Principles of healthy eating. Part 6.
By Roman Pawlak, Ph.D, RD
Research studies conducted in the last several decades quite convincingly showed that plant-based diets that are composed of a variety of unrefined products protect from a number of chronic health conditions. In some cases, such as heart disease or diabetes, such diets have been shown to reverse these diseases. These diets are relatively rich in micronutrients (vitamins and minerals). As a result, many people began taking vitamin and mineral supplements. Studies showed while some supplements may be necessary and while supplements of some vitamins might be helpful in disease prevention, others may actually be detrimental. Consuming higher amounts of micronutrients with food is what is associated with disease prevention. The same is not necessarily true of obtaining these compounds from supplements. Supplementation is not a new phenomenon. In 1924 the United States government mandated that food producers add iodine to salt. In 1933, the government authorized adding vitamins A and D to skimmed milk. Since 1941 vitamins B1, B2 and niacin have been added to flour and in 1998 flour fortification also included folic acid. Iron is another nutrient that is being added to flour. Iodine supplementation was a result of iodine deficiency in the soil, particularly in the mountainous areas. Vitamin A and D are fat soluble, therefore, reduced fat milk significantly reduces their content. The addition of vitamins B1, B2, niacin, folic acid and iron was the result of refining grain products, thus reducing the content of these and other nutrients in comparison to whole grain products. In the past several years, vitamin and mineral supplements as pills, powder or liquids have been made available to consumers. In many countries including the United States supplements are sold without a prescription and are available in grocery stores, pharmacies,
health food stores, and specialty stores that sell only supplements. Demand for supplements is the result of an increasing consumer interest in their own health. During the last ten to twenty years the supplemental industry has increased dramatically. According to industry data, in 1994 there were approximately 4,000 different dietary supplements. In 2008 the number of supplements had increased to about 75,000.
Who may benefits from taking supplements? In some cases, the use of dietary supplements is indicated. These include women of reproductive age taking a multivitamin (due to the presence of folic acid in a multivitamin, which reduces the risk of neural tube defects such as spina bifida). Also, many pregnant women may need to use an iron supplement, especially in the second and third trimesters. People who adhere to vegetarian diets and those over 50 years of age should be taking vitamin B-12 supplements to prevent deficiency. Someone with an elevated risk of heart disease can benefit from taking fish oil supplements. It should be noted, however, that the intake of supplements is not advisable for all people. In addition, not all dietary supplements reduce the risk of acquiring the disease. On the contrary, some supplements increase such risk. The vast majority of people can and should acquire most nutrients from food. In addition, foods don’t just provide vitamins and minerals. They are rich in thousands of phytochemicals, a class of compounds found only in plant products. Supplements are not able to replace all these beneficial ingredients, nor are they able to provide them in the same proportion as they appear in foods.
Why do people take supplements?
