New Zealanders increasingly turn to supplements for protection against everything from colds to Covid. But do our laws deny us access to products that may actually help us? Donna Chisholm reports.
Nowhere are New Zealanders’ conflicted attitudes to vitamin supplements better illustrated than in the Dunedin home of Dr Lisa Houghton, a professor of nutrition at the University of Otago, and her accountant husband Brett Dailey.
Ask Houghton whether it's a good idea to take multivitamins and she'll tell you the people who need them least are those who take them most; that we get the critical nutrients we need from our food. Apart from taking iron when she was younger, she doesn't use them. Then she laughs and adds, "But my husband loves them." Dailey, she says, has given each of their three daughters, now in their teens and early twenties, a multivitamin tablet each day since they were preschoolers.
All five have been vegetarians for several years and oldest daughter Erin is trying veganism, but Houghton, who does most of the cooking, ensures they get healthy, balanced meals. But Dailey says even before they moved to a plant-based diet, he offered multivitamins as a kind of dietary insurance policy. "From a young age, they had the chewable tablets and we just kept up with it the whole time. I always felt diet can't be perfect every day, that's for sure." He says Houghton "doesn't tell me not to do it, but sometimes she rolls her eyes at the supermarket when I'm buying them. I'm just trying to fill a gap." He says although healthy meals are always available, the girls "don't always eat everything they should".
Dailey accepts that his attitudes are based more on his heart than his head, but he’s not alone. In New Zealand, research by market analysts IRI shows the vitamin and supplements market is worth $473 million a year – up 65 per cent on 2015 – with multivitamins the largest sector at about $40 million. Research in the US suggests supplement users are typically older, healthier, wealthier and Caucasian – a demographic that’s unlikely to be very different here. “It still stands that the people who take them the most need them the least,” says Houghton.
Categorised as medicines
Sales increased further during Covid. In the six months to August 2020, sales of vitamins in the “cold and flu” category rose 8.9 per cent, when compared with the same period the year before, and sales of cold and flu products suggesting they could boost immunity were up nearly 6 per cent. And that’s with zero evidence that over-the-counter medicines make any difference.
Despite that, and the staggering cumulative cost, we rationalise that if they won’t hurt us, only our pocket, what’s wrong with a top-up just in case we go off the dietary rails from time to time. In December 2018, New Scientist magazine identified three groups for whom some supplements may be useful: women who are pregnant or trying to conceive should consider taking folic acid , which has been estimated to more than halve the risk of neural tube defects such as spina bifida; infants who are exclusively or partially breastfed may benefit from supplemental vitamin D, which is present at very low levels in breast milk; and adults over the age of 50 who may absorb less of certain nutrients, including vitamin D, because they produce less stomach acid.
Vitamin D and calcium supplements can increase bone strength and calcium supplements can reduce the risk of fractures. It’s also common practice for vegans to require supplementation with vitamin B12, which is not found in plants, although nut milks are often fortified.
Houghton says although physiological changes as we age can increase the need for some supplements, "Mother Nature does a lovely job of making sure we don't need as much as we used to of some things, including iron".
But at the University of Canterbury’s School of Psychology, Speech and Hearing, researcher Professor Julia Rucklidge is frustrated our laws mean that even when there is evidence that some supplements – such as a micronutrient combination she uses in her clinical trials – have a therapeutic effect, they can’t be sold in sufficient strength because they would then be categorised as medicines, which would require them to be regulated under the Medicines Act. It’s the reason dietary-supplement manufacturers are deliberately vague when they promote their products and avoid therapeutic claims, mostly resorting to the nebulous suggestion of “supporting” or “promoting” a bodily function such as sleep, joint, brain or digestive health. At present, dietary supplements are regulated as “foods”, so are not tested for efficacy or toxicity.
