Things to know and fascinating facts about nutrition.
The precise definition of one International Unit (IU) differs from substance to substance and is established by international agreement. There is no equivalence among different substances: e.g., one IU vitamin E does not contain the same number of milligrams as one IU vitamin A, vitamin C or vitamin D.
In 1898, English biochemist Frederick Hopkins suggested that some foods contained "accessory factors" in addition to proteins, carbohydrates, fats, etc that were necessary for the functions of the human body. In 1912, Polish biochemist Kazimierz Funk proposed the name "vitamin” for an isolated micronutrient with certain health benefits. The name was derived from "vital” (from the Latin meaning “necessary to the maintenance of life”) and “amine" (an organic compound that contains a basic nitrogen atom). The name soon became synonymous with the accessory factors first observed by Hopkins.
By the time it was shown that not all vitamins were amines (e.g., vitamin C), the word was already ubiquitous. Vitamins do not share a common chemistry, but they do share certain characteristics. They are all organic nutrients that are necessary in small amounts for normal metabolism and good health. Most vitamins are provided in the diet or by supplements. The body can manufacture only three vitamins from non-dietary sources: vitamin D, vitamin K and vitamin B7 (biotin).
It should be considered that:
*micronutrients cannot compensate for unhealthy lifestyles such as mainly living on junk food, smoking, or drinking; they are not “magic bullets”.
*micronutrients mainly show health benefits when they balance an existing deficiency
*the relationship between diet and chronic disease is very complex: it is almost certain that several factors have to vary simultaneously for a positive effect to be observed
*high doses do not necessarily mean high benefits.
While ‘retrospective studies’, for example, can be inaccurate, as they rely on data that have already been collected in the past or need to be recalled by study participants, ‘prospective studies’ can be more accurate, because they describe current occurrences (e.g., nutritional behavior and disease risk) over the course of time. While ‘observational studies’ can only observe associations and suggest (hypothesis-generating), ‘randomized controlled trials (RCT)’ can establish cause-and-effect relationships (hypothesis-testing). But even study results of RCTs can be misleading when, for example, results are pooled in a ‘meta-analysis’, mixing data from disease prevention in healthy people with data on slowing down disease progression in patients. Frequently, effects of high-dose micronutrient supplement use in patients (therapy) or vulnerable groups (e.g., smokers) are transferred to the average consumer who uses fortified foods and/or dietary supplements to prevent micronutrient deficiency (prophylaxis); this is not accurate.
It is important to note that many studies using dietary supplements do not show positive effects on health or disease prevention because they test individuals with an already existing disease or an increased risk of developing a certain disorder. In addition, these studies may not include enough individuals (too small) or may not run long enough (too short) to show a significant effect. Moreover, health status is influenced by so many individual factors (e.g., lifestyle) that it is extremely difficult to show a significant effect of micronutrients.
However, it should be kept in mind that dietary supplements are meant to “supplement”, but not “substitute” a healthy diet.
Eating a variety of fruit and vegetables provides us with plenty of vitamins and minerals, essential for a healthy life. Fruit and vegetable intake requirements depend on age, gender, health status, and health conditions.
Many people use fortified food and dietary supplements to fill nutritional "gaps": older individuals may struggle with eating enough or cooking to get required amounts of vitamins; for younger people today's fast paced culture is often characterized by diets poor in vegetables, fruits and whole grains. In addition, there are people with increased need for particular nutrients at certain times, such as pregnant and breastfeeding women, elderly people, sportspeople, dieters, heavy smokers and/or drinkers, people on long-term medication, and those with immune deficiency.
However, it should be kept in mind that dietary supplements are meant to “supplement”, but not “substitute” a healthy diet.
Fruit and vegetables available in the shops can contain considerable pesticide residues. In some cases levels of contamination are so high that harmful effects on health cannot be ruled out. To avoid pesticide-contaminated goods it is generally advisable to look for locally sourced fruit and vegetables in season, because plants grown in ideal environmental conditions are more vigorous and therefore need less chemical protection. Moreover, some of the products that travel long distances have to be protected against spoiling by use of more chemicals.
*Fruits advertised as “unwaxed” have merely not been treated with a protective coating. For preference, choose organic fruit if you want to consume the peel of oranges or lemons. In general, organically grown fruit and vegetables are mostly free from residues. For this reason, only organic products should be used in the preparation of infant food.