There are many reasons why people use dietary supplements. Research indicates that among the most common motivation to take them is prevention of chronic diseases, particularly heart disease and cancer. Most people who use a multivitamin, vitamin C and E, and beta carotene take them thinking that they will help them to prevent heart disease and/or cancer. Unfortunately, to their surprise, most of the studies that assessed the impact of these supplements in the prevention of these diseases (and also some other lifestyle diseases, including Alzheimer's disease, for example) do not confirm these anticipated benefits. On the contrary, many of these studies have shown that taking antioxidant supplements (such as vitamin E and C or beta carotene) may increase the risk of developing these diseases. Because of this, health organizations, stress that for prevention of chronic diseases people should consume a healthy diet that is based on whole grains, fruits and vegetables that are rich in micronutrients and that taking supplements be limited to special cases described in the previous section of this chapter. For example, the World Cancer Research Fund and the American Institute for Cancer Research, two prestigious organizations concerned with cancer prevention, on the basis of the results of many studies came to the conclusion that supplements of these nutrients should not be recommended for cancer prevention. Do antioxidant supplements reduce the risk of death? There are many studies that have estimated the impact of dietary supplements on chronic diseases. In 2007, the Journal of the American Medical Association published the results of a review of 68 randomized studies that assessed the effect of using beta-carotene, vitamins A, C, E and selenium on risk of death among 232,606 people 18 to 103 years of age. These studies used different study designs that included, among other things, different doses of supplements and different study duration. The supplements’ doses ranged from 1.2 to 50 mg (on average 17.8 mg)
for beta carotene, 1,333 to 200,000 IU (International Units) (on average 20,219 IU) for vitamin A, from 60 to 2,000 mg (an average of 488 mg) of vitamin C, from 10 to 5,000 IU (an average of 569 IU) of vitamin E and from 20 to 200 μg (on average 99 μg) of selenium. The supplements were used every day or every other day, from 28 days to 12 years (on average 2.7 years). The results showed a 5 percent increased risk of death among antioxidant supplement users compared to those who did not use them. The authors stated that: “we did not find convincing evidence that antioxidant supplements have beneficial effects on mortality. Even more, beta carotene, vitamin A, and vitamin E seem to increase the risk of heath.” They further added that: “Despite observational data suggesting strong associations between carotenoids, folic acid, and vitamin E, or metabolites altered by these nutrients, and decreased CVD (cardiovascular disease – author) risk, most intervention data using nutrient supplements at or above the Recommended Dietary Allowance values have not supported these relationships. There are also some data to suggest that unexpected adverse consequences may result from supplementation with nutrients traditionally thought to have a low risk of toxicity.”
Do supplements reduce the risk of heart disease and cancer? The above quote indicates that most studies did not confirm the theory that antioxidant supplements lower the risk of chronic diseases. Another example confirming this conclusion is the Vital Study. It included 77,721 men and women 50 to 76 years old, living in Washington State. In those who used vitamin E supplements for an average of 10 years, researchers noted a 5 percent higher risk of lung cancer with each 100 mg/day increase in use of vitamin E. Practically speaking, a person taking a dose of 400 mg per day had more than 20 percent higher risk of lung cancer than if these supplements are not used.
In a study known as the Physicians’ Health Study II, no beneficial impact of using vitamin C and E supplements on risk of prostate cancer was found. This study recruited 14,641 individuals over 50 years of age, who used 400 IU of vitamin E and 500 mg of vitamin C per day. The authors’ conclusion explains the disappointing results: “in this large, long-term trial of male physicians, neither vitamin E not vitamin C supplementation reduced the risk of prostate or total cancer. These data provide no support for the use of these supplements for the prevention of cancer in middle-aged and older men.” The same study estimated the impact of vitamin E and C supplements on cardiovascular disease and did not find any benefits. On the contrary, those consuming vitamin E had a 74 percent higher risk of stroke, compared to non-users. The authors stated that: “these data provide no support for the use of these supplements for the prevention of cardiovascular disease in middle-aged and older men.” In another study published in the Journal of the American Medical Association, authors found that vitamin E and C supplements reduced the risk of some cancers while increasing risk of cancers of other sites. For example, a supplement of vitamin E reduced the risk of colorectal cancer by 32 percent, but increased the risk of cancer of the lymph nodes by 24 percent, pancreatic cancer by 20 percent, leukemia by 71 percent and melanoma by 75 percent. Similarly, vitamin C supplements reduced the risk of pancreatic cancer by 14 percent and lymphoma by 16 percent, but increased the risk of leukemia by 30 percent and melanoma by 75 percent. One of the latest publications describing the effect of a vitamin E and selenium supplements on cancer was published in the Journal of the American Medical Association. This data is based on 35,533 men age 50 years and over living in the United States, Canada and Puerto Rico. Participants were divided into four groups. One of them received a 200 μg selenium
