This chapter will examine the enormous market for supplements and ask what is the evidence behind them and if we really need them.
It will contain the following sections:
- Where Supplements are Needed
- The Market for Supplements
- Supplements in Sport
- Supplements for Health
- Vitamin C
- Vitamin D
- Vitamin A
- Energy Drinks
- Boosting the Immune System
- Further Resources
- Site Index
If you wish to go directly to one of the topics above, click on the blue underlined title.
Where Supplements are Needed
Most people can get all of their necessary nutrients from a balanced, healthy diet. However, there are some for whom this does not suffice and supplements are needed to make up the shortfall.
Most women will get through pregnancy without the need for supplements but a significant number will benefit from additional iron and folic acid. It is a condition with an increased demand for nutrients. It is difficult to predict in advance who will need supplements and who will not, so they are given to all pregnant women as a matter of routine. Prevention of deficiency during pregnancy is better than treatment. However, some women get problems, especially with the iron which can often cause constipation, sometimes diarrhoea and sometimes upset the stomach. Folic acid is rarely a problem.
Folic acid deficiency may cause neural tube deformities in the baby. This means spina bifida or anencephaly, where the brain fails to develop. Anyone who has had a child with this must have folic acid supplements before getting pregnant again.
Some people have diseases in which there is difficulty in absorbing certain nutrients. Generally speaking, it is important to treat the underlying condition such as maintaining a gluten free diet in a person with coeliac disease but not all diseases can be treated so easily. If there is deficiency, it must be corrected. Sometimes, foods must be avoided because of allergy or intolerance. A person, especially a child who has to avoid dairy products, probably needs calcium and vitamin D supplements. There is also a very large group of people who eat a poor diet by choice. They need to start a healthy diet rather than just taking supplements.
In some diseases there is extra demand for nutrients. People with abnormalities of red blood cells that give a high turnover of these cells need folic acid supplements. The high turnover of skin cells in psoriasis may demand iron supplements and blood loss from menstrual problems or even some medication may require iron supplements. Alcoholics often have a poor diet and when detoxification occurs, it is usual to give vitamin supplements too.
Vitamins are important for health. There is no doubt about that. However, just because something is good for us, does not mean that even more is even better. Most people with a normal diet do not need any supplements. Taking extra vitamins is at best a waste of time and money if there is a normal diet and no underlying disease. A variety of foods with a variety of colours is a good guide to a balanced diet. A great many people have an inadequate diet by choice. In the television programme “Supersize vs Superskinny”, neither the morbidly obese nor the anorexic seems to have a single item of green on their plates. It is surprising that they do not suffer from scurvy. However, the answer is to eat a sensible diet, not to buy supplements.
Any so-called health food shop will offer a variety of vitamins and minerals for children, for teenagers, for the elderly, for middle aged people, for pregnant women, for athletes in training, for Uncle Tom Cobley and all. They are also available in pharmacies and supermarkets. Some people may tell you that these are a better way of treating disease as drugs are made by the pharmaceutical industry whose only interested is profits. Ask who makes the vitamin and mineral capsules. It is the same much maligned pharmaceutical industry. Are the snake-oil salesmen not interested in profit or do they do it from a sense of altruism? If parents think that their children are deficient in vitamins or minerals they should try feeding them proper food with fruit and vegetables. The worried well just need a sensible diet.