Rucklidge wants micronutrients for which there is evidence of benefit to be allowed to be sold in therapeutic doses without having to be categorised as medicines, because they have a strong track record of safety. She says they should be regulated under their own act, not one written for pharmaceuticals. "I want people to be able to make informed choices about improving their own mental health through supplements, for which there is a lot of evidence. They don't need to be legislated at the same level of a medicine because the risk is so much smaller. It's much harder to harm yourself with a nutrient than a drug." She says consumers shouldn't simply take very high doses of existing supplements to try to reach a therapeutic dose because the nutrients work synergistically. "You might push one of the nutrients into an area where you start to be concerned about toxicity."
She says an Annals of Internal Medicine article “shows outdated thinking. If you supplement with one nutrient and don’t balance it with others, you will run into problems, as they showed.” But she says this has little relevance to the approach she is taking in her research.
Rucklidge has been studying the effects of high doses of micronutrients on people with a psychological problem such as attention deficit hyperactivity disorder (ADHD), stress and pre-menstrual syndrome, and in small clinical trials has found that those who took them improved their well-being and symptoms more than those taking a placebo or an active treatment.
She uses the same set of micronutrients in all her studies. It contains vitamins A, C, D, E and all the Bs, magnesium, calcium, iron, phosphorus, iodine, zinc, selenium, copper, manganese, chromium, molybdenum, potassium and some amino acids. The nutrients are based on a formula developed in Canada, where she gained her PhD before coming to New Zealand in 2000. They assist in the manufacture of neurotransmitters as well as in other biochemical reactions and perhaps also alter the diversity of the gut microbiome. Most reports about the effects of supplements focus on physical, not mental, health, she says.
Rucklidge believes the evidence for the effects of nutrition on mental health is collectively overwhelming and wants nutrient interventions – diet manipulation and/or extra nutrients – to be mainstream in public mental health services. Of course, good nutrition is different from added nutrients – experts advise we should improve our diet before taking pills to plug the gaps. Supplements don't contain all the nutrients and antioxidants in fruit and vegetables, and the nutrients in food often function in combination with each other. "Manipulate your diet and take out all the ultra-processed food. You're not going to harm yourself by doing that," says Rucklidge.
Science-based approach
Clinical nutritionist Ben Warren, who founded “scientific holistic” health business BePure nine years ago, was three years into a doctorate in mental health and nutrients with Rucklidge when Covid hit, disrupting his research. He’s since abandoned his PhD, but still tries to bring a science-based approach to his business. As well as offering a range of tests including genetics, measures of organic acids, urine metabolites, blood markers and inflammatory levels, BePure sells a range of supplements including multivitamins, fish oil, zinc, probiotics and energy and wellness “packs”. They are pricy: his multivitamins cost $119 for a two-month supply or $69 for one month, and two months of his gut-health product nearly $150.
But Warren says his contain much higher doses of most nutrients than rival products and the price is therefore relatively cheaper. Even then, customers are advised to take five of the multivitamins a day. A therapeutic dose for mental-health benefits, according to Rucklidge’s studies, is much higher still.
Warren says he’s “way down the rabbit hole” of supplementation, and takes 36 pills a day – 18 in the morning and 18 in the afternoon. He swallows two handfuls during the interview, after explaining why: “That’s for the liver, that’s high-dose zinc, that’s curcumin, that’s co-enzyme Q10 … there’s fish oil, a herbal product for the kidneys, more zinc with B6, the BePure multivitamin and a special form of B12, because I have a genetic mutation that means my body poorly uses it.”
To those who say a half-hour jog every day might be better for him, Warren argues he struggles to fit in the time to go for a run or to the gym, even though he has no trouble completing strenuous workouts when he does. He believes it’s very difficult “if not impossible” to get all the nutrients we need from the modern diet.
Rucklidge says one of the biggest problems is that rules around labelling and therapeutic claims mean consumers are simply left in the dark about what would help them and how much to take.
Aggressive selling
Mark Honeychurch, former chairman of NZ Skeptics and secretary of the Society for Science Based Healthcare, says most people just don’t get the nuance of the wording of supplement ads. “I don’t think the average person on the street, when they see the word ‘supports’, knows that it’s about the Advertising Standards Authority considering that this isn’t a therapeutic claim.” He says although the major companies, which sell the supplements commonly available in supermarkets, for example, toe the legislative line, many other sellers of fringe products have no such scruples. “They’re so ubiquitous that it’s something of a whack-a-mole to stop them.”