supplement. The 2nd group received 400 IU of vitamin E supplement, the 3rd group received both selenium and vitamin E, and the 4th group received a placebo. The experiment lasted from 7 to 12 years. Individuals who took a vitamin E supplement had a 17 percent higher risk of prostate cancer. Among those who took a selenium supplement researcher detected a 9 percent increase in risk and those that took both of these supplements had a 5 percent increased risk. Researchers also found a higher risk of cancer in other organs among supplement users. For example, those who used both supplements (vitamin E and selenium) had a 21 percent higher risk of cancer of the colon and rectum and about 11 percent higher risk of lung cancer. The following statement by the authors of this study adequately summarizes the effectiveness of taking these supplements: “the lack of benefit from dietary supplementation with vitamin E or other agents with respect to preventing common health conditions and cancers or improving overall survival, and their potential harm, underscore the need for consumers to be skeptical of health claims for unregulated over-the-counter products in the absence of strong evidence of benefit demonstrated in clinical trials.� Do we need to take supplements because the soil is depleted with nutrients? As already indicated, there are several reasons why people believe it is necessity to use supplements. Many supplement users believe that the soil is depleted of nutrients. The same individuals often believe that a higher intake of micronutrients (vitamins and minerals) protects us against chronic diseases, and thus, they reach for supplements. The quote included in the previous section indicates that indeed high intake of some nutrients such as vitamins C, E or beta carotene lowers the risk of certain chronic diseases such as heart disease or cancer. However, the same quote clearly stresses that this is only the case when these nutritional compounds are consumed with food and not as dietary supplements. It is true that specialization and mono-
cropping (growing the same crops in the same field) does take a toll on the mineral content of the soil. As a result, mineral content may be lower than 50 or 100 years ago. However, fruits, vegetables and other products available in our stores come from all over the world. In the United States, bananas are imported from Costa Rica, Chile or Ecuador. Pineapples come from Costa Rica or Brazil. Grapes are brought from Chile, Mexico and other countries. Apples are shipped from New Zealand or Australia. In addition, in stores we can find products from different states, such as California, Washington or New York. Not everywhere the soil is depleted. In addition, in one place soil may be depleted of one mineral and elsewhere of another. So eating a wide variety of products, which is one of the most important principles of a nutritious diet, ensures we provide the body with the recommended amount of nutrients. In fact, current production methods and widely distributed commodity trading makes it possible to have a diet that is far superior in nutrient content than decades ago. Decades ago, especially during the winter months people had to rely on produce they were able to can or pickle. The supply of fresh fruits and vegetables was scarce. Today, there are no seasons in American grocery stores. A variety of fresh produce can be purchase regardless of a season or time of year. As a result, even if we assume that fruits and vegetables are not as rich in nutrients as they were half a century ago, due to the availability of produce from all over the world, regardless of the period of the year consumers can have a more nutritious diet compared to years past. Consumers should also be aware that, at least in America, more and more products are fortified with vitamins and minerals. For example, some breakfast cereals (such as those under the name Total) contain 100 percent of the recommended daily dosage of most nutrients per serving. This means that using just half a cup of Total cereal provides 100 percent of the
recommended amounts of most nutrients. Other products such as fruit juices are enriched with vitamin C, and some juices are fortified with calcium. Reduced fat milk has vitamins A and D added to it. Soybean products are fortified with a variety of nutrients. The number of products that are enriched with vitamins and minerals is increasing daily. This is one of the reasons scientists wonder whether people eat too much of certain vitamins or minerals. Many vitamins and minerals exhibit toxic side effects if their consumption exceeds the specified doses that are considered safe.
