Better Bee Food

Quite a while ago, I remember speaking with Randy Oliver (scientificbeekeeping.com) about some work he was interested in doing to look at pollen substitute bee-feed. He was, at that time, testing some propriety pollen patties and comparing them to natural pollen. Later, he went on to look at the ratios of the essential amino acids in patties. He was also curious about sterols¹, as these are essential nutrients for bees which are found in pollen, but perhaps not ‘pollen patties’ (unless they include real pollen).

In California, where Randy and his sons run over 1,000 colonies, the weather is often hot and dry. This means that for periods of time during the season, the bees cannot access fresh pollen. From the bees’ perspective, it is like winter. No pollen means no brood rearing, which may or may not be good for the beekeeper. Regardless of the temperature – frequently over 30℃ in California – the bees treat a long-term pollen dearth the same way. They stop most brood production and hunker down.

For those that rely on almond pollination in February, as well as those who want to prevent colonies from dwindling away during very long spells of drought, giving the bees an artificial supplementary feed has become accepted practice. It is very common in other forms of farming to have man-made food available to farmers which is nutritionally complete. Such as thing is not yet available to beekeepers. Luckily for us in the UK, pollen is not usually something that our bees are short of, although dearths can and do happen. My view is that a brood-free period every so often can be beneficial, especially when combined with oxalic acid treatment for varroa mites.

So, although the need for a nutritionally complete artificial food for honey bees is not something that many UK beekeepers need, it would not be terrible to have such a thing, just in case. It might be something used to boost colonies early in the season for fruit pollination, to help with queen rearing at certain times, and to keep bees alive during freak weather events that drag on for ages (droughts or periods of prolonged rain). There have been seasons when it basically rained all through the summer, which means that they go into the winter too small.

In 2020 Randy published the results of a field trial looking into whether a particular sterol, 24-methylenecholesterol, and/or the mineral zinc were ‘limiting factors’ in available pollen substitutes. He knew that there had to be some key ingredient missing because bees fed on patties alone could not sustain a brood nest for months. It can give them a ‘brood boost’ initially, but over time the amount of brood decreases, whereas with pollen this is not the case. Randy replaced rapeseed oil with borage oil in the pollen sub recipe, as borage oil is rich in 24-mCh.

Oliver reviews classic sterol literature (Svoboda et al.²) showing nurse bees can convert other plant sterols and maintain high levels of 24-mCh, sitosterol, and isofucosterol in brood food – even when incoming pollen is low in those sterols. He reported that the data didn’t support his hypothesis: colonies on the sterol- and zinc-supplemented test patty didn’t outperform those on the off-the-shelf patty under his conditions. He concluded that bees “appear able to convert other sterols into 24-mCh,” and canola oil “apparently works well as a lipid and sterol source” despite being low in 24-mCh. The data did not support his hypothesis, and he moved on to look at amino acid ratios.

Recent research³ has shown that Randy Oliver was on the right lines, but he picked the wrong sterol. Here’s what they did:

• The researchers created a pollen-replacing diet for honey bees that tries to supply everything a bee normally gets from natural pollen.
• They set up colonies under controlled conditions (for example with restricted access to natural pollen) and fed them different versions of the diet: some complete, some missing specific sterols (including Isofucosterol).
• They measured how well the colonies performed: brood production, adult bee health (including neuromuscular function), ability to sustain brood cycles over time.
  

And the key findings were:

• Colonies fed the complete diet (that included isofucosterol) were able to maintain brood production over six brood cycles between May and September.
• Colonies fed diets missing isofucosterol showed significantly reduced brood production and neuromuscular dysfunctions in adult bees.
• The implication is that isofucosterol is essential (or at least critically important) for honey bee colony growth and health under those conditions.
• The study also suggests that conventional pollen substitutes (without full sterol profiles) may be inadequate in stressful or high-demand situations (commercial pollination) unless they include the right sterols.
• Omitting 24-methylenecholesterol, the most abundant honeybee sterol, does not significantly affect brood production, and surprisingly, bees remain viable without it.
  

I did a bit of noodling about on the internet, but it was difficult to find the sterol content of typical UK pollens. As far as I could tell, many pollen types contain many of the sterols needed by bees, including 24-mCh and isofucosterol. I also tried to find a food that contains high amounts of isofucosterol, in case anybody was interested in experimenting with ‘home-brew’ pollen subs. The best I could come up with was something called black seed oil (Nigella sativa). That stuff is not cheap, and maybe a more sensible approach would be to collect natural pollen and add it to the patty before use.

Anyway, a company called APIX Biosciences, which was involved in the research, is furiously concocting a nutritionally complete bee food which, when combined with a nectar source (or sugar syrup), could keep bees going through any sort of dearth indefinitely. I am sure that when a commercially available product is one day released, it will be both expensive and popular. However, I don’t think it will be especially useful here in the UK, unless the climate changes radically. Currently, available pollen subs do work in the short term (say 3 – 6 weeks), and real pollen is normally available to our bees. There may also be a relatively cheap oil out there with abundant isofucosterol that will be revealed, once people start asking questions.

The season just ended was one in which flowers seemed to bloom a few weeks early. The brambles, in particular, were over almost a week after they began, in my area. Unusually for me, some ivy nectar has made its way into my colonies this season. That normally flows a bit too late for my bees, but not this time. As climate changes, so does the available forage; farmers plant different strains of a crop, or different crops, and the natural forage changes too. Who knows, perhaps one day we will be grateful for the inclusion of isofucosterol in pollen substitute bee food.

1. A sterol is a type of fat-like molecule found in plants and animals. It’s part of a broader family called lipids (fats, oils, waxes, etc.).
2. J.A. Svoboda, M.J. Thompson, E.W. Herbert, H. Shimanuki, Sterol utilization in honey bees fed a synthetic diet: Analysis of prepupal sterols, Journal of Insect Physiology, Volume 26, Issue 5, 1980, Pages 291-294, ISSN 0022-1910, https://doi.org/10.1016/0022-1910(80)90136-5. (https://www.sciencedirect.com/science/article/pii/0022191080901365)
3. Bogaert T, Reams T, Maillet I, Kulhanek K, Duyck M, Eertmans F, Fauvel AM, Hopkins B, Bogaert J. 2025 A nutritionally complete pollen-replacing diet protects honeybee colonies during stressful commercial pollination – requirement for isofucosterol. Proc. R. Soc. B292: 20243078. https://doi.org/10.1098/rspb.2024.3078