Supplements in Sport
Athletes have an increased need for certain nutrients but as they expend more calories than most and so eat more than most, they should be able to get their nutrients from their food. An American review found that poor manufacturing processes and intentional contamination with many banned substances continue to occur in dietary supplements sold in the United States. Certain sectors, such as weight loss and muscle-building supplements, pose a greater threat because they are more likely to be contaminated. It says that athletes will continue to be at risk for adverse events and failed doping tests due to contaminated dietary supplements until legislation changes how they are regulated.1Prohibited Contaminants in Dietary Supplements
Another survey found similar results. Weight loss and sports supplements listing the stimulant deterenol as an ingredient, contained 9 prohibited stimulants and 8 different mixtures of stimulants, with as many as 4 experimental stimulants per product. These cocktails of stimulants have never been tested in humans and their safety is unknown.2Nine prohibited stimulants found in sports and weight loss supplements
The use of various supplements in elite athletes is not so much common as almost universal. In view of this, the International Olympic Committee have produced a consensus statement which is pragmatic in the face of extensive use of supplements rather than supportive of them.3IOC consensus statement: dietary supplements and the high-performance athlete It does say that nutrition usually makes a small but potentially valuable contribution to successful performance in elite athletes, and dietary supplements can make a minor contribution to this nutrition programme. Even minor improvements can be the difference between a gold medal and no medal in elite sport. The appropriate use of some supplements can benefit the athlete, but others may harm the athlete’s health, performance, and career or reputation if they fail a drug test.
Supplements claiming directly or indirectly to enhance performance are typically the largest group of products marketed to athletes, but only a few (including caffeine, creatine, specific buffering agents and nitrate) have good evidence of benefits. Supplements intended to enhance performance should be properly tested in training or simulated competition before being used in competition. Inadvertently taking banned substances is a major risk of taking some supplements.
The American National Institutes for Health has produced extensive advice called,4Dietary Supplements for Exercise and Athletic Performance but it is for health professionals. They also produce a rather simpler guide for lay people called 5Dietary Supplement Fact Sheet. They include evidence from population studies, and advice about supplements for athletes and for people who are thinking of taking supplements. The American College of Sports Medicine says that vitamin and mineral supplements are not needed if adequate energy to maintain body weight is consumed from a variety of foods. However, athletes who restrict energy intake, use severe weight-loss practices, eliminate one or more food groups from their diet, or consume unbalanced diets with low micronutrient density may require supplements.6Nutrition and athletic performance I think they need a proper diet.
Elite athletes often take supplements. The position of the American College of Sports Medicine on nutrition and athletic performance was clear. Even top athletes should not need supplements.6Nutrition and athletic performance This is the same reference as in the previous paragraph.
Supplements for Health
The needs of those with medical conditions that necessitate the use of supplements do not account for the scale of the industry. It is worth many millions of pounds in the UK alone and billions of pounds worldwide. Most people buy supplements over the counter in the belief that they will improve their health or performance. If you go into any supermarket, pharmacy or so-called health food shop, there are a wide array of supplements for infants, for children, for young adults, for pregnant women, for athletes and for the elderly. They have food supplements for everyone.
Vitamin deficiency has been recognised in past centuries and various conditions have been described, related to various vitamin deficiencies. For example, vitamin C deficiency causes scurvy, Vitamin D deficiency causes rickets in children and osteomalacia in adults, Vitamin B1 or thiamine deficiency causes beri beri. However, this is not the issue here. We are looking instead at people who have a normal diet who choose to take vitamin supplements, giving an intake that is significantly higher than that required to prevent the recognised deficiency diseases. The question is if they do any good, if they do no good or if high doses of vitamins are even harmful.
The vitamin B complex and vitamin C are water soluble whilst the others are fat soluble. To a considerable extent, the water soluble vitamins, if taken in amounts above that which is needed, will be excreted in urine. The fat soluble vitamins are more of a problem and excessive amounts can cause troubles, especially vitamins A and D. Excess of vitamin D can raise levels of calcium with attendant problems. Excess of vitamin A can cause osteoporosis, liver and kidney damage, fatigue, headache, loss of appetite, nausea and vomiting.
The concept that vitamins and other supplements do only good has taken a severe battering. The Iowa Women’s Health Study found that in older women, several commonly used dietary vitamin and mineral supplements may be associated with increased total mortality risk. This association is strongest with supplemental iron, but calcium was associated with decreased risk.7Dietary supplements and mortality rate in older women The benefit of calcium is in contrast to most studies that found an increased risk.