What determines the nutritional value of foods? Nutritional content of fruits and vegetables depends on several factors including: the content of nutrients in the soil, the time of exposure to the Sun's rays, harvest time (the degree of ripeness at the time of picking), the nature, quantity and quality of fertilizers, the genetic selection and the storage conditions including duration, the concentration of carbon dioxide in the atmosphere, humidity and temperature. Many supplement users have heard of studies that showed that the nutrient content in certain food was higher in the past compared to nutrient content in produce harvested today. It’s true that some studies indicated a slight reduction in the nutritional content in certain products in comparison with their content years ago. However, it is also true that most of these studies showed very small differences in this regard and that today’s produce may have lower content of one nutrient and higher content of another, compared to the nutrient content found in past studies. It must also be kept in mind that in order to draw meaningful conclusions from these studies, someone would have to compare “apples to apples.” This means that all factors that play a role in a nutritional content of foods, including those factors mentioned above, would have to be the same. This would be the only way to assess
differences between an apple grown today with one harvested 50 years ago. In reality, this is not possible to accomplish since there are too many variations such as the weather conditions (amount of rain, temperature), harvest time and storage conditions may be different. Another important issue has to do with setting daily recommendations of nutrient intake. These recommendations are usually set a few to several times higher than the daily demand. For example, someone would have to consume less than 10 mg per day of vitamin C for at least a few weeks to develop scurvy, a disease associated with vitamin C deficiency. But the recommended vitamin C intake is 75 mg per day for women and 90 mg per day for men. So even if only 75 or 50 per cent of the recommended intake is ingested scurvy will likely never develop. In addition, just 1 cup of orange juice contains more than 100 mg of vitamin C. Thus, even if the content of nutrients from a given supply of oranges is reduced, regardless of the reason for the reduced nutrient content, these oranges would still likely provide a significant amount of this vitamin. Of course, vitamin C is also found in many other fruits and vegetables. Thus, if a person eats a variety of vegetables and fruits daily, he or she will relatively easily provide the body with the recommended amount of this vitamin and other nutrients. This is true also even if the nutritional content of produce was somewhat lower today in comparison to 50 or 100 years ago. Nutrients interact with each other in our body. They can help or hinder the absorption of other nutrients. When we ingest food, our body is perfectly suited to deal with nutrient interaction to ensure its adequate nutritional status. However, when we take supplements that provide mega-doses of one or a few nutrients, they may interfere with the absorption and handling of other nutrients and cause imbalance in our system. Thus, obtaining nutrients from foods is always preferable over obtaining them from supplements.
Individuals who do not provide their body with adequate amounts of vitamins and minerals, do not do so because of the depletion of the soil but rather because they consume too much refined food such as white flour, white rice and an insufficient amount of vegetables and fruit. Plant products contain thousands of beneficial compounds including micronutrients (vitamins and minerals) but also phytochemicals. For example, cereals are loaded with phenolic compounds, a specific group of phytochemicals. Therefore, eating a bowl of breakfast cereals made from refined grains enriched with a few vitamins and minerals is not equivalent to eating a bowl of cereals from whole grains. Similarly, the consumption of a supplement in the form of a pill will not replace a diet based on a variety of unrefined plant products.
Vitamin B12 As mentioned in the beginning of this chapter, in some cases it is advisable to use dietary supplements. They include supplements of vitamin B12 and vitamin D. Vitamin B12 is one of a few water soluble vitamins. Vitamin B12 has the most complicated chemical structure of all vitamins. It takes part in a chemical reactions occurring in every cell of the human body. It is essential to the normal functioning of the brain and nervous system, production of fatty acids, synthesis of energy and hematological (blood) cells. There is more than one type of vitamin B12, some of which are inactive in humans. The active form of vitamin B12 is produced only by micro-organisms (e.g. bacteria). Vitamin B12 deficiency is quite common around the world. There are several population subgroups that may develop a deficiency of this vitamin. They include vegetarians, especially vegans (individuals who do not eat meat or food of animal origin), older adults and elderly regardless of their diet, individuals who underwent a gastric surgery (e.g. stomach or small
