Heart and blood sugar, and why they go together

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

Mergers in science usually happen quietly, over twenty years, and you only notice afterwards. This one has a date on it.

When I trained, the heart people and the metabolic people worked in different rooms. Different journals, different conferences, and no particular hostility between them; they simply had no reason to be in the same building. If you worked on arteries you read the arteries literature, and glucose belonged to somebody else down the corridor. Nobody had decided any of this, which is what made it durable, because it was how the furniture had been arranged long before any of us arrived, and you could go most of a career without once noticing that you were reading half of a subject.

Then in October 2023 the American Heart Association, cardiologists, an organisation with the word heart in its name, published a presidential advisory that named a single field, cardiovascular-kidney-metabolic health, and gave it a five-stage staging system running from stage 0 up to clinical heart disease [1]. A cardiology body had written a staging system for a metabolic condition and put its own name at the top of it. If somebody asks me when the wall came down, that is the document I point at, not because the science changed that month but because that was the month it was admitted in public.

It had been coming for a while. The Emerging Risk Factors Collaboration pooled 102 studies covering 698,782 people and found that diabetes came with about twice the rate of vascular disease, and that the doubling held after allowing for the usual suspects, blood pressure and smoking among them [2]. The laboratory work pointed the same way, since the standard account has the same upstream damage hitting insulin signalling and the lining of the blood vessels together, one piece of cell biology presenting as two different clinical pictures [3]. By 2023 the European Society of Cardiology was publishing a full guideline on heart disease in patients with diabetes [4], which is cardiologists writing about glucose, at length.

Food is where the overlap is easiest to see. A global analysis attributed 11 million deaths a year to diet, of which 10 million were cardiovascular and about 339,000 were type 2 diabetes, and the same short list of salt, whole grains and fruit sits at the top of both columns [5]. The cleanest illustration is a single trial: PREDIMED put 7,447 people in Spain, aged 55 to 80, on a Mediterranean diet with olive oil, the same diet with nuts, or a low-fat control, followed them for about five years, and both Mediterranean arms had roughly 30% fewer major cardiovascular events [6]. The investigators then went back to the people who had not had diabetes at the start and found fewer new cases of it in the olive-oil arm as well [7]. One diet, one group of people, both endpoints, no extra effort, which is the argument of this entire page sitting inside a single study design.

So: one field, one set of foods, and a fairly short list of nutrients that keep turning up on both sides of the literature. Nine of them, in the case of the formula I ended up making. They are not equally interesting, and I would rather tell you which is which than hand you an index.

What I would read first

Coenzyme Q10 is where I would start, partly because your body makes it and puts it exactly where cells produce energy, which is why anyone thought to test it, and partly because of KiSel-10, in which 443 older people in Sweden took selenium and CoQ10 or placebo for four years and cardiovascular deaths came in at about 6% against about 13% [8]. A four-year trial counting deaths is rare enough in this category to deserve a page of its own, and CoQ10, what it is and what the research says goes through the forms, the doses and the ubiquinol argument; selenium, the other half of that Swedish capsule, was given at 200 µg a day [8] and appears in this story mainly as CoQ10's travelling companion. Zinc is the surprise of the nine, with quietly the best-replicated evidence of any of them and nobody marketing it, presumably because it costs nothing and has been in the cupboard since the 1960s. A 2019 analysis of 32 studies found improvements in fasting glucose and in a long-term blood-sugar measure [9], and a 2024 analysis of 19 trials found blood fats moving in the same direction [10]. Separate groups, separate decades, same answer, which is more than most ingredients in this field can say.

Berberine is here for a different reason, being far and away the most-searched thing in this library; its trials have measured blood sugar and blood fats, given across meals [11], and what they found, along with the reason less than 1% of what you swallow ever reaches your blood, is the subject of Berberine, what the research says. Vitamin K2 rests on one good trial and a sensible mechanism, K2's job being to direct calcium: over three years, 244 postmenopausal women taking MK-7 had better arterial stiffness measures than placebo [12], stiffness here meaning how fast a pulse travels down an artery, which is how you tell whether the artery has stiffened.

