Vegan for Life - Jack Norris [23]
To make adequate vitamin D for one day, a light-skinned person needs ten to fifteen minutes of midday (10:00 a.m. to 2:00 p.m.) sun exposure, without sunscreen, on a day when sunburn is possible. 21 Dark-skinned people need twenty minutes and older people need thirty minutes.22,23
If your sun exposure doesn’t match these guidelines, then you need to take a supplement or use fortified foods. We recommend 25 micrograms (1,000 IU) per day of vitamin D2.
Many foods, including most breakfast cereals, are fortified with vitamin D. Almost all use vitamin D3, which is derived from animals. Most brands of fortified soymilk and other nondairy milks use vitamin D2, which comes from yeast exposed to UV rays.
For food labeling purposes, the Daily Value for vitamin D is 10 micrograms (400 IU). So if a food provides 25 percent of the Daily Value for vitamin D, it contains 2.5 micrograms (100 IU) of vitamin D per serving. Vitamin D–fortified soy, almond, hemp, or rice milk normally has 2 to 3 micrograms (80 to 120 IU) per cup. You can see from these numbers that it’s not that easy to meet the recommended 1,000 IU per day from fortified foods. If your sun exposure isn’t adequate, you will probably need to use a vitamin D supplement. Most natural foods stores carry supplements of plant-derived vitamin D2, or you can order one from the online sources in the resource section of this book.
Bone Health: More than Calcium and Vitamin D
Calcium and vitamin D have well-deserved reputations as bone-strengthening nutrients, but they don’t act alone. The following are all important for protecting bone health.
• Stay physically active. Exercise is absolutely crucial to bone density and strength; it’s probably the single most important factor in preventing bone loss. Choose weight-bearing and high-impact exercise to get the greatest benefit, such as weight-lifting, jogging, and step aerobics. Biking and swimming are not especially valuable to strengthening bones.
• Maintain a healthy weight and by this, we mean don’t let your weight get too low. When it comes to bone health, being a few pounds above your ideal weight is better than being a few pounds below it. Rapid weight loss is associated with bone loss, so if you have some pounds to shed, aim for a slow reduction while building more muscle and protecting bones through exercise.
• Eat plenty of fruits and vegetables because they keep the blood more alkaline. In fact, some researchers have suggested that the best diet for maintaining healthy bones is one that is rich in calcium, contains plenty of protein to boost calcium absorption, and is generous in fruits and vegetables to keep the blood alkaline. But fruits and vegetables also provide nutrients that are good for bones, such as vitamin K and the minerals boron, potassium, and magnesium. Vitamin C also plays a role in bone formation and high vitamin C intake has been linked to better bone health. Plant foods are the best sources of vitamin K and potassium, and they are the only sources of vitamin C.
• Avoid excess sodium, which is linked to calcium losses. Lightly salting your food is fine, but an overdependence on processed foods can make vegan diets too high in sodium.
Building Healthy Bones on a Vegan Diet
Building and keeping strong bones depends on a number of lifestyle factors. They are all important.
• Aim for a diet that is rich in calcium, using the tips for meeting calcium needs on pages 46–47.