below resection), people diagnosed with AIDS, patients with diabetes who use the drug metformin and individuals who had a surgery with anesthesia. A deficiency may develop because of insufficient intake of vitamin B12 (as is the case of vegans and vegetarians), inadequate absorption (as in the case of older people and people with removed part of the intestine or stomach after surgery) or due to a destruction of this vitamin in the body (as in the case of those taking metformin or a surgery with anesthesia). Vitamin B12 deficiency can cause many different problems, some of them may be mild but others may be severe and some are irreversible. These include dementia, ataxia, optic nerve atrophy, catatonia (a condition of a number of mental and physical abnormalities), psychosis, moodiness, myocardial infarction and deep vein thrombosis, megaloblastic anemia and neurological disorders, such as neuropathy, myelopathy (a condition of the spinal cord), memory impairment, depression, brain atrophy, fatigue, memory lapses and weakness. Generally it is believed that an acute deficiency of vitamin B12 does not cause changes in the nervous system. However, prolonged deficiency leads to irreversible complications. The active form of vitamin B12 is called cobalamin. In the body, this form occurs as both methylcobalamin and adenosylcobalamin. In addition, cyanocobalamin, a form often added to fortified products, such as soy milk, can be converted in the body to one of the two active forms. In addition to the biologically active form, there are also pseudo vitamins B12, which do not have any value for the human body. They are produced by some organisms, such as algae and are also found in some fermented foods including fermented soybean products. These forms can contribute to deficiency of this vitamin in the body because they block the normal metabolic process of the biologically active forms. Bacteria located in the oral cavity and in the small intestine produce negligible amounts of vitamin B12. Thus, relying on synthesis of vitamin B12
by these bacteria surely leads to a deficiency. Sources of vitamin B12 include meat and animal products. The reason why meat and animal products contain this vitamin is that animals are able to absorb it from their digestive system. There, the bacteria produce it in large quantities. For example, 100 grams of cow's milk contains from 0.2 to 0.4 μg of vitamin B12. In milk, which has been boiled for 2 to 5 minutes, about 30 percent of vitamin B12 is destroyed by temperature. About 20 to 60 percent of vitamin B12 remains in cheese. Meat, fish and eggs contain a little more vitamin B12 as compared to milk and dairy products. Note, however, that meat and animal products are the main sources of saturated fat and cholesterol, and they are associated with an increased risk of various diseases including certain types of cancer and cardiovascular diseases. Therefore, limiting or eliminating them from the diet is advisable. Generally, it is recommended that vegans, vegetarians, elderly (above 50 years) regardless of the type of diet, and other population subgroups listed earlier take vitamin B12 supplements. A study published in 2005 in the Archives of Internal Medicine showed that “the smallest dose of cyanocobalamin necessary to disappearance of mild form of vitamin B12 deficiency is more than 200 doses recommended for human consumption in the diet, which is approximately 3 μg” (3 μg dose is recommended by the European Union, in American 2.4 μg per day is recommended). The results of this study indicate that the dose needed for the prevention of vitamin B12 deficiency with supplements should be at least 500 μg. Other studies have shown that the absorption of this vitamin with supplements was around one percent of the dose ingested. This means that a dose of 250 μg would be sufficient to prevent deficiency. People who already developed a deficiency should ingest at least 1000 μg two to three times a day for a few weeks and then can reduce the dose to 500 μg per day. Always remember to consult with your doctor to
make sure the diagnosis of vitamin B12 deficiency is correct and the course of treatment is supervised. Vitamin B12 taken as a supplement is absorbed in a different way than vitamin B12 provided with foods. In foods it is attached to specific proteins. The stomach’s gastric acid and pepsin (an enzyme needed to digest protein) disconnects vitamin B12. The stomach also secrets another substance called intrinsic factor. This compound binds with vitamin B12 once it is released from the protein and only then can vitamin B12 be absorbed into the blood stream. Absorption occurs in the lower part of the small intestine. Vitamin B12 from supplements is absorbed in a different way, namely by a process called simple diffusion that does not require splitting from the protein and binding to intrinsic