I used to look into health claims of all sorts of things with much greater regularity than I do now (different job, still do a fair bit as part of 'skeptic activism') but I thought I'd keep my hand in and 'rehearse' some arguments for myself, looking at the claims of Beneforte broccoli. It's a variant of regular broccoli that is higher in what is generally thought of as good chemical compound (glucoraphanin) to have in your broccoli.
Normally I don't publish a blog post until it's finished and I've pretty much settled on what side of the evidence I come down on. Exceptions include alternative health modalities I haven't previously researched and where I'm using the blog to store info and ideas and seek input from others. For example, even though it's not unreasonable to assume that iridology is utter bollocks it's a little unfair to be too dogmatic without looking into it. As it happens it is unmitigated bollocks, but it was interesting to learn what you can and can't tell about someone's health from looking at the surface of their eyes. And how you can tell from the literature.
So this post is 'me in the middle of some things about broccoli' and is more about the strategies and shortcuts I use in finding out about stuff, rather than actually what I found out. It's entirely possible that I will disagree with myself. It's quite fun (for me, dunno for you) to publish a post where I've actually not researched it in much depth, this is more of a thinking out loud exercise.
Note that I am not medically trained, not a dietitian and not a specialist in broccoli - therefore my feelings about broccoli should not affect yours :)
My first thought was "what do I actually need to know?" My second was "where do I need to look to find it?"
There are only a few things I can confidently answer without even looking in a book or at any research. Even if I know something pretty well, if a few months or more have passed, then my info may be out of date - or I may have forgotten the details!
If the claims imply that A, whatever A might be (in this case more glucoraphanin), are of some benefit to people in some way B then I'm probably hoping to find a human trial where people got more or better B when they consumed more A.
I suppose what I really want is a study which shows that [taking more Beneforte] leads to [less cancer, less diabetes, less other]. What I can fairly easily find are studies that indicate that [taking more Beneforte] leads to, or might lead to (not all that many studies done?) [presence of glucoraphanin in blood or urine] or [more good metabolites* in the blood or less bad metabolites in the blood]
*metabolites are the products of metabolism. In the case of glucoraphanin it is converted to the 'active' form, called sulforaphane.
This isn't disastrous at all though, and in fact it would be an unreasonable burden to ask for that proof. Most prescribed drugs are intended to stop people dying of X or suffering from Y. Both X and Y often take a long time to show up and it's really expensive to run a trial long enough for complications of conditions to show up so people use what are called 'proxy markers'.
Eg, a drug for diabetes is ultimately intended to keep blood glucose levels low enough so that the damage that excess glucose would do happens much more slowly. Though imperfect it is fairly reasonable to talk about a drug's effectiveness in terms of its ability to lower glucose levels in terms of a particular measure called the HbA1c (rather than its ability to stop people dying) because we're fairly confident that there's some causal link between raised glucose levels and bodily damage. However it doesn't automatically follow that lowering glucose levels (and by how much do you want to lower them?) will solve problems. Context is very important.
(And even this is imperfect as some people are naturally more resistant to this damage and some are more sensitive, but... on average...)
So levels of glucoraphanin metabolites may well be instructive. Dunno. If you were in the Southern Hemisphere and trying to get back to the Northern Hemisphere you might use a compass to tell you in which direction to head, but you'd not extrapolate from that bit of information to say that you were actually IN the Northern Hemisphere. It's just a pointer. Some pointers, or proxy markers, are better indicators of where you might be.
So it's not just about the evidence that one particular food is or isn't good for you but putting this bit of information in context with all the other bits of information.
Also, I wonder if the knob of butter many people might add to a portion of Beneforte negates its healthful effects ;)
OK I'm going to stop now cos I've got a bit bored... and it's time for tea (yes, I will be having broccoli!)
A note on comments
As this is an unfinished thinking out loud sort of post I'm not particularly interested in comments telling me how great or not Beneforte is. This post hasn't looked at that, it's looked at how I would typically go about finding that out.
Further things to look at
New Phytol. 2013 Jun;198(4):1085-95. doi: 10.1111/nph.12232. Epub 2013 Apr 8.
Genetic regulation of glucoraphanin accumulation in Beneforté broccoli.
Nothing to do with any health benefits of the broccoli, as far as I can tell from the abstract, but about how the plant manages its stores of glucoraphanin.
There are no trials listed at ClinicalTrials.gov that mention Beneforte (even with the acute e spelling) but five that mention glucoraphanin. ClinicalTrials.gov is where I generally expect to find evidence from a variety of clinical trials. There's also Controlled-Trials, a similar sort of site.
Here are some that mention the precursor, glucoraphanin and there's a link to more trials below looking at the active ingredient sulforaphane.
1 Completed Broccoli Sprout Intervention in Qidong, P.R. China
Condition: Environmental Carcinogenesis
Interventions: Drug: Broccoli Sprout Extract Beverage; Drug: placebo beverage
Just looking at metabolites, not really a trial of health benefits
2 Completed Cross-Over Broccoli Sprouts Trial
Intervention: Dietary Supplement: broccoli sprouts extract
Measuring metabolites (in urine) in healthy people given a broccoli sprouts extract, not really a trial of health benefits.
3 Not yet recruiting Pilot Study Evaluating Broccoli Sprouts in Advanced Pancreatic Cancer
Condition: Pancreatic Ductal Adenocarcinoma
Interventions: Dietary Supplement: Verum, broccoli sprout grain; Dietary Supplement: placebo
This one hasn't started yet but it will actually be looking to see if the supplements can increase the survival of people with a particular cancer that is being treated with chemotherapy.
4 Completed The Effect of Broccoli Sprouts as a Nutritional Supplement in the Prevention of Cardiovascular Disease
Conditions: Diabetes Mellitus; Hypertension; Hypercholesterolemia; Cardiovascular Disease
Intervention: Behavioral: Daily intake of broccoli sprouts
Although the title sounds promising it's a study of the effect of broccoli on blood vessel function - that's not to diminish the study, mind.
5 Active, not recruiting Diet and Vascular Health Study
Condition: Cardiovascular Disease
Interventions: Dietary Supplement: Diet and Vascular Health; Dietary Supplement: Diet and Vascular Health Study
They'll be measuring things ('markers') in the blood, like cholesterol, to determine if there are changes in these markers after eating this broccoli for a few weeks.
There are also 26 studies that mention the active metabolite of glucoraphanin: sulforaphane (some will be the same as those above)