An American study of nearly 8,000 men with prostate cancer found that many of them reported the use of complementary and alternative medicine. Multivitamins, omega-3 fatty acids and vitamin D were often used.8Trends in Complementary and Alternative Medicine Use among Patients with Prostate Cancer The report in Medscape News reported a professor as saying, “Most studies that have looked at multivitamins have shown no effect on lowering cancer risk, and some actually say they increase cancer risk”.9‘Concerning’: Vitamin Use in Men With Prostate Cancer Increasing The article noted that the SELECT trial suggested that selenium and vitamin E may increase the risk of prostate cancer and potentially increase the risk of mortality in prostate cancer.10Selenium on trial
To turn to a positive story, it seems that the blue in blueberries may have blood pressure lowering properties that are comparable with standard medication. However, it does require the equivalent of eating 100 grams of blueberries twice a day for four weeks.11‘Blue’ in Blueberries Tied to BP Lowering that Rivals Medication I would recommend not stopping the regular drugs. Blueberries may also improve thinking and memory skills in older people with memory loss called mild cognitive impairment. There have been several papers but a Systematic Review of the 12Effects of Blueberry on Cognitive Performance as We Age was cautiously optimistic.
Most of the water soluble vitamins, such as vitamin C and the B complex are rapidly excreted in the urine if taken to excess, but they can cause problems as will be discussed later. People who take “megadoses” of vitamin C every day may as well bypass the kidneys and put the tablets straight down the toilet. The fat soluble vitamins A, D, E and K, if taken to excess can cause toxicity and disease as they are not so readily eliminated. The vitamin that is most often claimed to have almost supernatural properties in vitamin C, also called ascorbic acid.
Linus Pauling (1901-1994) was an interesting person.13Linus Pauling biography from the Nobel Organisation He was awarded the Nobel Prize in Chemistry in 1954 and the Nobel Peace Prize in 1963 for his efforts to bring about a nuclear test ban. His interest in chemistry was in molecular bonding but despite a distinguished career he later took to bad science. He proposed that taking 1,000mg a day of vitamin C, compared with the recommended requirement of 40mg a day, can reduce the incidence of colds by 45% for most people. A PubMed search of “vitamin C and cold” finds a vast array of papers on the subject, especially from the 1970s. Most show little or no benefit.14A trial of ascorbic acid in the treatment of the common cold For the sake of simplicity just one paper is cited, chosen as it is in a British journal, the whole text is available free of charge and it cites a good number of other papers on the subject.
There is now overwhelming evidence that vitamin C is of no use for the common cold. However, many medicines to help a cold, such as cough mixtures or drugs to reduce aches and pains and to bring down the temperature are advertised as containing vitamin C. They do not actually claim that vitamin C is of the slightest value in a cold but they do mention it. They hope that somewhere in our minds we shall continue to associate vitamin C with relieving the common cold and this will make us more likely to buy their product. They are not actually telling lies but they are aiming to deceive. Another common claim from containers of vitamins and supplements is “enhances the immune response”. I would have thought that such a claim is worthy of a challenge from the regulators but none comes.
A Cochrane review has confirmed that vitamin C is useless for the common cold.15Vitamin C for preventing and treating the common cold
In 1976 Linus Pauling produced a paper in cooperation with a Scottish doctor called Ewan Cameron. It claimed that a majority of 100 supposedly terminal cancer patients treated with 10,000 mg of vitamin C daily survived three to four times longer than similar patients who did not receive vitamin C supplements.16Supplemental ascorbate in the supportive treatment of cancer However, his methodology was suspect and it was claimed that Dr Cameron’s “terminal” patients who were started on Vitamin C were less advanced than the control group and so the trial was worthless. The Mayo Clinic in New York conducted three double-blind studies involving a total of 367 patients with advanced cancer to test the hypothesis. The treatment group did no better than placebo.17Failure of high-dose vitamin C (ascorbic acid) therapy to benefit patients with advanced cancer
In 1990 Linus Pauling was back in the news again, this time with the claim that vitamin C may be useful in the treatment of AIDS.18Suppression of human immunodeficiency virus replication by ascorbate in chronically and acutely infected cells. The paper showed that high levels of ascorbic acid can reduce the replication of the HIV virus in cells in vitro. That means in glass, not in vivo or in life. Other researchers have confirmed that high levels of vitamin C in vitro may reduce retroviral replication but there is no paper to show that high levels of vitamin C help to cure the disease. Some supplementation may be desirable as AIDS patients are often malnourished but a very high dose of vitamin C reduces the activity of the antiretroviral drugs. Therefore it should be avoided. Highly active antiretroviral therapy (HAART) is very effective but does not cure the disease. No one has even attempted a head-to-head comparing it with vitamin C but that does not prevent the conspiracy theory advocates from promoting it. Linus Pauling’s paper did show impressive results but we live in a body, not in a test tube.
