Rough Guide To Supplements

July 15, 2009 at 3:45 pm (Bad Science, Business, Nutritionism, Supplements) (Evening Primrose Oil, Fish Oil, Food Supplements, Glucosamine, Hormone Balance, Hot Flushes, Mastalgia, minerals, Omega 3, Vitamins)

The vitamins & minerals sector of the food supplements industry was estimated to be worth $827 million in the UK in 2006 (link). The same source states that “The global nutraceuticals industry sales are forecast to touch $187 billion by 2010, owing to increasing sales in the U.S. and the European Union (EU), as also within the emerging markets like China and India.”

The supplements industry was estimated to be worth $19 billion in Europe and $56 billion worldwide by a report from the US Foreign Agricultural Service in 2004 (PDF). So what are people spending these billions of dollars on?

Apart from those pills bundled together as “other supplements”, the top performers in the UK, according to the page linked to in my first paragraph, are as follows: multivitamins, fish oils, single vitamins, glucosamine, evening primrose / starflower oils (omega-6 fatty acids), minerals, garlic, ginkgo, st john’s wort, ginseng.

Multivitamins are presumably taken by people who believe that the food on our supermarket shelves is of poor quality and deficient in nutrients*. Fish oils are presumably purchased by those who either (a) believe that these pills will help their child’s school performance, having perhaps been influenced by the positive press coverage of an initiative a trial an initiative (more here) that seems to have been little more than a publicity stunt or (b) have heard that fish oils ‘thin the blood’ – I’m not sure, though, why anybody in either of these groups (no matter what they have heard about the properties of fish oils) would believe that fish oil pills were a better bet than oily fish**.

Single vitamins include folic acid, which is recommended for women hoping to conceive, but also include the antioxidant pills that were the subject of this Cochrane review which found that “Vitamin A, beta-carotene, and vitamin E may increase mortality” and recommended that “Antioxidant supplements need to be considered medicinal products and should undergo sufficient evaluation before marketing.” It had been proposed that single vitamins that are antioxidants may help prevent cancer and cardiovascular disease. One of the trials included in the Cochrane review of antioxidant supplements found that in the group that were treated with beta carotene and vitamin A supplements, “the relative risk of death from any cause was 1.17 (95 percent confidence interval, 1.03 to 1.33); of death from lung cancer, 1.46 (95 percent confidence interval, 1.07 to 2.00); and of death from cardiovascular disease, 1.26 (95 percent confidence interval, 0.99 to 1.61)”. The authors concluded that “the combination of beta carotene and vitamin A had no benefit and may have had an adverse effect on the incidence of lung cancer and on the risk of death from lung cancer, cardiovascular disease, and any cause in smokers and workers exposed to asbestos”.

Glucosamine pills were the subject of another Cochrane review which found that “Analysis restricted to studies with adequate allocation concealment failed to show any benefit of glucosamine for pain (based on a pooled measure of different pain scales) and WOMAC pain, function and stiffness subscales” – the full text [PDF] states that “If only the best designed studies are included, the benefit in pain and WOMAC function is no longer present”. Some glucosamine supplements also contain chondroitin. This is a waste of money, in my opinion. David Colquhoun of Improbable Science has pointed out that Chondroitin doesn’t work. [“A new meta-analysis of clinical trials now shows that chondroitin on the symptoms of osteoarthritis is “minimal or nonexistent”.”]

