High Blood Pressure, MTHFR and B Vitamins: What the Irish Riboflavin Research Shows

High blood pressure (hypertension) is one of the most common long-term health conditions and a leading cause of stroke, heart attack and kidney disease. It usually has no symptoms, which is why it's called a silent condition. Many people only find out at a routine check.

In most people there's no single cause, which is called primary or essential hypertension. Online, you'll see this described as a mystery doctors don't investigate, with homocysteine as the hidden answer. The truth is more interesting, and includes some genuinely important research done on this island.

What counts as high blood pressure?

Blood pressure is written as two numbers, such as 120/80 mmHg. The top number is the pressure when the heart beats; the bottom is the pressure between beats.

• A reading consistently of 140/90 or above in a clinic is generally treated as high blood pressure.
• Readings between about 120/70 and 139/89 are considered elevated, and a reason to look at lifestyle and overall heart risk.
• Home readings are usually a little lower, so your GP may ask you to check at home or wear a 24-hour monitor to confirm a diagnosis.

What causes it?

Primary hypertension develops from a mix of genes, age, too much salt, excess weight, low physical activity, alcohol, stress and sleep problems. In around 5 to 10% of people there's a specific underlying cause, such as kidney disease, hormone problems, sleep apnoea or certain medicines. Your GP will look for these, especially if blood pressure is very high, starts young or is hard to control.

Homocysteine and blood pressure

Studies have found that people with higher homocysteine tend to have higher blood pressure on average. There are plausible ways homocysteine could affect blood vessel lining. But high homocysteine is also linked with kidney function, age and diet, which affect blood pressure too, so the direction of cause isn't settled. Homocysteine testing isn't part of routine blood pressure assessment.

The riboflavin research: a genuine Irish finding

This is where MTHFR becomes genuinely relevant. The MTHFR enzyme uses a form of riboflavin (vitamin B2) as its helper molecule. In people with two copies of the C677T variant (the TT genotype), the enzyme holds on to this helper less tightly, which is why riboflavin status seems to matter more for them.

Researchers at Ulster University have studied this for many years:

• People with the TT genotype tend to have somewhat higher blood pressure, particularly when riboflavin status is low.
• In randomised trials, a low dose of riboflavin (1.6 mg a day for 16 weeks) lowered blood pressure in people with the TT genotype. In one trial in patients with premature heart disease, average blood pressure fell from about 144/87 to 131/80 mmHg. People with other genotypes didn't respond.
• Most participants were already on blood pressure medicines, and the riboflavin was taken in addition to them.

Around 10% of people worldwide have the TT genotype, more in some populations. This is promising, targeted research, but it hasn't yet been adopted into blood pressure guidelines, and MTHFR testing isn't offered routinely for this purpose. If you know you have the TT genotype and high blood pressure, it's a reasonable conversation to have with your GP.

Riboflavin is found in milk, yoghurt, eggs, meat, mushrooms and fortified breakfast cereals. It contributes to normal energy-yielding metabolism and the reduction of tiredness and fatigue.

Folic acid and stroke in high blood pressure

In the China Stroke Primary Prevention Trial, adults with high blood pressure who took folic acid alongside their blood pressure tablet had about a fifth fewer first strokes than those on the tablet alone. The benefit was greatest in people with low folate to begin with. Folic acid didn't replace blood pressure treatment; it was added to it. More on this in our stroke article.

What lowers blood pressure most

These steps have strong evidence, and each can lower blood pressure by several points:

• Cut salt. Aim for less than 5 g a day (about a teaspoon). Most salt comes from bread, processed meat, ready meals, soups and sauces, so check labels.
• Eat more fruit, vegetables, beans and low-fat dairy, as in the DASH and Mediterranean diets.
• Move more. Regular brisk walking, cycling or swimming helps.
• Lose weight if you need to. Even a few kilos makes a difference.
• Keep alcohol low.
• Stop smoking, which hugely increases heart and stroke risk alongside high blood pressure.
• Sleep well, and get checked for sleep apnoea if you snore heavily and feel tired during the day.
• Take medication as prescribed. Blood pressure tablets are very effective at preventing strokes and heart attacks. Never stop them without talking to your GP.

Getting checked

• Adults should have their blood pressure checked regularly, and more often if it's been high before.
• Many pharmacies in Ireland offer blood pressure checks, and validated home monitors are widely available.
• The HSE chronic disease management programme offers regular GP reviews for eligible adults with high blood pressure.

This article is for general information and is not medical advice. Please speak to your GP about your blood pressure, and never stop or change prescribed medication without medical advice.