Equally concerning is the sale of unproven supplements – and, worse, homeopathic products – in pharmacies. "I get that they want to make money and I get it's a cut-throat business and the amount of money they can make from prescriptions is getting less and less. But it appears that they have been using the reputation they have to sell people basically ineffective supplements and sometimes they do it really aggressively. It's rare that you walk into a pharmacy and they don't have walls full of vitamins and supplements. But on top of this, pharmacy staff and pharmacists are quite often actively pushing these things. Having gone in asking when I'm legitimately ill, they'll say, 'You should buy this high-dose vitamin C or think about aged garlic leaf.'"
Despite dietary supplements having a generally strong track record of safety, there have been high-profile exceptions. In 2018, the Director-General of Health issued a public warning about the risk of liver damage from the natural product Arthrem, sold to "support joint health and mobility". The makers have since agreed to stop selling it.
In January 2019, three Healtheries detox teas were withdrawn from sale after a Consumer NZ investigation showed they contained the Medsafe-regulated laxative senna without approval.
The Pharmacy Council’s code of ethics, which until March 2018 required any product sold to have credible evidence of efficacy, now says pharmacy staff should tell consumers if products don’t have scientific evidence that they work. Honeychurch and others believe that’s simply not happening and that even homeopathic products are actively promoted. Professor Clare Wall, who heads the University of Auckland’s master of health sciences in nutrition and dietetics programme, says pharmacists and their staff need to be “upskilled” about the advice they’re offering, because most of their information would come from the supplement companies themselves.
“I’m not saying pharmacists don’t abide by those policies [the council’s code of ethics], but I’m not sure whether they even have that opportunity to discuss that with people who are coming into the pharmacy and buying the supplements. I know for pharmacists there is a tension because it is a business.”
She says her local pharmacy sold powdered broccoli that could be sprinkled on food as a "concentrated antioxidant". "It sounds reasonable, doesn't it? It's probably harmless, but totally unnecessary." So, isn't it simply a case of caveat emptor? "No, it's still misleading because there is no research to say that making broccoli into a powder and concentrating it is going to be better for you, and that's what it implies."
She believes supplement companies target pharmacies because of the apparent legitimacy they provide. The value of dietary supplements sold in pharmacies rose from $105 million in 2015 to $176.8 million in 2019, and pharmacies have around 37 per cent of the total market share.
Pharmacy Council chair Jeff Harrison says there would be important “unintended consequences” if complementary and alternative medicines were removed from pharmacies, because consumers would then entirely self-select, without a pharmacist to either suggest a product for which there was better evidence or advise them to see a doctor or other health professional. “At the same time, I accept there is credence given to products by their being available in pharmacies. This is a dilemma, but I think it illustrates the situation is not quite as binary as people might like to believe.”
Attempts to regulate supplements under the Natural Health and Supplementary Products Bill stalled in 2017 when the proposed legislation was shelved. The Government is now developing the Therapeutic Products Bill to update the Medicines Act. The Health Ministry says natural supplements are "inadvertently captured" by the Therapeutic Products Bill, but they are expected to be excluded by the time it returns to Parliament. It says this will allow work to continue on a separate regulatory regime for supplements. Said a ministry spokesperson: "The Government recognises the need for comprehensive and fit-for-purpose regulation of natural health products and dietary supplements, and is exploring how best to achieve this."
Right nutrients
Brett Dailey says he doesn't notice that the supplements make him feel any better, but he's happy to persevere. Daughter Erin is taking iron and vitamin C rather than multivitamins now that she's eating more vegan food since leaving home. "If you're on a restricted diet, it's your responsibility to make sure you're getting the right nutrients." Youngest sibling Ryan was the first in the family to become a vegetarian. She and sister Kennedy say they're so used to the daily regime that they don't even question it, and they admit their diet can fall short given their taste for sweet snacks and chips.