Then the plain ones, which manage to be plain and load-bearing at the same time. Thiamine contributes to the normal function of the heart [13]; it is vitamin B1, your cells need it to turn food into energy, and heart muscle contracts without a day off from before you are born, so it is among the first tissues where a shortage shows. Chromium contributes to the maintenance of normal blood glucose levels [13], and the interest in it came from a 1997 trial in 180 adults that reported improvements in glucose and insulin measures at supplemental intakes [14]; both nutrients, and the biology under both of those sentences, are in Thiamine, chromium, and the chickens in Java. The B group is where the argument about form lives, folic acid against the methylated form, 5-MTHF, and unusually for a marketing argument it has been tested head to head, with a trial in women finding 5-MTHF raised blood folate more effectively than folic acid did in both of the common genetic variants they looked at [15], which What methylated actually means takes at length. Vitamin D3 is in there for the least exotic reason available, which is that it is the most-studied vitamin of the last twenty years and most of us in Ireland run low on it over the winter.

The food on either side of the merger is where the biggest effects are, on both sides, and the two long pieces on it are Best vitamins, nutrients and supplements for heart health and healthy blood sugar levels and Vitamins and nutrition for healthy blood sugar, what the research says. I have been reading the papers on both sides of that wall for fifteen years, and for most of them it was still standing.

References

1. Ndumele CE, Rangaswami J, Chow SL, et al. Cardiovascular-kidney-metabolic health: a presidential advisory from the American Heart Association. Circulation. 2023;148(20):1606–1635. PMID 37807924.
2. Emerging Risk Factors Collaboration. Diabetes mellitus, fasting blood glucose concentration, and risk of vascular disease: a collaborative meta-analysis of 102 prospective studies. Lancet. 2010;375(9733):2215–2222. PMID 20609967.
3. Kim JA, Montagnani M, Koh KK, Quon MJ. Reciprocal relationships between insulin resistance and endothelial dysfunction: molecular and pathophysiological mechanisms. Circulation. 2006;113(15):1888–1904. PMID 16618833.
4. Marx N, Federici M, Schütt K, et al. 2023 ESC guidelines for the management of cardiovascular disease in patients with diabetes. Eur Heart J. 2023;44(39):4043–4140. doi:10.1093/eurheartj/ehad192.
5. GBD 2017 Diet Collaborators. Health effects of dietary risks in 195 countries, 1990–2017: a systematic analysis for the Global Burden of Disease Study 2017. Lancet. 2019;393(10184):1958–1972. PMID 30954305.
6. Estruch R, Ros E, Salas-Salvadó J, et al. Primary prevention of cardiovascular disease with a Mediterranean diet supplemented with extra-virgin olive oil or nuts. N Engl J Med. 2018;378(25):e34. PMID 29897866.
7. Salas-Salvadó J, Bulló M, Estruch R, et al. Prevention of diabetes with Mediterranean diets: a subgroup analysis of a randomized trial. Ann Intern Med. 2014;160(1):1–10. PMID 24573661.
8. Alehagen U, Johansson P, Björnstedt M, Rosén A, Dahlström U. Cardiovascular mortality and N-terminal-proBNP reduced after combined selenium and coenzyme Q10 supplementation: a 5-year prospective randomized double-blind placebo-controlled trial among elderly Swedish citizens. Int J Cardiol. 2013;167(5):1860–1866. PMID 22626835.
9. 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.
10. Khajeh M, Hassanizadeh S, Pourteymour Fard Tabrizi F, et al. Effect of zinc supplementation on lipid profile: a systematic review and meta-analysis of randomized controlled trials. Biol Trace Elem Res. 2024;202(11):4877–4892. PMID 38224402.
11. 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.
12. Knapen MHJ, Braam LAJLM, Drummen NE, et al. Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women: a double-blind randomised clinical trial. Thromb Haemost. 2015;113(5):1135–1144. PMID 25694037.
13. Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods, other than those referring to the reduction of disease risk and to children's development and health. (Source for the authorised wordings quoted above.)
14. 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.
15. Prinz-Langenohl R, Brämswig S, Tobolski O, et al. [6S]-5-methyltetrahydrofolate increases plasma folate more effectively than folic acid in women with the homozygous or wild-type 677C→T polymorphism of methylenetetrahydrofolate reductase. Br J Pharmacol. 2009;158(8):2014–2021. PMID 19917061.

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