factor. This is why vitamin B12 ingested from supplements can prevent a deficiency of this vitamin. Some people consume a sublingual form of vitamin B12, believing that it is better absorbed. The reason sublingual vitamin B12 can effectively prevent deficiency is the fact that it contains a sufficient dose (500 Οg) and not really because it is placed under the tongue. In addition to supplements, nutritional yeast is a good source of vitamin B12. Two teaspoon full or one tablespoon contains roughly the amount equal to the daily requirement. Be sure to read the label to make sure the nutritional yeast contains vitamin B12 since not all brands are fortified with this vitamin. A study published in the Annals of Nutrition Metabolism showed a significant reduction in the level of metylmalonic acid (which meant the correction of a deficiency of this vitamin) among people who ate vitamin B12 in the form of supplements or nutritional yeast. Some authors, relying on animal studies, argued that intake of large amounts of this vitamin can increase the risk of cancer. Published scientific studies do not confirm these
warnings. Today there are no known symptoms of toxicity of vitamin B12 in humans. On the contrary, some studies suggested that vitamin B12 can have a beneficial effect on the prevention of breast and colon cancers. Other studies, in which individuals consumed hundreds of times higher dose of this vitamin than the daily recommendation over a period of several years have not shown either positive or negative effects of this vitamin for the development of cancer. Despite this, in order to prevent deficiency there is no need to consume doses greater than 1000 Îźg. Vitamin D Vitamin D, like vitamins A, E and K, belongs to a group of fat-soluble vitamins. There are two forms of vitamin D: cholecalciferol and ergocalciferol. Cholecalciferol is produced in the skin of humans and animals under the influence of sunlight. Ergocalciferol is produced in some plants, provided that they have adequate sun exposure. Both cholecalciferol and ergocalciferol are forms that are not biologically active. Their activation occurs first in the liver and later in the kidneys. One of the functions of vitamin D is to maintain an adequate level of calcium in serum within a very narrow range of 2.2-2.6 mmol/L or 9-10.5 mg/dl. This level is necessary for the proper functioning of the nervous system, as well as adequate growth and maintenance of bones and teeth. For this reason, vitamin D plays a significant role in the prevention of bone diseases, such as rickets and osteoporosis. In addition, recent studies suggested that vitamin D may also be an important factor in the prevention of some cancers, especially breast, prostate and colon cancer, cardiovascular diseases (including hypertension) and the proper functioning of the immune system. Some researchers believe that other diseases are also associated with inadequate levels of vitamin D including autism, depression, and even multiple sclerosis.
By far the best way to provide the body with adequate doses of vitamin D is exposure to sunlight. Depending on geographic location, it is estimated that 20 to 30 minutes of sun bathing in the middle of the day in the period from mid-spring to mid-autumn may allow the skin to produce significantly higher than the recommended amount of vitamin D, provided that the face and forearms are exposed. This amount is not toxic because of the need for further activation of this vitamin in the body. It should be noted that the International Agency for Research on Cancer, an agency of the World Health Organization has classified solar radiation as a risk factor for causing skin cancer in humans. Therefore, it is a good idea to avoid prolonged sun exposure, especially in the summer. Although vitamin D is stored in the body, recent studies suggested that its serum level during the autumn and winter months may be insufficient for example in the prevention of cancer. Vitamin D is measured in nanomoles per liter of blood (nmol/L) or as nanograms per milliliter (ng/ml). Until recently, the serum level considered adequate (enough to make sure that all basic bodily functions related to vitamin D are not affected) was in the range between 16 and 80 ng/ml (40 to 200 nmol/L). Results of more recent research suggested that a higher level, 30 to 80 ng/ml and even 50 to 80 ng/ml allows for the best immune system function and cancer prevention. This higher level is recommended by an organization called the Vitamin D Council. Researchers from the Institute of Sunlight, Nutrition and Health Research Center estimated that if Europeans increased their serum vitamin D level to 40 ng/ml, 187,000 lives would have been saved each year. In order to maintain between 50 and 80 ng/ml of vitamin D in the serum, the Vitamin D Council recommends that supplements in a dose of 5000 IU should be taken on a daily bases in autumn and winter. This dose is much higher than that recommended by the Institute of Medicine, and even higher than the level designated as the highest level safe for
