Best vitamins, nutrients and supplements for heart health and healthy blood sugar levels

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

Somewhere in the machinery of Brussels there is a register of everything ever proved, to a regulator's satisfaction, to do something about cholesterol. It runs to three items, and two of them are porridge.

Looking after your heart and keeping your blood sugar steady are two of the most useful things you can do for the years ahead of you, and when you go looking for a supplement to help you find hundreds of products making similar claims, very few of which explain why they contain what they contain, or whether the doses in them were ever tested on anyone. This page is my attempt to explain. It goes through the food first, because that is where the strongest evidence is, and then through the nine nutrients I put in a bottle, with the trials behind each one and the doses those trials used.

The European Union keeps two lists. On the ordinary one you may say that a nutrient contributes to something, provided the science holds up in a general way, which is a bar most familiar ingredients clear. The other list is the hard one, where you submit a dossier and have to convince a panel of scientists that your substance actually causes the effect you claim, on an outcome that matters to a person rather than to a laboratory. Applications go in steadily. Most of them come back out with a refusal attached.

For cholesterol, in the entire history of that list, three things have ever got through. Plant sterols and stanols, at two grams a day [1]. Oat beta-glucan, at three grams [2]. Barley beta-glucan, also at three [3]. That is the register, complete. The same regulation that let oat beta-glucan through refused the application for soy protein in the next paragraph, on the grounds that no cause-and-effect relationship had been established [2], and at the ordinary tier the wording is barely more expansive: plant sterols and stanols contribute to the maintenance of normal cholesterol at eight-tenths of a gram a day, beta-glucans at three grams from oats or barley [4].

What isn't on that list is the part worth sitting with. Not the ingredient with the biggest advertising spend, not the one with the podcast deal, nothing in a dark bottle with a gold label. What cleared the highest bar in European food law was a fraction of a gram of sterols and two kinds of porridge. I find that clarifying rather than depressing, because it tells you what this subject looks like once somebody demands proof instead of enthusiasm, and what survives that demand is food. The rest of this piece is what happens when you go back through the heart-and-nutrition literature with that in mind, which is that the same ranking falls out all the way down, and it is not the ranking you would guess from a shop shelf.

Seven thousand Spaniards and a litre of olive oil

The largest thing ever done in this field is PREDIMED [5], which took 7,447 people in Spain, aged 55 to 80, and randomised them to a Mediterranean diet with extra-virgin olive oil, the same diet with mixed nuts, or a control diet advising less fat. The olive-oil group were given a litre a week. Everyone was followed for about five years, and rather than counting markers the researchers counted heart attacks, strokes and cardiovascular deaths, of which both Mediterranean groups had roughly 30% fewer than the control group. Hard outcomes, five years, thousands of people: in nutrition that combination is close to unique, since counting events costs a fortune and takes a decade, which is why most diet research counts something cheaper instead.

DASH counts a marker, and counts it beautifully [6]. Four hundred and fifty-nine adults were fed a set diet of fruit, vegetables and low-fat dairy with less saturated fat, while salt and body weight were deliberately held steady so that whatever moved could only be the food. Roughly five and a half points came off the top blood-pressure number, which is the pressure inside the artery at the instant the heart pushes, read in millimetres of mercury, and sits somewhere around 120 in a person whose pressure is fine and 140 or above in a person whose doctor has started watching it. Five points is a modest move for any one individual and it was better than twice that in the 133 people who came in with high pressure already, which is the pattern worth noticing: the food did most for the people furthest from where they should be. A follow-up trial cut the salt as well, and the drop got bigger again [7]. I have reviewed this literature formally, and the same two patterns keep coming out in front [8]; a group paper I co-wrote in Heart landed in the same place, that a Mediterranean-style pattern is the reasonable default and that you should think in foods rather than macronutrients [9].

The bowl of porridge, again

Then fibre, which is where the numbers get almost embarrassing. A 2019 analysis in the Lancet pooled 185 prospective studies and 58 trials, close to 135 million person-years, meaning the total of everyone's follow-up added together, so that a thousand people watched for ten years each makes ten thousand of them [10]. The people eating the most fibre had 15 to 30% less of nearly everything anyone worries about: deaths of all kinds, heart disease, stroke, type 2 diabetes, bowel cancer. Observational data always carry the same problem, in that people who eat 29 grams of fibre a day differ from people who eat 12 in a hundred ways that are not fibre, but the trial half of the analysis pointed the same direction and the dose-response was orderly, with the benefit largest somewhere between 25 and 29 grams a day and the curve still climbing at the end of it. Of everything in this article that is the finding I hold most tightly, and notice where it has landed us: back at the oats, which is exactly where the register left off.