The next supplement listed as a top performer is the evening primrose oil / starflower group of omega-6 fatty acid supplements. An interesting bit of history here: licenses were withdrawn for three products containing evening primrose oil because, in the words of this BMJ obituary, “the stuff didn’t work”. The obit pithily refers to evening primrose oil as a product which “may go down in history as the remedy for which there is no disease”. EPO is sometimes claimed to be beneficial for “maintenance of hormonal balance” or for mastalgia (thinknatural.com claims that EPO is “useful for women with cyclical breast pain [and] premenstrual syndrome”). Regarding mastalgia, a 2006 paper concluded that “There is presently insufficient evidence to recommend the use of evening primrose oil (EPO) in the treatment of breast pain”, while a meta analysis published in 2007 stated that: “EPO did not offer any advantage over placebo in pain relief”. A search of Pubmed for evening primrose oil and hormone balance returned no results. Searching for evening primrose and hormones turned up several papers relating to various conditions. I looked at a couple of reviews. The first was published in Alternative Medicine Review and the author stated that “used to treat premenstrual syndrome (PMS) and menopausal symptoms” and cited a single trial that looked at hot flashes in 56 women. The author (Hazel Philp) stated that “There was a statistically significant reduction in night time flushing in the treatment group compared to the control group, but not of daytime hot flashes.” The author also claimed that everything from acunpuncture to vitamin C with hesperidin had been shown to be effective in treating hot flashes. [Full text as PDF.] The next review I looked at was published in the Annals of Internal Medicine. It includes the single trial cited by Hazel Philp in Alternative Medicine Review, but adds the information that only 35 of the 56 women completed the trial. This review also states that “no differences were found between a group of patients using evening primrose oil and a placebo group” and described the differences between the control and treatment groups as follows: “Frequency of daytime hot flashes decreased in placebo but not evening primrose oil group; no difference between groups in frequency of night time hot flashes (decreased in both groups)”. The full text of this review is available here: pdf. Because the two reviews differed in their reporting of this single study, I checked the abstract on Pubmed: the conclusion was that “Gamolenic acid offers no benefit over placebo in treating menopausal flushing.” Their results section states that “The mean (SE) improvement in the number of flushes in the last available treatment cycle compared with the control cycle was 1.9 (0.4) (P < 0.001) for daytime flushes and 0.7 (0.3) (P < 0.05) for night time flushes in women taking placebo; the corresponding values for women taking gamolenic acid were 0.5 (0.4) and 0.5 (0.3).” That looks to me as if the women in the placebo group had a greater improvement in both daytime and night time flushes (my italics). The authors then state that “In women taking gamolenic acid the only significant improvement was a reduction in the maximum number of night time flushes (1.4 (0.6); P < 0.05).” Abstract is here: PMID: 8136666. So, there was not “a statistically significant reduction in night time flushing in the treatment group” as was reported by Hazel Philp – there was a reduction in the maximum number of night time flushes. Not only is EPO a poor remedy for hot flushes, but the only positive report of it being useful for this is a poor “review” in a poor “journal” that is able to provide a positive view of EPO only because it misrepresents the findings of the single paper it cites.

Summary

Most of the money spent on supplements is probably not money well spent. Some of the supplements being purchased may even do more harm than good. Buying chondroitin to help with the symptoms of osteoarthritis, for example, is a waste of money (as is buying evening primrose oil for hot flushes or breast pain) – while smokers would be well-advised to avoid antioxidant pills such as the beta carotene and vitamin A supplements used in the 1996 trial I linked to earlier. Buyer beware…

*Is Modern Food of Poor Quality or Deficient in Nutrients?

Well, first I should point out that even if people were failing to meet the RDA for certain vitamins and minerals it would not be a disaster – “The term [RDA] recognises that particular groups of individuals (E.g. infants and those over 60) have different needs and for each group, the intention was to be sufficiently generous to encompass the presumed (but unmeasured) variability in requirement among people. This meant that the value was usually set deliberately high” [Derek Shrimpton]. Then there’s the data from the National Diet and Nutrition Survey of Young People aged 4 to 18 years, which refers to RNIs: “After excluding low energy reporters, mean dietary intakes of most nutrients exceeded the reference nutrient intake, except for zinc.” [doi: 10.1017/S0007114508981484]. Here’s how this was reported on Eurekalert: “the National Diet and Nutrition Survey found that the average child consumed levels of vitamins and most minerals that met recommendations, and in many cases, comfortably exceeded them. These conclusions were based on records from 7-day weighed food diaries and were confirmed by biochemical measurements of blood samples”. Then there’s the USDA Nutrient Database. I looked at vitamin C and found that one medium kiwi fruit (76g) or one cup of broccoli (88g) provided more than the RDA for vitamin C, while a single red pepper (119g) or a cup of green peppers (149g) would provide double the RDA for this vitamin (pdf). I also looked at a fat-soluble vitamin (vitamin A) and found that one cup of raw carrots (110g) provides over 18,000iu of vitamin A – the RDA is equivalent to 2,667iu, which is only slightly more vitamin A than is contained in 19.6g of chicken liver (2,612iu). [PDF.] How about minerals? I looked at the calcium [PDF] content of several foods – 3oz of sardine (85g) contains 325mg of calcium, I found an 8oz carton of yoghurt (227g) that contained 452mg of calcium, ricotta cheese contains 500-670mg of calcium per 246g (depending on whether it’s made from whole or skimmed milk) and some fortified cereals contain 1,000mg of this mineral. The RDA is 800mg. I don’t see anything in the USDA database to suggest that the food on American supermarket shelves is of poor quality or deficient in nutrients. I don’t imagine that UK supermarkets sell food that is inferior in quality or more depleted in vitamins and minerals compared to their US counterparts (although the lack of a UK equivalent of the USDA service would hamper my efforts to check this).

