Cognitive decline sits on a spectrum from mild cognitive impairment to dementia.
Mild cognitive impairment (MCI) causes problems with memory or thinking clearing and may be a precursor to dementia. Often MCI is caused by other health conditions, medications, sleep disorders or nutrient deficiencies.
Alzheimer’s disease is the most common cause of dementia effecting memory and behaviour. Vascular dementia causes difficulty thinking and/ or moving, muscle weakness and mood changes. Dementia with Lewy bodies results in memory loss, episodes of alertness or drowsiness, hallucinations, falls or fainting and sleep disturbances.
As of 2023, the World Health Organisation reports that more than 55 million people are living with dementia globally. A figure that is predicted to rise to a staggering 150 million by 2050.
Risk factors for cognitive decline:
- brain injury
- central adiposity (carrying extra fat around your abdomen)
- high blood pressure (130/80 mmHg or higher)
- smoking
- diabetes
- inactivity
- history of depression
- prolonged sleep disturbances
- nutrient deficiencies (especially B vitamins, omega 3 fatty acids and vitamin D)
- low socioeconomical status
- isolation and loneliness
- genetics (single nucleotide polymorphisms in the ApoE gene)
Although dementia has significantly grown in prevalence, the good news is there are plenty of dietary and lifestyle interventions that can reduce your risk of developing cognitive decline and dementia.
Dietary nutrients to prevent cognitive decline
B12 (cobalamin)
B12 is a cofactor needed for the synthesis and stabilisation of myelin sheaths that surround nerve cells. Without sufficient B12 myelin sheaths become damaged causing nerve fibre damage leading to numbness or tingling in hands and feet, memory problems and cognitive decline. B12 also supports the production of brain-derived neurotrophic factor (BDNF) which is vital for the development and survival of neurons.
Serum B12 <200 ng/L indicates deficiency. Healthy B12 levels are 300 ng/L to 1000 ng/L. Dietary sources of B12 include: meat, seafoods, eggs, dairy and nutritional yeast fortified with B12.
People at high risk of vitamin B12 deficiency include: vegans, vegetarians, those with pernicious anaemia, individuals taking antacids/ proton pump inhibitors, anyone with IBD (Crohn’s or Ulcerative colitis), Celiac disease and those over 60 years of age.
B12 requires hydrochloric acid (stomach acid) and healthy intestines in order to be digested, transported and absorbed. Those with stomach or intestinal issues may require sublingual supplementation (under the tongue) or B12 injections. Vegans should supplement with either methylcobalamin or adenosylcobalamin. There is no upper tolerable limit for B12 as risk of toxicity is very low.
! Always check with your healthcare provider before supplementing.
Folate (B9)
Without sufficient folate an amino acid called homocysteine can build up. Elevated homocysteine can be inflammatory and increases the risk of Alzheimer’s disease. Other nutrients needed to lower homocysteine are: B12, B6, B2, choline and betaine.
Unfortunately, in the UK homocysteine levels are not routinely tested for but if you have low B12 or folate it suggests homocysteine may be elevated. Serum folate <4 ng/mL is considered deficient.
We cannot synthesis folate so it must be obtained from the diet. Dietary sources of folate include: dark leafy green vegetables (spinach, cabbage, kale, brussels sprout, broccoli, asparagus, collard greens, chard, romaine lettuce), beans, legumes, whole wheat, sunflower seeds, avocado, beetroot, oranges, papaya, eggs and beef liver.
If you need to supplement with folate, it is best to use an active form (5-methyltetrahydrofolate/ 5-MTHF) rather than synthetic folic acid which has to be converted to 5-MTHF in order for the body to be able to use. The upper tolerable limit for folate is 1000 mcg per day. B vitamins are often best taken as complex, in other words together, as they work synergistically in the body.
! Always check with your healthcare provider before supplementing.
Vitamin D (calcitriol)
When serum vitamin D levels fall, the risk of dementia increases and this correlation is more profound in females. Insufficient levels of serum vitamin D are <50 nmol/L and optimal serum levels are 75 – 100 nmol/L.