A meta-analysis involving vitamin D supplementation in more than 83,000 individuals in 21 randomized clinical trials found that it had no benefit on heart attacks, stroke or cardiovascular deaths.19Vitamin D Supplementation and Cardiovascular Disease Risks. There have been many studies published on the use of vitamin D to improve health or to prevent disease but time and again the results do not show any benefit from supplementary vitamin D.
A US study of more than 30,000 participants over the age of 20 found that taking dietary supplements of any sort did not have any effect on mortality rates.20Association Among Dietary Supplement Use, Nutrient Intake, and Mortality Among U.S. Adults However, the study also found that taking high-dose calcium supplements appeared to increase the risk of dying from cancer. High-dose vitamin D supplementation prescribed monthly for up to 4 years without calcium may not prevent cancer.21Monthly High-Dose Vitamin D Supplementation and Cancer Risk Another study with more than 25,000 participants found that vitamin D supplements do not prevent cancer or heart disease.22Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease
A review called Effects of Nutritional Supplements and Dietary Interventions on Cardiovascular Outcomes: An Umbrella Review and Evidence Map, looked at a vast amount of evidence and yet came to very mild and unspectacular conclusions.23Effects of nutritional supplements and dietary interventions on cardiovascular outcomes Reduced salt intake, omega-3 LC-PUFA use, and folate supplementation could reduce risk for some cardiovascular outcomes in adults. Combined calcium plus vitamin D might increase risk for stroke.
A study on the 24Effect of Prenatal Supplementation With Vitamin D on Asthma or Recurrent Wheezing in Offspring by Age 3 Years seemed promising but when the children were followed to 6 years old, any benefit disappeared.25Six-Year Follow-up of a Trial of Antenatal Vitamin D for Asthma Reduction.
Vitamin D supplementation is often recommended and used for bone health, especially in postmenopausal women. It is important to distinguish between the effects of supplements in those who may be deficient and high dose supplements in those who are not. By and large, low dose supplements may be beneficial but without previous deficiency this is dubious but high dose supplements can have the opposite effect. In a study of 311 healthy men and women aged 55 to 70-years old, they took very high-dose vitamin D supplements at either 4000 IU/day or the previously identified “upper safe limit” of 10,000 IU/day, for 3 years. Those on the high dose had a significantly greater loss of total bone mineral density (BMD) at the radius and tibia than women who took 400 IU/day. However, this effect was not seen in men.26Adverse effects of high-dose vitamin D supplementation on volumetric bone density are greater in females than males A paper by mostly the same authors, a year earlier, showed that there is a dose-related loss of bone in those on vitamin D supplements and this is far more marked in women than in men.27Effect of High-Dose Vitamin D Supplementation on Volumetric Bone Density and Bone Strength: A Randomized Clinical Trial.
The table shows Bone Mineral Density loss after 3 years of vitamin D supplements:
|Bone Loss||Vitamin D supplement, 400IU/day||Vitamin D supplement, 4,000IU/day||Vitamin D supplement, 10,000IU/day|
This shows that bone mineral density is lost with vitamin D supplements, that the higher the dose, the more marked the effect and it is more marked in women than in men. Once again we must conclude that because a little of something may be good, it does not mean that a large amount is even better. Indeed, it may make things worse rather than better. Keep all things in moderation. The study looked at people with normal bone mineral density. For those with osteoporosis, vitamin D supplementation is still recommended. However, I would recommend a moderate rather than a high dose.
