Next time you’re choosing or restocking your supplements, you’re bound to see your chosen nutrients offered in different strengths or concentrations. The various doses are there for a reason, and what someone chooses to take will depend on various factors such as lifestyle, specific health issues, appetite, and age.
Starting with vitamin D—a nutrient with many different roles, ranging from contributing to the maintenance of normal bones, teeth, and normal muscle function to the normal function of the immune system. Vitamin D is found only in a small number of foods such as oily fish, meat, and eggs, but is also made in the skin upon exposure to sunlight. The NHS recommends that adults and children over the age of 4 take at least 400 IU (IU stands for international units) daily in the autumn and winter when there is little sun, although some people choose to take a supplement year-round if they are not exposed to the sun much at all, or if their diet could do with some extra support (for what it's worth, I take 1000 IU daily year-round).
There are several reasons why you might choose to take vitamin D3 at levels such as 2,200 IU or 4,000 IU rather than a more modest dose. One of the most common is to address a deficiency which has been properly identified by a health practitioner. A blood test may have been requested that measures vitamin D as 25-hydroxyvitamin D, and if levels are deemed low, then you may choose to take a supplement that offers 2,200 IU or 4,000 IU per capsule. These levels may be suggested for a few months before retesting and, if the blood test shows that vitamin D levels have risen, then switching to a maintenance dose of, say, 1,000 IU should be sufficient—although you should always seek the guidance of the right health professional.
Another reason to consider higher doses may be a digestive issue such as Crohn’s Disease or reduced levels of bile, the latter potentially affecting the degree to which fats are broken down, which in turn can reduce the absorption of fat-soluble nutrients such as vitamins D, A, K, and E. But there is a sometimes unexpected outcome: fat-soluble nutrients, as well as circulating in the blood, can also accumulate in fat cells. Therefore, if someone is carrying extra weight, it is possible for the levels of circulating vitamin D to be impaired as the nutrient is instead stored away. In this type of scenario, taking 2,200 IU or 4,000 IU might make sense to help support the levels in the blood.
Age may also play a part here, as vitamin D production in the skin can reduce over time and so increasing one’s intake from a supplement is one way to offset this. As vitamin D plays a role in the absorption of calcium, maintaining bone health is a potential concern as we age, and so increasing one’s intake of vitamin D in line with this may be advisable.
But it’s not just the dose, it’s also the type of supplement one chooses. For example, if you prefer not to take capsules, then vitamin D is available in liquid form, such as the Liquid Vitamin D3, which delivers 2,200 IU in 0.5ml of orange-flavoured liquid which one can add to water or a smoothie.
The general safe upper limit for vitamin D is 4,000 IU a day, and doses up to this level are considered safe, but my advice is to ensure that you take appropriate advice rather than dive headlong into a higher dose with no specific reason.
The other nutrient that is also offered in various doses is vitamin C. Unlike vitamin D, vitamin C is water-soluble and so we need an adequate intake every day. As always, the diet is the first place to start, and vitamin C is found in fruits and vegetables, but if your intake is inadequate, or you have a smaller appetite or restrictive diet, then getting enough in the diet can be a challenge. In such cases, taking 500mg–1,000mg of vitamin C once or twice a day could be a wise move.
Another factor to consider is age, as vitamin C contributes to normal collagen formation which is in turn required for gums, teeth, skin, and cartilage. As collagen production can itself reduce with age, many people may choose to supplement a little more vitamin C for extra support. Vitamin C cannot be stored in the body and so when demand is high, we may choose to take extra. As the nutrient contributes to the normal function of the immune system and can also contribute to the reduction of tiredness and fatigue, many people choose to take a supplement when feeling under the weather, be that 500mg or 1,000mg once or twice a day.
However, taking vitamin C in excess can lead to urgent or loose stools, and so I do not recommend taking more than 1,000mg at a time. Although if you have never taken vitamin C before, then you may wish to start with a more modest 500mg and build up tolerance over a week or so.
Whatever your reason for considering how much of a nutrient to take, it’s wise to seek guidance, so that you take the right amount of the right nutrients for your needs.