Lipid Profile
The blood donation significantly decreased the total cholesterol in the post-24h visit (-7.78% P < 0.001), which may be due to the amount of blood loss during the donation. The total cholesterol level recovered through the week-1 to week-3 visits, with no significant change compared with the pre-24h visit. Borai et al. also explained that blood donation might temporarily decrease the HDL-C after blood donation, but it would subsequently recover (14). We found that the blood donation decrease the HDL-C significantly the following day (-7.71%, P < 0.01). Nevertheless, the HDL-C recovered non-significantly during week-1 (2.66%), week-2 (3.17%), and week-3 (2.63%) compared to the baseline visit. We suggest that blood donation may affect the HDL-C level favorably. HDL-C behaves as an antioxidant protecting against CVD (21, 22).
The effect of the blood donation on the serum LDL-C level vary. Borai et al described that the blood donation have a temporary effect that may lower the LDL-C level after 24 hours following blood donation, with a non-significant increase subsequently (14). Riško et al in 2018 found that the LDL-C is higher in the donor group than the non-donor group (23), and Bani-Ahmad et al reported that repeated whole blood donation elevate the serum LDL-C levels insignificantly (24). However, van Jaarsveld and Pool found that donating blood on three occasions with six week intervals may decrease the LDL-C (13). Initially, our findings indicate that the LDL-C was moderately elevated at the baseline visit. This elevation could be due to the majority (78.78%) of our sample being overweight, and the LDL-C was significantly decreased the next day (-8.70%, P < 0.01). This may be due to the amount of blood loss during the blood donation. The level steadily increased compared with the baseline during week-1, week-2, and week-3 (-0.36%, 2.46%, and 2.81%), respectively. Our results support current literature (13, 14). LDL-C in its own original state is not atherogenic, but once oxidized to oxLDL, it can develop atherosclerotic plaque (25). To fully understand the effect of blood donation on LDL-C, we recommend additional evaluation of oxLDL.
Van Jaarsveld and Pool, in 2002 reported that blood donation elevates the Apo A lipoprotein beneficially. However, our results show that the blood donation significantly decreased the Apo-A post-24h of the blood donation (-5.45%, P < 0.01), possibly due to the amount of blood loss during the blood donation. The Apo-A recovered again during the other visits to the baseline level, with no significant changes. ApoA-I and ApoA-II are major apolipoproteins found in HDL-C. An ApoA-I decrease would be expected due to decline of HDL-C post-24h of the blood donation (26–28).
Apolipoprotein-B
Van Jaarsveld and Pool reported that blood donation would not affect the Apo-B significantly (13). However, our results show that the blood donation may decrease the Apo-B significantly (-7.01%, P < 0.01) 24-h post blood donation. The Apo-B increased again with no significant change during the other visits, compared with the pre-24 h visit. The decline of the LDL-C may reflect the decrease of Apo-B post-24h as the Apo-B is present on the VLDL, IDL, and LDL (29). The amount of blood loss may be responsible for this effect.
Triglyceride
Literature agrees regarding the effect of blood donation on triglycerides, specifically that there is no effect on the triglycerides. For example, Riško et al. reported no significant difference in the triglyceride between long-term donors versus non-donor men (23). However, Bani-Ahmad et al demonstrated that donating blood frequently during a year might be associated with an unfavourable effect on the serum triglyceride (24). Triglycerides are influenced by a number of hormones, such as insulin, growth hormone and adrenocorticotropic hormones. In 2016, Borai et al. observed that blood donation stimulates the production of insulin 2-hr post blood donation and the triglycerides decreased insignificantly on week 1 and three months after the donation. Our study found no significant changes in the triglyceride level. The triglycerides decreased insignificantly during week 1, 2 and 3, compared with the pre-blood donation level. We suggest that the reduction of triglyceride is due to the effect of blood donation in lowering growth hormone and the stimulation of insulin.
Iron Parameters
Iron
The decrease in the iron after blood donation has been investigated. Borai et al. investigated the changes in the iron level, and reported that the iron was not different in the 24-h post blood donation visit. The iron decreased significantly 1 and 2 weeks after the blood donation compared with the baseline level and after three months recovered to the baseline level. We observed that the blood donation may not reduce the iron level immediately the next day (-0.80%). Our results showed that the serum iron decreased significantly in the week-1 visit (-25% P < 0.01). However, the iron was still low during week-2 and week-3 (-20.24% and − 16.12%), respectively, with no significant difference compared with the baseline visit. Our results are in line with Borai et al. (2016). The Fenton's reaction previously explained that the iron is involved as a free radical. Free transition metals, including iron, would be eliminated by blood donation (30). Free radical production would be reduced and the risk of oxidative damage due to the release of Fe3+ from binding proteins might be decreased (31, 32). We posit that reducing the serum iron by donating a unit of blood could reduce free radical production and may decrease the effects of oxidative damage.