Vitamin A deficiency is well recognised and is a possible cause of blindness. In a western population with a normal diet it is rare. In countries with a low level of vitamin A in their food, infection can precipitate deficiency as stores of vitamin A are exhausted. There is no doubt that in populations with low levels of vitamin A, they need more. Here I want to address the question of vitamin A supplements in a basically healthy, western population. Much has been claimed about reducing coronary heart disease and cancer, but a very large review has thrown this into question.
A paper called 28Dietary Supplements and Risk of Cause-Specific Death, Cardiovascular Disease, and Cancer: A Systematic Review and Meta-Analysis of Primary Prevention Trials found unconvincing results. Despite having 49 trials involving more than 280,000 participants, they were unable to support the use of vitamin A supplements for the reduction of either coronary heart disease or cancer. A Cochrane review called 29 Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases also found no evidence to support antioxidant supplements for primary or secondary prevention. Beta‐carotene and vitamin E seem to increase mortality, and so may higher doses of vitamin A. They suggested that antioxidant supplements need to be considered as medicinal products and should undergo sufficient evaluation before marketing.
For those who regularly take vitamin supplements, very high levels can be harmful. Beta-carotene, which is converted to vitamin A by the body, has been found to increase the risk of lung cancer in heavy smokers and in people who have been heavily exposed to asbestos. It may also lead to osteoporosis. High levels of niacin (vitamin B3) can cause skin flushes in some people. Too much vitamin B6 can lead to loss of feeling in the arms and legs. Levels of vitamin C above 1,000mg a day can cause abdominal pain and diarrhoea. Safe upper limits of many vitamins and minerals have been set by the Food Standards Agency and can be found on their website.30Safe Upper Levels for Vitamins and Minerals Adverse effects from very high levels of the fat soluble vitamins A,D,E and K have been described for all of them.
At best, vitamin A supplements seem to be useless. At worst, they may increase the risk of cancer.
Despite the absence of evidence, selenium is often recommended to prevent cancer and heart disease.
Multiple supplements often contain minerals as well as vitamins and the most common mineral to be included is selenium. Selenium deficiency due to soil deficiency can occur in some part of China, Tibet and Siberia. Outside these areas clinical deficiency of selenium is rare. It causes a cardiomyopathy and a type of osteoarthritis. Cardiomyopathy is a disease of the heart muscle rather than the usual disease of the coronary arteries. The incidence of coronary artery disease, hypertension and cancer are similar to those in countries with far higher intake of selenium. Selenium deficiency may increase the risk of male infertility and cretinism which is a congenital underactive thyroid gland. Meats, eggs, dairy products and bread are the main sources of selenium. Kidneys, liver, seafood and the legumes are particularly rich. Selenium supplementation may be of value in those who are deficient, but otherwise it confers no benefit.31Selenium and human health
A Cochrane review found no evidence that selenium supplements prevent cancer.32Selenium to prevent cancer The evidence with regard to asthma is far too scanty to support any claim. There is no reduction of coronary heart disease risk with selenium supplements and the Cochrane review suggests that they may even increase the risk of type 2 diabetes.33Selenium supplements for the prevention of cardiovascular disease
If you want to find evidence about selenium in other conditions, go to the Cochrane website at http://www.cochrane.org/ and type in “selenium for..” whatever you choose.
Despite the absence of evidence, selenium is often recommended to prevent cancer and heart disease, but what the protagonists fail to mention is that selenium has a very low ratio of deficiency to toxic levels. Toxicity produces an odour of garlic in the breath, fatigue, nausea, diarrhoea, lines on the nails, hair loss and damage to peripheral nerves. Chelating agents are unhelpful but stopping the source of excessive intake usually leads to recovery in a few weeks. Selenium tables are often 200 micrograms (µg). The maximum safe dose is estimated at 400µg and this includes dietary intake whilst toxicity starts to show at 750 to 800µg daily.