Twenty people, seven days

My own randomised trials are on dietary nitrate, which mostly means beetroot juice, which mostly means a fridge full of dark red bottles and a small number of volunteers being very patient with me. My PhD was on nitrate and nitric oxide, the molecule that widens blood vessels and whose discovery won the Nobel Prize in Medicine in 1998, and I have published eight human intervention studies in that area. The one I would point to ran for a week, double-blind, placebo-controlled and crossover, in 20 adults whose blood-pressure medication was not getting the job done, and nitrate lowered their 24-hour pressure by about 8 points on the top number and 4 on the bottom [11]. An earlier pilot had already hinted at that, and at something more interesting, which is that the reductions turned up in the people whose pressure was uncontrolled and not in the people whose was already fine [12].

Twenty people, seven days, a marker rather than an event, and it will never appear in the Lancet. I am not going to inflate it into something it isn't. But I know what those participants ate, I know what dose they got and I know who they were, because I recruited them, and that is the reason I read everyone else's papers the way I do: once you know how thin twenty people looks from the inside, you know what to ask of a study of fifteen, and you know what a register with three items on it is telling you about everything that never made it on.

Which is roughly what the panel concluded, in its own dry way, when it asked for proof and got three answers back. A litre of olive oil a week, thirty grams of fibre a day, a fraction of a gram of sterols and a bowl of porridge. Nobody is going to build an advertising campaign out of that. It happens to be where the evidence is.

So: the vitamins

That is the food, and I have put it first because it is the truthful order, and because you will not often get it from someone selling capsules. Now the question you actually arrived with, which is what to do about the nutrients. I can answer that one directly, because I spent a decade reading this literature and then put my answer in a bottle.

Nine of them earned a place. Here is what is behind each, where the research is strongest, and which doses were actually studied, because the dose is the part most supplements get wrong.

CoQ10 and selenium, the two that decided the rest

Coenzyme Q10 is where I would start. Your body makes it and puts it exactly where cells produce energy, which is why anyone thought to test it at all, and the heart, which never gets a day off, holds more of it than almost any other organ. Two things about it set up everything that follows. Levels in heart tissue fall as heart failure worsens: in biopsies taken from 43 patients, the CoQ10 content of the heart muscle dropped step by step with the severity of the disease [13]. And your own production declines with age, peaking around twenty and falling steadily from there [14]. Food does not close that gap. The richest sources are organ meats, and even eating well the average diet supplies a few milligrams a day, which is why a capsule is a different proposition here from a vitamin you could eat your way to.

The dose matters, and the history of the trials shows why. The early studies used around 100 mg a day and reported little. A 1994 trial in Rostock gave 100 mg of CoQ10 with 100 µg of selenium to people who had just had a heart attack and found no difference in early complications, although fewer cardiac deaths in the treated group by the end of a year [15]. A 1999 trial at the Prince Charles Hospital in Brisbane gave about 100 mg a day to 30 people with heart failure for three months and found no change in how well the heart pumped [16]. The trials that changed the field used double that.

The one that matters most is KiSel-10: 443 people in Sweden aged 70 to 88, living in a rural region where the soil, and therefore the food, is low in selenium, given 200 µg of selenium yeast and 200 mg of CoQ10 every day for four years against placebo. Cardiovascular deaths came in at about 6% against about 13% [17]. That same group has been followed and re-analysed out to twelve years [18,19]. A four-year trial counting deaths rather than markers is rare enough in this field that I have followed it for most of my career.

That pairing is why the bottle carries the numbers it carries. Not a dose picked to look good beside a competitor, but the two doses that were actually tested, on the schedule they were tested on, which is why the CoQ10 is split across two capsules rather than given as a single daily hit. Q-SYMBIO, run by cardiologists across Europe, Australia and India, gave 300 mg a day to 420 patients with heart failure over two years and reported serious heart events at 15% against 26%, fewer hospital admissions for heart failure, and better symptom scores [20], and a 2024 review pooled 33 trials in heart failure [21]. At 200 mg a day in a smaller trial of 64 people with type 2 diabetes, twelve weeks of CoQ10 improved LDL cholesterol, HbA1c and a marker called ADMA that blocks the body's production of nitric oxide, with nitric oxide itself rising [22]. That is one small trial, but it is the dose in the bottle, tested on the thing the bottle is for. The forms, the doses and the ubiquinol argument are all in CoQ10, what it is and what the research says.

