In recent years, there has been a surge in vitamin D supplements, based on claims that vitamin D supplementation may have various beneficial effects on health. These supplements have been marketed to reduce the risk of developing cardiovascular disease, osteoporosis, dementia, depression and even cancer. However, the evidence to support these claims remains inconclusive and additional clinical trials are needed. Instead of going for supplements, many experts recommend getting your vitamins from natural sources.
Vitamin D is not a single nutrient, but a group of steroids which help the intestines absorb more calcium, iron, magnesium, phosphate and zinc. Apart from absorption, vitamin D plays a crucial role in maintaining ideal levels of calcium and in related metabolic processes.
Benefits of Vitamin D
Vitamin D was first discovered in 1922 in cod liver oil. Researchers were trying to find which dietary substance was lacking in patients suffering from rickets, a childhood disease marked by skeletal deformities and other symptoms caused by poor bone mineralisation. Even today, vitamin D is mainly prescribed to treat or to prevent osteomalacia (the softening of the bones), since it improves bone metabolism and increases the levels of calcium and phosphate in the bloodstream.
In addition to this, some researchers claim that increasing the intake of vitamin D has a number of additional health benefits, including:
- weight loss
- decreased risk of respiratory tract infections
- treatment for multiple sclerosis
- activating the innate immune system
- improving cognition
- positive effect on patients with severe depression
- reduced risk of cardiovascular disease
- potentially reduced risk of cancer
- better outcome for some cancers
- reduced risk of fractures in older patients
- decreased mortality in the elderly
It is important to note that evidence to support these benefits remains inconclusive and additional research is necessary in most cases.
Vitamin D Deficiency
Vitamin D deficiency has been linked to a number of different conditions, primarily:
- weakened immune system
- increased risk of viral infections (e.g. HIV, influenza)
- (in pregnancy) pre-eclampsia, gestational diabetes, small infants
- Crohn’s disease
- ulcerative colitis
- risk of developing Alzheimer’s disease
- risk of developing colon cancer
- increased risk of stress fractures
While additional clinical trials are required to determine the precise benefits of vitamin D supplementation, low levels of vitamin D have been proven to have a series of adverse effects on overall health, which is why it is necessary to maintain at least a stable, recommended level of vitamin D.
Vitamin D Sources
Unlike most vitamins, the primary source of vitamin D is not our diet. Vitamin D is one of the two vitamins that the human body can produce on its own (the other being vitamin K). It is synthesised in the skin from cholesterol, with sun exposure as the necessary catalyst. Therefore, spending time outdoors and enjoying the sunlight is one way to increase the levels of vitamin D in the body. On the other hand, there are some controversies about the cancer risk from too much exposure to sunlight, which is why the US Institute of Medicine ignores sun exposure as a source of vitamin D and issues its Dietary Reference Intake under the assumption that all of a person’s vitamin D comes from food.
Vitamin D Foods
The list of foods containing vitamin D is unfortunately quite short, which is why, if you’re looking to stay out of the sun, but don’t like supplements, these foods are absolutely indispensable:
- Eggs, particularly egg yolks. One egg will provide you with about a fifth of your daily vitamin D needs. We’ve put them so high up on the list since, compared to a lot of these other foods, eggs are the most easily accessible.
- Cod liver oil. If it was good a hundred years ago, it is just as good today. Sure, its aroma may not be for everyone, but a single teaspoon is enough for all of your daily needs. It is also very rich in omega-3 fatty acids.
- Fish, fish, fish. Fatty fish tops the list, like mackerel (a single portion should be enough), tuna (fresh, wild-caught tuna works best), salmon (cooked salmon is recommended), herring and sardines. When it comes to freshwater fish and vitamin D, catfish is king. In the absence of better options, canned fish should be more than good enough.
- Sun-dried mushrooms, primarily shiitake and button mushrooms (portobello mushrooms).
- Milk and other dairy products, like yoghurt
- Almond milk and soy milk
- Orange juice
- Beef liver
- Oysters, low in calories compared to a lot of the other options and also rich in other nutrients (vitamin B12, copper and zinc).
Even apart from these food items, there are a lot of products that have been fortified with vitamin D, including breakfast favorites like cereals, milk and orange juice, so look for those when you start craving the D. In essence, a healthy, balanced diet and spending time outside, in the fresh air and sunlight, are good for overall health, not only for vitamin D levels. That is why it is hard to pinpoint exactly which health benefits come from vitamin D, and which ones are the result of other factors. Still, if the result is better health and decreased risk of developing a number of different conditions, what does it really matter?