smokers. An inadequate supply of iron, calcium, beta-carotene, folic acid and vitamin E can also occur. An increased need for micronutrients results from physical strain under extreme demands, as in competitive athletes. Supplementation with magnesium and iron can be useful.
Chronic diseases are often associated with nutrient deficits: for example diabetes mellitus (vitamin C and above all vitamin E), chronic dialysis (zinc, iron, calcium and all water-soluble vitamins), cancer (supplementation with multivitamin and mineral preparations). In particular, there is also a risk of nutrient deficits in various diseases of the intestinal tract. In diseases of the stomach, the absorption of vitamin D, folic acid and vitamin B12 in particular is impaired. Diseases include: coeliac disease, chronic inflammatory bowel diseases (Crohn’s disease, ulcerative colitis) and short bowel syndrome.
Rheumatic diseases also involve an increased need for micronutrients, because more free radicals are formed in the body through oxidative stress when the joints are inflamed. Attention must be paid to an optimal intake of selenium, vitamin E and beta-carotene. Fish oil fatty acids have a positive effect.
Other cases where vitamin preparations are recommended: in newborns: vitamin K; in infants: vitamin D and fluoride daily; in women wishing to conceive and pregnant women in the first trimester: folic acid; and in pregnant and breastfeeding women: iodine, possibly iron.
Which vitamins and minerals must be obtained from food?
The name “vitamins” derives from life (“vita”) and the group of substances called amines, to which not all vitamins belong, however. They are essential nutrients that must be supplied to the bodythrough food. An exception here is vitamin D – the sunshine vitamin, which can be obtained via the skin. Niacin can also be synthesised by the body. It can be produced from the amino acid tryptophan. Vitamins play an important role in metabolism and are involved in cell building. Certain vitamins can protect against cardiovascular diseases and cancer.
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Vitamins can be divided into two main groups: fat-soluble and water-soluble vitamins. The body needs a total of 13 vitamins. The fat-soluble vitamins are vitamins A, D, E and K. The water-soluble vitamins include the B vitamins – B1, B2, B3, B5, B6, B8, B11 (folic acid), B12 – and vitamin C. They are hardly stored in the body; an exception is vitamin B12. As a rule, they are excreted again via the kidneys. A continuous supply through food is therefore necessary.
The minerals known to be essential are calcium, magnesium, potassium, sodium, chloride and phosphorus. Essential trace elements are iodine, iron, chromium, copper, zinc, manganese, selenium and molybdenum.