Houghton, however, says the evidence for vitamin supplements being useful as a nutritional-insurance policy is usually based on theory because it’s practically impossible to do the clinical studies necessary to prove it.
"In the case of supplements, we can't take away a nutrient entirely to create a placebo – people consume nutrients every day in the food they eat." She says the evidence for benefits usually comes when people are deficient in some nutrients, which most New Zealanders aren't. However, the country's last nutrition survey was more than 10 years ago and Houghton says we don't have a clear picture of what we're eating and whether we are at risk of lower intakes of some nutrients.
In past surveys, most Kiwis had low intakes of calcium, selenium and vitamin D, and one in four had inadequate intakes of zinc. "A better understanding of the gaps in the diet of the population would allow better recommendations for the type and dose of supplements to take."
Until then, Dailey – and many others – will keep heading to the supermarket supplement aisle. Houghton and her colleagues, meanwhile, will linger in the fruit and vege section.
The D dilemma
We should be fortifying foods with vitamin D, says an Auckland epidemiologist, and spending more time in the sun.
For more than 40 years, epidemiologist Professor Robert Scragg was tantalised by the possibility that vitamin D might be a public health game-changer. Recognising in the late 1970s that deaths from heart disease occur less commonly in summer than in winter, Scragg hypothesised that increased exposure to ultraviolet light – and therefore increasing levels of vitamin D – might be the cause. A couple of years later, in Auckland, he and his colleagues won research funding for a study of heart attacks that confirmed people with heart disease had lower vitamin D levels than controls. Later, repeated international studies confirmed that people with the lowest vitamin D levels had a greater risk of premature death than those with normal or high levels.
Now, Covid has sparked renewed interest in the vitamin. Groups that are traditionally vitamin-D-deficient, such as older people, residents of nursing homes, and black, Asian and minority ethnic populations have also been disproportionally affected by Covid. Increased time in lockdowns has also triggered fears that deficiencies will be worsened by the lack of sunlight. Last December, the UK Government allowed clinically vulnerable people to receive a free four-month supply of vitamin D supplements, despite the lack of evidence that it helped treat or prevent Covid. Researchers there argued supplementation was generally safe and any likelihood of toxicity would likely be strongly outweighed by the potential for a protective effect.
In a study published in Nature in November, a group of Indian researchers found vitamin D deficiency markedly increased the chance of hospitalised patients having severe disease after Covid infection and the intensity of their inflammatory response was also higher, increasing morbidity and mortality. They recommended supplements for at-risk populations.
For Scragg, however, the potential in other conditions has never been backed up by research results. Daily vitamin D supplements, he found, do not reduce the risk of cancer, heart disease, fractures or falls.
His study, of 5000 people over four years, proved that the higher vitamin D levels found in people who were less likely to get cancer and heart disease were because they were simply healthier, having lower rates of obesity, more physical activity and greater exposure outdoors. The vitamin D was the result of their better health, not the cause of it.
That’s not to say, however, that vitamin D is not vital to our health – far from it. Deficiency causes the bone disorder rickets and has been linked to an increased risk of autoimmune diseases and greater susceptibility to viral infections.
Scragg’s study confirmed that people with low vitamin D levels who took supplements improved their bone-mineral density and arterial and lung function. The US has been fortifying foods such as dairy products, bread and even orange juice with vitamin D for decades – it was introduced primarily because of rickets – and despite the negative findings of his own work, Scragg believes we should be doing the same.
That’s because Ministry of Health nutrition surveys suggest nearly 5% of the population is vitamin D deficient. Deficiency is more common among south Asians and Pacific people whose darker skin means they don’t absorb sunlight as readily, and the elderly who aren’t outside as much. Scragg says between 6.5 and 10% of Māori and Pacific people are thought to be deficient, and about 6.5% of elderly people.
However, Rucklidge says one of her studies found vitamin D deficiency in almost 30% of the sample. Controversially, Scragg advocates for a change in health policy, which is firmly against sun exposure at peak hours in the middle of the day when UVB is at its highest.
