Dwayne N. Jackson, PhD
With the abundance of muscle building, strength boosting, energy liberating, and focus enhancing supplements out there, it’s easy to overlook the importance of “foundation level” nutrients like minerals. Dietary minerals are inorganic elements that the body needs to function properly. Since minerals can only be acquired through ingestion, they are considered essential. They are commonly categorized as either major minerals (macrominerals) or trace minerals (microminerals); both are equally important, but microminerals are needed in smaller amounts than macrominerals.
For those who don’t train, but follow a perfectly balanced diet, there is a high likelihood that you are getting close to what you need from food alone. However, if you live in North America, train or compete regularly, and follow a regimented diet (like most athletes), chances are you can benefit by supplementing a few key microminerals.
Chromium enhances the effects of insulin, thus it helps to maintain normal blood sugar. The ergogenic potential of super-doses of chromium is in question, but maintaining proper levels of this trace mineral is important for strength athletes, as normal insulin sensitivity ensures optimal muscle glycogen levels and decreased fat storage. Chromium also seems to be directly involved in carbohydrate, fat, and protein metabolism and storage. Importantly, research has shown that after exercise urinary excretion of chromium goes way up, which can promote chromium deficiency.
Sources: Meats, whole grain products, broccoli, grape juice, molasses, brewer’s yeast
Signs of deficiency: Chromium deficiency is rare; however, in several cases where hospitalized patients presented with diabetes-like symptoms (impaired glucose tolerance, weight loss, etc) their symptoms were reversed when chromium was added to their feeding solution.
Dosage: The most bioavailable form of chromium is chromium picolinate. The verdict on optimal dose is variable but taking 50-200 mcg per day will ensure that chromium levels are topped up.
Iodine is needed for normal thyroid function. The thyroid gland actively absorbs iodine from the blood to be used for the production of thyroid hormones. Thus, iodine plays an important, but indirect role in regulating metabolism and energy levels. As strength athletes, we want to optimize thyroid function and metabolism to ensure we are getting the most out of our diet and training.
Sources: Iodized table salt, cod, sea bass, haddock, kelp
Signs of deficiency: Hypothyroidism, goiter (enlargement of thyroid gland)
Dosage: Because of the low bioavailability of iodine in iodized salt and the fact that athletes tend to limit their table salt intake, iodine supplementation is a good idea. If you are taking a multivitamin, be sure you are getting 150 mcg per day.
Iron is of great importance to human health, as it is the central molecule of hemoglobin, the oxygen carrying component of red blood cells— thus iron plays an indirect role in ensuring we have adequate oxygen delivery to working muscles. Iron is also involved in DNA production, immune system function, protein synthesis, and is very important in thyroid hormone production. Since only about 10% of dietary iron is absorbed, then it may be beneficial to take an iron supplement, especially if you are dieting or avoiding red meat or other dietary sources of iron.
Sources: Red meat, oysters, spinach, kelp, fortified breakfast cereals
Signs of deficiency: Fatigue, irritability, muscle weakness, grooved and brittle nails
Dosage: If you are experiencing signs of iron deficiency, talk to your doctor about having your blood tested. Iron is toxic in high doses, so take as directed. If you are already taking a multivitamin with iron, then you are likely getting enough. The Tolerable Upper Intake Level (UL) for iron is 45 mg per day.
Selenium is a trace element that, when ingested, combines with proteins to form antioxidant enzymes (selenoproteins). Selenoproteins are potent free radical scavengers that help to protect cells throughout the body and keeping them running smoothly. As well, selenoproteins regulate thyroid function and support the immune system.
Sources: Brazil nuts, tuna, beef, wheat, corn, potatoes
Signs of deficiency: Deficiency is rare in North America, as our soil has high levels of selenium.
Dosage: 200 mcg per day, best acquired through diet. The safe upper limit for selenium is 400 mcg per day.
Zinc is required for the activity of over a hundred enzymes in the body, many of which are involved in energy metabolism. Zinc is also integral to many cellular signaling events including those associated with proper liver function, cellular repair, and hormone maintenance. Of importance to athletes, one of zinc’s fundamental roles is to initiate protein synthesis through activating the mechanistic target of rapamycin (mTOR), a necessary cell-signaling event for muscle growth. Studies show that stress, regular heavy weight training, cycling exercise, and even just sweating can lead to zinc deficiency. Studies in humans illustrate that even mild dietary zinc deficiency leads to decreased serum testosterone levels, low sperm count, decreased immunity, and loss of lean body mass. As well, these studies suggest that dietary zinc intake for some athletes may be inadequate (especially female athletes) further promoting zinc deficiency. Support for zinc supplementation in athletes comes from a study where elite strength athletes completed 4 weeks of exhaustive training with and without supplemental zinc. It was reported that those who did not receive zinc supplements had significant declines in testosterone and thyroid hormone levels; whereas, those who received daily zinc had augmented testosterone and thyroid hormone levels.
Sources: Beef, chicken, pork, seafood (especially oysters). Although grains, nuts, and legumes contain zinc, it is poorly absorbed due to the presence of phytates in these sources.
Signs of deficiency: Impaired growth, loss of appetite, hair loss, and impotence. In athletes, zinc deficiency can lead to anorexia, significant loss in bodyweight, latent fatigue with decreased endurance, and a risk of osteoporosis.
Dosage: The recommended daily allowance is 8 to 13 mg per day. However, many formulas suggest athletes take from 15 to 50 mg per day to make up for losses from sweating etc. Avoid taking too much zinc as it can impair the absorption of copper and iron and leads to deficiencies in these minerals. For best results we suggest taking 30 mg of zinc with 450 mg of magnesium, 30-60 minutes prior to sleep. This stack will help you sleep better and keep your hormone levels peaked. Alternatively, you can use a ZMA supplement at night.
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