Zinc is another trace element that is very important for the healthy function of the body, but that does not mean that taking more makes us healthier. A Cochrane Library search for zinc supplements brought up many results. I have selected just two. One shows that zinc supplements do not reduce the risk of getting type 2 diabetes. 34 Zinc supplementation for the prevention of type 2 diabetes mellitus The other examined zinc supplements in pregnancy. Looking around the world, they found that in impoverished communities, zinc supplements may reduce the risk of small and premature babies and infant death. 35 Zinc supplementation for improving pregnancy and infant outcome. However, this finding was confined to very poor communities.
A search of NHS conditions found that men need about 9.5mg of zinc a day and women need around 7mg daily. They state that this is easily acquired from diet. They warn against taking more than 25mg daily as it can cause problems, including poor absorption of copper and weak bones.
A systematic review and meta-analysis of randomized controlled trials for zinc for the common cold found that oral zinc formulations may shorten the duration of symptoms of the common cold. However, large high-quality trials are needed before definitive recommendations for clinical practice can be made. Adverse effects were common and should be the point of future study, because a good safety and tolerance profile is essential when treating this generally mild illness. 34 Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials A similar result came from a Cochrane review.36 Zinc for the common cold It seems that any benefit from zinc for the common cold is exceeded by the problems it causes.
With regard to wound healing, as with so many supplements, it seems that the substance is necessary, but unless there is deficiency, there is nothing to be gained by taking more. 37 Zinc and Wound Healing I had expected a rather more positive result for wound healing. Again, a normal diet should suffice and again, beware of taking too much and inducing toxicity.
The addition of vitamins and minerals to drinks has increased considerably in recent years. Although they are seen by many as a healthy option, they are not metabolically inert but can result in greater insulin secretion and changes in gut hormone secretion. These effects are short-lived but may have long-term consequences.38Metabolic consequences of discretionary fortified beverage consumption containing excessive vitamin B levels in adolescents
Nowadays, many teenagers and young adults seem incapable of walking down the road without a bottle or can of something in their hands. The issue of hydration has been addressed in an earlier chapter but so-called energy drinks are a major problem. Excessive use of stimulants, especially caffeine, may affect the heart and brain and cause poor sleep.39Energy drinks and their adverse health effects Use of these strong stimulants may predispose to drug or alcohol abuse.40Caffeinated energy drink consumption and predictors of use among secondary school students There are many papers expressing concern about energy drinks and we should not forget that they include sugar too. From the evidence above, it seems that if these young people find that they need something to counteract lethargy and depression, they should stop the sugar and caffeine drinks, get a good night’s sleep which may involve not taking caffeine after 6pm, and eat a healthy diet of proper food rather than fast food junk and snacks.
Boosting the Immune System
The most common reason for buying nutritional supplements is to improve the body’s immune system. It is illegal to make claims for benefit in a specific disease unless a product is registered as a medicine. Therefore, non-specific claims are made. “Boosts the immune system” and “enhances natural immunity” are the sort of meaningless phrases that are used. Sometimes they claim that the product is essential to the normal function of the immune system. The last claim may be true and if this substance is deficient, the immune system will be deficient too. However, if there is not a deficiency, there is no evidence that taking more of that substance will make the immune system function any better.
An excellent article on the BBC website was called 41How important is diet for a healthy immune system? They acknowledge that a healthy, balanced diet is important for supporting the immune system and poor nutrition can compromise it. They quoted Sarah Stanner, Science Director at the British Nutrition Foundation. She said that there is “no individual nutrient, food or supplement that will boost immunity, or stop us getting highly infectious viruses like Covid-19”. She advised eating a wide range of fruit and vegetables to ensure getting all the nutrients the immune system needs. She added, “Each micronutrient plays a different role in the immune system – don’t make a hero of just one”.
