Vitamin D intake is a bit mystifying the only vitamin that’s also a hormone, and the only vitamin people don’t have to consume from food. You manufacture it when your skin is exposed to the sun. See how you do on this quick quiz.
How much Vitamin D intake do I need? for Vitamin D benefits and vitamin D deficiency
True or false
For healthy bones, vitamin D intake is as vital as calcium
Answer: True. Without vitamin D, you cannot absorb calcium.
The latitude you live in can make you deficient in D
Answer: True. In Canada and the northern U.S., the reduced sunshine in winter months causes the skin to manufacture little or no D.
Two cups of milk supply the daily requirement for vitamin D intake
Answer: True, but only for most people under 50. Older people, especially those living at northern latitudes and others getting inadequate sun exposure, need to consume more D. In the U.S., milk is almost always fortified with 100 IU of vitamin D per cup and is the primary dietary source.
Yogurt and cottage cheese are good source
Answer: False. Yogurt and cottage cheese are not made from fortified milk, so they have no D.
Cod liver oil is your best source of D
Answer: False. It’s very high in D, but poses health problems.
The hormone your bones need
First, a few basics. The current recommended daily intake of vitamin D is 200 IU (international units) for those under 50; 400 IU for people aged 50 to 70; and 600 IU for those 70 and older.
Unlike other vitamins, D is a hormone. It is crucial for calcium absorption, thus enabling the body to build and maintain strong bones and teeth. It also helps maintain muscle strength, and a lack of it may be partly responsible for leg muscle weakness and a tendency to fall in older people (often leading to fractures).
A deficiency of D produces weak bones, known as rickets in children and osteomalacia in adults, and may cause aches and pains.
The latest research has also linked D to good health in other ways. People who get little or no exposure to the sun tend to have higher rates of breast, colon, and prostate cancer–and mortality rates for these cancers tend to be higher in northern regions, where there’s less sun.
Since sunlight’s ultraviolet radiation is responsible for producing vitamin D in the body, many scientists now believe that lack of Vitamin D intake may be the explanation. Some research suggests that chronic D shortages may also play a role in multiple sclerosis, diabetes, and rheumatoid arthritis. In addition, vitamin D appears to help regulate cell growth and the immune system.
Yet studies show that people over 50 tend to fall short of vitamin D–and not only in northern countries. Black Americans and other people with dark skin are particularly at risk.
Where D comes from
As noted, D is the only vitamin you make yourself. (Some vitamin K and some B12 is produced in our bodies, but by intestinal bacteria). You manufacture some or all the D you need just by being out in the sun.
Depending on your location, the time of year, the darkness of your skin, and your age, if you get just 10 to 15 minutes of sun exposure on your face, hands, and arms (without sunscreen) at least twice a week, you may not need to consume any D from foods at all. Most of us get that much sun without even trying.
And because D is a fat-soluble vitamin, most people can store enough to supply them in the days, or even months, when they don’t get any sun.
Vitamin D is not plentiful in the diet. Fortified milk (including some soy milks, but not yogurt or most cheeses) is the major source. Some orange juice, margarines, and breakfast cereals are also fortified with D.
Fatty fish, such as salmon, tuna, and sardines, are good sources. If you drink three glasses of milk, that’s 300 IU. A glass of fortified orange juice (100 IU) and a serving of tuna (200 IU) would boost you up to 600 IU– Vitamin D intake even if you got no sun.
But it isn’t as easy as it sounds
- People over 60 are often deficient in vitamin D for several reasons. They tend to be out in the sun much less, and they produce much less D from the sun exposure they do get. They usually have poorer diets, eat less, and thus consume less D. Many of them don’t drink much milk. And their bodies are less able to utilize the D they consume or produce.
- If you live in the north, have dark skin, or are rarely outdoors, it’s harder for your body to make enough D. In Canada and the northern U.S. there isn’t enough sunshine in winter to stimulate sufficient D production in the skin. In Boston, Detroit, and Chicago, for example, there’s enough sunshine only from April through October; in the southern U.S. there’s enough sunshine year round. However, many people stay indoors, or always use sunscreen when outside. In addition, if you have dark skin, you need longer exposure to sunlight–perhaps up to twice as much–to produce the same amount of D as a light-skinned person, since pigmentation screens out sunlight and reduces D production. Sunscreen is still a good idea when you’re out in the sun for more than short periods. But experts now argue, sometimes angrily, over whether total sun avoidance is such a good idea after all.
- Increasingly, scientific evidence suggests that for many people the optimal dietary vitamin D intake is higher than the current recommended levels. Thus, the government’s new dietary guidelines highlighted recommendations of 1,000 IU a day for older people and other high-risk groups. Some researchers think that levels as high as 2,000 IU a day should be considered.
Vitamin D intake Not enough, too much
Vitamin D can be harmful in large doses, probably starting at 2,000 IU a day, which can lead to kidney stones, kidney failure, and the deterioration of muscle and bone. But a daily intake of 1,000 IU is known to be safe.
We now believe that 800 to 1,000 IU is a good goal for those 70 and older. It’s nearly impossible to get this much without taking a supplement. People living in the northern third of the U.S. and in Canada, those with dark skin, those who are housebound or institutionalized, and those who consume no milk or other fortified foods should also consider supplementation to Vitamin D intake.
The chart below lists good food sources of D. Most multivitamin/mineral supplements have 400 IU. That’s an economical way to get extra Vitamin D intake. If you take calcium, consider a calcium supplement that contains D. Many brands supply 200 IU along with 300 milligrams of calcium per tablet.
Cod liver oil note: Cod liver oil is very rich in D, one tablespoon supplying about 1,400 IU. On top of what your body manufactures and what you get from food, this might well constitute an overdose. Furthermore, cod liver oil also contains very high levels of vitamin A, which can weaken bones. And it may contain contaminants. You should avoid it.
Amount of Vitamin D (UI) in Foods
- Salmon, cooked (3.5 ounces)*: 360
- Sardines, canned (1.75 ounces)*: 250
- Tuna, canned (3 ounces)*: 200
- Milk, cow’s (1 cup): 100
- Milk, soy, fortified (1 cup): 100
- Margarine, fortified (1 tablespoon): 60
- Breakfast cereal, fortified (1 serving): 40
- Egg (1 whole): 20
Miodrag Kablinovic is a martial artist, runner, crossfit-fan and blogger. He loves to write about nutrition, healthy smoothie recipes, weight loss and health. You can read more about him on his blog Miosuperhealth.com.