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Vitamins & Minerals Q&AGeneral questions about vitamins and minerals

What are the effects of enzymes, light, heat, and preparation method, etc. on vitamins and minerals?

Sources: Vitamins by Osamu Igarashi (Maruzen Library), and Kojima et al.:Vitamins (Japan), 91 (1), 1-27 (2017)
  1. 1Acidic:0<pH<7
  2. 2Neutral:pH=7
  3. 3Alkaline:7<pH<14

Is there any difference in the effects when taking vitamins in different forms (pills, drinks)?

If the pill and liquid both contain the same amount of the same ingredients, the effects are essentially identical.
Generally speaking, liquids are absorbed and metabolized more rapidly, while pills are absorbed more gradually and stay around longer. Simply put, liquids are immediately effective, while pills are persistently active.
In addition to improving your basic dietary balance, use these pills and liquids wisely. One option is to take pills daily and use drinks for their added refreshment. Moreover, whatever form you take, be careful not to exceed the tolerable upper intake level.
Reference: New Vitaminology by Yoshinori Itokawa (Footwork Publishing), et al.

What is the absorption rate for vitamins (including supplements) in the digestive tract?

There are several factors that affect the absorption rate of vitamins, so there is no comprehensive consensus on what percentage is absorbed. The following factors affect the absorption rate of vitamins.

  1. 1Amount of vitamin taken: The absorption rate of vitamins tends to be higher when a smaller amount of the vitamin is taken.
  2. 2Whether the vitamin is taken with food: The absorption rate of fat-soluble vitamins is higher when taken with other fats than when taken alone.
  3. 3Level of vitamins in the body: The absorption rate tends to be higher when vitamin levels in the body of the person taking them are low, while at the same time, the rate of absorption of nutrients tends to decrease with ageing.

Reference: Vitamin Handbook

What are the differences between medicines and food vitamins?

In Japan, vitamins in pill or capsule form used to be treated as medicines, but since the loosening of regulations in the 1990s, they can now be treated as foods.

About ingredients
Most people seem to think that medicinal types contain more effective ingredients, but there are many cases in which medicinal types and food types contain the same ingredients.
Types of vitamins include products extracted from nature (natural types), chemically synthesized products with the same components as compounds that exist in nature (synthetic types), and derivative types in which the naturally occurring compound has a side group, etc.
Since natural and synthetic compounds have the same composition, their physiological activity is also the same in most cases. (Vitamin E is an exception. See below.) Derivatives are products developed as medications with the goal of improving absorption and safety etc. Compared to naturally occurring vitamins, they may have a shorter history of use, and information on side-effects may be limited, so they are only permitted as an additive to medicine. Products which use derivatives often indicate the derivative compound on the label. Derivatives are only treated as medications, but synthetic compounds and natural types can be treated as both medications and foods, with the exception of certain vitamins. In other words, for natural and synthetic compounds there is no difference in the ingredients in medicinal and food vitamins.
People tend to think that medicines contain a larger quantity, but for vitamins B1, B2, B12, and C sold as foods, there is no established maximum quantity, so foods may contain the same quantity as medicines. However, the dosage for medicines is set for effectiveness in treating illnesses, so the daily dose may be higher than the safe daily intake (maximum amount) as given in the Dietary Reference Intakes for Japanese (2015 edition).
About Regulation
Medicinal vitamins have met the standards for the content of ingredients, etc. established under the Pharmaceuticals and Medical Devices Law, so claims can be made as to their efficacy. Medicinal drugs which require a prescription and over-the-counter drugs that can be sold in drug stores are classified into a total of 4 types: 3 types of non-prescription drugs and 1 type of drugs requiring guidance. Conversely, vitamins treated as foods are limited to those vitamins which are permitted as food additives under the Food Sanitation Law, and claims cannot be made as to their efficacy or daily dosage, etc.
  • Research on vitamin E has shown that the rate of uptake in the body for natural sources is double that of synthetic sources, so the rate of uptake in the body is higher for D-alpha tocopherol, the naturally-occurring type of vitamin E (the synthetic type is DL-tocopherol).

Which vitamins are associated with metabolizing fat?

The main vitamins associated with metabolizing fat are vitamin B2, niacin, and pantothenic acid. These vitamins are coenzymes of the enzymes necessary for metabolizing fats, so when there is a lack of them, metabolism may be impaired. A lack of vitamin B2 in particular halts the metabolism of fatty acids and their use as energy. While there are many vitamins associated with the metabolism of fatty acids, this is the reason only vitamin B2 is called the “fat metabolism vitamin.” The above vitamins, as well as vitamin B1, are also involved in the breakdown of carbohydrates.