“For a given sun exposure, the most amount of vitamin D you make is in the middle of the day not the beginning and the end.” The key, he says, is not to avoid the sun then, but to avoid getting burnt.
C for a cure?
Vitamin C will shorten the life of a cold, but any other effects remain unproven.
Ever since Nobel Prize-winning scientist Linus Pauling declared in 1970 that vitamin C would relegate the common cold to the sodden-tissue-filled dustbin of history, proving – or disproving – the worth of the antioxidant has been an elusive Holy Grail for hundreds of researchers. Pauling urged people to take 3000mg of vitamin C a day, which is about a third as much again as the recommended safe upper limit.
Fifty years on, even the Oregon State University’s Linus Pauling Institute is measured when it refers to the purported benefits of vitamin C. Overall, it says, regular use shortens the life of the cold, but doesn’t reduce the risk of catching one in the normal population. There is insufficient data to link vitamin C status with the risk of developing cancer and there is no proof intravenous vitamin C changes outcomes in cancer patients. And, although higher levels are associated with lower risks of high blood pressure, heart disease and stroke, the evidence hasn’t progressed beyond an association to causation.
In recent years, the vitamin has enjoyed a sales renaissance with the launch here in 2012 of liposomal vitamin C, a product in which the vitamin is encapsulated in a type of lipid that manufacturers say increases the body’s ability to absorb it. But New Zealand’s foremost researcher in vitamin C, Professor Margreet Vissers at the University of Otago’s Christchurch campus, says there’s no evidence it’s better absorbed in that form.
“It’s a water-soluble compound and the body is perfectly adapted to handling it this way. It’s taken up into cells in this form and we don’t actually know that the vitamin C in liposomes is handled by the body in the same way.” The body’s regulatory system limits the amount of vitamin C it transports into cells from the bloodstream. Anything above a certain level (for the boffins, that’s a concentration of 100 micromolar per litre) is surplus to requirements and we simply pee it out. How cells handle liposomal vitamin C is unclear, she says.
Vitamin C sales through grocery and pharmacies alone are worth $28 million annually and rose $3 million in 2019 compared with 2018. Liposomal products, with a year-on-year increase of $2.4 million, are the main contributors to that increase. Vissers recommends that those who need a vitamin C supplement increase their intake initially through diet. If that’s not possible, chewable tablets are “highly effective” at restoring healthy levels.
Vissers and her colleagues, Associate Professors Gabi Dachs and Anitra Carr, have invested decades of research effort into finding out whether, and how, vitamin C might work as part of traditional treatments for cancer and septic shock. Dachs and Vissers have investigated whether giving high doses of vitamin C to bowel cancer patients results in better access of the vitamin into the tumour. A second trial will try to establish what, if anything, it does when it gets there.
“My interest for the past 28 years has been to understand why cancers in certain patients, or certain types of cancers, are so aggressive. Why do they not get killed by normal therapy?” says Dachs. They’re investigating the role of a cell factor HIF (hypoxia inducible factor), which regulates responses to oxygen deprivation. In cancer patients, its production “goes rogue”, she says, and may play a role in the resistance to therapy. Dachs says vitamin C introduced into cancer cells in mice reduces the HIF factor. “Tumours that are high in vitamin C are low in HIF and the other way around. We need to see if we change the vitamin C levels, whether that has an effect on HIF.”
It’s thought about 70-80 enzymes in the body need vitamin C to work. We can’t make our own and without it, we die. Eating the recommended “5+ a day” fresh fruit and vegetables should be ample to provide all our vitamin C needs, but Vissers says only about 20% of us are thought to have “optimal” levels. However, patients with cancer and sepsis often have dangerously low levels and require much more, hence the research into intravenous delivery that can get blood levels higher than anything in oral form. Dachs says about 20% of the cancer patients coming through Christchurch Hospital have “very, very low levels” and some are bordering on scurvy.
