This article from The Age is appealing to the eye and tastebuds, but is unfortunately another example of mis-informed reporting. Then again, it’s from the Wellbeing section, which sits alongside Astrology in the online version of the paper.
The article purports to tell us about the possible benefits of a range of berries, and while it shows a reasonable skepticism of the effects of the berries themselves, it is entirely credulous about the effects of antioxidants. In fact, the article takes their efficacy as a given. Here are a couple of ‘juicy’ quotes to illustrate:
“In general, berries are naturally high in antioxidants – compounds that may slow cancer growth.”
“What we know: One of the few naturally blue-hued foods humans eat, blueberries are packed with antioxidant power, which comes from high levels of anthocyanins, a type of flavonoid or plant compound.”
“Raspberries have higher levels of ellagic acid than strawberries; ellagic acid has been shown “to be a powerful antioxidant and toxic to cancer cells.”
“Researchers showed black raspberries, which have antioxidant, anti-cancer and anti-inflammatory properties, can also prevent colorectal tumours in animal studies.”
“Strawberries are also potent antioxidants and have been shown to reduce cardiovascular risk factors in several animal and human studies, such as elevated blood pressure, hyperglycemia and inflammation.”
“Just two tablespoons of powder – sprinkled on cereal, yogurt or smoothies – meets the suggested daily dose of antioxidants.”
You get the idea.
The author of the study, one Arpita Basu is an assistant professor of nutrition at Oklahoma State University, and has impressive list of publications. However, her findings just don’t seem to correlate with those of mainstream biomedical research. In fact, the whole area of nutrition has been slapped down by some, none more so than Ben Goldacre in his excellent book ‘Bad Science’ (briefly reviewed here), in which he devotes an entire chapter to the subject. Ben likens nutrition to alternative therapies, and brands it as pseudo-science, largely because it’s outputs and recommendations are rarely evidence-based. Rather, they are a mish-mash of pop-psychology and urban myths. He quotes one notable British nutritionist as claiming that “Cloudy urine is a sign that your body is damp and acidic”, and, “The spleen is your energy battery”.
Anyway, back to antioxidants. Ben Goldacre also points out at some length what a mirage the whole antioxidant movement is. The key claim made by the nutrition industry, which is now in the zeitgeist, is that you should eat more antioxidants. The claim at least has some superficial plausibility, in that highly reactive free radicals in the body are known to cause damage to cells, and that these can be mopped up by antioxidants. At this point Ben offers his ‘T-shirt slogan’ of “I think you’ll find it’s a bit more complex than that”, and points out that there are at least three problems with the theory:
1. There is no evidence that eating stuff containing antioxidants gets them to where they’re needed
2. Free radicals engage in reactions which are also very useful – for example, your immune system uses them to blast unwanted bacteria, and,
3. Antioxidants in the wrong place can damage the desirable components of cells – for example, the lining of arteries and also DNA itself.
So while the early theory and evidence for the benefits of antioxidants were promising, the accumulated science on the subject now indicates not only a lack of benefit, but the possibility of harm. The Pubmed people have done a review of the epidemiology of ‘the antioxidant hypothesis’, which you can find here. Key extracts are:
Although scientific rationale and observational studies have been convincing, randomised primary and secondary intervention trials have failed to show any consistent benefit from the use of antioxidant supplements on cardiovascular disease or cancer risk, with some trials even suggesting possible harm in certain subgroups. These trials have usually involved the administration of single antioxidant nutrients given at relatively high doses. The results of trials investigating the effect of a balanced combination of antioxidants at levels achievable by diet are awaited.
The suggestion that antioxidant supplements can prevent chronic diseases has not been proved or consistently supported by the findings of published intervention trials. Further evidence regarding the efficacy, safety and appropriate dosage of antioxidants in relation to chronic disease is needed. The most prudent public health advice remains to increase the consumption of plant foods, as such dietary patterns are associated with reduced risk of chronic disease.
Here are some more results from individual studies from here, indicating both positive and negative outcomes:
- The first large randomized trial on antioxidants and cancer risk was the Chinese Cancer Prevention Study, published in 1993. This trial investigated the effect of a combination of beta-carotene, vitamin E and selenium on cancer in healthy Chinese men and women at high risk for gastric cancer. The study showed a combination of beta-carotene, vitamin E, and selenium significantly reduced incidence of both gastric cancer and cancer overall.
- A 1994 cancer prevention study entitled the Alpha-Tocopherol (vitamin E)/ Beta-Carotene Cancer Prevention Study (ATBC) demonstrated that lung cancer rates of Finnish male smokers increased significantly with beta-carotene and were not affected by vitamin E.
- Another 1994 study, the Beta-Carotene and Retinol (vitamin A) Efficacy Trial (CARET), also demonstrated a possible increase in lung cancer associated with antioxidants.
- The 1996 Physicians’ Health Study I (PHS) found no change in cancer rates associated with beta-carotene and aspirin taken by U.S. male physicians.
- The 1999 Women’s Health Study (WHS) tested effects of vitamin E and beta-carotene in the prevention of cancer and cardiovascular disease among women age 45 years or older. Among apparently healthy women, there was no benefit or harm from beta-carotene supplementation. Investigation of the effect of vitamin E is ongoing.
The thing that impacted on me the most while reviewing this subject was a reminder that the body is a very complex set of interlocking processes. Enzymes break down food into molecules, which are absorbed and re-used to construct muscles, nerves, bone, hair, and our basic energy. There are also feedback loops, which function (normally) to keep the supply of the various bits and pieces stable. With this in mind, the notion that we can ingest one thing that will go and magically treat a variety of ailments is fanciful.
A big lesson for us all is that when we are dealing with a complex system, we’d better be sure of the outcome before we tinker with it. And this is where good research comes in, and myths and pop-remedies go out.