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Why we need vitamin D
Vitamin D3 is also highly regarded for its role in assisting both muscle and bone structures by enhancing the absorption of calcium in the small intestine. As it circulates through your bloodstream, vitamin D aids the absorption of calcium and phosphorus, which in turn helps to keep your bones strong, reducing the risk of fractures and improves muscle strength. Further, when we have sufficient levels of vitamin D3 in our diet, we increase our potential for achieving a higher peak bone mass in adulthood, which thereby helps to prevent osteoporosis.
However, if your body doesn't have enough vitamin D available to effectively absorb calcium, it will draw calcium from your bones instead, which in turn causes the bones to weaken, and if allowed to progress can potentially lead to fractures and osteoporosis.
According to EFSA, vitamin D:
- contributes to normal absorption/utilization of calcium and phosphorus
- contributes to normal blood calcium levels
- contributes to the maintenance of normal bones
- contributes to the maintenance of normal muscle function
- contributes to the maintenance of normal teeth
- contributes to the normal function of the immune system
- has a role in the process of cell division
Risk factors
- Babies and young children, and adolescents who spend little time playing outside.
- Pregnant and breastfeeding women.
- People over the age of 65 (the skin is less apt to produce vitamin D as we age).
- People with darker skin tones (Asian, African, Afro-Caribbean and people of Middle Eastern descent living in northern climates).
- People who cover most of their skin when outside.
- People living further north will be exposed to sunlight that is not strong enough to induce vitamin D synthesis in the skin.
- Anyone who spends very little time outside during late spring and summer (the housebound, shop or office workers, night shift workers, etc.).
- People living and working in areas with high levels of pollution in the air.
Age
Older people tend to lose their appetite, reduce their intake of vitamin D3-rich foods such as fatty fish and spend more time inside than their younger counterparts. Also, the synthesis of vitamin D in the skin decreases with age.
Skin type
People with dark skin need up to 6 times more sunlight exposure than those with fair skin.
Sunscreen
We get around 80% of our vitamin D from sunlight exposure. However, the use of sunscreen reduces the amount of sunlight that reaches the skin and reduces the vitamin D3 production in the skin.
Overweight and obesity
Research has found that serum 25(OH)D is about 20% lower in obese people. One likely factor causing this dilution is the increased volume of fat, but also because overweight people are more likely to wear clothes that cover up their bodies and thus limit skin exposure to the sun.
Physical inactivity
In our muscles, vitamin D3 deficiency is associated with a decline in neuromuscular function, strength, walking speed, and balance. By increasing your daily levels of physical activity outdoors and exercise, you help to counteract these negative effects, whilst also creating more opportunities to stimulate your body’s own production of vitamin D3.
Latitude/season
In general, supplementation is recommended during the winter months to people living at latitudes of 40n and above. The skin is unable to produce vitamin D from October to March as the available sunlight is not strong enough.