Why do we need vitamin D?
Sunshine, not food, is where most of your vitamin D comes from. So even a healthy and well balanced diet, that provides all the other vitamins and nutrients, is unlikely to provide enough vitamin D. To get enough vitamin D you need to spend some time outside with some bare skin on most days during the summer months. Vitamin D is a nutrient required for optimal bone health and essential for overall health. The vitamin can be found in two forms: vitamin D3, the form of vitamin D your skin makes in response to sun exposure, found in a few foods naturally, added to other foods, and as a dietary supplement, and vitamin D2, the form available in dietary supplements and added to certain foods. It is measured in international units (IU) where 1 IU is 0.025 micrograms of vitamin D. No single recommendation for adequate sunlight exposure can be made for people, because the amount of vitamin D3 produced from sun exposure varies based on skin type, use of skin protection, length of sun exposure, season of the year, and time of day. Vitamin D is needed for normal absorption of calcium and phosphorus and makes sure you absorb enough calcium for your bones and teeth. Even if you have a calcium-rich diet, without enough vitamin D you cannot absorb calcium into the body. New research is showing vitamin D may also help prevent other chronic diseases.
Higher vitamin D levels in a person’s blood may protect against certain types of cancers, strengthen the immune system, and reduce risk of type 1 and 2 diabetes. Population studies suggest that lack of vitamin D may increase the risk of chronic health conditions such as multiple sclerosis. You make vitamin D under your skin when you are outside in daylight, which is the reason vitamin D is sometimes called the sunshine vitamin. By definition, a vitamin is a nutrient that we cannot make in our body. Vitamin D is actually a hormone rather than a vitamin and very few foods contain vitamin D naturally.
Vitamin D may help couples and people trying for a baby and they should take a sunshine holiday as sunlight boosts fertility in both men and women by increasing their levels of vitamin D. Vitamin D is also very important in balancing sex hormones in women and improving sperm count in men. For women, vitamin D helps boost levels of the female sex hormones progesterone and oestrogen by 13 per cent and 21 per cent respectively, regulating menstrual cycles and making conception more likely. For men it increase their fertility because vitamin D is essential for the healthy development of each sperm’s nucleus. It also increases levels of the male sex hormone testosterone, improving a man’s libido. The vitamin’s effect on both male and female sex hormones may explain why conception rates fall in the winter and peak in the summer in Northern European countries.
What happens if we don’t get enough vitamin D?
Lack of vitamin D affects bones and many other parts of the body and Low levels of vitamin D have been linked to depression. Babies and growing children who do not get enough vitamin D may have bones that can’t support their weight (rickets). Adults deficient in vitamin D can develop soft bones (osteomalacia). They also can lose bone mass.
• Very young babies sometimes have fits.
• Adults can get osteoporosis (brittle bone disease) or osteomalacia which causes pain in their bones.
• Adults are also more likely to get breast cancer or prostate cancer.
• Scientists believe that more people are getting Type 1 diabetes, rheumatoid arthritis, multiple sclerosis and some bowel diseases because of not having enough vitamin D
How much vitamin D do we need?
The amount of vitamin D you make depends on how strong the sunlight or ultraviolet light is. You will make more in the middle of the day than early morning or late afternoon. Similarly you will make more when you are in direct sunlight than in the shade or on a cloudy day. Ultraviolet B rays enable vitamin D to be made, yet sun damage caused by excessive ultraviolet B exposure increases the incidence of malignant melanoma and other skin tumours. You do not have to sunbathe to make enough vitamin D and most people make enough by spending some time outside on most days in the summer with some bare skin such as hands, face and arms or legs. You need to make enough during the summer to build up a store to last you through the winter. We need to get enough vitamin D from all sources to have adequate levels of this vitamin in our blood. Recent research indicates that Americans need to get more vitamin D than we used to think was needed. Older adults and persons with dark skin are at higher risk than others for having low levels of vitamin D in their bodies. Babies and young children who are growing quickly need a lot of vitamin D
• Pregnant women and breastfeeding mothers need more than other women.
• Pregnant teenagers are vulnerable because their own bones are still developing and they need extra for their baby
• The elderly because their skins are not as good at making vitamin D
• People with darker skins living in the UK or other northern climates – that is those of Asian, African, Afro-Caribbean and middle-eastern origin. They make less vitamin D than white people do
• If you always cover most of your skin when you are outside
• Children and adolescents who spend little time playing outside
• Anyone who spends very little time outside during the summer – the housebound, shop or office workers, night shift workers.
• If you are housebound, or rarelyleave work during lunchbreaks
• The further north you live
• If the air is quite polluted
• When you use sunscreen above factor 8
Which foods contain vitamin D?
We get vitamin D from three sources—food, supplements, and sunlight.
Food: Eggs, sardines, and salmon contain vitamin D. Most fluid milk and some brands of yogurt are fortified with vitamin D. Fortified breakfast cereals, breads, and orange juice also may contain this vitamin.
• Oily fish such as salmon, sardines, pilchards, trout, kippers, eel are the only foods which naturally contain reasonable amounts of vitamin D.
• Cod liver oil contains a lot of vitamin D.
• Eggs and meat contain small amounts.
• Margarine, some breakfast cereals and infant formula have added vitamin D.
If you can’t get enough vitamin D from your diet, and you don’t get out in the sun much, a supplement can help. It is recommended that older adults and persons with dark skin get extra vitamin D from fortified foods or supplements. Since skin synthesis of vitamin D varies so much, the latest dietary recommendations assume minimal sun exposure.
How much is too much?
Vitamin D toxicity can cause nausea, mood changes, and organ damage. The latest recommendation is to not get more than 4000 IU (less for children younger than nine) of vitamin D each day from food and supplements. Taking a vitamin D supplement as well as spending a lot of time outside in sunshine will not be a problem. However do not take two or more supplements with vitamin D. Remember that cod-liver oil contains vitamin D and should be counted as a vitamin D supplement. Always choose a supplement tailored to the age group or condition, as fish liver oils and high dose multivitamin supplements often contain vitamin A, too much of which can cause liver and bone problems, especially in very young children, and the elderly.