Can nutrients or vitamins prevent or delay dementia?

As populations age, dementia is a problem across the developed world. Might nutrients or vitamins provide a solution?  

Unfortunately there is no drug treatment available to prevent dementia or bring about lasting improvements. So can what we eat prevent or delay a decline in our memory and reasoning as we get older?  

Can B vitamins help?  

A  2012 review showed that some studies revealed a relationship between B-vitamin status and mental function but others seemingly did not.  

While research continues, proper intake of the B vitamins seems sensible, as an insurance policy. These are provided by food such as eggs, dairy products, fish, liver, meat and fortified breakfast cereals. If this isn’t possible vitamin B complex (supplements containing all eight B vitamins) can be taken. There is usually little risk of overdosing with the B vitamins because they are water soluble and readily passed out in urine.  

What about Vitamin D? 

The importance of this vitamin (D3) in dementia seems a little clearer than that for the B vitamins -  although studies tend to show an association, rather than definitely proving that Vitamin D deficiency causes dementia.  For example lower vitamin D (serum) concentrations are usually seen in patients showing mental decline (poorer cognitive function) and early Alzheimer's. That was the verdict of a systematic review published in Neurology in 2012. In a small scale study of 95 older people also published in 2012, low Vitamin D levels were associated with mild cognitive impairment, which increases the risk of progression to dementia.

To avoid Vitamin D deficiency:  

  • Try to take advantage of 20 minutes or so of sunshine per day (a little less if you are fair skinned, a little more if you have darker skin) from April to October in the UK.
  • Make sure you include foods which provide vitamin D in your diet (like oily fish, eggs and fortified breakfast cereals).
  • Alternatively take a Vitamin D supplement as recommended by the UK NHS for the over 65s (up to - but no more than - 25ug/day).  

And omega-3 fatty acids and fish oils?  

The omega-3 fatty acids found in oily fish may help reduce the risk of mental decline and dementia. However once again the clinical evidence is often conflicting.  

Much of the potential benefit of omega-3 fatty acids has previously been thought to be due to their cardiovascular effects. They minimise arteriosclerosis (fatty deposits on the blood vessel walls) and hence maintain brain blood circulation. A detailed review in 2012 seemed to support the important role of omega 3 in dementia although another study published that year seemed to show little support for that view. This may however be related to whether or not there was a dietary deficiency to begin with.  

Until the scientific evidence becomes clearer, it seems worthwhile ensuring we eat 2 – 3 helpings per week of oily fish, such as herring, mackerel, salmon, tuna and sardines. These are a useful source of omega -3 fatty acids and also believed to help reduce the risk of cardiovascular disease. Fish oil capsules are a possible alternative.  

Can antioxidants make a difference?  

Various clinical studies have suggested so-called "oxidative stress" as a possible factor in bringing about cognitive decline and dementia. Antioxidants (including vitamins E and C, carotenoids such as beta carotene, and flavonoids) are believed to combat oxidative stress. Once again however the evidence is conflicting. A combination of several antioxidants may help cognitive performance. That’s according to a 2011 study of 4,447 French participants aged 45 – 60. However some studies have found that taking vitamin E and beta carotene in excess increases the risk of some cancers. For instance a 2011 study in the US concluded that dietary supplementation with vitamin E significantly increased the risk of prostate cancer among healthy men.  

A  systematic review of studies, published in 2013, on the use of Gingko biloba concluded that it improved cognitive function and activities of daily living in patients with dementia.   

Or a healthy diet?  

A recent study looked at a combination of two diets, the so-called MIND diet. This combined a Mediterranean Diet with a DASH (Dietary Approach to stop Hypertension) Diet. The study showed that participants who stuck rigorously to this were 52% less likely to be diagnosed with Alzheimer's disease. The diet includes foods thought to protect the brain such as  olive oil, wholegrains, green leafy vegetables, other vegetables, berries, fish, poultry, beans and nuts, and a daily glass of wine - but restricts red meat and meat products, fast or fried food, cheese, butter, pastries and sweets. 

NHS Choices comments that we should be wary of saying the diet protects against Alzheimer’s, as this is a complex disease with many causes. However, they did accept that there seems to be a link between eating a healthy diet and a lower risk of getting Alzheimer's disease.  

Furthermore a number of studies of the role of flavonoids on cognition have suggested they may help inhibit the develop of Alzheimer’s type symptoms. Flavonoids are found in varying concentrations in plant-based whole foods such as berries, tea, cocoa, soybeans and grains.  


  • Preventing mental decline and dementias through what we eat is an appealing idea - but obtaining good evidence for this is likely to take some time.
  • This is partly because an association between nutrients and vitamins and reduced risk of dementia doesn’t necessarily mean these are causing the reduced risk - and partly because some of the research has been into cognitive issues like Mild Cognitive Impairment rather than dementia.
  • As we report elsewhere on Age Watch an adequate intake of the B and D vitamins and omega 3s (ideally from a healthy diet and sunshine but if not from supplements) have health benefits and few risks.
  • So it seems sensible to ensure an adequate intake in case research confirms they also help delay the onset of dementia.
  • However overuse of supplements may result in health risks in some cases - although this applies mainly to Vitamin E and beta carotene.

Reviewed by Richard Franklin February 2016, next Review January 2020

Mediterranean Diet