*Contamination with pesticides varies greatly with the season: Early strawberries on offer from January to May usually contain more pesticide residues than domestic strawberries harvested in season from June onwards.
*Always wash fruit and vegetables thoroughly under running water. Then rub with a microfiber cloth or vegetable brush, for example. This will only remove a small part of the pesticides – but it’s better than nothing.
*After handling the peel of citrus fruits, bananas and mangos, give your hands a quick wash. In this way you avoid transferring pesticides from the peel to your fingers, from your fingers to the fruit and from there to your mouth.
*Also: Don’t cut bananas with the peel left on – otherwise residues from the peel can get onto the flesh.
*Choose iceberg lettuce: Current research shows it to be less contaminated. But the amount of pesticide residues in food can also be reduced during preparation. Remove the outer leaves of lettuce – they contain the greatest amounts of residues.
*Since potatoes grow deep in the soil they are only slightly, if at all, contaminated with residues, despite the intensive use of pesticides. But if it says on your sack of potatoes that they were “treated after harvesting” you should always peel them before eating.
*Cooking helps: When vegetables are cooked, pesticide residues are also reduced. But to avoid destroying all the valuable nutrients vegetables should not be overcooked. Braise briefly, starting with a hot pan and then reducing the temperature to a low heat.
Vitamin D (calciferol) is a fat-soluble steroid hormone precursor, meaning that it has no hormone activity itself, but is converted to the active hormone form through a photochemical (ultraviolet B radiation-induced) synthesis mechanism in the skin. After production in skin or consumption in food, it is converted in the liver and kidney to form 1,25 dihydroxyvitamin D, (1,25(OH)2D) the physiologically active form of vitamin D (calcitriol), which plays an important role in the maintenance of organ systems.
When ‘vitamin A’ was discovered, the next active substance was termed ‘vitamin B’. Later it transpired that ‘vitamin B’ is not actually a single substance, but a group (‘complex’) of different vitamins. As the following letters were already assigned, the various substances were given numbers, resulting in the names vitamin B1, B2, B6 and B12. Other B vitamins were discovered later and were given their own names (e.g., folic acid). The gaps in the numbering are due to the fact that a number of substances initially mistaken for vitamins have been removed from the complex.
Among the animals that need to consume vitamin C to survive are guinea pigs, bats, sparrows, and large primates including humans.
The skin, as contact area to the outside world, is put under particular strain. Not least for this reason it is subject to a rapid renewal process, which requires an intensive metabolism and the provision of building materials. Therefore, the body needs a sufficient supply of nutrients, such as vitamins, to optimize skin texture.
Vitamin deficiency often leads to changes in the skin. These deficiency symptoms disappear when the supply of nutrients is optimized. Thus, normal skin texture as well as the growth and the appearance of nails and hair are diet-dependent.
The compilation of a reliable diet for weight loss is rather difficult. By cutting out certain foods and by reducing the overall quantity of food, the intake of vitamins and minerals can be significantly reduced. Most nutritionists agree that is very difficult to meet vitamin needs with a diet of 1,500 calories a day; and with drastic reduction diets of than 1,000 calories per day it is almost impossible.
Eating ‘just a little less of everything’ is problematic, since there is no systematic control over nutrient intakes given. One-sided diets, which increase certain foods, but do not allow others (e.g., Atkins diet, potato diet, egg diet) are very risky. The body's vitamin reserves are exhausted most rapidly with radical dietary restriction (fasting).
Nutrition-related weight loss can only be achieved by restricting energy (caloric) intake. The body must be encouraged to drain its own energy (fat) reserves.
The long-term ingestion of certain drugs may imbalance the vitamin equilibrium as they can influence uptake, utilization, storage, and excretion rate of vitamins in the body. Oral contraceptives (the ‘pill’), for example, may affect the need for vitamin B6 and vitamin B9 (folic acid). Diuretics can increase the excretion of some vitamins with urine, which increases the demand. Other drugs that can intervene in the vitamin balance are, for example, certain antibiotics and sulfonamides, anti-malaria drugs and anti-tuberculosis cure. In some cases, the ‘anti-vitamin effect’ is used in disease treatment, for example in cancer chemotherapy.
