B vitamins and certain beverages protect against Alzheimer’s disease

Lack of vitamin B12 and folic acid increases the risk of Alzheimer’s disease, which is because these B vitamins regulate blood levels of homocysteine that must be below a certain threshold. Apparently, men and women react differently to B vitamins and folic acid with regard to cognitive functions, according to a study that is published in Nutrients. The risk of developing Alzheimer’s disease is also lower among younger people and among those who drink tea or coffee. Unfortunately, many older people lack these particular B vitamins because of poor diet habits, low stomach acid, or the use of various medical drugs.

Alzheimer’s disease is characterized by a progressive decline of cognitive functions like memory, sense of direction, language, and problem solving. Studies have shown that Mediterranean diets and the so-called DASH diet (Dietary Approach to Stop Hypertension) can improve cognitive functions in older people. In recent years, science has been focused on specific nutrients. For example, it is known that low blood levels of vitamin B12 and folic acid (vitamin B9) or elevated homocysteine levels are linked to cognitive decline. In the current study, the researchers wanted to see how diet habits and blood levels of vitamin B12 and folic acid affected the risk of developing Alzheimer’s disease. Also, they wanted to see if men and women reacted differently.
The study included 592 patients with Alzheimer’s disease (246 men and 346 women). The scientists made blood profiles and collected data about the participants’ demography. Their diet habits were assessed by using the so-called Food Frequency Questionnaire (FFQ), and the participants’ cognitive skills were evaluated with help from the Mini-Mental State Examination (MMSE) dementia assessment scale. The higher the score, the better their cognitive function.
The study showed that a higher MMSE score was related to better education, lower BMI, younger age, and consumption of tea and coffee. Diet (including dairy products and meat) was positively linked to blood levels of homocysteine and folic acid plus vitamin B12, which is only found in animal foods.
The scientists could also see among the male participants that there was a direct link between blood levels of vitamin B12 and their MMSE score. In women, homocysteine levels were a more critical and determining factor.
Based on their findings, the scientist conclude that diet and blood profiles are linked to the risk of cognitive decline and Alzheimer’s disease. There also appears to be a gender difference with regard to how blood levels of vitamin B12 and homocysteine affect cognitive skills in patients with Alzheimer’s disease.

Why is elevated homocysteine a risk factor?

Homocysteine is an amino acid that is synthesized in all cells in the body after breaking down another amino acid called methionine. Homocysteine is also released by the cells and is found in the blood, but it is important to contain homocysteine levels within a certain range as the compound is potentially harmful. Homocysteine is an intermediary compound and must be broken down into a third amino acid called cysteine, which is involved in multiple metabolic processes. Also, cysteine is involved in the body’s production of essential antioxidants like glutathione and glutathione peroxidase (GPX), which calls for a certain balance between homocysteine and cysteine.
Elevated homocysteine, which is often seen in combination with low cysteine, may cause oxidative stress and inflammation that can damage nerve cells. Elevated homocysteine levels may also lead to dysfunctions in the endothelial cells that affect our circulatory system and in dysfunctions in DNA methylation, apoptosis, and the blood-brain-barrier.
Studies have shown that elevated blood levels of homocysteine can increase the risk of dementia disorders such as Alzheimer’s disease, cardiovascular disease, stroke, blood clots, chronic fatigue, depression, and cancer.

How do B vitamins regulate homocysteine levels in the blood?

The body needs vitamin B12, folic acid, and vitamin B6 to convert homocysteine into cysteine. A deficiency of one or several of these B vitamins can therefore result in elevated homocysteine levels and an increased risk of Alzheimer’s disease and other ailments. It is therefore essential to have a sufficient intake of the different B vitamins that are found in the following sources:

•Vitamin B12: Animal foods such as meat, liver, fish, shellfish, eggs, and dairy products.

•Folic acid (vitamin B9): Legumes, spinach and other vegetables, liver, eggs, and wholegrains.

•Vitamin B6: Meat, fish, shellfish, vegetables, eggs, and wholegrains

The new study suggests that the widespread problems with vitamin B12 and folic acid deficiencies are particularly relevant for Alzheimer’s disease. Deficiencies of both B vitamins are often seen in combination.

Why are B vitamin deficiencies so common?

Lack of various B vitamins can be a result of poor diet habits, low stomach acid, and excessive intake of sugar or alcohol. Lack of vitamin B12 can also hinge on lacking intrinsic factor, which is a “carrier protein” that conveys vitamin B12 from food into the bloodstream. In addition, stress, antacids, antibiotics, metformin (for treating type 2 diabetes), methotrexate (anti-rheumatic drug), levodopa (for treating Parkinson’s disease), and corticosteroids can disrupt the body’s uptake and utilization of various B vitamins.

References:

Chi-Ping Ting et al. Diet Pattern Analysis in Alzheimer´s Disease Implicates Gender Differences in Folate-B12-Homocystein Axis on Cognitive outcomes. Nutrients 2024

Tahniat Rehman et al. Cysteine and homocysteine as biomarker of various diseases. Food Science & Nutrition. 2020

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