Ferritin
We observed that the blood donation slightly decreased the ferritin level the day after the blood donation (-3.29%), and the ferritin decreased in week-1, week-2 and week-3 (-26.31%, -40.34%, and − 36.73%), respectively (P < 0.001) after the blood donation. A decrease in the ferritin level would be expected due to the low iron level, as ferritin is considered an iron store (30). This observation is in line with literature (14, 23). Ferritin is a protein involved in iron transportation, metabolism and play a role in iron compensation (33).
Iron Binding Capacity
The increase in the iron binding capacity following blood donation has been investigated by Riško et al. In the current study, we indicated that the iron binding capacity, after a single blood donation, may become significantly increased post-blood donation. However, Riško et al. reported the comparison between long-term donors versus non-donor men. We observed that blood donation might slightly decrease the UIBC level the day after the blood donation (-1.96%). The UIBC increased in week-1, week-2 and week-3 (15.76%, 17.37%, and 18.60%), respectively (P < 0.001). We also observed that the blood donation might slightly decrease the TIBC level the day after the blood donation (-1.52%). The TIBC increased in week-1, week-2 and week-3 visits (2.18%, 5.53%, and 8.22%). It has been reported that the UIBC and TIBC increased in low iron states (Wolf, 2002, Murtagh et al., 2002, Gambino et al., 1997).
Transferrin Saturation
In 2002, Van Jaarsveld and Pool reported that the transferrin saturation decreased in the blood donor group, who donated blood three times with six weeks intervals. However, our results show that the transferrin saturation, after one donation, decreased significantly on week-1, week-2 and week-3 ( -27.24%, -24.63%, and − 23.93%) respectively. This observation may reflect the low iron status and the increased iron-binding capacity that enter into the circulation. Clinical evidence linked the transferrin saturation to CVD mortality (34). Normal transferrin saturation is 20% − 50%, but in iron-overload states such as hemochromatosis, the high iron level increased the transferrin saturation > 50%. Regular venesection is frequently a treatment that reduces the saturation to < 30% for patients with a high transferrin saturation (33). Blood donation may reduce the transferrin saturation and keep the level < 30%, which may protect or decrease the iron overload. We suggest that the low iron and transferrin saturation due to donating a unit of blood would inhibit free radical production and their effects on lipids and other cardiovascular events.
Enzymatic Antioxidants
Superoxide Dismutase
Literature reports the effect of blood donation on the SOD enzyme activity. Yunce et al in 2016 reported an increase in SOD activity at 24h after the blood donation compared with the pre-donation sample (35). Mehrabani et al suggested that repeated donation of whole blood might stimulate the SOD enzyme and increase its activity. However, we found that the blood donation effectively stimulate and continually release SOD during the post-24 h (17.96%), week-1 (35.71%), week-2 (31.18% ) and week-3 (36.62%) visits. We also found a significant correlation between SOD and the time of visits [r (165) = 0.50, P < 0 .01]. Copper is an essential component of superoxide dismutase (CuZn-SOD) (36, 37). Iron plays a role in decreasing the Cu/Zn SOD activity (38). Increased iron reduces copper absorption and reduce the SOD production (39). We suggest that lowering the iron stores after the blood donation could increase SOD, reducing the toxicity of the ROS, which may result in the initiation of CVD. The current study indicated that the plasma SOD level is decreased compared to the European reference range and is similar to Yunce et al. (2016).
Glutathione Peroxide
The effect of the blood donation on the GPx was investigated by Mehrabani et al. We found that the blood donation significantly reduced the GPx in the week-1 visit (-25.02%, P < .001). The Mehrabani et al study classified the sample in five groups according to their donation time per year (40). The reduction in the GPx would be expected due to the low iron in week-1, as the GPx is dependent on iron for its synthesis (41). Literature reported a decreased activity of the GPx enzyme in iron deficiency anemia patients (42, 43). However, in our research, the GPx improved again during week-2 (-5.95%) and week-3 (-5.67%) with no significant changes to the pre-24h visit.
Glutathione Reductase
We found that the blood donation significantly decreased the glutathione reductase at the post-24 visit (-5.75%, P < 0.001), compared to the pre-24h visit. The glutathione reductase increased slightly above the pre-24h visit throughout week-1 (1.07%), week-2 (1.75%) and week-3 (1.77%), and that the GR positively correlate over the time [r (165) = 0.3, P < 0.01]. The glutathione reductase mainly acts on glutathione to keep it in a reduced status (41). The GR essentially works to supply GPX with a reductive substrate (5). We posit that the elevated glutathione reductase levels after blood donation might be reflected by lowering GPx levels.