An article in The Times quoted a professor of immunology and infectious diseases at Imperial College London who said, “The simple message is that unless you are undernourished or have a specific condition that weakens your immune system, it is very unlikely that a dietary supplement will provide any significant benefit to the immune response to infection.” He added that a normal healthy diet contains everything we need to keep our immune systems running optimally and adding vitamins or other substances usually makes no difference.
The use of vitamin C to boost the immune system is not supported by the evidence. However, vitamin D may play a crucial role in regulating how T cells operate. T-cells, or thymus dependent lymphocytes, are an important part of the immune system.42 1,25-Dihydroxyvitamin D3 Restrains CD4+ T Cell Priming Ability of CD11c+ Dendritic Cells by Upregulating Expression of CD31 Although I have given the reference, I would recommend it only if you are well versed in immunology and biochemistry. Otherwise, it will simply mystify you.
Even if vitamin A is the exception, and this may only be beneficial in deficiency, the basic message remains the same. Despite repeated warnings from scientists that “immune-boosting” formulations do nothing for the vast majority of those who take them, sales remain buoyant. has not dampened sales. In early 2020, anxiety about coronavirus may have boosted sales and profits, but it has provided no extra protection.
Vitamin and mineral supplements are an enormous market, estimated to be £12 billion a year worldwide. For most people, they should be totally unnecessary if they eat a balanced and varied diet. Growing children have a high demand, but this should be met by a proper diet containing very little processed, fast and take-away food. In pregnancy, most women would suffice without supplements, but iron and folic acid are given to all, as prevention is more satisfactory than treatment of deficiency. Some diseases may limit diet or lead to poor absorption whilst others put an increased demand on nutrients. These do require supplements. For the majority of the population, we need a good and varied diet with plenty of fresh fruit and vegetables and try to have as many colours as possible to cover the range of trace minerals. Even vegetarians or those who do not eat red meat, can get enough iron from the correct amount of green vegetables.
Vitamin C is totally useless in preventing or treating the common cold, but the myth remains. For those who regularly take vitamin supplements, very high levels can be harmful. Beta-carotene, which is converted to vitamin A by the body, has been found to increase the risk of lung cancer in heavy smokers and in people who have been heavily exposed to asbestos. It may also lead to osteoporosis. High levels of niacin (vitamin B3) can cause skin flushes in some people. Too much vitamin B6 can lead to loss of feeling in the arms and legs. Levels of vitamin C above 1,000mg a day can cause abdominal pain and diarrhoea. Safe upper limits of many vitamins and minerals have been set by the Food Standards Agency and can be found on their website.43Safe Upper Levels for Vitamins and Minerals Adverse effects from very high levels of the fat-soluble vitamins A, D, E and K have been described for all of them.
If evidence abounds that supplements are of no value or may even be harmful, why does this multibillion pounds industry continue to grow? An article was called 44 Supplements and CVD: Why Negative Data Don’t Dampen Sales. Only 25% of respondents said they would cease using a supplement if public health authorities stated that it was ineffective. A survey of 770 Italian students surprisingly found that very few (2.9%) cited dietary deficiencies as the main reason for taking supplements. The most popular reason given (41.7% of respondents) was to enhance sport performance, and many did so on the advice of their coach.
In a very similar question, we may ask why belief in fake news stories persists even after it has been thoroughly debunked. It is very easy to get people to believe what they want to believe, no matter how tenuous the evidence and very difficult to get people to believe what they do not want to believe, no matter how cogent the evidence.
As Paracelsus observed in the 16th century, The difference between a medicine and a poison is the dose. Even vitamins can be toxic in excess.
- The truth about sports drinks. BMJ.
Free article about sports drinks from the BMJ
- IOC consensus statement: dietary supplements and the high-performance athlete.
The International Olympic Committee statement is pragmatic in the face of extensive use of supplements by athletes of all grades.
- Sex and drugs and sport and cheating by Paul Anthony. JMD Media 2014 available as hard copy or for Kindle
Takes the lid off cheating in sport but includes a whole chapter on sports products and their promotion.