For those who wish to increase fat metabolism, in addition to exercise and diet, it is important to replenish B-complex vitamins.

How do the various types of vitamins related to skin and mucous membranes function?

Vitamins contribute to metabolic processes throughout the body. A lack of them can manifest as a deficiency, but in many cases, it manifests through changes in the skin and mucous membranes. The following are examples of the links between vitamins and the skin and mucous membranes.

Vitamin A
If you lack vitamin A, you will become dehydrated more easily. It is believed that the reason for this is that the functioning of sweat glands and the skin is reduced, leading to reduced sebum production and incomplete keratinization that reduces the moisture-retaining function of keratin. It also increases the occurrence of bacterial infections of the skin, harming the condition of the skin and mucous membranes as a result.
Vitamin B2
Vitamin B2 strengthens blood vessels throughout the body, especially capillaries in the skin, and improves blood circulation. It is well-known that having a deficiency causes inflammation of the lips and corners of the mouth. Vitamin B2 deficiency causes capillaries to dilate, which increases transparency to sunlight, raising sensitivity to external stimuli and causing extreme sensitivity to sunlight.
Vitamin B6
If you lack vitamin B6, skin conditions such as eczema, seborrheic dermatitis, and inflammation of the tongue and corners of the mouth can appear, so it is believed to be a necessary vitamin for skin.
However, much remains unclear about the mechanism which causes these clinical symptoms to appear.
If you lack niacin, a type of skin inflammation called pellagra can develop. There are many aspects of the mechanism by which pellagra develops that remain unclear, but it is believed to be caused by a hypersensitive reaction to sunlight by the skin.
Vitamin C
Vitamin C is required for the creation of collagen, which accounts for one-third of the proteins in the body.
Collagen is the main component of the connective tissue that joins cells together, and it gives shape to tissues and organs, including skin. Accordingly, a lack of it presents as scurvy, which results in bleeding from the skin and mucous membranes.

For foods with nutrient function claims, the nutrients which in Japan are permitted to be labeled “This nutrient helps maintain the health of skin and mucous membranes” are vitamin A, beta carotene, vitamins B1, B2, and B6; vitamin C, niacin, pantothenic acid, biotin, and zinc.

Reference: Dictionary of Vitamins. ed. The Vitamin Society of Japan, et al.

Which vitamins and minerals should pregnant women take and which they should they avoid?

While vitamins and minerals are essential at every stage of life, according to the Dietary Reference Intakes for Japan (2015 edition), pregnant women are recommended to increase their intake of vitamins and minerals such as vitamin A, vitamin D, folic acid, and iron in comparison to women who are not pregnant.

Vitamin D is necessary for the formation of bones, so the intake guidelines for pregnant and nursing women are set higher. Folic acid is a necessary nutrient for cell division and DNA replication, and it is known that taking an additional 400μg of folic acid daily from 4 weeks before conception to the 12th week of pregnancy in particular reduces the occurrence of neural tube disorders.
Conversely, while there are no vitamins pregnant women should avoid, there are some vitamins which can cause problems if you take too much. Toxicity specific to pregnant women has been reported for vitamin A, and there are reports that fetal abnormalities have been observed in cases in which 10,000IU (3,000μgRE) were taken daily over an extended time period.
The American Council for Responsible Nutrition (CRN) has stated that side-effects do not occur for doses of 10,000IU (3,000μgRE) and below, but in Japan, making a more conservative estimate for the sake of safety, the safe amount which will not produce negative health effects in almost all people is set at 9,000IU (2,700μgRE). As it is an important vitamin that is essential for growth, it is best to take some vitamin A in the form of beta carotene, which does not have any risk of overdose.

Finally, a woman’s nutritional status may worsen during pregnancy due to changes in the sense of taste or reduced dietary intake caused by morning sickness, etc. The most important point is to get three balanced meals, but using supplements to compensate for nutrients that tend to be lacking is another available option.

Can I get enough nutrients just from everyday meals?

Not all nutrients humans need can be produced in the body. Consequently, we replenish our supply of water and nutrients, etc. every day. Supplements differ in that they supply only the components of food, come in pill or capsule form, and are not satisfying in the sense of taste, but they are the same in the sense that they supply nutrients.
Generally speaking, as the Ministry of Agriculture, Forestry and Fisheries (Japan) advocates, "The foundation of a healthy diet is a main dish, a main vegetable, and side dishes," so you should try to prepare balanced meals. However, getting only specific nutrients from foods, such as getting all the vitamins you need from normal meals when trying to lose weight, or smokers taking more vitamin C, which they tend to lack, can be extremely difficult. In such cases, taking vitamins as a supplement is thought to be beneficial.