human consumption of 4000 IU, known as Tolerable Upper Intake. Even though this level exceeds the tolerable intake, studies have not demonstrated that such high doses can cause vitamin D toxicity. The Institute of Medicine in the United States has recommended taking a daily dose of 600 IU for adults, 800 IU for elderly and 400 IU for infants. The recommendation for pregnant and nursing women is the same as for other adults. The intake and serum level are vigorously debated by scientists. There is some evidence that the middle ground may be adequate for the most benefits. Providing adequate vitamin D in late fall and winter in most parts of America and Europe is challenging for all people, with the exception of individuals who live in the most southern areas. There are not many foods that provide vitamin D. They include skim milk or soymilk, both of which are fortified with this vitamin. Vitamin D supplements should be recommended during a period of low sun exposure. The important question is what is the correct dose to take? Studies have shown that intake of vitamin D in doses of 400 IU per day may not be sufficient to prevent fractures and reduce the risk of cancer. Other studies have shown a beneficial effect of consuming 800 to 2000 IU of vitamin D from supplements. This dose, not only seems to be effective in reducing the risk of bone fractures or cancer, but also it may help in combating some viral infections. In both America and Europe the use of tanning salons has become increasingly popular. In the United States, tanning salons are one of the fastest growing areas of business. Some manufacturers of tanning beds claim that the benefits of vitamin D production is greater than the risk of acquiring cancer due to the exposure to UV rays. On the other hand, in 2009, the International Agency for Research on Cancer identified tanning beds as a factor in causing
cancer. The same organization found that the use of tanning beds carries risks similar to other carcinogenic substances such as asbestos, tobacco and arsenic. Although the synthesis of vitamin D by exposure to the radiation produced by tanning beds is possible, their potency is much lower than exposure to sunlight. This is because sunlight contains two types of UV rays: UVB and UVA. Of these two, UVB rays are most effective when it comes to production of vitamin D. Tanning or sun beds, on the other hand, produce mainly UVA rays. A study on the impact of tanning beds on the production of vitamin D showed that the vitamin D levels among people using tanning salons an average of 6 to 12 minutes each day had an increase from11 nmol/L to 27 nmol/L after nine days. It should be noted, however, that people involved in this study experienced various unwanted side effects that are common among regular users of tanning salons. Therefore, taking also into account the fact that the use of tanning devices is associated with skin cancer, the authors of the study stated that “sunbed use as vitamin D source is, however, not generally recommendable due to the well-known carcinogenicity and high frequency of acute side effects.” A similar conclusion was reached by Dr. Woo and Dr. Eide, who evaluated scientific evidence of the impact of tanning beds on cancer and vitamin D: “Given the relative inefficiency of UVA-emitting tanning devices in increasing serum vitamin D levels, especially in those most at risk of vitamin D deficiency, indoor tanning is not recommendable as a way to achieve optimal vitamin D levels in the general public.” Individuals who want to achieve the most beneficial levels of vitamin D should spend a moderate amount of time in the sun light during the late spring, summer and early fall. In the other part of the year, regularly taking vitamin D supplements with a dose of from 800 to 2000 IU on most days of the week or even daily (depending on the dose of supplements and geographic location) would ensure an adequate serum level. Regular intake of foods fortified
with vitamin D will help in maintaining a sufficient level of this vitamin but since the dose of fortification is relatively small, relaying just on fortified foods may not provide the best results in terms of ensuring optimal serum level of vitamin D. In conclusion, it should be noted that while some dietary supplements (e.g. supplements of vitamin B12 or vitamin D) may help to reduce the risk of a deficiency and associated symptoms, supplements of other nutrients are generally not needed and may even increase the risk for some health conditions. In general, a diet based on a variety of whole grain products, fruits, vegetables, nuts and seeds provides the body with the best mixture of nutritional compounds.
Roman Pawlak, Ph.D, RD is an Associate Professor of Nutrition at East Carolina University in North Carolina. He is the author several books including “Forever young. Secrets of delaying aging and living disease free,” “Healthy diet without secrets,” “In defense of vegetarianism” and “I am the Lord who heals you,” and a co-author of “Vegetarian mother and her baby.”