Carr’s research into whether vitamin C infusions can help patients in septic shock is winding up this year. Forty patients in intensive care have been recruited, 20 of whom received a placebo and the others intravenous vitamin C. The results are awaiting statistical analysis. About 50% of patients in septic shock – a condition in which critically ill patients’ blood pressure bottoms out and is often resistant to treatment – will die. “We are coming in right at the last step,” she says. “In an ideal world, I would rather patients were given vitamin C earlier.”
Sepsis and septic shock are major complications of severe Covid-19. Carr says studies have shown that people with severe infections have low vitamin C status and giving it intravenously appears to provide some positive outcomes. “Even the World Health Organisation supports its potential use in these patients.”
What they do
Vitamin claims and counterclaims.
Vitamin A
- Main sources: Liver, oily fish, green leafy vegetables, broccoli, carrots, squash, fruits including apricots and mangoes, and dairy products.
- What it’s for: Growth, vision and development.
- Deficiency: Can cause eye inflammation and blindness in low light.
- Evidence: Most people get enough in their diet and deficiency is rare. But premature infants can have low levels in their first year and people with cystic fibrosis are also more likely to be deficient. High intakes can be harmful and high-dose supplementation with beta-carotene, which converts to vitamin A, has been shown to increase the risk of lung cancer in smokers.
B Vitamins
All the B vitamins help the body turn carbohydrates into glucose and to metabolise fat and protein.
B1 (thiamine)
- Action: Aids muscle and nerve function.
- Main sources: Small amounts in most foods but particularly in whole grains, meat, fish, poultry, eggs, milk, seeds, nuts and vegetables.
- Deficiency: Can cause beriberi, weight and appetite loss, confusion, memory loss, muscle weakness and heart problems.
- Evidence: Scientists are studying whether thiamine supplements can improve blood sugar levels and glucose tolerance in people with type 2 diabetes, and whether they can help people with heart failure or Alzheimer’s. Most people will get enough thiamine in their diet.
B2 (riboflavin)
- Action: Keeps skin, eyes and nervous system healthy. It’s the vitamin that turns your pee bright yellow when you take supplements.
- Main sources: In many foods, including yeast, almonds, liver, whole grains, wheat germ, wild rice, mushroom, soybeans, milk, yogurt, eggs, broccoli, brussels sprouts and spinach. Flour and cereal are often fortified with riboflavin.
- Deficiency: May cause itching and burning eyes, sensitivity to light, itching and peeling skin and mouth sores.
- Evidence: It may help prevent cataracts and reduce the frequency of migraines, but more research is needed.
B3 (niacin)
- Action: Maintains the nervous and digestive systems.
- Main sources: Yeast, meat, fish, milk, eggs, green vegetables, and cereal grains.
- Deficiency: Causes pellagra.
- Evidence: Can increase the “good” HDL cholesterol, but usually recommended only for people who can’t take statins. Limited evidence it may help with clogged arteries and heart disease, but excess niacin has been linked with liver damage and stroke.
B5 (pantothenic acid)
- Action: Needed for normal growth and development.
- Main sources: Peas and beans (except green beans), lean meat, poultry, fish, and wholegrain cereals.
- Deficiency: None known.
- Evidence: Claims it can treat nerve damage, breathing problems, itching and poisoning, prevent grey hair, allergies and arthritis or improve mental ability are unproven.
B6 (pyridoxine)
- Action: Aids production of haemoglobin.
- Main sources: Grains, legumes, vegetables (carrots, spinach, peas, and potatoes), milk, cheese, eggs, fish, liver, meat, and flour.
- Deficiency: Can affect the nerves, skin, mucous membranes and circulation. Can occur in people with kidney failure complications, alcoholism and overactive thyroid.
- Evidence: B6 supplements with other B vitamins can lower blood levels of the amino acid homocysteine, which may be a risk factor for heart disease.
B7 (biotin)
- Action: Helps to make hormones.
- Main sources: Meat, fish, eggs, organ meats, seeds and nuts, and some vegetables including sweet potatoes, spinach, broccoli.