Does taking supplements every day reduce absorption from food?

The vitamins in foods and the vitamins taken as supplements are absorbed and metabolized by the body in essentially the same way, so it is believed that taking supplements does not change the way in which vitamins originating from foods are used.
As for the frequency of intake, to maintain a constant state of saturation of vitamins in the body and be prepared for expending a large amount of vitamins through exercise or stress, it is recommended that you proactively get vitamins from food and supplements daily, and not only when fatigued.
For reference, the maximum tolerable intake for vitamins and minerals, etc. which carry a risk of negative effects from excessive intake are established by the Dietary Reference Intake for Japanese (2015 edition). These amounts have been determined to be safe for daily intake. Generally speaking, as long as the amount is within the daily recommended intake listed on product labels, there should be nothing to worry about.
(Response from Dr. Osamu Igarashi, Professor Emeritus, Ochanomizu University)

What are the synergistic and additive effects of vitamins?

Here are three representative examples of synergistic and additive effects.
The B-complex vitamins include vitamin B1, B2, niacin, pantothenic acid, and biotin, and they are involved in each step of the metabolism of carbohydrates. Accordingly, if you lack even one of them, your body will become unable to metabolize carbohydrates properly.
Among B-complex vitamins, folic acid and vitamins B6 and B12 are known to be involved in the metabolism of homocysteine. High levels of homocysteine are said to increase the risk of stroke and heart attack. Patients with high levels of homocysteine in their blood were administered folic acid and vitamin B6 and B12, both alone and in combination, and it was reported that homocysteine levels were reduced more when vitamins were administered in combination than when administered alone. Beta carotene, vitamin C, and vitamin E all function as antioxidants, and have been administered in combination in various clinical trials. Among them, vitamin C is known to reactivate the antioxidant action of vitamin E that had become inactive.

Reference: Know Your Vitamins by Toshikazu Yoshikawa (Shufunotomo Co., Ltd.)
Vitamins by Osamu Igarashi (Maruzen Library)

I have heard that taking some medicines can cause deficiencies in some vitamins. Which ones are they?

  • If you are taking medication, please consult your doctor.

There have been many reports of vitamin deficiencies caused by medications, so we will focus on medications frequently carried by pharmacies, and present a number of cases where you should be careful. Please contact a specialist such as a doctor or pharmacist for detailed information.
Additionally, among over-the-counter medicines, vitamin B12, folic acid, and iron deficiencies have been reported for H2 receptor antagonists, medications for stomachaches and heartburn. One of the symptoms of these deficiencies is anemia.
Avmard J P et al; Haematological adverse effects of histamine H2 receptor antagonists.; Med Toxicol&Adverse Drug 3(6), 430-, 1988
Itokawa Y. The interaction of Vitamins and drugs. Prog Med 5, 623-. 1985.

The following are examples for other prescription drugs.

  1. 1Vitamin B2 deficiency caused by antibiotics
    There have been many reports of the appearance of symptoms of vitamin B2 deficiency such as a sore throat and inflammation of the tongue and corners of the mouth due to administering penicillin, chloramphenicol, tetracycline, streptomycin, and other antibiotics. This is listed on the labelling about side-effects for these drugs.
    Yoshinori Itokawa; Interaction of the vitamins and folic acid; Prog Med 5, 623-, 1985
  2. 2Folic acid deficiency caused by anti-epilepsy drugs
    Long term use of anti-epilepsy drugs such as phenytoin is known to reduce blood serum levels of folic acid, which can cause polyneuritis. In fact, patients taking phenytoin over an extended period are frequently administered folic acid.
    Tomokazu Obi; On folic acid deficiency and polyneuropathy frequently occurring in long-term use of phenytoin; Clinical nerve 28(12), 1530, 1988
    Yoshinori Itokawa; Interaction of the vitamins and folic acid; Prog Med 5, 623-, 1985

If I don’t smoke myself, but am around heavy smokers, are there any vitamins I should take more of?

Harm from smoking affects not only smokers themselves, but also the non-smokers around them. This is because tobacco smoke, particularly secondhand smoke, contains carcinogens and many other harmful substances.
In comparison to non-smokers, it is known that smokers metabolize vitamin C more rapidly in order to counteract the harmful substances that are inhaled, reducing the overall amount of vitamin C in the body. It is also said to reduce the absorption of vitamin C in the small intestine.
Accordingly, to protect your body against harm from smoking, it is recommended that you take sufficient amounts of antioxidant vitamins such as vitamin C, vitamin E, and beta carotene.
(Reference: New Vitamin C and Health, Vitamin Mineral Book)