And now for a new and occasional feature. From time to time a paper hits my desk (and apparently everyone else’s) that is interesting, novel, applicable, and in some cases, controversial. This feature is where I weigh in on the science, and the implications for us as apiculturists, beekeepers, and those concerned with our continued ability to eat.
This week’s Paper Pick deals with a topic close to my heart, and of utmost (although ubiquitously overlooked) importance – honey bee nutrition.
Mao, W., M.A. Schuler, and M.R. Berenbaum. Honey constituents up-regulate detoxification and immunity genes in the western honey bee Apis mellifera. PNAS. Published online before print April 29, 2013. DOI: 10.1073/pnas.1303884110.
Well this is exciting! A new paper linking High Fructose Corn Syrup (HFCS) to Colony Collapse Disorder (CCD). As such it has been picked up by various outlets (here, here, here, and here, among others) and is currently being discussed by my colleagues via bee-l, twitter, and the good old fashioned rumour mill. Well, it seems to me that someone jumped the gun on this one. Let’s take a closer look at what the science says, what’s being reported, and my own, personal, opinion, shall we?
Always start with the assumptions. Every trial has them, and we need to identify if they’re reasonable. I can identify 5 in this work, all of which seem to be backed up by previous research, and common knowledge.
1. Bees fed pollen are more resistant to both pathogens and pesticides (for example)
2. When insects need to deal with pesticides, one of the primary mechanisms is through a group of enzymes known as Cytochrome P450 monoxygenases (P450’s). Honey bees have relatively few genes related to P450’s compared to other insects (for example)
3. Honey bees are increasingly exposed to pests, pathogens, pesticides, and all around stressfull environments in recent years.
4. Honey bees evolved to eat honey. This probably has some bearing on their health.
5. Beekeepers commonly feed some type of sugar (e.g. sucrose, HFCS, fondant) to their hives to ensure that they don’t starve over winter.
The question these authors seem to be asking is “how does the diet of a honey bee act to improve or weaken its immune system?” More specifically “do the phytochemicals found in honey, pollen, and propolis atc to up-, or down-regulate the genes involved in producing P450’s and other detoxification enzymes.”
It seems that the answer is, in short, yes. Three chemicals – p-coumaric acid (found in pollen), pinocembrin (found in propolis), and pinobaskin-5-methyl ether (also found in propolis) – seem to act to up-regulate the genes that produce a variety of enzymes involved in pesticide detoxification and peptides with antimicrobial activity. Wow. Good news indeed.
The implications of this are interesting. If bees are fed only sugar, and not honey, pollen, and propolis, their immune systems, and ability to detoxify pesticides (among the variety of toxins they encounter on a daily basis) will be compromised. Specifically if beekeepers steal all the honey, and feed sugar (a “honey substitute”) hives may not be able to deal with environmental toxins, pesticides, or the diseases they regularly encounter (the authors suggest that maybe p-coumeric acid could be added to honey substitutes to boost immunity). Also, if researchers test pesticides (e.g. most of the recent work on neonicotinoids) by feeding it in sugar or HFCS instead of nectar they may get misleadingly high toxicity estimates (maybe this in one reason field trials don’t seem to bear out lab results?).
If the science was good (and it was), then the authors will have carefully qualified their results, making suggestions for what future work needs to be done, the range of applicability, and so on (and they did). Thus reporters will have to go to great lengths for a sensational story (and they did). There have been some sensational titles, for example ”Researchers find high-fructose corn syrup may be tied to worldwide collapse of bee colonies.” Every article seems to cite p-coumeric acid, and the practises of harvesting honey (where do you think the honey on the store shelf comes from?) and feeding sugar – in most cases HFCS. Oh, and some of them are linking back to a paper that was published this time last year, and has been widely criticized by some of my colleagues (the “Harvard Study” ). As a general rule, reporting on this has focused on tenuous links with CCD (a connection barely mentioned by the authors, aside from briefly highlighting the plight of honey bees in the first paragraph), and of course, the evil HFCS, rather than what I see as the most important implication of this work.
What Do I Think?
I think science is good. The authors report the results from a couple of different experiments, and have analyzed their data using several techniques, all of which point to the same answer. This is called consilience (a convergence of lines of evidence from independent analyses), and is one of the strongest indications to a scientist that we are, in fact, looking at a real effect. But, I think the inferences and implications made by the authors, and built upon by reporters, go too far. Of particular importance to me is the implication that “widespread apicultural use of honey substitutes, including high-fructose corn syrup, may thus compromise the ability of honey bees to cope with pesticides and pathogens and contribute to colony losses,” and the subtle inference that the practice of feeding sugar is a leading cause in our bees’ inability to handle the mess of endemic and introduced pests and pathogens, and natural and synthetic toxins that bees are exposed to on a daily basis.
The big deal, as I see it, is the authors’ assumption that the nutrients bees rely on to survive and thrive are obtained by eating honey. But wait – the chemicals (we’ll call them nutrients) that the authors demonstrated were responsible or up-regulation of detoxification and immune genes are found in pollen and propolis. Can you see where I’m going with this? The assumption implicit in this work – or at least the assumption behind the inferences made by the authors and reporters – is that the bees are obtaining these nutrients incidentally through the small amount of pollen and propolis that invariably ends up in honey stores. If this is the case than the implication that feeding sugar prevents bees from obtaining these nutrients would be correct. But bees in the hive get these nutrients by eating pollen lining the hive with propolis. The authors know this – they based the dose of p-coumeric acid in one of their experiments on levels found in pollen and bee bread – and yet they discuss these nutrients as if the only source is honey. Now, I’m the first to agree that the substitutes we feed to bees are not as good as the real thing; but I’ve yet to encounter a hive that is surviving only on HFCS (or any other honey substitute) and does not have any exposure to pollen or propolis. The implications of this work are not that p-coumeric acid should be added to sugar syrup. The implication of this work is that bees need pollen as well as a carbohydrate source (e.g. honey, sugar, HFCS). We know this already! In fact most of the beekeepers I know add pollen when they’re feeding pollen substitutes, because it’s healthier and more attractive to the bees. It’s nice to know which of the chemical in pollen and propolis are responsible, but, for the beekeeper, it doesn’t matter; the message that bees need more than just carbohydrates (pollen is also their source of protein, lipids, vitamins, minerals, sterols, etc.) remains the same. In fact, I would go so far as to suggest that focusing on how to add p-coumeric acid to sugar syrup (or HFCS, fondant) will distract beekeepers from good beekeeping practice.
There is an important implication in this paper that has so far been overlooked: all the recent research into neonicotinoid insecticides – where bees are fed the insecticide at varying concentrations (field realistic or not) in sugar, candy, or HFCS – may be completely misleading! Whoa, there’s a lot of it out there, and many of us have been wondering why we’re not seeing clear cut effects in the field when such a variety of significant effects have been observed in the lab. Maybe we’ve found one of the culprits. In the field, the bees get pollen and propolis, and may be better able to detoxify the pesticides (although they also encounter many and varied other toxins, for a good discussion see recent American Bee Journal articles by Randy Oliver e.g. April 2013). I think this deserves a lot more attention than it’s currently getting – don’t you agree?
I love good science. Reading about it, talking about it, and writing about it. This is good science. Why do we feel the need to sensationalize it? I’d be excited anyway, and hopefully so would anyone who enjoys bees and/or food.