- Deficiency: Rare, but may cause skin rash, hair loss or heart problems. More common in people dependent on alcohol, and pregnant and breastfeeding women.
- Evidence: Claims supplements improve hair, skin and nail health or are effective in the treatment of acne or eczema are unproven.
B9 (folate, including folic acid)
- Action: Helps to make red and white blood cells in bone marrow, convert carbs into energy and produce DNA and RNA.
- Main sources: Dark-green leafy vegetables (especially spinach and brussels sprouts), fruit and fruit juices, nuts, beans, seafood, eggs, dairy products, meat (especially liver), poultry and grains.
- Deficiency: Associated with poor diet and alcoholism. Can cause weakness, fatigue, irritability, headache, heart palpitations and shortness of breath. Women with too little folate have increased risk of having babies with neural tube defects, including spina bifida.
- Evidence: Recommended for women before and during pregnancy, and those with coeliac and inflammatory bowel disease, which can reduce their folate absorption. No evidence that folic acid supplements reduce the risk of some types of cancer, but some studies have found it reduces the risk of stroke.
B12
- Action: Critical to DNA synthesis, red blood cell formation.
- Main sources: Fish, shellfish, meat, eggs, dairy products. Plants have no B12 unless they are fortified.
- Deficiency: Causes tiredness, weakness, constipation, loss of appetite and weight loss. Many older people don’t absorb enough B12 from their food, and digestive disorders such as Crohn’s or coeliac disease can also decrease absorption.
- Evidence: Supplements can be a boon for vegans and vegetarians, but they do not reduce the risk of heart disease or improve energy or endurance. Almost all multivitamins contain B12, which can also be administered by injection.
Vitamin E
- Action: Helps prevent clots and maintain immune defences.
- Main sources: Vegetable oils, nuts, seeds, green vegetables.
- Deficiency: Rare in otherwise healthy people, but can lead to muscle weakness and vision problems.
- Evidence: No evidence of benefit in a range of conditions for which it’s been touted as effective, from macular degeneration to heart disease and dementia.
Calcium
- Action: Important for strong bones and teeth.
- Main sources: Dairy products, salmon, sardines, kale, broccoli, chinese cabbage, bread, cereals, pasta.
- Deficiency: Can lead to fractures and osteoporosis.
- Evidence: Calcium and vitamin D work together to build and maintain healthy bones. Many adults, especially post-menopausal women, take both the nutrients in supplements to stave off osteoporosis. Some studies have suggested that calcium supplements may increase heart disease risk, but others do not.
Iron
- Action: A major component of haemoglobin, which transports oxygen in the blood.
- Main sources: Meat, fish, poultry, beans, nuts, dried fruit, iron-fortified cereals.
- Deficiency: Can cause anaemia and tiredness. Conditions such as rheumatoid arthritis and inflammatory bowel disease can interfere with the body’s ability to use its stored iron.
- Evidence: Boosting iron can reduce tiredness, but overload can cause fatigue as well, so seek medical advice. Menstruating, pregnant or breastfeeding women can require more iron.
Magnesium
- Action: Many enzymes need magnesium, including those involved in nerve and muscle function, and in regulating blood glucose and blood pressure.
- Main sources: Nuts, legumes, seeds, whole grains, green leafy vegetables and fortified breakfast cereals.
- Deficiency: Rarely causes illness, but has been linked to loss of appetite, nausea, vomiting, fatigue and weakness.
- Evidence: Conflicting results of studies in stroke and heart disease. Only a very small, if any, impact on lowering blood pressure.
Selenium
- Action: Helps form selenoproteins, vital for DNA production.
- Main sources: Fish, meat, grains, brazil nuts, dairy products.
- Deficiency: Is rare. Though New Zealand soils are low in selenium, Medsafe says there is no indication this causes adverse effects. Too much selenium can cause diarrhoea, nausea, skin rashes and irritability.
- Evidence: Research into whether selenium supplements could lower the risk of heart disease and some cancers has been contradictory or inconclusive. It is also unknown if supplements can help treat or reduce the risk of thyroid disease.