Selenium is the other half of that Swedish capsule, and it earns its place on its own account. It is a trace element your body needs for its antioxidant defences, and where the soil lacks it the heart is where the shortage shows: Keshan disease, a heart-muscle disease of the selenium-poor regions of inland China, was brought under control by giving people selenium [23]. In eastern Finland, where soil selenium is also very low, people with the lowest blood selenium had about three times the risk of dying from coronary heart disease over the following years [24]. Those are populations with far less selenium than most Irish diets provide, which is worth saying, but they are why the Swedish trial paired the two nutrients at all.

The KiSel-10 group kept measuring, and the sub-studies are where the mechanism starts to show. Compared with placebo, the people on selenium and CoQ10 had lower levels of NT-proBNP, the protein a stressed heart releases into the blood, and a better cardiac function score on echocardiography [17]; better kidney function [25]; lower levels of the markers that track scarring of heart tissue [26]; lower inflammatory markers [27]; and less oxidative stress [28]. On quality of life and days spent out of hospital the main analysis found no difference, but a matched comparison found the supplemented group declined less over the four years [29]. The researchers describe these follow-on findings as hypothesis-generating, which is the correct word, and I have not listed the outcomes that were never measured.

Zinc, the one nobody markets

Zinc is the surprise of the nine, and it has quietly the best-replicated evidence of anything in the formula. A 2019 analysis of 32 studies found improvements in fasting glucose and in a long-term blood-sugar measure [30], and a 2024 analysis of 19 trials found blood fats moving in the same direction [31]. Separate groups, separate decades, the same answer, which is more than most ingredients in this field can say. Nobody advertises it, presumably because it costs almost nothing and has been in the cupboard since the 1960s. It is in the formula as zinc picolinate.

Thiamine, the only heart claim on the register

Thiamine contributes to the normal function of the heart [4]. That sentence is authorised, and it is worded exactly as the law requires it to be, which is worth knowing when you read any label.

Underneath it is the tidiest piece of biology in the formula. Thiamine is vitamin B1, your cells need it to turn food into energy, and heart muscle contracts continuously from before you are born, with no reserve to coast on and no shift it can skip. When the supply runs short, the tissue with the highest standing demand is the first to show it, which is why a shortage of something in a rice husk announces itself as a heart problem. How that was worked out, by accident, in a laboratory in Java, is Thiamine, chromium, and the chickens in Java.

Vitamin K2, and the pulse travelling down an artery

K2's job is to direct calcium, towards bone and away from the walls of your arteries, where it stiffens them. The reason researchers took an interest in it beyond bone is a three-year trial by Knapen and colleagues. It gave MK-7 to 244 healthy postmenopausal women for three years and measured how quickly a pulse travels down an artery, which is how you tell whether an artery has stiffened, and reported an improvement on it [32]. Vitamin K contributes to normal blood clotting and to the maintenance of normal bones [4]. The formula carries K2 as MK-7, which is the form that trial used.

The evidence has moved on since. A 2026 trial in JAMA Cardiology gave 360 µg of MK-7 a day to 180 people for two years and tracked the calcium building up in their coronary arteries on CT scans. It built up in both groups, as it does with age, but about a third more slowly in the people taking MK-7 [33]. That is a slowing, not a reversal, and the authors say so. On the blood-sugar side, a 2025 review of six trials of MK-7 reported improvements in glycaemic control [34], a review the year before found K2 did more for insulin resistance than K1 [35], and a 2026 pooled analysis of eight trials of vitamin K reported lower fasting glucose, HbA1c and insulin resistance [36]. Small trials, mixed populations, and the reviewers flag the inconsistency between them, so I read this as promising rather than settled. One practical note: anyone on warfarin or a similar blood-thinner should talk to their doctor before taking any vitamin K, because it acts directly on the pathway those medicines work through.