Regular heavy alcohol consumption is detrimental to the uptake and the use of vitamins, especially the vitamins B1, B2, B6, and B9 (folic acid). Moreover, the ‘empty’ calories in alcohol reduce food intake and thus vitamin intake. In such cases, additional intake of vitamins is needed; however, they cannot solve the other problems heavy drinking can cause.
Smokers consume vitamin C faster than non-smokers. In studies it has been demonstrated that heavy smokers (at least 20 cigarettes per day) clearly need more vitamin C than non-smokers. However, an adequate vitamin intake cannot compensate for the damage of smoking.
National health authorities have established recommendations for micronutrient intake. These reference values define the adequate quantity of a micronutrient that healthy individuals should achieve to avoid deficiency. In addition, there are so-called preventive recommendations, which are somewhat higher than the actual reference values. In healthy people, it is neither necessary nor desirable to significantly exceed the reference values. Exceptions can occur for individuals with special requirement or diseases, which, in this case, need medical attention.
A balanced diet, in accordance with personal needs, can sufficiently provide micronutrients. Furthermore, it must be ensured that the content of micronutrients is not destroyed through inappropriate treatment of the food. The diet should be versatile and varied, with a focus on a variety of vegetables. Extremes should be avoided.
The vitamin content can considerably vary depending on climate and soil conditions, variety, fertilization, maturity, harvesting methods, transport and storage.
The preparation of food also has a significant influence. Many vitamins are sensitive to heat, light and oxygen, and watering fruits and vegetables can lower vitamin levels. Gentle processing helps to keep vitamin loss as low as possible: avoid soaking fruits and vegetables before chopping, scrubbing, and washing them. Eat raw fruits and vegetables if possible. Cook vegetables in little water or use a food steamer. Do not put vegetables into the water before it boils. Where possible, the water used for cooking vegetable can be re-used for soups or sauces as many vitamins are retained in it.
Depending on the type of food and storage conditions, the vitamin content in food can be significantly reduced. Normal stored potatoes, for example, lose up to one third of their vitamin C content after three months of storage. Vitamin C is destroyed even faster – within two to three days – in non-processed leafy vegetables. Equally vulnerable are most B vitamins (especially folic acid).
To keep vitamin loss as low as possible it is best to store fruit and vegetables in separate trays at the bottom of the refrigerator. Cold-sensitive fruit and vegetables (such as tropical fruits, potatoes) are best kept in a cool cellar or storage room.
Vitamin C (ascorbic acid) is oxygen-sensitive and water-soluble. It can therefore be partially destroyed in food during processing, through exposure to air during storage, or through treatment with water. Manufacturers are able to protect food against oxidation by adding vitamin C. The addition of the antioxidant ascorbic acid must be labelled accordingly in the list of ingredients of the consumer product.
Storage at low temperatures is superior to other methods of food storage. If frozen food is properly produced and stored, it often contains more vitamins than fresh food after several days of storage and transportation time until it reaches the consumer.
Vegans who do not consume any meat, eggs or dairy products may receive too little vitamin B2, B6, B12, A and D. To prevent defects in their children, pregnant and lactating women who do not consume animal-derived foods need certain additions to their diet, particularly supplemental doses of vitamin B12.
Vitamins can help to convert food into energy, but they do not act as energy source themselves. One cannot increase physical performance simply by taking extra vitamins. Only if a deficiency exists, can the additional intake of vitamins increase the performance by compensating for the deficit.
Consumers are well aware that oranges, lemon and paprika are important sources of vitamin C. However, it may come as a surprise that meat products like Wiener and Frankfurter sausages, liver paté and cooked ham can also be good sources of vitamin C.
Such cured meat products usually contain ascorbic acid or sodium ascorbate as antioxidants in order to aid the nitrite curing process. These additives are labeled in the list of ingredients, either by the names above, or by the E-number E300 or E301.
Most of the added ascorbic acid or ascorbate is even retained in the ham or sausage after manufacturing and storage until the end of shelf-life. Typically 20–25 mg vitamin C per 100 g is contained when consumed. That means, by consumption of a pair of Wieners or Frankfurters (200 g) about half of the recommended daily allowance (RDA) for vitamin C is provided.