Vitamins and nutrition for healthy blood sugar, what the research says

By Dr Conor Kerley, PhD, cardiovascular and nutrition researcher.

People arrive at this subject asking which vitamin to take. The trial that changed my mind was not about vitamins at all, and it is the reason the rest of the page is worth reading.

In 2018 a trial reported out of ordinary GP surgeries in Scotland and Tyneside, which is not where results like this usually come from: no research hospital, no metabolic ward, just practices with nurses fitting the work around their day. One hundred and forty-nine people with type 2 diabetes were taken off their medication on the first day, stopped rather than tapered, and given a formula diet of around 825 calories a day for three to five months, after which they were walked back onto real food and helped to hold the weight they had lost. At twelve months, 46% of them were in remission, against 4% on ordinary care. The trial is called DiRECT [1].

That word remission is doing a great deal of work, so it is worth saying what the trial meant by it, which was an HbA1c below 6.5% with no medication for at least two months. HbA1c is the average of your blood sugar over the previous three months or so, reported as a percentage, and unlike a single fasting test it cannot be flattered by being careful the night before. On that scale, 6.5% is where the diagnostic line is drawn, and people entering trials like this one commonly start around 8 or 9. Remission in DiRECT was therefore not a marker drifting in a promising direction. It was the whole distance back across the line, and staying the other side of it with the drugs withdrawn.

The 46% is the number that made the trial famous, and it is not the number that convinced me. This is: the result tracked weight almost exactly, so that nobody who gained weight went into remission at all, while among those who lost 15 kg or more it was 86%. Two years in, 36% were still there against 3% in the comparison group [2], down from 46% but a long way from nothing, and durability is the whole question. Most nutrition trials shift a marker by a decimal point and get written up as a breakthrough. This one shifted the thing the marker stands for, in general practice, using food, which is why everything further down this page has to be measured against it rather than read on its own terms. It was not a freak result either: the Diabetes Prevention Program [3] had already split 3,234 adults at high risk into a dummy pill, a common medication or a lifestyle programme, and the lifestyle arm beat the drug by a wide margin.

Half a point, and what half a point is

If you asked me which single component of food has the most data behind it, I would not hesitate. A Lancet review [4] pooled 185 studies and 58 trials, and the people eating the most fibre had 15–30% lower death rates along with less heart disease, stroke and bowel cancer, the benefit still climbing at 25–29 g a day. That is observational work, which has well-known problems, so the trials matter more: viscous fibre, the gel-forming sort, at around 13 g a day, moved HbA1c by roughly half a point [5]. On the scale above, half a point is the largest number in this article that comes out of something you eat, and set beside those 149 people it is also a fraction of the distance they covered. Both are true, and holding them together is the point of the page.

Exercise is unglamorous and enormously well evidenced. A pooled analysis of 47 trials in 8,538 people [6] found that structured training moved that same measure by about two-thirds of a point, with nearly a full point above 150 minutes a week and roughly half as much below it, and the dose-response is unusually clean: more of it, more effect, close to a straight line. That is a bigger number than the fibre one, from something with no ingredients list at all. I am putting it in a nutrition article deliberately, because it outperforms most of what follows, and any honest account has to say so before it starts talking about capsules.

And then the nutrients, which is where you came in

Everything above is the honest order, and I would rather lead with it than bury it. But almost nobody eats that way, most people are not going to, and the question you typed into a search box deserves a straight answer rather than a lecture about porridge. So here are the nutrients, what is behind them, and what I did with them.

Zinc, the quiet winner

Zinc has the best-replicated evidence of anything on this page. A pooled analysis of 32 studies found fasting glucose and a long-term blood-sugar measure both improved [7], and an independent group, working separately from different data, landed in the same place [8]. Separate teams and the same answer is the shape a real finding has. Almost nobody markets it, presumably because it costs next to nothing and has been in the cupboard since the 1960s, which is exactly why it is in the formula, as zinc picolinate.

Chromium, and the only authorised claim on this page

Chromium contributes to the maintenance of normal blood glucose levels [9]. That is the authorised wording, worded exactly, and it is the only sentence of its kind anyone may write about anything on this page.

