Why do I need minerals? What do they do?
There are over 2 dozen minerals which your body requires to function properly. Minerals are critical for keeping the metabolic processes running smoothly and for maintaining your bones, muscles and red blood cells (to name a few). See Table 9 Minerals -- RDA & Function. Fortunately, minerals are stable to light, heat and air, and are stored in sufficient quantities in a healthy body so that you may skip a day and not feel any ill-effects. That is, unless you began the trek already depleted/compromised. And that's not altogether unlikely when it comes to iron.
Why do I need iron?
Iron is the "active ingredient" (the cofactor) for hemoglobin, myoglobin, cytochromes and catalase,, and many more enzymes/proteins. As a component of hemoglobin and myoglobin, iron is involved in delivering oxygen to the muscles. You may have sufficient iron to supply the oxygen transport molecules during your quiet days at the office, but what happens when you begin to demand more? The red blood cells transport more hemoglobin and the muscles make more myoglobin, which means more iron is necessary. On top of your increased oxygen demand, you'll also be needing more ATP, which is generated by the electron transport system through the action of iron-dependent cytochromes. So in order to supply oxygen to the muscles AND then turn fuel into energy, iron is necessary. [This is one very good reason to train before you hit the trail.]
Iron serves as a cofactor in many other enzymes, but one worth mentioning is catalase, an antioxidant enzyme. Since active tissue is more likely to be exposed to oxidative damage, more catalase will be required. So to stay healthy and fit, get adequate iron. ("Adequate" is defined as 10 mg for males and 18 mg for females "of child-bearing age.")
What are good sources of iron?
Meat, ( beef, tuna, chicken --even jerky) will have a readily absorbable form of iron ("heme iron"). The rest of the food sources do not supply iron in a form that is most readily absorbed, but if you drink/eat Vit.C along with your iron-rich food, it will aid absorption. Other non-meat sources: iron-fortified cereals, beans and peas, tofu, dried fruit and even dried broccoli.
Supplements are not necessary for individuals on a balanced diet, but if there's a nagging doubt about how "balanced" your diet is, and you opt for a One-A-Day multiple vitamin with iron, be forewarned. Supplemental iron is not readily absorbed--most will go right through you, turning your stools black, and making you constipated. Never exceed the RDA, or you may "rob Peter to pay Paul." Minerals are delicately balanced within your body. If you get too much of one, you'll inhibit absorption of other important minerals such as calcium and zinc. So stay within the RDA. And be consistent. The iron transport proteins will adapt to a certain normal level of incoming iron. If you vary radically from that level, most of the iron will be wasted on days when you take a larger-than-normal dose.
Aside from iron, what other minerals are "At Risk"?
Calcium warrants special attention, since it is critical for muscle contraction, nerve transmission, and the obvious--building strong bones. Even if you think you're not building strong bones, subtle changes are going on as you hike. By carrying an unaccustomed load on your back, the skeletal system will be receiving messages to increase bone density in your spine and lower extremities. The pull of the muscles on your skeleton will also send signals to lay down thicker bones. (Women: backpacking is a wonderful way to decrease your risk of developing osteoporosis because it strengthens your skeleton. Exercise can be as important as getting enough calcium for building strong bones, so do both! With the additional demands on your system, you'll be needing more calcium than usual. The "usual" is supposed to be between 800 and 1200 mg calcium/day. Set 1200 mg/day as a reasonable goal. That is easily achieved if you eat/drink 3-4 servings of milk or dairy each day. If you don't, good alternatives are salmon, sardines (or any fish with bones in it), eggs, dried beans and peas and dark green vegetables (broccoli again!).
If you normally take a calcium supplement at home, continue to take it on the trail. Familiar lesson, repeated: enzymes need a consistent message. In this case, it's the calcium transport molecules that need a consistent message, but the outcome is the same. The transport molecules get accustomed to seeing a certain level of calcium and adjust their activity accordingly. Don't send them mixed messages, or your bones will pay the price. Be consistent!
What are good sources of calcium?
On the trail, try to add 1-2T powdered skim milk to every meal. Even if you are allergic to milk, 1-2 T mixed with your meal is not likely to cause you intestinal discomfort. If you don't "do" milk, nuts and seeds (including sesame seeds) are rich sources of calcium, so eat some everyday. In baking trail goodies, use blackstrap molasses rather than white sugar. Molasses is a good source of most minerals--calcium, iron, zinc, copper, chromium--you name it. BUT beware sulfur. Sulfur promotes excretion (loss) of calcium and some people are allergic to sulfites (headaches, disorientation, GI problems). Sulfured molasses is a "mixed blessing"--providing calcium but then promoting its loss. Unsulfured molasses allows better utilization of calcium. Dried fruits generally have sulfites added to prevent browning. To avoid sulfites, dry your own fruit or shop at the health food/organic store, and always, read labels.
Can I know if I'm not getting enough calcium?
Although there are other causes, "Charley horses" or muscle cramps are
often caused by inadequate calcium, so your body may send you a message
loud and clear if you are not getting enough calcium. Fortunately, the
calcium deficiency may be quickly remedied by boosting your calcium intake.
Iron deficiency, on the other hand, leaves you feeling tired/lethargic
and it will take weeks to correct an iron deficit. So prevention is the
best medicine. Get 4 servings/day of calcium rich foods.
Table 9. MINERALS -- RDA & FUNCTION
|Calcium (mg)||800 / 800||Bone formation, enzyme regulation, muscle contraction, nerve transmission,||Muscle cramps, osteoporosis|
|Phosphorus (mg)||800 / 800||Bone formation, acid-base balance, the P in ATP!||deficiency unlikely|
|Magnesium (mg)||350 / 280||Stabilizes ATP, regulates enzymes in glucose & protein metabolism||Muscle cramps & twitching, weakness|
|Sodium (mg)||500 / 500||Muscle contraction, nerve transmission, acid-base balance, glucose transport||Muscle cramps; dizziness, nausea, vomiting|
||Muscle contraction, nerve transmission, acid-base balance||Muscle cramps, irregular heartbeat|
|Chloride (mg)||750 / 750||Muscle contraction, nerve transmission, digestion in stomach||(rare: convulsions)|
|Iron (mg)||10 / 15||Oxygen transport in hemoglobin & myoblobin; functional part of cytochromes (ETS)||Anemia|
|Zinc (mg)||15 / 12||Functional part of many enzymes involved in producing energy, protein synthesis and immunity||Delayed wound healing|
|Copper (mg)||3.0 / 3.0*||Synthesis of connective tissue (muscles & bones); assists in utilization of iron||(rare: anemia)|
|Chromium (mg)||0.2 / 0.2*||Part of glucose tolerance factor, enhancing insulin function||Glucose intolerance|
|Manganese (mg)||5.0 / 5.0||Fat metabolism and bone formation||Poor growth|
|Selenium (mg)||0.070/0.055||Part of important antioxidant, glutathione peroxidase||Heart damage|
|Iodine (mg)||0.15 / 0.15||Part of thyroid hormones, regulating rate of energy production||Enlarged thyroid (goiter)|
|Fluoride (mg)||4.0 / 4.0||Bone and tooth formation||Increased tooth decay|
|Molybdenum (mg)||0.25 / 0.25*||Fat and carbohydrate metabolism-->ATP||(none)|
*Maximum RDA value for adult male or female when a range is given.
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