Alzheimer’s disease may be linked to a marginal vitamin A deficiency

Alzheimer’s disease may be linked to a marginal vitamin A deficiencyAlzheimer’s disease causes brain malfunctions, and the condition is the leading cause of dementia. According to a studies of humans and mice, there may be a link between borderline vitamin A deficiency and an increased risk of Alzheimer’s disease. Vitamin A is important for the immune system, but it is also a powerful antioxidant that protects neurons and other cells. Vitamin A deficiencies are widespread globally. In the industrialized countries, we mainly see vitamin A deficiencies in connection with unbalanced diets, ageing, and chronic illness.

Alzheimer’s disease causes neurons in various parts of the brain to perish. The disease is believed to be a result of imbalances in the neurotransmitters of the brain. Scientists have also found in brain tissue accumulations of proteins called amyloid plaque. Some studies suggest that insulin resistance in the brain causes an energy deficit in the neurons. Alzheimer’s disease, in any case, is a slowly progressive condition, which typically leads to death after 7-10 years. Therefore, it is vital to focus on proper prevention.

Vitamin A facts

Pure vitamin A (retinol) is a lipid-soluble vitamin that is primarily found in lipid-containing animal food sources like meat, oily fish, eggs, and dairy products. Vegetable sources such as carrots and spinach contain a water-soluble precursor called beta-carotene. Vitamin A and zinc work together in such a way that a deficiency of one nutrient weakens the other

Vitamin A and Alzheimer’s disease

The mentioned studies were carried out by researchers from Children’s Hospital of Chongqing Medical University, China, and the University of British Columbia in Canada. It is commonly known that lack of vitamin A is quite ordinary among pregnant women, older people, and children in underdeveloped countries. On a global scale, older people are generally more likely to be vitamin A deficient.
The scientists even point to the possibility of a genetic predisposition in the early pregnancy stages, if the expecting mother is vitamin A deficient. In such a case, there is an increased risk of developing the disease early in life.

The aim of the study

The whole purpose with the study was to take a closer look at the relation between vitamin A deficiency and cognitive impairment in old age, including skills like linguistic performance, reasoning, memory, and problem solving. The scientists also used mouse studies to investigate if lack of vitamin A was linked to amyloid plaque accumulation and memory loss, and to see if this could be prevented with vitamin A supplements.

How the study of humans and mice went

The human study included 330 older people with an age average of 77 years, recruited from 15 different retirement homes in China. The scientists excluded individuals with mental diseases, Parkinson’s disease, and also those who already took supplements of vitamin A. The researchers looked at the participants’ cognitive function and assessed their daily activities using an Alzheimer’s rating scale (ADAS-Cog) and a special dementia rating scale (CDR). Also, they took blood samples from the participants to measure their levels of vitamin A. 61% of the participants had normal levels, while 26% were borderline deficient, and 13 percent were deficient.

In the animal study, the scientists used mice that were genetically modified to produce amyloid plaque and develop a condition similar to Alzheimer’s disease. These mice were divided in two groups. For a four-week period prior to the study, the two groups received either a normal diet or a diet that was borderline-deficient in vitamin A. The mice were allowed to breed. Six months after the baby mice had been born, the scientists tested their skills in a water maze. Blood samples were drawn as part of the process, and the researchers also modified the vitamin A content in the diets of the animals. After the mice had died, brain tissue samples were analyzed.

The study results: Even minor deficiencies increase the risk of Alzheimer’s disease

According to the two scales that were used in the human studies, one relating to Alzheimer’s disease, the other to dementia, the scientists found that those older people who had minor vitamin A deficiencies (26% of the participants) had a significantly lower score. At the same time, the group that did not lack vitamin A performed significantly better in terms of cognitive functions.
In the animal study where one group of mice got a diet that was borderline vitamin A deficient, the scientists found an increased amount of those enzymes that are involved in the production of amyloid plaques. They also observed that baby mice of mothers with minor vitamin A deficiency had poorer orientation.

Still, the researchers warn, we cannot draw premature conclusions from the human study, as all the participants are from China where vitamin A deficiencies are more common. A similar study from a western country may show a different result. Nonetheless, it is important to pay attention to those factors that are known to lead to vitamin A deficiencies.

Vitamin A deficiency and poor utilization of the nutrient may be caused by:

  • ageing processes
  • unbalanced diets
  • alcoholism
  • impaired lipid absorption due to gastro-intestinal diseases or use of medical drugs
  • diabetes with poor ability to convert beta-carotene
  • long-term of antacids
  • pregnancy and lactation

Recommended daily intake:

Adults: 11 years and older: 800 micrograms/) RE

Children: 1-10 years of age: 400 micrograms/RE

Important: Pregnant and lactating women should not ingest more than 1,000 micrograms/RE daily

RE = retinol equivalents

Other good ways to prevent Alzheimer’s disease:

  • Take good care of your cardiovascular health with healthy eating habits and exercise
  • Avoid unbalanced diets and maintain stable blood sugar levels
  • Make sure to get enough zinc, B vitamins, and omega-3 fatty acids
  • Challenge yourself mentally (reading, crossword puzzles, etc.)
  • Avoid tobacco
  • Do not drink too much alcohol
  • Keep track of your blood pressure
  • If you are diabetic you should stick with your diet, maintain normal body weight, and take your prescribed medicine

Did you know that type-2 diabetes increases your risk of Alzheimer’s disease?

References

Zeng J, Chen L, Wang Z et al. Marginal vitamin A deficiency facilitates Alzheimer´s pathogenesis. Published online January 27 2017

http://www.nhs.uk/Conditions/Alzheimers-disease/Pages/Prevention.aspx

http://www.netdoktor.dk/sygdomme/fakta/alzheimer.htm

http://www.diabetes.co.uk/type3-diabetes.html

Oulhaj et al: Omega-3 Fatty Acid Status Enhances The Prevention of Cognitive Decline by B-vitamins in Mild Cognitive Impairment. Journal of Alzheimer’s Disease. 2016