The trial people start with is Anderson and colleagues, 1997 [10], which gave 180 adults in Beijing a dummy pill or chromium picolinate for four months. The three-month blood-sugar average came in at 8.5% on the dummy pill and lower on chromium. On the scale set out above, that is a meaningful move. The formula uses chromium picolinate, which is the form that trial used. What an authorised claim does and does not mean is worth understanding properly, and it is set out in Thiamine, chromium, and the chickens in Java.

Berberine, the one everybody asks about

Berberine has the largest recent trial literature of anything here, anchored by Yin and colleagues in 2008 [11] and pooled across 46 trials and 4,158 people in 2021 [12]. Those trials gave it across meals, and the with-meals part is not incidental, because it is how the formula gives it too. It is the most-searched thing in this library by a distance, and I go through those papers one at a time in Berberine, what the research says.

Thiamine sits elsewhere again, its claim resting on the heart rather than on glucose: thiamine contributes to the normal function of the heart [9].

Which brings me back to the 149

What that trial demonstrated was not that any one thing is powerful, but that the system handling sugar in the blood moves when it is pushed hard enough, in the right place, for long enough. Everything else on this page is an argument about where to push.

My answer to that argument was to stop expecting people to assemble it themselves. The nutrients above are not obscure and they are not expensive, and yet the ordinary way to get them is five or six bottles on a kitchen counter, each at whatever dose a different brand happened to settle on, which by February has become an admin job that nobody does. So I put the ones that keep turning up in this literature into a single bottle, at the doses the research actually used, two capsules a day with food.

References

1. Lean MEJ, Leslie WS, Barnes AC, et al. Primary care-led weight management for remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial. Lancet. 2018;391(10120):541–551. PMID 29221645.
2. Lean MEJ, Leslie WS, Barnes AC, et al. Durability of a primary care-led weight-management intervention for remission of type 2 diabetes: 2-year results of the DiRECT open-label, cluster-randomised trial. Lancet Diabetes Endocrinol. 2019;7(5):344–355. PMID 30852132.
3. Knowler WC, Barrett-Connor E, Fowler SE, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med. 2002;346(6):393–403. PMID 11832527.
4. Reynolds A, Mann J, Cummings J, Winter N, Mete E, Te Morenga L. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. Lancet. 2019;393(10170):434–445. PMID 30638909.
5. Jovanovski E, Khayyat R, Zurbau A, et al. Should viscous fiber supplements be considered in diabetes control? Results from a systematic review and meta-analysis of randomized controlled trials. Diabetes Care. 2019;42(5):755–766. PMID 30617143.
6. Umpierre D, Ribeiro PAB, Kramer CK, et al. Physical activity advice only or structured exercise training and association with HbA1c levels in type 2 diabetes: a systematic review and meta-analysis. JAMA. 2011;305(17):1790–1799. PMID 21540423.
7. Wang X, Wu W, Zheng W, et al. Zinc supplementation improves glycemic control for diabetes prevention and management: a systematic review and meta-analysis of randomized controlled trials. Am J Clin Nutr. 2019;110(1):76–90. PMID 31161192.
8. Jayawardena R, Ranasinghe P, Galappatthy P, Malkanthi R, Constantine G, Katulanda P. Effects of zinc supplementation on diabetes mellitus: a systematic review and meta-analysis. Diabetol Metab Syndr. 2012;4(1):13. PMID 22515411.
9. Commission Regulation (EU) No 432/2012 of 16 May 2012 establishing a list of permitted health claims made on foods. Official Journal of the European Union. L 136, 25.5.2012:1–40.
10. Anderson RA, Cheng N, Bryden NA, et al. Elevated intakes of supplemental chromium improve glucose and insulin variables in individuals with type 2 diabetes. Diabetes. 1997;46(11):1786–1791. PMID 9356027.
11. Yin J, Xing H, Ye J. Efficacy of berberine in patients with type 2 diabetes mellitus. Metabolism. 2008;57(5):712–717. PMID 18442638.
12. Guo J, Chen H, Zhang X, et al. The effect of berberine on metabolic profiles in type 2 diabetic patients: a systematic review and meta-analysis of randomized controlled trials. Oxid Med Cell Longev. 2021;2021:2074610. PMID 34956436.

Last reviewed: 10 September 2026. This article is educational and is not medical advice.