- Both Sense About Science and the American Quackwatch will tell the truth about false claims and stupidity.
Always instructive. Often quite amusing
- Matthews NM Prohibited Contaminants in Dietary Supplements. Sports Health. 2018 Jan/Feb;10(1):19-30 [full text]
- Cohen PA, Travis JC, Vanhee C, Ohana D, Venhuis BJ. Nine prohibited stimulants found in sports and weight loss supplements: deterenol, phenpromethamine (Vonedrine), oxilofrine, octodrine, beta-methylphenylethylamine (BMPEA), 1,3-dimethylamylamine (1,3-DMAA), 1,4-dimethylamylamine (1,4-DMAA), 1,3-dimethylbutylamine (1,3-DMBA) and higenamine. Clin Toxicol (Phila). 2021 Mar 23;1-7 [full text]
- Maughan RJ, Burke LM, Dvorak J, Larson-Meyer DE, Peeling P, Phillips SM et al. IOC consensus statement: dietary supplements and the high-performance athlete. Br J Sports Med. 2018 Apr;52(7):439-455. [full text]
- Dietary Supplements for Exercise and Athletic Performance. Fact Sheet for Health Professionals. National Institutes of Health
- Dietary Supplement Fact Sheet. National Institutes of Health
- American Dietetic Association; Dietitians of Canada; American College of Sports Medicine, Rodriguez NR, Di Marco NM, Langley S. American College of Sports Medicine position stand. Nutrition and athletic performance. Med Sci Sports Exerc. 2009 Mar;41(3):709-31
- Mursu J, Robien K, Harnack LJ, Park K, Jacobs DR Jr. Dietary supplements and mortality rate in older women: The Iowa Women’s Health Study. Arch Intern Med. 2011;171:1625-1633. [full text]
- Zuniga KB, Zhao S, Kenfield SA, Cedars B, Cowan JE, Van Blarigan EL, et al. Trends in Complementary and Alternative Medicine Use among Patients with Prostate Cancer. J Urol. 2019 May 15. [full text]
- Veronica Hackethal. Medscape 19 September 2019. ‘Concerning’: Vitamin Use in Men With Prostate Cancer Increasing
- Sharma AK, Amin S. Post SELECT: selenium on trial. Future Med Chem. 2013 Feb;5(2):163-74
- Damian McNamarra. ‘Blue’ in Blueberries Tied to BP Lowering that Rivals Medication. Medscape News 1 March 2019
- Hein S, Whyte AR, Wood E, Rodriguez-Mateos A, Williams CM. Systematic Review of the Effects of Blueberry on Cognitive Performance as We Age. J Gerontol A Biol Sci Med Sci. 2019 Jun 18;74(7):984-995
- Linus Pauling biography from the Nobel Organisation.
- D A Tyrrell, J W Craig, T W Meada, and T White. A trial of ascorbic acid in the treatment of the common cold. Br J Prev Soc Med. 1977 September; 31(3): 189–191.
- Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane 2013.
- Cameron E, Pauling L. Supplemental ascorbate in the supportive treatment of cancer: Prolongation of survival times in terminal human cancer. Proc Natl Acad Sci U S A. 1976 Oct;73(10):3685-9. [full text]
- Creagan ET, Moertel CG, O’Fallon JR, Schutt AJ, O’Connell MJ, Rubin J, Frytak S. Failure of high-dose vitamin C (ascorbic acid) therapy to benefit patients with advanced cancer. A controlled trial. N Engl J Med. 1979 Sep 27;301(13):687-90.
- Harakeh S, Jariwalla RJ, Pauling L. Suppression of human immunodeficiency virus replication by ascorbate in chronically and acutely infected cells. Proc Natl Acad Sci U S A. 1990 Sep; 87(18): 7245–7249.
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This website is now completed, although I shall continue to do updates. The following list shows the sections or chapters. Just click on the topic in blue to go to that part of the site.