Does lutein from avocado protect your eyesight?
Avocado raises your lutein intake and appears to improve macular pigment density, but the direct evidence for this is limited and partly funded by the avocado industry. Combine avocado with dark leafy vegetables for a better overall lutein intake.
Lutein and zeaxanthin accumulate in the macula, the central part of the retina. They filter blue light and act as antioxidants. A higher concentration in the macula is associated with a lower risk of age-related macular degeneration, a common cause of vision loss in older age. Several large studies, including a large clinical trial, confirm this association, although the optimal daily amount has not yet been definitively established. Suggested amounts for at-risk groups range from 5 to 10 mg per day.
One avocado per day measurably increased macular pigment density in healthy older adults in a six-month randomised study; the control group (potato/chickpea) showed no improvement. That same study also found a 25% rise in blood lutein levels, compared with 15% in the control group. Note: this study was funded by the avocado industry, which should be taken into account when interpreting the results.
Avocado is not, incidentally, a rich source of lutein when compared with spinach or kale: half an avocado provides roughly 185 micrograms of lutein and zeaxanthin, whereas the daily amounts being studied for protective effects run into several milligrams. What does make avocado notable are its monounsaturated fats. These help the body absorb lutein more effectively, not only from the avocado itself, but also from other vegetables eaten at the same time.
Not everyone responds equally strongly to a higher dietary lutein intake. Genetic and metabolic differences play a role in this. Safe upper limits for pregnant and breastfeeding women have not yet been well established, so extra caution is warranted in those groups. More broadly, dietary surveys show that people are on average consuming less and less lutein, which increases the importance of sources such as avocado, eggs and dark leafy vegetables in the daily diet.
This answer is based on one randomised study (sponsored by the avocado industry) and several broad review studies on lutein and eye protection, including work related to a large clinical supplement trial. The direct evidence for avocado as a protector of eyesight is therefore limited and partly coloured by commercial interests. The broader evidence that lutein protects the macula is stronger, but even for that, cause and effect have not yet been fully established.
Does avocado help you absorb vitamins?
Avocado measurably helps with the absorption of fat-soluble vitamins and carotenoids from other vegetables. A few slices on your salad or alongside your carrot dish is already enough to make a difference.
Does avocado help lower your blood sugar spike after a meal?
If you eat half or a whole avocado in place of carbohydrates, there is preliminary evidence that your post-meal blood sugar spike will be lower. If you simply add avocado to what you are already eating, that effect does not appear to be present.
Do antioxidant supplements make sense?
For healthy people, antioxidant supplements such as beta-carotene and vitamin E are not useful as protection against cancer or heart disease, and beta-carotene is frankly inadvisable for (ex-)smokers. The only well-supported exception is the AREDS formula for advanced macular degeneration: discuss this with your ophthalmologist.
How harmful is too little daylight or sunlight?
Too little sunlight is demonstrably harmful, especially for your bones. For broader disease risks the associations are plausible but not yet proven causes, and a daily dose of 5 to 30 minutes of sunlight is already sufficient for most people.
Are there dietary patterns that have been proven to reduce your risk of cancer?
The Mediterranean diet and sufficient vegetables and fruit are consistently associated with a lower cancer risk, although the effects are modest and the findings are associations. The evidence is strongest for colorectal cancer; ideally combine diet with other healthy habits for the greatest effect.
Do you live longer by following the Mediterranean diet?
In large population studies, the Mediterranean diet is consistently associated with lower mortality and less cardiovascular disease; those who want to follow the diet as a whole have the strongest evidence on their side.