Do tanning beds give you vitamin D?
A tanning bed 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 tanning beds demonstrably increase the risk of skin cancer, a vitamin D supplement is the safer choice.
Most commercial tanning beds emit predominantly UV-A. UV-A, however, is barely capable of producing vitamin D in the skin. Only tanning beds that also emit UV-B (at a wavelength of roughly 290-315 nm) raise your vitamin D level. Whether a specific tanning bed does this therefore depends entirely on the type of lamp.
Tanning beds that do emit UV-B raise vitamin D levels noticeably. In one comparative study, people who used such a bed at least once a week had nearly double the vitamin D levels of non-users, as well as higher bone density. That sounds impressive, but this was not a controlled experiment: other lifestyle differences may be a factor. Even a tanning bed with barely any UV-B was shown in a small study to produce some increase, which the researchers themselves described as surprising.
There is a serious downside to this: using a tanning bed increases the risk of skin cancer, including the dangerous melanoma. That risk is strongest in people who started using tanning beds at a young age. Multiple independent sources classify this as a preventable cause of skin cancer.
The good news is that you do not need a tanning bed to maintain your vitamin D levels. Vitamin D supplementation in tablet form works just as well, without the skin risks. Multiple research groups explicitly mention this as a safe alternative. Note also that even a low-factor sunscreen (SPF-8) already blocks 95% of vitamin D production in the skin, and clothing blocks it entirely. For people who cannot absorb vitamin D through food, such as with certain intestinal diseases, a UV lamp under medical supervision may be an option, but that is a different matter from ordinary tanning bed use.
This answer is based on multiple reviews and a systematic review on skin cancer risk, supplemented by several smaller studies on vitamin D levels in tanning bed users. The skin cancer risk is solidly supported by multiple independent sources. The vitamin D effects are less robust: the comparative data come from a cross-sectional study (no proof of cause and effect), and the studies on UV-A tanning beds and patients with intestinal diseases are small and provide only preliminary indications.
How much vitamin D should you take per day?
For healthy adults under 75, extra vitamin D is probably not necessary, but for children, people aged 75 and older, pregnant women, and those at high risk of diabetes, supplementation is worthwhile. If you are unsure whether you belong to a risk group, it is worth discussing this with your general practitioner.
Can you get too much vitamin D?
Too much vitamin D is genuinely harmful, but that risk only arises at blood levels far above the recommended values. Stick to the dosage on the packaging, and unsure about your level? Have it measured by your GP.
Is taking extra vitamin C worthwhile?
Extra vitamin C offers little benefit for most people. Intensive athletes and people following a carnivore diet do have a good reason to supplement, and those who take it daily tend to experience slightly milder symptoms when they catch a cold.
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.
Does sunbathing boost your immune system beyond the vitamin D effect?
Sunlight has real effects beyond vitamin D through nitric oxide and hormonal pathways, but randomised evidence for improved immune defences is lacking. At the same time, the immunosuppressive effect of chronic exposure is well documented, so moderate sun exposure makes more sense than a great deal of it.
Does vitamin D help your immune system, or is that overrated?
Vitamin D genuinely supports your immune system, but the benefit of taking extra applies mainly when you have a deficiency. If your level is already adequate, you have little to gain from higher doses.