The retina at the back of the eye develops as an outgrowth from the brain, which means that some conditions that affect the brain are detectable in the eyes. Take dementia for example. Levels of the yellow carotenoid pigments (lutein, zeaxanthin and meso-zeaxanthin) that are concentrated within the macula (the part of the retina responsible for fine vision) reflect those found in brain tissue.
Lutein readily crosses the blood brain barrier and is the most abundant carotenoid in the brain, where it protects brain cells from the harmful effects of oxidative stress that plays an important role in the development of dementia.
Lutein and dementia
Many studies suggest that dietary intakes of lutein are closely related to age-related cognitive decline and the risk of developing Alzheimer’s disease.
Researchers have found that levels of yellow pigment in the macula of the retina are significantly lower in people with Alzheimer’s disease compared with healthy controls of the same ages, for example.
Those with Alzheimer’s also have lower blood levels of lutein and zeaxanthin, poorer vision, and are more likely to develop age-related macular degeneration. Blood carotenoid levels are even linked with the severity of Alzheimer’s, so that those with the more severe disease have much lower lutein levels than those with mild dementia.
A study involving 1,092 healthy older French people measured their blood carotenoid levels then followed them for up to 10 years. After adjusting for other known risk factors for dementia, those with the highest lutein concentrations were 20% less likely to develop any form of dementia, and 24% less likely to develop Alzheimer’s dementia that those with the lowest levels. The researchers suggested that maintaining higher intakes of lutein may decrease the risk of dementia.
Another study, involving 6,958 US adults over the age of 50 who had their blood levels of antioxidants measured and were then followed for up to 12 years. After taking other risk factors into account, those with the highest blood levels of lutein and zeaxanthin at the start of the study had a 57% lower risk of dying from Alzheimer’s than those with the highest levels. This study also found that another carotenoid, lycopene, was also protective – those with the highest levels were 74% less likely to die from Alzheimer’s than those with the lowest levels.
As lutein must come from the diet, these findings could just reflect a worsening quality of diet and low intakes of kale, spinach and sweetcorn once dementia becomes established. But what if these findings are due to a cause and effect relationship? Is it possible that a diet which supplies plenty of lutein and zeaxanthin might protect against Alzheimer’s, or improve symptoms or slow the progression in those who are already affected?
Lutein supplements and dementia
The best lutein supplements supply natural lutein obtained from vibrant marigolds. In a recent clinical trial, published in the Journal of Alzheimer’s Disease, the effects of carotenoid supplements plus omega-3 fish oils (to boost absorption) were tested against disease progression in people with Alzheimer’s disease. Numbers were low, but 12 people with mild to moderate dementia took carotenoids (10mg lutein, 10mg meso-zeaxanthin, 2mg zeaxanthin per day) while another 13 with mild to moderate dementia (1 severe) took the same carotenoid blend plus 1g omega-3 fish oils (430 mg DHA, 90 mg EPA) per day for 18 months. In a third trial, 15 people who were free of Alzheimer’s disease took just the carotenoid supplements for 6 months as a control group.
The researchers reported that blood carotenoid concentrations increased greater in those who also took the fish oils (carotenoids are fat soluble) and progression of dementia was significantly less in this group: carers reported worthwhile benefits in memory, sight, and mood.
While early days, and only small numbers, this suggests that ensuring a good intake of carotenoids – especially lutein, from which you can make zeaxanthin when needed – is key to maintaining long-term cognitive health. Whether or not lutein is one of the best supplements to prvent against dementia remains controversial but I’ve certainly started to take it! Taking lutein together with fish oil not only improves absorption but fish oil has beneficial effects against Alzheimer’s disease in its own right.
Lutein rich foods
You can’t make lutein in the body, and it must therefore come from the diet. Strangely, lutein is not (yet) classed as an essential nutrient, even though low intakes are associated with macular degeneration – the commonest cause of sight loss in later life.
You get lutein from dark green leaves, and from red, orange and yellow fruit and veg. Egg yolk is also a good source and the fats present also boost absorption of any vegetable lutein eaten at the same time.
You can make zeaxanthin and mesozeaxanthin from lutein, however, so the key is to get sufficient lutein from your food.
Lutein per typical serving
|Sweet corn||2 mg|
|Green peas (tinned)||2 mg|
|Broccoli (cooked)||2 mg|
|Green beans (cooked)||0.8mg|
|Eggs (2 large)||0.3mg|
|Orange (1 medium)||0.2mg|