Potassium
- Action: Works with sodium to regulate blood volume and get rid of excess salt and fluids through urine.
- Main sources: Fresh fruit and vegetables, lentils, kidney and soy beans and nuts.
- Deficiency: Can increase blood pressure, deplete calcium in the bones and increase the risk of kidney stones.
- Evidence: Many people have lower than recommended intakes, and people with inflammatory bowel disease, or those who use laxatives or some diuretics, may have trouble getting enough. No evidence supplements are useful for treating high blood pressure or preventing kidney stones, but increasing potassium in the diet and reducing the amount of salt can help. Over-the-counter supplements contain less than 3% of the 3400mg recommended daily intake.
Zinc
- Action: Plays a vital role in cell division and is required for about 100 enzymes to work. Helps metabolism, wound healing and production of DNA.
- Main sources: Beef, pork, shellfish, peanuts and legumes.
- Deficiency: Can cause weakened immune system, hair loss and mental slowness.
- Evidence: Can reduce duration of colds once you’re sick.
Other supplements
Complementary medicine doesn’t just refer to vitamins and minerals, however, but also includes fish oil, herbs and other botanicals. In the US, the most popular natural supplements are:
- Fish oil capsules 7.8% of the population
- Glucosamine and/or chondroitin 2.6%
- Probiotics and prebiotics 1.6%
- Coenzyme Q10 1.3%
- Echinacea 0.9%
- Cranberry pills or capsules 0.8%
- Garlic supplements 0.8%
- Ginseng 0.7%
- Ginkgo biloba 0.7%
Fish oil
- Action: Contains omega-3 fatty acids, building blocks for nerve and brain tissue.
- Main sources: Made naturally by deep-sea algae and found in fish that eat it.
- Deficiency: Populations with lower levels of omega 3 may have higher heart disease rates.
- Evidence: The reputation of omega 3 and fish oil took a major hit in June 2018 when a meta-analysis by the respected Cochrane Collaboration of 79 studies involving 112,000 people concluded the supplements had little or no effect on the risk of heart disease, stroke, or death from any cause. In 2014, research by Auckland’s Liggins Institute that analysed 32 fish oil brands sold in New Zealand found more than half were oxidised, or “off”, by the time consumers bought them. Fish oil sales are worth about $20 million a year here.
Glucosamine
- Action: A building block of cartilage and component of the fluid around joints.
- Main sources: Made naturally in the body.
- Evidence: Small trials suggest it can reduce arthritis pain and inflammation, but meta-analyses found little difference when compared with a placebo. The UK’s National Institute for Health and Care Excellence recommends against using glucosamine for arthritis, because of the lack of strong evidence and the potential risks – it may hinder the body’s ability to process glucose.
Probiotics & prebiotics
- Action: Probiotics: Micro-organisms found in yogurt and other fermented foods that are similar to those that naturally live in our bodies, for example, bacteria. Prebiotics: Non-digestible, typically high-fibre foods that may stimulate the growth or improve the balance of good gut bacteria.
- Evidence: Probiotics have shown promise for preventing antibiotic-associated diarrhoea, preventing sepsis in premature babies, treating infant colic, treating periodontal disease and inducing or maintaining remission in ulcerative colitis. But mostly, scientists don’t know which ones are helpful, which aren’t, and how much to take. Research continues.
Coenzyme Q10
- Action: An antioxidant that cells use for growth and maintenance. Levels decrease with age.
- Main sources: Made naturally in the body.
- Evidence: Not shown to be of value in treating cancer, and the few studies that examined its use in preventing heart disease are also inconclusive. Studies suggest it doesn’t have a meaningful effect on blood pressure and there is only limited evidence it may be effective in preventing migraines. It’s been shown to not be helpful for Parkinson’s symptoms.
Sources: US National Institutes of Health Office of Dietary Supplements, Mayo Clinic, Harvard Health.
This feature was first published in the February 20, 2021 issue of the Listener.