Are seed oils such as sunflower oil bad for you?
Seed oils such as sunflower oil are probably not outright bad, but cannot be endorsed without qualification either: ideally, also include sufficient omega-3-rich foods such as oily fish or flaxseed in your diet to keep the ratio in balance.
Seed oils such as sunflower oil are high in linoleic acid, an omega-6 fatty acid. When you use them to replace saturated fat, your LDL cholesterol (the 'bad' cholesterol) consistently falls. That is classically considered beneficial for the heart. At the same time, HDL cholesterol (the 'good' kind) also drops slightly, which partially offsets that benefit.
Larger international studies that tracked blood levels of linoleic acid in more than 68,000 people show that higher blood levels are associated with less cardiovascular disease, fewer cardiovascular deaths and fewer strokes. These are associations observed in long-term follow-up cohorts; whether linoleic acid is the cause has not been established.
Yet the picture is not straightforwardly positive. The Sydney Diet Heart Study, a randomised trial in men who had previously had a heart attack, found the opposite: the group that replaced saturated fat with safflower oil (also an omega-6-rich seed oil) had higher mortality than the control group. This was a specific high-risk group, so the findings cannot be translated one-to-one to healthy people, but it does make the picture more complex.
The ratio of omega-6 to omega-3 also plays a role. In the Western diet that ratio is heavily skewed, while a lower ratio is linked in observational studies to less inflammatory disease and less cardiovascular disease. Seed oils contribute to a higher omega-6 intake, and that can reduce the effect of omega-3 fatty acids in the body. At the same time, in healthy people who eat more linoleic acid, many inflammatory markers in the blood remain unchanged.
There is also a hypothesis that linoleic acid, when consumed in excess, forms harmful breakdown products that disrupt metabolism. This idea comes from animal research and mechanistic reasoning, but has not been properly tested in controlled studies in humans. At present it remains speculative.
This answer draws on multiple sources: a large international study that followed more than 68,000 people, a randomised trial in cardiac patients (the Sydney Diet Heart Study), a randomised trial in 200 cardiac patients over two years, and several review articles. The evidence on the effect on LDL cholesterol and the association with cardiovascular outcomes is the strongest. Whether linoleic acid causes or prevents cardiovascular disease in healthy people has not been conclusively answered: the long-term follow-up cohorts show associations but cannot prove causation. The hypothesis regarding oxidative breakdown products and mitochondrial damage is barely supported by controlled studies in humans.
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.
Is soy healthy, or not because of the phytoestrogens?
Soy is probably harmless and possibly beneficial for most healthy adults, but caution is advised for children with thyroid problems. Anyone who eats a lot of soy and has doubts is best off discussing this briefly with a doctor or dietitian.
Do tanning beds give you vitamin D?
A sunbed can raise your vitamin D level, but only if the light also contains UV-B, and most commercial beds emit very little of it. Because sunbeds demonstrably increase the risk of skin cancer, a vitamin D supplement is the safer choice.
Is too much zinc harmful?
Too much zinc is certainly harmful: as an adult, stay below 25 mg of elemental zinc per day (EFSA limit) and be cautious with high-dose zinc supplements, because even moderate over-supplementation can disrupt copper balance.
Are ultra-processed products bad for your longevity?
Eating a lot of ultra-processed products is associated with a shorter lifespan and more chronic disease, but the effect varies considerably by product type and largely disappears when your overall diet quality is good. Eating less processed meat and improving your overall eating pattern offers the greatest benefit.
Are beans and legumes good for longevity?
Large observational studies consistently show that people who eat more legumes have a lower risk of death. For most people, a daily serving of legumes is well supported by the evidence; older adults should also pay attention to getting sufficient protein overall.