Dietary sources of vitamin D include: oily fish (salmon, trout, mackerel, sardines, herring), egg yolks, mushrooms exposed to ultra violet light and fortified dairy.
The main source of vitamin D is sunshine but as we age the skin’s ability to synthesis vitamin D declines, as does the liver and kidney’s ability to activate it. This is why those over 65 years are at increased risk of vitamin D deficiency. In the UK it is recommended that vitamin D3 is supplemented from October to March (800 IU daily). Vitamin D increases calcium absorption, taking a vitamin D3 supplement with vitamin K2 helps ensure the calcium gets integrated into bones rather than soft tissue.
! Do not take vitamin K if you are on blood thinners like Warfarin.
Omega 3
Inflammation is at the heart of most diseases including Alzheimer’s disease. Omega 3 fatty acids are anti-inflammatory and are neuroprotective as they can help quell brain inflammation.
The best source of omega 3 fatty acids come from oily fish. Aim for 2 portions of oily fish a week. Plant sources include: flax seeds, chia seeds, hemp seeds, walnuts and algae.
If you wish to supplement with fish oil, ensure it is tested for heavy metal toxicity. Docosahexaenoic acid (DHA) seems to be more important than eicosapentaenoic acid (EPA) for brain health, although both are beneficial.
Polyphenols
Polyphenols are plant compounds that have a myriad of health benefits from feeding good gut bacteria to lowering risk of dementia. Polyphenols act as antioxidants which help to reduce oxidative stress, a proposed contributor to dementia. The polyphenol curcumin, found in turmeric, may modulate β-amyloid peptide development and assist in clearing β-amyloid deposits thus potentially reducing amyloid plaques.
Rich sources of polyphenols include: blueberries, cherries, cranberries, citrus fruit, pomegranate, dark chocolate (70% +), olives, extra virgin olive oil, dark green leafy vegetables, onions, nuts, seeds, herbs, spices (especially turmeric), black tea, green tea, coffee, red wine (in moderation).
! Grapefruit and green tea can interact with a lot of medications. Check with your healthcare provider.
The Mediterranean diet is rich in polyphenols as well as colourful nutrient dense whole foods. A huge number of studies support the use of the Mediterranean diet for preventing cognitive decline.
Lifestyle to prevent cognitive decline
Sleep
You have probably heard of the lymphatic system but did you know you also have a glymphatic system which is your brain’s waste removal system. The glymphatic system is far more active whilst you sleep and one of its roles is to help clear the brain of neurotoxic waste such as β-amyloid.
Aim to sleep for 7 to 9 hours a night with a regular sleep and wake schedule. Ensure your bedroom is cool, comfortable, dark and quiet.
Exercise
Regular exercise is associated with a reduced risk of all forms of dementia. The benefits of exercise on brain health are multifactorial from decreasing β-amyloid to improving oxygen rich blood flow to the brain.
The NHS recommends at least 150 minutes of moderate-intensity exercise per week which equates to around 30 minutes a day, 5 days a week. Great options include: swimming, yoga, Pilates, strength training, dancing and walking.
Socialise
Isolation, loneliness and loss of enjoyment in life can inhibit BDNF. BDNF is Brain-derived neurotrophic factor it plays an important role in neuronal survival and growth, serves as a neurotransmitter modulator, and participates in neuronal plasticity, which is essential for learning and memory. In mouse studies loneliness increased amyloid and tau protein accumulation which can increase neurodegeneration.
If possible, get involved in community activities, join a fitness class, chat to a neighbour or organise a games night with friends or family.
Brain games
Whether you are 9 or 90 the brain can create new brain cells and neural connections. Keeping your brain active by learning new skills, or challenging yourself with mental puzzles, helps stimulate the growth of new brain cells and thus helps prevent cognitive decline.
It is never too late to learn a new skill. Why not learn to play an instrument, polish up your Spanish or try a pottery class.
Author: Elle Frizzell, Part-Qualified in Nutritional Therapy
References
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