**Fish Oil Pills and Oily Fish

Buying oily fish can be more economical than purchasing fish oil pills and has the added benefit of providing a tasty meal with a decent amount of protein – and sardines, for example, will also provide vitamin D and calcium (if you eat the bones). Asda’s sardines cost 45p for 100g, while Sainsbury’s does 350g of sardines for £1.89 (54p per 100g of sardines). I believe that Tesco were offering sardines in tomato sauce at a price of 17p per 120g tin in their value range at one point, but cannot find Tesco sardines on mysupermarket.com at the moment. Waitrose have a table showing the levels of Omega 3 in various foods and sardines come out at 2.2g per 100g. If you ate oily fish (salmon, mackerel, sardine etc) at least once or twice per week as per the FSA advice on the minimum amount of fish we should consume (eat at least two portions of fish per week, one portion of which should be oily) then you would be getting roughly 3 grams of omega 3 per week from your single portion of oily fish or 6 grams per week from two portions (a portion of fish is defined by the FSA as 140g). I found a supplier offering fish oil at £7.45 for 180 pills and each pill provided 240mg of omega 3 fatty acids. To get 6 grams of omega 3 fats per week from these supplements (equivalent to two portions of oily fish), you would need to consume 25 capsules per week – at a cost of £1.03. To get 6 grams of omega 3 from two portions of oily fish would cost £1.26 if the oily fish was in the form of sardines purchased from Asda and would have cost 40p if you had taken advantage of the Saver range that was available at Tesco. This is a slightly false comparison though – because while you would buy fish oil pills as well as your normal grocery shopping, purchasing oily fish for a meal would be instead of another purchase that made up part of your normal grocery shopping. It really is more economical to buy your omega 3 fatty acids in the form of fish rather than pills. The £1.03 you would have spent on fish oil pills would not have bought you any protein, calcium, or any of the other nutrients found in oily fish.

Useful Supplements

It is recommended that folic acid be taken by women while they are trying to conceive and they “should continue taking this dose for the first 12 weeks of pregnancy, when the baby’s spine is developing” (the amount recommended is 0.4mg, or 400 microgrammes). Vitamin D supplements were recently provided by a PCT in Bradford in order to prevent rickets – “Those at risk include people who are South Asian, African or African-Caribbean; have low exposure to sunlight (eg women who observe Hijab or spend little time outside); or have a poor diet or a diet restricted to certain food groups.” [Link.] Iron-deficiency anaemia is not that uncommon in premenopausal women – netdoctor.co.uk tells me that it affects 8% of premenopausal women, while an article in the BMJ gives a range of 5-10% (“In the 5-10% of premenopausal women who develop IDA the commonest cause is menorrhagia”) – so iron supplements may be prescribed by a GP. These are examples of supplements that have been recommended, provided or prescribed for good reasons. I can’t think of any other examples of evidence-based supplements off the top of my head, with the exception of iodine (large amounts of which should only be taken under the supervision of a doctor, due to the potential for adverse effects).

Reliable Information

Your GP can arrange tests if vitamin or mineral deficiency is suspected. The NHS website contains useful information (e.g., the article on folic acid for pregnant women I linked to earlier). Registered dietitians are properly trained and are accountable to the Health Professions Council and, as Holford Watch tell us, “RDs are not allowed to make recommendations for diet that are not based on good quality clinical evidence”. The Food Standards Agency has websites that provide decent information on diet – including a section on vitamins and minerals. These links: www.food.gov.uk/ and www.eatwell.gov.uk/ are to the two homepages the FSA maintains. Note that I have not included the websites of food supplement manufacturers or the books written by nutritionists as recommended sources of reliable information on supplements.