Question: Regarding a column on dementia prevention (“A diet to remember”, October 9, 2021), do vitamin supplements have beneficial effects in preventing dementia?
Answer: Although most New Zealanders have an adequate intake of B, C and E vitamins, it is typically not high enough to lower our risk of chronic diseases such as cardiovascular disease, cancer, dementia and cognitive decline. And although vitamin supplements may seem like a shortcut to optimising your health, growing evidence suggests that micronutrient supplements are not the best solution for maintaining cognitive faculties. So instead, we must look at what we eat.
Vitamin E, for example, is a powerful antioxidant that plays a significant role in protecting polyunsaturated fatty acids from oxidation, including the essential fatty acids that form the walls of our body cells, ensuring the integrity of these cells.
But with dietary supplements, sometimes entirely unexpected results can occur. For example, researchers long hoped that vitamin E supplements would reduce cardiovascular disease risk, given this vitamin’s antioxidant abilities and the observation that people whose diets were high in vitamin E were less likely to develop coronary heart disease. However, clinical trials revealed supplementation did not lower the risk of cardiovascular mortality and high doses may in fact increase the risk of premature death.
Bearing that in mind, a recent Cochrane review assessed the impact of vitamin and mineral supplementation for preventing dementia or delaying cognitive decline in people with mild cognitive impairment. It concluded from clinical-trial evidence that vitamin E supplementation had no significant effect on overall cognitive functioning. The analysis of trials produced a similar finding for B vitamin supplementation, although one study merited replication.
However, the vitamin E clinical trials that were reviewed used only one of the eight different forms of vitamin E, known as alpha-tocopherol. And recent research has shown the other vitamin E derivatives may also play critical biological roles alongside their antioxidant function. For example, research on alpha-tocotrienols, another form of vitamin E, suggests they may have neuroprotective properties in brain tissue. Indeed, researchers have shown that individuals with Alzheimer’s disease have lower levels of these different forms of vitamin E than healthy individuals.
But clinical trials to date have not identified a benefit to cognitive health from tocotrienol variants of vitamin E supplementation. And given the increased mortality risk associated with vitamin E supplementation, there is certainly good reason to caution against the slavish use of vitamin supplements to maintain or improve cognitive well-being.
It’s doubtful any single dietary component will play a significant role in maintaining cognitive function or in preventing other chronic diseases such as cardiovascular. So instead, most nutrition science now focuses on dietary patterns – that is, the combinations of foods associated with improved health.
Promising clinical-trial evidence shows that Mediterranean-style diets reduce cardiovascular disease risk among people at high risk of this condition and may help with blood-glucose control in people with diabetes. More recently, a randomised clinical trial of the Mediterranean diet, including olive oil or nuts, demonstrated improved cognitive function in older adults.
People increase carotenoids, vitamin A and vitamin E levels circulating in their blood by following a Mediterranean-style dietary pattern, a 2011 Italian study published in Nutrition Journal found. All of these are associated with higher anti-inflammatory factors that are neuroprotective (as pointed out in my October 9 column).
Foods rich in vitamin E, such as vegetable oils and fats, nuts and seeds and avocados, are central to Mediterranean-style diets. In addition, the wholegrains encouraged in a Mediterranean diet are also a rich source of B vitamins. If good health is your goal, rather than focusing on individual nutrients, focus instead on achieving an overall healthier dietary pattern, such as the Mediterranean diet.
This story was originally published on November 20, 2021.
