Stroke, commonly known as “stroke”, is the first cause of death in China, and its high rate of disability and recurrence, often “one person with the disease, dragging down the whole family”, has brought a heavy burden to society and countless families. The epidemiological characteristics of hypertension differ greatly between the West and China. The ratio of stroke to heart attack risk in hypertensive patients in the West is 1:1, while in China it is 5:1. “Why is this? Why? And what is the relationship between folic acid, hypertension and stroke? Let’s talk about this topic today.
Let’s start with a few terms. Homocysteines (Hcys), hyperhomocysteinemia, and H hypertension.
Homocysteine is an intermediate metabolite of methionine (one of the 20 essential amino acids) and is produced in 3 different ways by different enzymes and different cofactors. When there is a mutation in the genes of these enzymes or a lack of cofactors, or for some other reason, the concentration of Hcys in the blood will increase, and when it rises above 10umol/L, we call it “hyperhomocysteinemia”, and hypertension with hyperhomocysteinemia is called Hypertension with hyperhomocysteinemia is called “H-type hypertension”.
What are the risks of homocysteinemia?
Simply put, homocysteine can have toxic effects on vascular endothelial cells, promote the formation of atherosclerotic plaques and interfere with the normal function of vascular smooth muscle. Epidemiological studies have shown that patients with hypertension accompanied by hyperhomocysteinemia, or H-hypertension, will have a much higher risk of stroke.
Second, what causes elevated Hcys?
1, methionine intake or more, that is, excessive intake of animal protein (especially in men);
2, insufficient intake of vitamin B6, B12 and folic acid, especially folic acid intake is most closely related;
3, gene mutations, such as one of the enzymes called dimethyltetrahydrofolate reductase (MTHFR) mutation;
4, renal insufficiency, hypothyroidism, etc.
In our country, the traditional diet and cooking habits have made the intake of folic acid insufficient in our country generally. Folic acid in food is very unstable and will lose 50-90% of its activity during processing and cooking, plus our residents tend to eat too much fried and stir-fried food, the destruction of folic acid is even more, while folic acid is a water-soluble vitamin, the way of boiling also makes folic acid easy to lose, and the bioavailability of natural folic acid is only about 60%. Therefore, folic acid deficiency is very serious in China, and the proportion of people with H-type hypertension is very high. Data show that among hypertensive patients in China, the proportion of H-type hypertension is 90.9% in men and 59.6% in women, and the combined proportion is 75.3%, which means that more than 3/4 of hypertensive patients have H-type hypertension and the incidence of stroke is therefore high. In contrast, in regions such as North America, the mandatory policy of fortification of cereals with folic acid (i.e., adding folic acid to flour, similar to iodized salt in China) has made it less likely that there is a deficiency of folic acid. This explains why hypertension goes to the heart in Western countries and the brain in our country.
Having said that, it is better to understand the conclusion of Prof. Huo Yong’s team’s study: In Chinese adults with hypertension without stroke and myocardial infarction, the addition of folic acid to antihypertensive drugs significantly reduced the risk of new strokes. In Professor Huo’s 4.5-year follow-up study, additional folic acid supplementation of 0.8 mg per day reduced the risk of stroke in the population by 21%.
Who would benefit more from folic acid supplementation?
1. Men, it may be related to the fact that men prefer to eat meat and not vegetables;
2.People with low basal folate level;
3.People with high homocysteine level;
4, Dimethyltetrahydrofolate reductase (MTHFR) gene mutation for TT type.
Therefore, homocysteine levels should be routinely tested in patients with hypertension (note that they should be measured in the morning on an empty stomach!) This was recommended in the 2013 Chinese Expert Consensus on Cardiovascular Risk Assessment in Asymptomatic Adults, and the dimethyltetrahydrofolate reductase (MTHFR) genotype can be tested if available. If necessary, additional folic acid supplementation of 0.8 mg/day on top of antihypertensive drugs can be used as primary prevention of stroke.
Fourth, finally, I think two more points need to be emphasized
1. Although supplementation with pharmacogenic folic acid can reduce the risk of stroke, a good lifestyle is still the cornerstone of hypertension treatment. In Prof. Huo Yong’s study, both control and experimental groups adjusted their diets appropriately under the guidance of physicians. Although the elevated folic acid in the control group was only about 1/3 of that in the experimental group, it also shows that dietary habits can affect folic acid levels. Spinach, fennel, soybeans, and other green leafy vegetables are rich in folic acid, and proper cooking can increase the intake of folic acid, while fruits such as kiwi and bananas are also rich in folic acid and can be consumed more often.
In the CSPPT study, the supplemental folic acid was 0.8mg/day, while commercially available folic acid tablets are 5mg/tablet. Some studies have reported that excessive intake of folic acid may increase the risk of cancer in the population, so we should pay attention when purchasing.