The B group, and what "methylated" is doing on the label

The B vitamins are in their methylated forms, folate as 5-MTHF and B12 as methylcobalamin. For folate that is not a marketing prefix, and unusually for a marketing argument it has been tested head to head: 5-MTHF raised blood folate more effectively than the same dose of folic acid, and left less unconverted folic acid circulating behind it [37]. Folate, B6 and B12 each contributes to normal homocysteine metabolism [4], and homocysteine is the reason cardiologists take an interest in this group at all. In a Dutch study of 608 people, low blood levels of 5-MTHF went with poorer function of the blood-vessel lining, measured by how well an artery widens when blood flow rises [38]. A small 2024 trial in 54 people chosen for folate-pathway gene variants and high homocysteine gave methylfolate with B6 and B12 for three months and reported homocysteine down by 30% and LDL cholesterol down by about 7% [39]; it was run by the product's maker, so I hold it loosely, but the direction matches everything else in the field. Why the underlying finding is more interesting than the word on the label is in What methylated actually means.

Riboflavin, vitamin B2, is there for a more specific reason. It holds together the enzyme that makes methylfolate inside you, and a research group in Coleraine showed that in people who carry two copies of a common variant of that enzyme's gene, riboflavin lowered blood pressure, while doing nothing in everyone else [40]. That is a targeted effect in roughly one person in ten, not a general one, and it is also why riboflavin gets a considered slot in a B complex rather than an afterthought. Its own authorised claim is that it contributes to the reduction of tiredness and fatigue [4].

Methylcobalamin, the B12, is one of the two forms your cells make for themselves. Whether swallowing it in that form gets more B12 into you than the ordinary form does has not been settled, so I will not tell you it is better absorbed; what matters is that you are getting B12 at all. Adults over fifty absorb it less well, people on vegetarian or vegan diets get little of it from food, and anyone taking metformin should know that in a four-year trial metformin lowered B12 levels and raised the risk of deficiency [41]. If you are on it, have your B12 checked, or take a supplement that contains it every day.

Vitamin D3

My first research was on vitamin D, and I have published a dozen papers on it, in asthma, which I have myself, in sleep apnoea, in infections, and most recently in COVID-19. It is in the formula at 50 µg for the least exotic reason available: it is the most-studied vitamin of the last twenty years, almost none of it comes from food, and most of us in Ireland run low on it over the winter. Vitamin D contributes to the normal function of the immune system, to the maintenance of normal bones and muscle function, and to the normal absorption of calcium [4]. On blood sugar, the best evidence is a 2023 pooled analysis of three trials in people with prediabetes, in which vitamin D reduced the risk of progressing to type 2 diabetes by 15% and increased the chance of returning to normal glucose regulation by 30% [42]. The absolute difference over three years was about three people in a hundred, which is a real effect from a cheap nutrient rather than a dramatic one.

Berberine

Berberine is at 450 mg across the day, with food, which is how the trials gave it; it is far and away the most-searched thing in this library, and the reason less than 1% of what you swallow ever reaches your blood is the subject of Berberine, what the research says. Its trials measured blood sugar and blood fats, and what they found, dose by dose, is in that piece. It is the ingredient I am asked about more than any other.

Where that leaves it

If you sorted this page by the weight of the evidence, the food would still come first. A Mediterranean-style pattern, 25 to 29 grams of fibre a day, attention to salt: that is where the trials with hard endpoints and large numbers are, and I am not going to pretend a capsule outranks them, because it doesn't, and because you should hear that from me rather than work it out later.

But there is a difference between what is best and what actually gets done. After years of reading this literature I could not find a single supplement I would confidently recommend to my own family, friends or clients, at the doses the trials used, so I made one. It takes the nine nutrients that keep turning up on both sides of this literature, at the doses the research actually used rather than the doses that fit a price, and puts them in one bottle, two capsules a day with food, so that taking them stops being an admin job. Every ingredient in it was chosen to support normal heart function, the normal metabolism of fats and carbohydrates, and normal blood sugar levels, which are the three things the law lets me say and the three things I set out to do. The reasoning behind every dose on the panel is in Why I formulated Heart & Blood Sugar Phix, and if you have a question about any of it, ask me in our free WhatsApp group.

References

1. Commission Regulation (EC) No 983/2009 of 21 October 2009 on the authorisation and refusal of authorisation of certain health claims made on food and referring to the reduction of disease risk and to children's development and health. Official Journal of the European Union. L 277, 22.10.2009.
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Last reviewed: 10 September 2026. This article is educational and is not medical advice.