For years, the media have trumpeted the vital role calcium plays in preventing osteoporosis, a silent disease of the bones that makes them weaken and prone to fracture.
The calcium clamor is so loud it sometimes drowns out messages about another nutritional necessity - vitamin D. Without enough vitamin D, the body cannot absorb calcium and deposit it in the bones. In such cases, the blood raids the skeleton for the calcium it needs, thus raising the risk of osteoporosis and fractures. About 10 million Americans have this condition, with another 34 million at risk.
Vitamin D difficult to get
The human body makes its own vitamin D when ultraviolet-B (UV-B) rays from the sun interact with a chemical in the skin. But the sunshine method isn't reliable for everyone. This is especially true of older people, who are at the highest risk for weakened bones and fractures. In addition:
- The skin's ability to make vitamin D from UV-B becomes less efficient as we age.
- Depending on where you live, vitamin D production may decrease or be completely absent during the winter.
- Darker skin blocks out up to 95 percent of UV-B rays.
- Concerns about the connection with sun and cancer keep people out of the sun.
- If you choose to go in the sun but use sunscreen (as most people do), the sunscreen will absorb the UV-B before the skin can form vitamin D.
- Those who are housebound (usually the elderly) do not get any sun exposure.
These and other findings mean that dietary and supplemental sources of vitamin D become ever more important as we age. Vitamin D not only strengthens bones, it benefits your muscles and helps to improve strength and balance in older persons.
How much is enough?
According to the Institute of Medicine, the recommended daily dietary allowance for vitamin D is:
- 400 IU (international units) in adults ages 50 to 70
- 600 IU for people older than 70
- 200 IU for younger adults and teens
For the elderly, people who are housebound and people in general during the winter months, 400 IU to 600 IU is suggested.
The guidelines of the National Osteoporosis Foundation are slightly higher. They suggest that adults under 50 get 400 IU to 800 IU per day, and those ages 50 and older get 800 IU to 1,000 IU of vitamin D each day.
You can talk to your doctor about which dose may be right for you.
If you are concerned about your vitamin D status, a simple blood test can tell you if you are deficient.
Getting the D you need
Vitamin D can be obtained in three ways:
1. Sun-exposed skin. Solid research is lacking as to how much sun exposure is needed to get adequate vitamin D. Also, many things can affect absorption, including time of year and day, where you live, cloud cover, smog, skin shade and sunscreen use. Some experts suggest that 10 to 15 minutes of sun exposure between 10 a.m. and 3 p.m. a few times a week to the face, arms, legs or back without sunscreen may be enough for vitamin D synthesis. More research is needed, though.
2. Food. Food sources of vitamin D are limited, and include:
- Fortified milk (100 IU/cup)
- Fortified yogurt (80 IU/cup)
- Fortified breakfast cereals (40 IU/serving)
- Egg yolks (25 IU/yolk)
- Fortified orange juice (100 IU/cup)
- Salmon (750 IU/3 ounces)
- Mackerel (380 IU/3 ounces)
- Tuna (150 IU/3 ounces)
Some breakfast and nutrition bars and drinks provide 100 IU to 140 IU of vitamin D per serving.
3. Supplements of vitamin D are often needed, considering limited food sources and the unreliability of sun exposure. Supplements would include vitamin D alone, multivitamins and calcium supplements with added vitamin D.
Be aware that too much vitamin D can cause toxic side effects. Symptoms of vitamin D poisoning may include nausea, headache, excessive urination, high blood pressure, kidney stones, kidney damage and other problems.
